(BDS)
Thesis submitted to Queen’s University of Belfast in fulfilment of the requirement for the degree of
(PhD)
2007
School of Medicine and Dentistry Queen’s University of Belfast (QUB)
DECLARATION
I declare that
(i) The thesis is not one for which a degree has been or will be conferred by
any other university or institution;
(ii) The thesis is not one for which a degree has already been conferred by
this University.
(iii) The work for the thesis is my own work and that, where material
submitted by me for another degree or work undertaken by me as part of a
research group has been incorporated into the thesis, the extent of the work
thus incorporated has been clearly indicated.
(iv) The composition of the thesis is my own work.
Signed: Date:
I
TABLE OF CONTENTS
Declaration ...... I
Table of Contents...... II
List of Figures ...... XI
List Of Tables...... XV
Abstract ...... XVII
Acknowledgements ...... XX
Overview of the study...... XXII
1.1.1 Introduction ...... 1
1.1.1.1 The ESE document outlines the undergraduate curriculum ...... 3
1.1.1.2 Non surgical endodontics ...... 3
1.1.1.3 Surgical endodontics...... 5
1.1.2 Quality guidelines for endodontic treatment...... 5
1.1.2.1 History, clinical examination, diagnosis and treatment planning ...... 6
1.1.2.2 Records...... 7
1.1.2.3 Informed consent...... 7
1.1.2.4 Record of treatment ...... 7
1.1.2.5 Review of treatment ...... 8
1.1.2.6 Infection control...... 8
1.1.2.7 Treatment planning...... 8
1.1.2.8 Indication for root canal treatment...... 8
II
1.1.2.9 Contraindications to root canal treatment...... 9
1.1.2.10 Indication for endodontic surgery...... 9
1.1.2.11 Contraindications to endodontic surgery...... 10
1.1.3 Root canal treatment...... 10
1.1.3.1 Preparation of tooth...... 10
1.1.3.2 Isolation of the tooth...... 11
1.1.3.3 Access cavity preparation...... 11
1.1.3.4 Determination of working length ...... 12
1.1.3.5 Preparation of the root canal system...... 12
1.1.3.6 Irrigation...... 12
1.1.3.7 Inter‐appointment disinfection...... 13
1.1.3.8 Intra‐canal medicament ...... 13
1.1.3.9 Obturation of the root canal system...... 13
1.1.4 Assessment of endodontic treatment ...... 14
1.1.5 Studies evaluating root canal treatment performed by undergraduates...... 15
1.1.6 Studies evaluating the pattern of undergraduate endodontic teaching ...... 22
1.1.7 History of endodontics...... 24
1.1.7.1 The role of radiograph in endodontics...... 26
1.1.8 Root canal treatment performed by general dentists ...... 28
Location...... 38
1.2.1 Introduction ...... 40
1.2.2 Properties of an ideal irrigant...... 42
1.2.2.1 Sodium Hypochlorite...... 43
1.2.2.1.1 Sodium Hypochlorite properties...... 44
III
1.2.2.2 Ethylenediamine tetraacetic acid (EDTA)...... 50
1.2.2.3 Chlorhexidine (CHX) ...... 51
1.2.2.4 Electrochemically activated water (ECA) ...... 52
1.2.2.5 Photo activated disinfection (PAD™)...... 56
1.2.2.6 Endox system (Lysis S.r.I, Nova Milanese, Italy) ...... 57
1.2.2.7 MTAD ( BioPure®)...... 57
1.2.2.8 Lasers...... 58
1.2.2.9 Ozone ...... 60
1.2.2.9.1 The use of ozone in endodontic treatment ...... 63 1.2.2 Microflora of the infected root canal...... 65
1.2.2.1 Introduction ...... 65
1.2.2.2 Microbiological aspects of persistent periapical disease ...... 67
1.2.2.3 Types of endodontic infection ...... 69
1.2.2.3.1 Primary root canal infection...... 69 1.2.2.3.2 Secondary root canal infection...... 70 1.2.2.4 Requirements for an endodontic pathogen ...... 70
1.2.2.2 History of endodontic flora...... 71
1.2.2.3 Causes of Endodontic Failures ...... 71
1.2.2.3.1 Microbial factors ...... 72
1.2.2.3.1.1 Intraradicular infection ...... 72 1.2.2.3.1.2 Extraradicular infection...... 74 1.2.2.3.2 Microbial involvement in special situations ...... 75
1.2.2.3.2.1 Overfilling...... 75
1.2.2.3.2.2 Coronal sealing ...... 76
1.2.2.3.2.3 Nonmicrobial factors...... 77
1.2.2.4 Success of endodontic therapy ...... 78
IV
1.2.2.5 Smear layer...... 78
1.2.2.6 Scanning electron microscopy...... 81
1.2.2.6.1 History ...... 81
1.2.2.6.2 Type of electron microscopes ...... 81
1.2.2.7 Removal of the smear layer...... 83
1.2.2.7.1 Introduction ...... 83
1.2.2.7.2 Chemical removal...... 84 1.2.2.7.3 Ultrasonic removal ...... 87 1.2.2.7.4 Laser removal ...... 88 1.2.2.7.5 Smear clean™...... 89 1.3.1 Introduction ...... 90
1.3.2 Ozone delivery system...... 92
1.3.2.1 Introduction ...... 92
1.3.2.2 History of ozone...... 94
1.3.2.3 Chemistry of ozone ...... 95
1.3.3 Clinical applications of ozone ...... 96
1.3.2.1 The four primary current methods of administering medical ozone ...... 96
1.3.3 Potential applications of ozone treatment in dentistry...... 98
1.3.4 Effect of ozone on bond strength and surface hardness of dental bonding materials...... 105
1.3.5 Ozone in endodontics ...... 106
1.3.5.1 Effect of ozone on oral microorganisms...... 107
1.3.6 Safety of ozone ...... 113
1.3.7 Conclusion...... 115
1.4.1 Introduction ...... 119
1.4.1.1 Definition...... 119
V
1.4.2 Types of Endodontic pain ...... 121
1.4.2.1 Preoperative pain...... 122
1.4.2.2 Postoperative pain ...... 122
1.4.2.3 Flare‐up pain...... 123
1.4.3 Prognostic factors associated with incidence of pain...... 123
1.4.3.1 Preoperative pain, vitality and periapical pathology ...... 123
1.4.3.2 Single versus Multiple session endodontic treatment...... 125
1.4.4 Prognostic factors associated with flare‐up incidence...... 127
1.4.5 Prognostic factors and success of endodontic treatment ...... 128
1.4.6 Aetiology of endodontic pain...... 129
1.4.7 Methods for assessment of the post‐obturation pain...... 131
1.4.8 Efficacy of various treatment protocols for endodontic pain ...... 134
1.4.8.1 Efficacy of intra‐canal medicament...... 134
1.4.8.2 Role of Calcium Hydroxide ...... 136
1.4.8.3 Role of intra‐canal irrigant...... 137
1.5.1 Introduction ...... 141
1.5.2 The use of NiTi in endodontic treatment...... 143
1.5.3 Summary of Nickel‐ titanium alloy...... 144
1.5.2 Canal preparation with rotary and hand nickel‐titanium...... 145
1.5.3 Canal preparation methods...... 152
1.5.3.1 Introduction ...... 152
1.5.3.2 Standardized preparation...... 153
1.5.3.3 Flaring techniques ...... 153
1.5.4 Working Length Determination...... 157
VI
1.5.4.1 Methods of canal length determination ...... 158
1.5.4.1.1 Radiographic technique ...... 159 1.5.4.1.2 Electronic apex locators ...... 160 1.5.4.1.3 Tactile sensation ...... 163 1.5.4.1.4 Paper point evaluation ...... 164 1.5.5 Summary...... 164
Aims of the study...... 165 hypothesis...... 166
2.1 Quality of the first root canal treatment performed by undergraduate students.184
2.1.1 Introduction ...... 184
2.1.2 Material and methods ...... 189
2.1.2.1 Statistical analysis ...... 190
2.1.3 Results...... 194
2.1.4 Discussion ...... 196
2.1.5 Conclusion...... 203
2.2 Quality of the second root canal treatment performed by undergraduate...... 204
2.2.1 Introduction ...... 204
2.2.2 Material and Methods...... 206
2.2.2.1 Statistical analysis ...... 207
2.2.3 Results...... 208
2.2.4 Discussion ...... 212
2.2.5 Conclusion...... 217
3.1 Efficacy of some irrigants to remove the smear layer in root canals...... 218
3.1.1 Introduction ...... 218
3.1.2 Material and Methods:...... 221
VII
3.1.2.1 Statistical analysis ...... 224
3.1.3 Results...... 225
3.1.4 Discussion ...... 247
3.1.5 Conclusion...... 256
3.2 Antimicrobial effect of ozone on microorganisms in an in‐vitro study ...... 257
3.2.1 Introduction ...... 257
3.2.2 Material and Methods...... 260
3.2.2.1 Test organisms...... 260
3.2.2.2 Ozone application...... 261
3.2.2.3 Statistical analyses ...... 261
3.2.3 Result...... 265
3.2.4 Discussion ...... 269
3.2.5 Conclusions...... 276
4. Antimicrobial aspects, postoperative pain incidence and practicalities of irrigation with and without ozone: a clinical study ...... 277
4.1 Study population ...... 277
4.2 Treatment groups...... 278
4.3 Inclusion and exclusion criteria ...... 279
4.4 Sample size calculation...... 280
4.1 To investigate sodium hypochlorite with and without the use of ozone as an antimicrobial agent in RCT irrigation...... 282
4.1.1 Introduction ...... 282
4.1.2 Material and Methods...... 286
4.1.2 Equipment used ...... 286
4.1.2.1 Ozone delivery system...... 286
VIII
4.1.2.2 Apex locator Elements Diagnostic Unit...... 290
4.1.2.3 K3 TCM Endo motor with W&H handpiece...... 291
4.1.3 Clinical procedure...... 292
4.1.3.1 K3 System Features ...... 297
4.1.4 Statistical analyses...... 304
4.1.5 Microbiological analyses...... 305
4.1.3 Results of study ...... 307
4.1.4 Discussion of the study...... 312
4.1.5 Conclusion...... 326
4.2 Influences of ozone treatment on post‐operative pain after rct in‐vivo...... 327
4.2.1 Introduction ...... 327
4.2.2 Material and methods ...... 329
4.2.2.2 Statistical analysis...... 332
4.2.3 Results of the study ...... 333
4.2.4 Discussion of the study...... 342
4.2.5 Conclusion...... 352
Further research...... 353
5. References...... 354
General conclusion ...... 461
Submission for publication ...... 464
Appendices...... 466
Flow chart of the study 3.1...... 467
Ethical Approval for the in‐vivo study ...... 470
IX
Information letter to patients and their parents/guardians. evaluation of the safety and efficacy of the use of ozone for the root canal treatment...... 474
Consent form for the in‐vivo study (4.1& 4.2) ...... 479 flow chart of the clinical study (4.1) ...... 480
X
LIST OF FIGURES
Figure 2-1-1 Well-shaped and obturated root canals using gutta-percha sealer and lateral compaction ...... 195
Figure 2-1-2 Improper root canal obturation that lack proper canal shape, in addition to poorly compacted root canal fillings...... 195
Figure 3-1-1 Coronal third of a sample irrigated with 0.5% NaOCl showing peritubular and intertubular surface dentine which appeared smooth and flat. Individual orifices of dentinal tubules were clearly observed (original magnification x 4000)...... 225
Figure 3-1-2 Middle third of root canal irrigated with 0.5% NaOCl showing some areas of smear layer and several open tubule orifices...... 226
Figure 3-1-3 At the apical third region of a sample irrigated with 0.5% NaOCl had pulpal remnants present with collagenous matrix spread along the root canal walls and some smear layer is shown (original magnification x 4000) ...... 227
Figure 3-1-4 Coronal third of root canal irrigated with 0.5% NaOCl and ozone bubbled in for 10 seconds after each file. Erosion of peritubular and intertubular dentine was observed, with irregularly enlarged dentinal tubules (original magnification top, x 4000, bottom x 500) ...... 228
Figure 3-1-5 Middle third of root canal irrigated with NaOCl and ozone bubbled in for 10 seconds showing clean, exposed dentinal tubules, some debris was observed (original magnification x 500, x 1000, x 4000) ...... 229
Figure 3-1-6 Some specimens irrigated with NaOCl and had ozone bubbled in for 10 seconds showed a moderate smear layer in localised AREAS IN the apical third. Excessive erosion has led to conjugation of two or more dentinal tubules (original magnification x 1500, x 1000, x 4000) ...... 230
Figure 3-1-7 Coronal third of root canal. Surface totally covered by a thick smear layer and tubule orifices are blocked (original magnification x 4000) ...... 231
Figure 3-1-8 Middle third showing heavy smear layer and extensive amounts of loose debris (original magnification X 2000)...... 232
Figure 3-1-9 Specimen irrigated with distilled water. Apical third of canal wall showing a moderate smear layer (x 4000)...... 232
XI
Figure 3-1-10 Specimens irrigated with distilled water and ozone bubbled in for 10 seconds after each file. The root canal walls showed, at the apical third, a moderate smear layer on the openings of the dentinal tubules ...... 233
Figure 3-1-11 Specimen in the middle third where dentinal tubules were clearly observed with visible smear layer...... 234
Figure 3-1-12 At the coronal third, the dentinal tubules were clearly observed and some smear layer was visible (original magnification x 4000)...... 234
Figure 3-1-13 Presence of smear layer on the surface of the coronal third of a root canal irrigated with physiological saline ...... 235
Figure 3-1-14 Middle third showing a smooth and slightly porous smear layer with fully or partially blocked tubules evenly distributed throughout the surface and with some loose debris ...... 236
Figure 3-1-15 Apical third of the root canal instrumented and irrigated with saline. The smear layer covered the dentinal tubules ...... 236
Figure 3-1-16 Middle third of the root canal irrigated with saline and ozone bubbled in for 10 seconds. Large areas of thin smear layer with fully or partially blocked tubule orifices are shown ...... 237
Figure 3-1-17 Coronal third specimens irrigated with saline and ozone bubbled in for 10 seconds showing a moderate smear layer remaining on the surface of the root canal...238
Figure 3-1-18 In the apical third the specimens irrigated with saline and ozone bubbled in for 10 seconds showed a thin smear layer covering the surface, with a few dentinal tubules clearly visible...... 238
Figure 3-1-19 Specimen in the coronal third after sterilox irrigation showing clean root canal walls with considerable smear layer missing (original magnification x 4000) ....239
Figure 3-1-20 Smear layer covering the dentine wall and some of exposed dentine tubules in the middle region treated by sterilox irrigation (original magnification x 4000) ...... 240
Figure 3-1-21 Specimen in the apical third treated with sterilox showing the root canal covered with a heavy smear layer and debris with very few exposed dentinal tubules (original magnification x 1000, x 4000) ...... 240
Figure 3-1-22 Coronal third of root canal irrigated with sterilox and ozone bubbled in for 10 seconds after each file. This resulted in open dentinal tubules and removal of the smear layer. Scattered loose dentine debris is present in some areas ...... 241
XII
Figure 3-1-23 Middle third of root canal irrigated with sterilox and ozone bubbled in for 10 seconds after each file. Individual orifices of dentinal tubules are clearly observed, with loose dentine debris also present...... 242
Figure 3-1-24 Presence of the smear layer on the surface of the apical third of a root canal irrigated with sterilox and ozone bubbled in for 10 seconds. Partially blocked tubules are lightly distributed through the surface (original magnification x 4000)...... 242
Figure 3-1-25 Distribution of scores among the groups in the coronal third...... 243
Figure 3-1-26 Frequency of scores in the experimental groups in the middle one third ...... 244
Figure 3-1-27 Distribution of scores among the groups in the apical one third...... 244
Figure 3-1-28 Middle third of root canal irrigated with NaOCl and ozone bubbled in it for 10 seconds. This shows clean, exposed dentinal tubules but with some debris and some localised smear layer. This specimen was prepared for SEM using a saw...... 249
Figure 3-1-29 Middle third of root canal irrigated with NaOCl and ozone bubbled in it for 10 seconds. This show clean, exposed dentinal tubules but with some debris. This specimen was prepared for SEM using a chisel...... 250
Figure 3-2-1 HealOzone Unit (KaVo, Germany) ...... 262 Figure 3-2-2 HealOzone (KaVo) handpiece used for ozone delivery with different disposable removable silicone cups ...... 263 Figure 3-2-3 The needle (KaVo) to deliver ozone into root canals ...... 264
Figure 3-2-3-1 Median level of C.F.U. remaining after different exposure times (in seconds) to ozone, NaOCl with air or air...... 267
Figure 4-1 Statistical methods for rates and proportions 2nd Ed, Wiley, 1981. pp.38-45 ...... 281
Figure 4-1-2-1-1 Ozone delivery system ...... 287 Figure 4-1-2-1-2 The head of the handpiece delivering ozone, with the opening for the ozone gas through a needle ...... 288 Figure 4-1-2-1-3 Handpiece with a cup ...... 289
Figure 4-1-2-2-1 Apex locator Elements Diagnostic Unit...... 290
Figure 4-1-2-3-1 TCM Endo iii motor with handpiece for K3 files ...... 291
XIII
Figure 4-1-3-1 Preoperative radiograph to assess the root canal length ...... 293
Figure 4-1-3-2 Measurement of the working length of the K3 file before starting the procedure...... 294
Figure 4-1-3-3 K3 files ...... 296
Figure 4-1-3-4 Cross section of K3 with various features appropriately labeled...... 297
Figure 4-1-3-5 Picture of the needle ready mounted to the Healozone handpiece to be used for ozone delivery (right) and the 30 gauge endodontic irrigating needle...... 302
Figure 4-1-3-6 Ozone or air treatment using the appropriate silicone cup size, sealed around the tooth and previously treated with NaOCl. Ozone safely delivered through the prototype needle mounted to the Healozone handpiece...... 303
Figure 4-2-2-1 Vitality Scanner ...... 330
Figure 4-2-3-1 Percentages of pain in the first day with regard to irrigation groups....334
Figure 4-2-3-2 Comparison between gender on the level of pain...... 338
Figure 4-2-3-3 Histogram of the irrigation groups (NaOCl with air and ozonated NaOCl) between bacterial reduction and x-rays findings...... 340
XIV
LIST OF TABLES
Table 1-1-1 Studies evaluating success and failure of root canal treatments performed by general dentists...... 38 Table 1-1-2 Studies investigating the quality of obturation performed by general dentists ...... 39
Table 1-3-1-1 Studies evaluate the use of ozone...... 91
Table 1-5-1 Overview of different existing NiTi rotary systems...... 143 Table 1-5-2 Classification of electronic root canal length measurement devices...... 162
Table 2-1-1 Studies evaluating endodontic treatments performed by undergraduates at different dental schools ...... 186 Table 2-1-2 Subjective Quality Rating of Radiographs ...... 190 Table 2-1-3 Rating of Quality of Apical Root Filling-Density and Lateral Fill ...... 191 Table 2-1-4 Rating of Quality of Remaining Root Filling-Density and Lateral Fill....191 Table 2-1-5 Rating of Quality of Root Filling-Relationship to Apex ...... 192 Table 2-1-6 Rating of Periapical Condition ...... 192 Table 2-1-7 Rating of Coronal Seal...... 193
Table 2-2-1 Proportion of grades 1, 2 and 3 for the radiographs from the 1st and 2nd RCT’s. There was a significant difference overall (chi-square of 6.503, DF =2, P ≤ 0.05)...... 208 Table 2-2-2 Quality of root canal fillings in relation to the apex...... 210 Table 2-2-3 Quality of the Coronal Seal ...... 211
Table 3-1-1 P values- statistical significant difference between the coronal, middle and apical thirds of the root canal (significant in bold) ...... 245 Table 3-1-2 Result of the Mann-Whitney test comparing smear layer removal in each group (statistically significant difference in bold) ...... 246
Table 3-2-3-1 Antimicrobial efficacy of medication ...... 266 Table 3-2-3-2 Descriptive statistics between the treatment groups ...... 268 Table 3-2-3-3 Descriptive statistic for the treatment groups...... 268
Table 4-1-1 Composition of reduced transport fluid (RTF)a...... 306
XV
Table 4-1-3-1 Bacterial growth (CFU) and percentage reduction determined for root canal samples of 38 teeth, before and after chemo-mechanical preparation with NaOCl with air as the irrigating substance...... 309 Table 4-1-3-2 Bacterial growth (CFU) and percentage reduction determined for root canal samples of 42 teeth, before and after chemo-mechanical preparation with ozonated NaOCl as the irrigating substance...... 310 Table 4-1-3-3 Comparison of groups characteristics ...... 311 Table 4-1-3-4 Median values for the treatment groups...... 311
Table 4-1-4-1 Data from different clinical studies, showing the incidence of positive cultures ...... 325
Table 4-2-2-1 Data recorded for each case...... 332
Table 4-2-3-1 Occurrences of postoperative pain in the first day...... 334 Table 4-2-3-2 Occurrences of postoperative pain in the second day ...... 335 Table 4-2-3-3 Result of the appropriate test used ...... 336 Table 4-2-3-4 Comparison between genders on the level of pain in the first day postoperatively ...... 337 Table 4-2-3-5 Cross tabulation of x-rays changes with regards to irrigation groups ...341
XVI
ABSTRACT
Introduction:
Healing and non-healing in the periapical region after endodontic treatment in humans was first studied radiographically by Strindberg (1956).
Subsequent reports (Bergenholtz et al.1979, Ehnevid et al. 1993, Caliskan & Sen 1996,
Waltimo et al. 2001, Huumonen et al. 2003) have published radiographic studies of the periapical healing process. They all report a high percentage of failures after endodontic treatment. Furthermore, in a bacteriological and radiographic study, Engstrom (1964) found a higher healing rate after endodontic treatment when bacteriological samples from the root canal showed no traces of bacteria before root filling. Therefore,the use of antiseptic irrigation is an important part of chemomechanical root canal preparation. It enhances elimination of microbiota and facilitates removal of necrotic tissue and dentine debris from the root canal system. Based on its unique capacity to dissolve necrotic tissue remnants, NaOCl remains the most widely recommended irrigating solution in endodontics (Zehnder 2006).
A novel concept for the treatment of dental caries using ozone gas, as a potent microbicide, has recently been introduced (Baysan et al. 2000, Baysan & Lynch 2004,
2006, 2007). A number of studies have been undertaken on the effects of ozone on treating dental caries and the reduction of oral microorganisms (Holmes 2003, Abu-
Salem 2004, Nagayoshi et al. 2004a, b, Huth et al. 2005, Huth et al. 2006, Huth et al.
2007, Estrela et al. 2007, Baysan & Beighton 2007).
XVII
Previous data had suggested that ozone delivered as a gas on root carious lesions or as ozonated water to bacteria in vitro (Baysan et al. 2000) was extremely bactericidal. Such effects would also be expected if the gaseous ozone became dissolved in water since ozonated water is well established as an antimicrobial in many industrial situations (Kim et al. 1999).
Aims: The study aims at the following: to investigate the quality of the first and second root canal fillings performed by undergraduate dental students at the School of
Dentistry, Belfast, UK; to investigate the efficacy of ozone for removal of the smear layer and to kill microorganisms including E. faecalis in-vitro; to examine clinically the ability of ozone to reduce the number of bacteria in root canals and its effect on postoperative pain after root canal therapy in an in-vivo study and to assess radiographic the effect of the use of ozone into NaOCl on periapical radiolucencies after 6 months recall.
Materials and Methods: 230 postoperative periapical radiographs were assessed. All the radiographs were interpreted using strict criteria. Entercoccus faecalis microorganisms and 80 extracted single rooted teeth were used to assess the ability of ozone to remove the smear layer as well as to kill microorganisms in an in-vitro study.
One hundred patients were enrolled and subjected to clinical examination of the root treated tooth and a periapical radiograph and a sample was taken for microbiological analysis and the postoperative pain scores were quantified (no pain to severe). Eighty periapical x-ray where examined at the baseline and at 6 months recall using strict criteria.
Results: There was no statistically significant difference between the quality of the first and second root canal fillings performed by undergraduate dental students. The
XVIII
application of ozone for 40s, 60s or 120s was able to kill all the E. faecalis in an in-vitro study. The irrigation of ozonated NaOCl and Sterilox with ozone significantly improved the removal of the smear layer in-vitro. The application of ozone for a period of 10s at each stage was capable of reducing the number of colony forming units in-vivo with no adverse side effects. The ozone delivery system was easy to use.
Conclusions: Radiographic examination of endodontically treated teeth demonstrated that there was no statistically significant difference in the first and second root canal fillings performed by undergraduate dental students. From the obtained data, it can be concluded that the introduction of ozone in routine root canal disinfection when used with NaOCl and with Sterilox in-vitro helped to remove the smear layer. Ozone gas can kill more E. faecalis in vitro than NaOCl with air. The use of ozone is capable of reducing microorganisms with a trend for less postoperative pain in one session RCT using ozone. Two cases, which were treated with NaOCl and air, got worse and both cases had x-ray scores of one at baseline and were two at 6 months, whilst in the ozonated NaOCl group no case got worse.
XIX
ACKNOWLEDGEMENTS
I would like to convey great respect, regards, and gratitude to:
Professor Edward Lynch MA BDentSc FDS RCSED, FDSRCSLond PhD, Professor of Restorative Dentistry and Gerodontology. Special appreciation for believing in me and giving me a chance to be a doctoral student in Queen’s University, for his encouragement, excellent inspiration and wonderful enthusiasm, for always being there to offer help and advice and always pointing me in the right direction. I am so grateful to
Professor Philip-John Lamey BSc, BDS, MBChB, DDS, FDSRCPS, FFDRCSI,
FDSRCS, Professor of Oral Medicine for his help in many ways and for his constructive comments, and for his important support throughout this work.
I am deeply grateful to my third supervisor, Dr Zuhair Al-Khatib, consultant endodontists at Rashid Hospital, Government of Dubai. His support indeed has been generous and I cannot imagine how this research could have proceeded without his guidance.
My sincere thanks are due to Dr. Chris Patterson for his guidance in statistical analysis, and for his essential assistance in reviewing the data entry and the methods of analysis of this study.
I wish to thank all staff in the Department of Restorative Dentistry for their support, care and assistance and all participant patients, without their participant this study would not be completed.
I am of course, extremely grateful to the staff in the Microbiology Department in the
Saqar Hospital, Ministry of Health, UAE. It is difficult to contemplate how this work
XX
could have been undertaken without their support and confidence in me and for this.I wish to express my thanks.
I would like to give my special thanks to Dr. Leo Cunningham for being so supportive and encouraging.
I feel a deep sense of gratitude for my Family, my Father and Mother who formed part of my vision, taught me the good things that really matter in life, and who taught me the value of hard work by their own example.
I am grateful for my three brothers, and one sister, for rendering me the sense and the value of family, I am glad to be one of them. My loving thanks are due to my sister
Fareeda for her continuous support and encouragement since the first minute I arrived in Belfast.
The chain of my gratitude would be definitely incomplete if I would forget to thank the first link in this chain, namely the Ministry of Higher Education in UAE, for providing me with a scholarship to undertaken my PhD, as well as the UAE, Ministry of Health, Government of Dubai, RAK District and RAK Dental centre colleagues for their support.
I would like to thank SybronEndo for providing me with the RCT tools.
Finally, I wish to offer a personal note of thanks to all others who have generously granted me their assistance and support and precious time in his/ her field of specialization, in this regard, praying to almighty God to direct us all to whatever is beneficial.
XXI
OVERVIEW OF THE STUDY
Root canal therapy is principally concerned with the elimination or prevention of pulpal and periapical diseases. It is a predictable form of dental treatment with a reported success rate as high as 94%. Root canal therapy has generally shifted from treatment performed in two or three stages to a one-visit treatment. Furthermore, the use of modern tools has increased the chance of a higher success rate. The aim of this study was to assess novel methods to remove the smear layer in vitro, the ability of ozone to remove the smear layer and microorganisms in vitro, the ability of ozone therapy to reduce or eliminate the number of microorganisms in the root canal system in a clinical study and to assess if the use of ozone had any effect on postoperative pain.
The first part of this study, assessed the quality of root canal treatment (RCT) performed by undergraduates. The study concluded that there was no statistically significant improvement in the quality of the second root canal filling when compared radiographically with the first clinical attempt of RCT. It could be concluded that the standard reached pre-clinically allowed the students to be competent to carry out RCT on a real patient. The fact that the quality did not improve with the second root canal filling supports competency training. It suggests that the students have reached a plateau in their learning. However, the quality achieved was far from perfect.
The second part of this study assessed the antimicrobial effect of ozone treatment on microorganisms in root canal systems. The study also aimed to evaluate the ability of ozone to kill a strain of E. faecalis in an in vitro study. The study concluded that the irrigation of gaseous ozone for 60s or 120s killed all E. faecalis, when its concentration
XXII
in suspension was 106/ml and lower and for 40s when its concentration in suspension was 104 /ml and for sodium hypochlorite to kill all E. faecalis at exposure times of 60s or
120s when its concentration in suspension was 104/ml.
In the clinical study, 80 samples showed positive microbiological cultures after completing mechanical preparation by the rotary instrument K3 system and after applying the irrigation treatment. The results indicate that there was a statistically significant difference between the reduction of microorganisms with NaOCl with air compared with ozonated NaOCl (p = 0.004). A significant reduction in total colony forming units was observed in the ozonated NaOCl group. Secondly, the study aimed to evaluate the postoperative pain experience of subjects having RCT with and without ozone therapy. The incidence of pain was not influenced by bubbling ozone into the irrigant compared to air.
These studies will help clinicians and endodontists understand some of the use of ozone in RCT, which should be further investigated to assess if ozone can improve the success rates of RCT.
XXIII Literature Review1.1
Undergraduate curriculum for root canal therapy
1.1.1 INTRODUCTION
Endodontology is the branch of dental science concerned with the study of the form, function and health of injuries to and diseases of the dental pulp and periradicular region and their treatment. The aetiology and diagnosis of dental pain and disease are integral parts of endodontic practice. Endodontic treatment is an essential part of quality comprehensive dental care.
The scope of the specialist area of dental practice known as endodontics is defined by the educational requirements for the training of a dentist (ESE 1992). Endodontic treatment encompasses procedures that are designed to maintain the health of all or part of the pulp. When the pulp is diseased or injured, treatment is aimed at preserving normal periradicular tissues. When pulpal disease has spread to the periradicular tissues treatment is aimed at restoring them to health. This is usually accomplished by root canal treatment, occasionally in combination with endodontic surgery.
Dentistry's main goal is to maintain a healthy natural dentition for the public and the aim of endodontic treatment is to preserve functional teeth without prejudice to the patient's health.
The British Endodontic Society (BES) in 1983, published guidelines for root canal treatment. The guidelines were revised in 1990’s and after discussion with the European
Society of Endodontology, these guidelines were cited and published by the European
Society of Endodontology (ESE). These guidelines addressed two essential elements: namely, appropriateness of treatment and quality of treatment provided. Every dental
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Undergraduate curriculum for root canal therapy undergraduate receives standard instructions and training in endodontics therapy as part of their training (ESE 1992).
These guidelines are designed to ensure good practice and thus determine that patients receive the highest standard of care by general dental practitioners.
ESE published guidelines for an undergraduate endodontic curriculum in 1992. These guidelines were subsequently revised and updated following studies by De Cleen et al.
(1993), Weiger et al. (1997) and Marques et al. (1998).
The American Association of Dental Schools (AADS) developed the first curriculum guidelines in 1981 in response to a request from the American Dental Association's
Council on Dental Education. Their guidelines were revised in 1985. In March 1989, the officers of the section of endodontics organized a workshop to review the guidelines using information and recommendations received from its constituents.
The revision was unanimously approved by the section on endodontics at the March
1991 AADS annual session.
The underlying principles of both ESE and AADS guidelines were a minimum level of undergraduate skills to be reached by all graduates with an emphasis for continued learning in the graduate curriculum (AADS 1993).
In many countries, endodontics comes under the discipline of conservative dentistry and in a number of European countries endodontics is not recognised as a speciality, but the majority of the committee felt that endodontics should be taught in clinical areas dedicated to that purpose. It is clearly important that students should have adequate experience of the treatment of endodontic emergencies and to ensure that the
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Undergraduate curriculum for root canal therapy undergraduate training programme in endodontics is comprehensive and of a high standard to ensure adequate standards of endodontic care.
1.1.1.1 THE ESE DOCUMENT OUTLINES THE UNDERGRADUATE CURRICULUM AND INCLUDES THE FOLLOWING:
An adequate knowledge base of: ♥ Applied anatomy, oral histology and oral physiology
♥ Pathology and microbiology
♥ Clinical pharmacology and medicine
♥ Dental material science
1.1.1.2 NON SURGICAL ENDODONTICS
The undergraduate should be:
1. Able to perform an examination of a patient with an endodontic related problem, evaluate the status of the pulp and periradicular tissues of teeth and provide good quality endodontic treatment in the context of the overall welfare of the patient.
2. Understand the physiological and anatomical changes that take place in the pulp dentinal complex of teeth because of dental caries, trauma, tooth surface loss and age.
3. Have an understanding of biomaterial science in relation to endodontics.
4. Have a detailed knowledge of the differential diagnosis of various complaints that mimic pulpal and periradicular disease.
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5. Demonstrate a detailed knowledge of the principles and practice of the use of rubber dam in endodontically related procedures and have extensive experience of the application of rubber dam for a variety of cases.
6. Manage the medically needs of medically compromised patients.
7. Understand when referral to an endodontic specialist is required.
8. Have an understanding of the pharmaco-theraputic agents used in the management of pulpal and periradicular disease.
9. Have a detailed knowledge of the aetiology, pathology, clinical presentation and treatment options for diseases affecting the pulp and periradicular tissues.
10. Have a detailed knowledge of the differential diagnosis of various complaints that may mimic pulpal and periradicular disease and employ the use of various diagnostic tests.
11. Have a detailed knowledge of the differential diagnosis of orofacial pain.
12. Be able to communicate with the patient to obtain a complete history of their condition, identify principle problems for the patient and patient's expectations for non surgical root canal treatment and present realistic treatment outcomes and thus promote endodontic treatment as part of holistic care.
13. Be able to undertake treatment for different patient groups including children and the elderly.
14. Have a detailed knowledge of the principle and practice of dental radiology in respect to endodontic treatment and image creation.
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15. Have a detailed knowledge of the principle and practice of various vital pulp treatment and preventive endodontics.
16. Have a detailed knowledge of the principles and practice of non-surgical root canal retreatment.
17. Have knowledge of the principle and practice management of various dental trauma.
18. Undertaken procedures to restore the root filled tooth to function using intracoronal and extra coronal restoration.
19. Understand the clinical and radiographic criteria used to determine success or failure of treatment.
20. Identify the treatment options available when failure of root canal treatment has been established. (By ADDS 1993).
1.1.1.3 SURGICAL ENDODONTICS
The undergraduate should be familiar with the diagnosis and technical procedures involved in endodontic surgery.
(AADS 1993)
1.1.2 QUALITY GUIDELINES FOR ENDODONTIC TREATMENT
In developing this guideline, the European Society of Endodontology in co-operation with the British Endodontic Society responded to a public and professional need. In receiving care of a specialized nature such as endodontic treatment, patients need and deserve treatment that meets the standard of care generally given by competent
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Undergraduate curriculum for root canal therapy practitioners. The European Society of Endodontology and the British Endodontic
Society have the expertise and professional responsibility necessary to assist the dental profession by instituting guidelines on the standard of care in the special area of endodontics.The European Society of Endodontology and the British Endodontic
Society have formulated this consensus of treatment guidelines that are intended to represent current good practice.
They have recommended the following:
1.1.2.1 HISTORY, CLINICAL EXAMINATION, DIAGNOSIS AND TREATMENT PLANNING
The history of presenting complaint is recorded briefly in the patient’s own words. The medical and dental history should be recorded. Pain history should be recorded to give information on the pain but phrased to avoid leading questions.
The patient should be examined both extra- orally for asymmetry, presence and extent of swelling in the head and neck region, lymphadenopathy, presence of sinus tracts, presence of temporomandibular joint dysfunction and intra-orally for the standard of oral hygiene, condition of the oral mucosa, presence of swellings and sinus tracts, condition of teeth present, periodontal condition, quantity and quality of restorative work.
The dental practitioner should be able to identify the cause of the patient's complaint.
Some, or all, of the following diagnostic tests may be applied: palpation, mobility test, percussion, periodontal examination, occlusal analysis, testing for possible cracked teeth, pulp sensitivity tests, transillumination, selective local anaesthesia, radiography
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(preferably by using the paralleling technique and a beam guiding device for good reproducibility), colour matching and sinus tract exploration.
It may be necessary to take off-angles radiographs, sometimes supplemented with bitewing and occlusal plane radiographs.
1.1.2.2 RECORDS
It is essential for the practitioner to make adequate records of the patient’s complaint.
This should include presenting symptoms, history of the present complaint with a dental history related to this and results of clinical examination, sensitivity tests, report on radiographs taken and proposed treatment plan so that treatment may be undertaken to a proper standard. These records allow other operators to take over treatment if required.
Additionally, records are essential for medico-legal reasons.
1.1.2.3 INFORMED CONSENT
The practitioner should explain and discuss with the patient the alternatives to non- surgical root canal treatment including special problems and it should be recorded that the patient has agreed to the planned treatment and to the pay any cost involved.
1.1.2.4 RECORD OF TREATMENT
Records should state of medication prescribed including analgesics and antibiotics, use of local anaesthesia, method of isolation, working length of canals and their reference points; size to which canal(s) are prepared, intra-canal dressing applied, type of temporary coronal restoration, root filling materials sealer and technique.
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In addition number of radiographs any complications, iatrogenic incidents and suggestions for final restoration.
1.1.2.5 REVIEW OF TREATMENT
The result of the treatment should be reviewed periodically and recorded.
1.1.2.6 INFECTION CONTROL
The operator and dental nurse should wear gloves and use an aseptic technique.
All instruments used within the oral cavity should be sterilized. The treated teeth should be isolated with rubber dam.
1.1.2.7 TREATMENT PLANNING
The practitioner should plan the treatment for those teeth which are functionally or aesthetically important and have reasonable prognosis.
1.1.2.8 INDICATION FOR ROOT CANAL TREATMENT
Specific indication are: (a) an irreversibly damaged or necrotic pulp with or without clinical and/or radiological findings of periradicular involvement and (b) elective devitalization, for instance to provide post space, prior to construction of an overdenture, consideration should also be given to teeth with doubtful pulpal health prior to restorative procedures and the likelihood of pulpal exposure when restoring a
(misaligned) tooth prior to root resection or hemisection.
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1.1.2.9 CONTRAINDICATIONS TO ROOT CANAL TREATMENT
(a) Teeth that cannot be made functional or restored
(b) Teeth with insufficient periodontal support
(c) Teeth with poor prognosis, uncooperative patients or patients where dental treatment procedures cannot be undertaken.
(d) Teeth of patient with poor oral condition that cannot be improved within a reasonable period.
Indications for root canal retreatment
(a) Teeth with inadequate root canal filling with radiological findings and/or symptoms.
(b) Teeth with inadequate root canal filling when the coronal restoration requires replacement or the coronal dental tissue is to be bleached.
1.1.2.10 INDICATION FOR ENDODONTIC SURGERY
(a) Obstructed canal with radiological finding and /or symptoms.
(b) Extruded material with clinical or radiological findings and /or symptoms.
(c) Failed root canal treatment when retreatment is inappropriate.
(d) Perforation of the root canal or the floor of the pulp chamber with radiological findings or symptoms.
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1.1.2.11 CONTRAINDICATIONS TO ENDODONTIC SURGERY
(a) Local anatomical factors such as an inaccessible root apex.
(b) Tooth with inadequate periodontal support.
(c) Uncooperative patient.
(d) Patient with a compromised medical history.
1.1.3 ROOT CANAL TREATMENT
Root canal treatment is performed when the pulp is non-vital. A preoperative radiograph, preferably taken with a paralleling technique, which projects the tooth as near as possible to its actual size and showing the full root and 2-3 mm of the periapical region, should be examined prior to treatment.
1.1.3.1 PREPARATION OF TOOTH
The need for local anaesthesia (LA) should be considered and LA given as appropriate.
All caries and defective restorations should be removed and, if necessary, the occlusion adjusted and the tooth protected against fracture.
The tooth should be capable of being restored, and isolated and the periodontal status should be sound or capable of restoration.
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1.1.3.2 ISOLATION OF THE TOOTH
Root canal treatment procedures should be performed only when the tooth is isolated by rubber dam in order to prevent salivary and bacterial contamination. This minimises inhalation and ingestion of instruments and prevent irrigating solutions escaping into the oral cavity.
In exceptional cases when rubber dam cannot be used even after crown-lengthening procedures such as gingivectomy and removal of bone or building up of the tooth with a restorative material, alternative methods to consider are a butterfly sponge or gauze pack which provides some protection for the pharynx.
1.1.3.3 ACCESS CAVITY PREPARATION
The objectives of access cavity preparation are to remove the roof of the pulp chamber so good visibility of the canal orifices can be obtained and obtain straight line access to offer sufficient retention for a temporary seal or restoration and conservation as much sound tooth tissue as possible.
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1.1.3.4 DETERMINATION OF WORKING LENGTH
The objectives of determining the working length are to enable the root canal to be prepared as close to the apical cemento-dentinal junction which is between 0.5-2mm from the radiographic apex.
Recommended methods used to determine the WL are radiographic and electronic apex locators (EAL).
1.1.3.5 PREPARATION OF THE ROOT CANAL SYSTEM
The objectives of root canal preparation are to remove the remaining pulp tissue to eliminate microorganisms, remove debris and shape the root canals so that the root canal system can be obturated. Preparation should be undertaken with copious irrigation.
The final length of the preparation should correspond to the end point previously determined for working length.
1.1.3.6 IRRIGATION
The objectives of irrigation are to eliminate microorganisms, flush out debris, lubricate root canal instruments and dissolve organic debris.
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The irrigant solution should be delivered in copious amount as far up the canal as possible without risking extrusion beyond the apical foramen.
The irrigant can be delivered by ultrasonic and mechanical reciprocating instruments equipped with an irrigating system. The irrigant solutions have disinfectant and organic debris dissolving properties.
1.1.3.7 INTER-APPOINTMENT DISINFECTION
These can be used between visits in addition to proper cleaning and irrigation to prevent growth and multiplication of microorganisms left in the canal system despite careful cleaning.
The requirements of an interappointment disinfectant area disinfectant action, non irritating to peri-radicular tissues, no adverse systemic effects and no damage to tooth structure or restorative materials.
1.1.3.8 INTRA-CANAL MEDICAMENT
An effective temporary coronal restoration is essential to prevent contamination of the canal system between visits.
1.1.3.9 OBTURATION OF THE ROOT CANAL SYSTEM
The objectives of obturation are to prevent the passage of microorganisms and fluid along the root canal, to fill the whole canal system and to seal accessory canals.
The requirement for a material to be used to obturate the root canal system include
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Undergraduate curriculum for root canal therapy biocompatibility, dimensionally stable, sealing capability, being insoluble, not enhancing bacterial growth, being radiopaque and easily removable from the canal.
The objective of any endodontic dental procedure should be to apply a biocompatible hermetically sealing canal filling that obturated the prepared canal space from the pulp chamber to the apical termination. The root canal filling should be mainly made up of a semi solid material in combination with a root canal sealer to fill the voids between the semi solid material and root canal wall.
The quality of obturation should be checked with a radiograph. This radiograph should show the root apex with preferably at least 2mm of the periapical region clearly identifiable.
The prepared and filled canal should taper towards the apex and contain the original canal. No space between canal filling and canal wall should be seen. There should be no canal space visible beyond the end point of the root canal filling.
1.1.4 ASSESSMENT OF ENDODONTIC TREATMENT
Clinical as well as radiographic follow-ups at regular intervals are essential for assessment of root canal treatment. Observation periods of 4 years are desirable.
Root canal treatment should be assessed at least after 1 year and subsequently as required. The following findings indicate success: absence of pain, swelling and other symptoms, no sinus tract, no loss of function, and radiographic evidence of a normal periodontal ligament space around the root.
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Root canal treatment is not considered a success if radiographs reveal that a lesion has remained the same or has only diminished in size, the treatment is not considered a clinical success. In this situation it is advised to assess further the lesion until it has resolved, or for a period of 4 years. If after 4 years no total repair has occurred root canal treatment is considered a failure.
Root canal treatment is considered a failure if radiographs reveal that: (a) a lesion appears subsequent to endodontic treatment or a pre-existing lesion increases in size
(b) a lesion has remained the same or has only diminished in size during a 4-year assessment period; (c) there is conflicting evidence with respect to symptoms and radiographic evaluation or (d) signs of continuing root resorption.
Secondary failures: factors which may lead to failure of a previously successful endodontic treatment include: recurrent caries and coronal leakage, caries extending into the root canal or function, root fracture or root perforation. (European Society Of
Endodontology 1994).
1.1.5 STUDIES EVALUATING ROOT CANAL TREATMENT PERFORMED BY UNDERGRADUATES
Several studies have been performed to evaluate the success and failure rate of root canal treatments performed by undergraduates.
Engstrom et al. (1964) investigated the effect of the presence of persisting infection at
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Undergraduate curriculum for root canal therapy the time of the root canal obturation on the prognosis of the root canal treatment performed by undergraduates at the Department of Endodontics at the Royal School of
Dentistry at Stockholm. They concluded that persisting infection at the time of obturation was the most important factor affecting the prognosis of root canal treatment when compared to apical over instrumentation periapical radiolucency and excessive over obturation.
Grossman et al. (1964) evaluated clinically and radiographically 432 teeth, which received root canal treatment by undergraduates at the School of Dentistry, University of
Pennsylvania. They found that of the vital pulp extirpation cases, 90% were successful
9% failed and in 1% of cases, the outcome was uncertain. They could not determine whether successful treatment, was greater in anterior or posterior teeth.
Storms (1969) followed up 158 root treated teeth that were treated by undergraduates at the University of Toronto's Faculty of Dentistry. He found that patient's age and systemic health status, accessory root canals, location of the root treated tooth, aetiology of pulp disease and the subsequent function of the root treated tooth had little influence on the outcome of endodontic treatment.
Heling and Tamshe (1970) evaluated the success rate in 213 teeth that were treated in the undergraduate clinic of the School of Dental Medicine in Jerusalem. They concluded that over all success rate for their study was 70%. The success rate was 71% in single rooted teeth and 68% in multirooted teeth.
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Heling and Kischinovsky (1979) investigated 127 root canal treated teeth performed by undergraduates at the School of Dental Medicine in Jerusalem, over an observation period of one year. The quality of root canal obturation affected the success of the treatment. They found that 81% of the cases were successful.
The success rate depended on the patient's age as it was higher in younger patients.
Teeth with no apically extruded obturating material demonstrated a higher success rate than those with apically extruded obturating material. Higher success rate of 88% occurred in teeth restored with a permanent restoration at the time of completion of obturation.
Kerekes and Tronstad (1979) assessed the long-term results of endodontic treatment performed with a standardised technique. Undergraduates, at the Department of
Endodontics at the Dental Faculty, University of Oslo, performed all the root canal treatments. They concluded that an optimal mechanical preparation of the root canal is easily obtained with a standardised technique, leading to an ease of control of instrumentation and thus an improvement in the technical standard of the root canal obturation and furthermore this technique would be used in all patients.
Swartz et al. (1983) undertook a study to determine the success and failure of conventional root canal treatment performed by undergraduates at West Virginia
University School of Dentistry, over an observation period of 20 years. A total of 1007 teeth (1770 root canals) were included in their study.
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They concluded that the presence of a pre-existing periapical radiolucency led to a significantly lower success rate than cases with no radiolucency.
Molven and Halse (1988) investigated the postoperative success rate for gutta percha and Kloroperka N-O obturation in 526 roots treated teeth after 10-17 years performed by undergraduates at the School of Dentistry, University of Bergen. They concluded that the results of their study demonstrated an overall success rate of 91% for cases without periapical radiolucency and 68% for cases with periapical radiolucency. The failure rate for the periapical radiolucency group was not accepted as a satisfactory outcome.
Sjőgren et al. (1990) investigated the influence of various factors that may affect the outcome of root canal treatment performed on 849 root canals at an observation period of 8-10 years. All patients received treatment by undergraduate students at the
Department of Endodontics, at the University of Umea. They found that the overall success rate was 91% and 96% of the success rate for root canals with vital pulps.
They concluded that teeth without preoperative periapical radiolucencies do not represent a therapeutic problem. 96% of teeth with periapical lesions undergoing endodontic retreatment had a success rate of 86% and 62%, respectively.
Instrumentation of the root canal system to its full length and the level of root obturation significantly affected the outcome of treatment. Best prognosis was observed for roots obturated ≤ 2 mm from the radiographic apex.
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Orstavik (1996) assessed radiographically the time-course and risk of the development and healing of chronic apical periodontitis in 571 teeth (810 roots) without a preoperative radiolucency which were performed by undergraduates at the University of
Oslo. Clinical and radiographic findings were assessed before, during treatment, and after 1, 2, 3 and 4 years post operatively. He observed that periapical lesions developed in 6% of root canals that had no such lesion preoperatively. He concluded that the risk analyses might provide relevant information in addition to or in substitution for success / failure analyses, and factors other than the root canal treatment itself may contribute to chronic apical periodontitis developing later than one year after treatment.
Molven et al. (2002) assessed the post-operative periapical changes in 265 obturated root canals. All the root canal treatment was undertaken before 20-27 years and was performed by undergraduates at the School of Dentistry, University of Bergen, Norway.
Their initial observations were that the percentage of cases with periapical radiolucency reduced from 50% at the time of obturation to 17% at 10-17 years post-operatively, and to 6% 10 years later. Their final observation was that 86% of cases were successful, 5% failed and 9% were associated with a slight widening of the periodontal space apically.
The authors concluded that they could observe more favourable late periapical changes when the case were assessed after 20-27 years as compared to a 10-17 years follow-up observation period.
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Benenati and Khajotia (2002) conducted a radiographic recall evaluation of 894 endodontic cases treated by dental students at the University of Oklahoma College of
Dentistry. They found that 62% of cases were successful, 29% were acceptable, 7% were questionable and 2% failed.
They suggested that the evaluation of endodontically treated teeth at a recall beyond 6- months is recommended for validating the effectiveness of a given endodontic technique.
Fristad et al .(2004) undertook the study to identify periapical changes in nonsurgical retreated root filled teeth 20-27 years after root canal treatment. The evaluated 429 roots, retreated by undergraduates students in a teaching clinic. 112 roots in 70 individuals were evaluated radiographically 20-27 years after treatment. They concluded that late periapical changes, were recorded when a 10-17 years follow-up after root canal treatment was extended for another 10 years. They stated that persistent asymptomatic periapical radiolucencies, especially those with overfill, should generally not be classified as failures, as many of them will heal after an extended observation period.
Arbab-Chirani & Vulcain (2004) undertook a study to evaluate the impact of rotary nickel-titanium (NiTi) instruments on undergraduate teaching and clinical use in a
French dental school and to evaluate the impressions of dental students when learning and using these techniques. They reported that there was a national consensus over the need for undergraduate teaching of rotary NiTi systems in France.
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Eleftheriadis & Lambrianidis (2005) carried out a study to evaluate the technical quality of root canal treatment (RCT) and detect iatrogenic errors in an undergraduate dental clinic at the Aristotle University of Thessaloniki, Greece. They found that the technical quality was acceptable more often in anterior teeth. Ledges were identified more often in curved canals in molar teeth.
Er et al. (2006) undertook a study to evaluate the radiographic technical quality of root fillings performed by undergraduates at a dentistry faculty in Turkey. They found that the percentage of adequate root fillings performed by undergraduate students was only
(33 %) and the highest percentage of adequate root fillings was found in the maxillary canine (55.5%).
Peru et al. (2006) performed a study to evaluate root canals instrumented by dental students using the modified double-flared technique, using the NiTi rotary sysem GT files and NiTi rotary Protaper files by micro-computed tomography (MCT). They concluded that the inexperienced dental students were able to prepare curved root canals with rotary files with greater preservation of tooth structure, lower risk of procedural errors and much quicker than with hand instruments.
Eckerbom et al. (2007) carried out a study to assess a 20-year follow-up of endodontic variables and apical statues in a Swedish population and they concluded that there is stil a great need for endodontic treatment in the Swedish population and no improvement in apical health was found during this 20-year follow-up.
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1.1.6 STUDIES EVALUATING THE PATTERN OF UNDERGRADUATE ENDODONTIC TEACHING IN DENTAL SCHOOL
Qualtrough and Dummer (1997) determined the pattern of undergraduate endodontic teaching within Dental Schools of the UK. Data was gathered by a questionnaire returned from all 14 undergraduate dental schools and supplemented with further detailed enquiries where necessary.
The study confirmed that a number of topics were either not included or were covered only briefly. However, the average time devoted to the preclinical instruction of root canal treatment in the first clinical year had increased from 14 to 24h. Additional time was provided in subsequent years by the majority of schools. In most instances, staff- teaching Endodontology in the UK had no specialist training.
Dummer (1991) indicted that a more consistent pattern of teaching had evolved, and that the stepback preparation technique and lateral condensation of gutta-percha were universally accepted. At that time, few schools had introduced contemporary approaches towards canal preparation and filling.
E.V.Cruz et al. (2000) evaluated the pattern of undergraduate endodontic teaching in
Philippine Dental Schools. The result of this study have demonstrated that there is a need to review endodontic teaching in the majority of the Philippine Dental Schools to ensure that the course content and curriculum employed by all schools met specified standards and that appropriate measures should be considered to enhance the learning experience of students.
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Many follow-up studies have been performed on endodontically treated teeth. It is generally accepted that the success rate of root canal treatment is positively correlated with a good technical quality of the root filling, which is well adapted to the canal walls with no voids and is obturated within the radiographic apex (Strindberg 1956, Kerekers and Tronstad 1979, Sjőgren et al.1990).
Several European studies of various population groups have examined the prevalence and technical standard of endodontic therapy, as well as the presence of periapical pathologic conditions (Petersson et al. 1986, Eckerbom 1993). Assessment of these studies showed that the incidence of root canal therapy increased with the age of the population group from 3% to 6% for younger adults to 18% to 20% for patients more than 60 years old (Buckley and Spangberg 1995). Surprisingly, these studies showed that technically satisfactory endodontic treatment was performed in only 30% to 40% of the cases.
Success of root canal treatment depends on a number of factors but chiefly diagnosis
of the pulp and periapical condition, root canal anatomy, canal preparation and
obturation. Radiography remains an essential part of root canal therapy, mainly for
control of length of the root canal, the form and extent of the coronal pulp, the
degree of curvatures, quality of root canal obturation and bone pathology can be
identified and monitored.
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There are many methods to evaluate the success or failure of root canal treatment the
most accurate determinations of healing or non healing are based on signs and
symptoms and radiographic and histological examinations. Obviously clinical
findings and radiographic criteria play an important role in the estimation of the
success of root canal treatment.
1.1.7 HISTORY OF ENDODONTICS
The history of endodontics was established many years ago. According to Grossman, the endodontics history is divided into five different periods. The first period was called the
Pre-Science period 1776-1826. In this period, endodontic therapy consisted of crude treatment modalities like pulps being cauterized with red hot cauterisers.The second period extended from 1826-1876 and was called The Age of Discovery. This period witnessed the discovery of anaesthesia. This had a great impact on dental treatment and made dental treatment much easier and tolerable.
Gutta-percha points were created to fill root canals and barbed broaches became available for cleaning and enlarging the canals. In addition, medications for treating pulpal infections were invented.
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The third period was called The Dark Age 1876-1926, and it was so called because of the limited development in endodontics that took place at that time. Despite of the name of this period, the discovery of X-ray technology and the advancement of general anaesthesia into local anaesthesia took place at that time. From 1926-1976 the
Renaissance period took place. This period was considered the golden period in endodontics. This period witnessed many improvements in anaesthesia, radiographs, root canal instruments and filling materials. This period also saw the introduction of rotary instruments and the introduction, rise and subsequent decline of the silver point for filling of root canals. Gutta-percha became the material of choice for obturation in a variety of techniques.
The last period was the innovation period 1976-1998. This period witnessed a breakthrough in endodontics at a rapid pace. Improved techniques in canal preparation using different kinds of instruments were used. Obturation techniques becoming much simpler and faster. The single visit endodontic therapy was gaining wide popularity and acceptance.
Endodontic treatment aimed to maintain the health of pulpal tissues of a tooth. It involved the removal of a nerve from the pulp tissue of teeth which had become inflamed or nonvital.
The main objective of non-surgical endodontic treatment is to achieve adequate cleaning and shaping of the root canals and the complete obturation of them using the appropriate filling materials.
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1.1.7.1 THE ROLE OF RADIOGRAPH IN ENDODONTICS
The number of films usually required during endodontic therapy is four these are:
Preoperative films, the diagnostic film, the master point and the final postoperative film
(BES 1983).
The quality of the radiograph is dependent on the x-ray source, the film type, the projection in the mouth and the way that the film is processed (Preece & Jensen 1983).
Radiology has always played an important role in the evaluation of the success of root canal treatment. The most common methods for intraoral radiography are the paralleling and bisecting angle techniques. Radiographs are two-dimensional images of three- dimensional structures. As a result, their appearance is open to a wide range of interpretation.
The presence of rubber dam, rubber dam clamps and instruments in the root canal make the exposing of radiographs at this stage of the treatment difficult to acquire an excellent or acceptable image. Therefore, any method of measurement that calculates the length of the root canal before treatment commences will simplify the procedure. It will reduce over instrumentation, reduce contamination of the unsealed root canal during radiography, reduce the number of retake radiographs required and reduce the collective radiation dose to the population. Any further information that could be gleaned from the preoperative film without the need for the diagnostic wire film could substantially reduce the radiological requirements for successful endodontics.
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The correct measurement of the length of a root canal is necessary for successful preparation, cleaning, obturation and long term prognosis of the root filled tooth. The positioning of the root fillings at the apical constriction (apical dentinocemental) junction to produce an apical seal is a fundamental requirement of endodontics (Cohen
& Schwartz 1987). The determination of the working length should be within 0.5 mm and 2.0 mm from the radiographic apex, whenever possible (ESE 1994). The avoidance of over-instrumentation will reduce the likelihood of complications, protracted treatment, postoperative pain and ensure a favourable prognosis.
The primary radiograph used in the periapical evaluation of a tooth is the periapical radiograph. In diagnosis, this film is used to identify abnormal conditions in the pulp and periradicular tissues and to determine the number of roots and canals, location of canals, and root curvatures. Because the radiograph is a two dimensional image, it is often advantageous to take additional radiographs at different horizontal or vertical angulations when examine multicanaled or multirooted teeth and those with severe root curvature. These incremental radiographs enhance visualization and evaluation of the three dimensional structure of the tooth.
During treatment, periradicular radiographs are used to determine canal working lengths. This length is typically determined in millimetres and it is measured from a reference point on the tooth's cavosurface that is within the clinician's field of view. In the case of an anterior tooth this is usually the incisal edge, and on a posterior tooth, a cusp or marginal ridge. This reference point must remain sound and reproducible through the treatment.
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Following completion of the root canal procedure, a radiograph is taken to determine the quality of the root canal filling or obturation.
The main objective of obturation of the cleaned and shaped root canal is the three dimensional filling of the root canal system.
1- To prevent percolation of periradicular exudates into the pulp space via the apical foramina and /or lateral and furcation canals.
2- To prevent microorganisms left in the canal after preparation from proliferation and escaping into the periradicular tissues via the apical foramina and /or lateral canals.
3- To seal the pulp chamber and canal system from leakage via the crown in order to prevent passage of microorganisms and /or toxins along the root canal filling and into the periradicular tissues via the apical foramina and /or lateral canals.
1.1.8 ROOT CANAL TREATMENT PERFORMED BY GENERAL DENTISTS
Heling et al. (2001) undertook a study to measure the differences in the size of periapical radiolucency, pre- and post-root canal treatment in 319 teeth. They also investigated if the quality of the root canal treatment and the type of the coronal restoration influenced the outcome of endodontic treatment in teeth with a periapical radiolucency. They reported that 53% of root canals contained well condensed obturation < 2 mm from the radiographic apex. Thirty percent of root canals were obturated short by > 2 mm from the radiographic apex. Ten percent of cases revealed apically extruded obturating material and 7% contained poorly condensed obturation.
Of the root treated teeth 6% had no coronal restoration, 8% had a temporary restoration,
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16% were restored with amalgam or composite, 62% were restored with post-retained restorations and 9% were restored with cast crowns. In 65% of the root treated teeth the periapical lesion healed and in 35% the periapical lesion enlarged in size. They could not observe any significant correlation between the quality of root canal treatment, type of the coronal restoration and the success rate of the root canal treatment.
They concluded that teeth with periapical lesions >10 mm2 had a higher success rate than smaller lesions. There was no significant difference between the quality of root canal treatment, type of final coronal restoration and the length of follow-up period on the outcome of the treatment.
Kirkevang et al. (2001a) radiographically investigated the incidence of endodontically treated teeth and periapical lesions in 614 Danish patients (15984 teeth).
They observed that 3% of the total examined teeth were associated with periapical radiolucencies. Of the total teeth, examined 5% were endodontically treated. Of these
52% were associated with a periapical lesion. The incidence of periapical radiolucency in connection with molars was significantly higher (7%) than in premolars (3%) and anterior teeth (2%). They concluded that the frequency of endodontically treated teeth associated with a periapical radiolucency was higher in their study as compared to that demonstrated in other epidemiological studies.
Kirkevang et al. (2001b) compared the quality of root canal treatment in two Danish subpopulations. Group one consisted of 975 root treated teeth examined in 1974-75 while group two consisted of 753 root treated teeth which were examined in 1997-98.
They observed that most of the root treated teeth in group one were premolars (43%) and
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Undergraduate curriculum for root canal therapy in group two were molars (39%). Adequate coronal restorations were recorded in 57% of the root treated teeth in group one and 59% in group two. Of the root treated teeth,
44% had inadequate coronal restorations in group one as compared to 41% in group two.
In group one, 27% of the obturated root canals had no voids in the obturation compared with 44% in group two. Root canal obturations containing voids were 73% in group one while it was 56% in group two. In group one, 43% of the root canals were obturated < 3 mm from the radiographic apex or flush obturation to the radiographic apex compared with 54% in group two. In group one, 57% of the root canals were obturated short by >
3 mm from the radiographic apex or revealed apically extruded obturation compared with 46% were in group two. Fifty one percent of the root treated teeth in group one were associated with periapical radiolucencies as were 58% in group two. They concluded that the technical quality of root canal treatment demonstrated improvement during the last 24 years. Basic differences between the populations prevented the assessment of the impact of this change on disease frequencies.
The results of their study indicated that great care should be taken when comparing different patient populations, in particular more emphasis should be placed on the selection and description of study groups.
Peak et al. (2001) undertook a retrospective study to investigate clinically and radiographically the influence of several factors on the outcome of root canal treatment performed on 406 teeth by dental practitioners within the Royal Air Force dental service, at observation periods of at least one year. They reported that 59% of the examined teeth were maxillary and 41% were mandibular. Of the total examined teeth, 69%
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Undergraduate curriculum for root canal therapy demonstrated a preoperative periapical radiolucency. Sixty four percent of the cases were obturated with cold lateral condensation. Twelve percent of the cases were obturated with a single-cone gutta percha technique. Eleven percent of the cases were obturated with a silver or titanium point technique. Five percent were obturated with
Endomethasone alone. Cold lateral condensation was the most successful technique
92%, followed by endomethasone 89%, silver/titanium 73% and for single-cone gutta percha was 68%. The lowest success rate was 25% for silver or titanium followed by
30% single gutta percha when followed-up within the first three years. The highest success rates were observed for endomethasone. 100% followed by lateral condensation
91%.
Those teeth reviewed after more than three years had a higher success rate mainly as a result of the improved outcome in the single cone techniques (80%). Fifty percent of the teeth were obturated < 2 mm from the radiographic apex, 32% were obturated short by > 2 mm from the radiographic apex and 18% were over-obturated. Maxillary anterior teeth that were obturated with lateral condensation had a higher success rate
(96%) than other tooth types. Teeth with preoperative periapical radiolucencies had higher success rates of 87% as compared to those cases where there was no preoperative periapical radiolucency (80%). Roots obturated < 2 mm from the radiographic apex had a higher success rate (88%) than those that were obturated short by > 2 mm from the radiographic apex (77%). Fifty seven percent of the cases were recorded as successful,
28% were probably successful and 15% were failures. When combining successful and probably successful cases the overall success rate was 85%. Maxillary anterior teeth and
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Undergraduate curriculum for root canal therapy mandibular molars that were over-obturated demonstrated failure rate of 23% and 25%, respectively. They concluded that obturating the root canals < 2 mm from the radiographic apex with cold lateral condensation technique were associated with the best outcome. Single-cone gutta percha and silver/titanium point techniques had higher failure rates when reviewed within three years. Maxillary anterior teeth had a higher success rate than only other tooth type.
Boucher et al. (2002) examined the prevalence and technical quality of root canal treatment and the periapical status of root treated teeth in a French subpopulation. They obtained periapical radiographs from 208 adult patients seeking dental care within the dental service provided by the Hôtel-Dieu in Paris. They observed that 19% of the total examined teeth were endodontically treated. Of the endodontically treated teeth 21% contained acceptable obturation. Of these 16% were associated with periapical radiolucency. Of the endodontically treated teeth 79% contained unacceptable obturation. Of these 27% were associated with periapical radiolucency. Of the endodontically treated teeth 26% contained posts. Of these 29% were associated with a periapical radiolucency. Sixty percent of endodontically treated teeth contained an extra-coronal restoration, of which 24% had a periapical radiolucency. Ten percent of endodontically treated teeth had no coronal restoration. Of these 33% were associated with a periapical radiolucency. They concluded that the results of their study demonstrated a high prevalence of root treated teeth and poor technical quality of root canal treatments. Roots with acceptable obturation were associated with a lower prevalence of periapical radiolucencies. Root treated teeth containing posts were
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Undergraduate curriculum for root canal therapy associated with periapical radiolucencies significantly more than roots without posts.
Hommez et al. (2002) investigated the influence of the quality of coronal restoration on a clinical and radiographic basis and the quality of the root canal obturation on the periapical health. They collected periapical radiographs of 745 root treated teeth, from 228 patients attending the Ghent University Dental School, Ghent,
Belgium, for dental treatment. Their study revealed that 33% of the examined teeth were associated with periapical radiolucency. Seventy five percent of the coronal restorations were clinically acceptable and 78% were radiographically acceptable.
Periapical radiolucencies were associated with 31% of teeth with clinically acceptable restorations and 37% with poor restorations. Periapical radiolucency was observed in
24% of teeth with radiographically acceptable restorations and 49% with radiographically unacceptable restorations. Marginal caries were observed clinically and/or radiographically in 21% of cases. Periapical radiolucencies were observed in
41% of teeth restored with composite and in 28% of teeth restored with amalgam. Sixty percent of the teeth had a post-retained restoration. The presence of a post in the canal had no influence on the periapical health. Forty two percent of the teeth were obturated
< 2 mm from the radiographic apex. Of these 27% were associated with a periapical radiolucency. Fifty three percent of the teeth were obturated short by > 2 mm from the radiographic apex. Of these 35% were associated with periapical radiolucency. Five percent of the teeth demonstrated an over-extended obturating material. Of these 53% were associated with a periapical radiolucency. Thirty four percent of the teeth contained acceptable obturation. Of these 23% were associated with periapical
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Undergraduate curriculum for root canal therapy radiolucency. Sixty six percent of the teeth contained an unacceptable obturation. They concluded that a good coronal restoration and a well-performed root canal treatment are both important for the treatment to be successful.
Boltacz-Rzepkowska and Pawlicka (2003) assessed 355 periapical radiographs of
282 root treated teeth and 73 teeth following pulpotomy to evaluate factors that might affect the long-term results of root canal treatment in Poland. They selected periapical radiographs from the records of patients who were referred to the Institute of Dentistry,
Medical University of Łódź and two private dental practices. They found that 49% of the root treated teeth contained adequate obturation < 2 mm from the radiographic apex.
Of these 9% were associated with periapical radiolucency. Thirty nine percent of root treated teeth were obturated short by > 2 mm from the radiographic apex. Of these 49% were associated with radiolucencies. Twelve percent of root treated teeth were over- obturated. Of these 9% were associated with radiolucency. The incidence of periapical radiolucencies did not increase with time, irrespective of the technical standard of the obturation. Sixty seven percent of pulpotomy cases demonstrated periapical lesions.
Sixty four percent of teeth containing adequate obturation the treatments was performed at the Institute of Dentistry and 53% were carried out at the private clinics. The poorest results were observed in the dental outpatients' departments (National Dental Health
Care System), with 71% having inadequately obturated teeth. They concluded that more than 50% of the obturated teeth were not treated according to the endodontic guidelines.
However, 76% of the obturated teeth were not associated with periapical radiolucencies at the time of evaluation. For the teeth treated with the pulpotomy, 67% were associated
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Undergraduate curriculum for root canal therapy with periapical radiolucencies. Adequate root obturation were observed more frequently in patients attending the Institute of Dentistry than dental outpatients' departments.
Dugas et al. (2003) studied the prevalence of apical periodontitis, the quality of root obturation, restorations, the providers of endodontic treatment and reasons for extractions of missing teeth in two Canadian populations (Toronto and Saskatoon) differing in the availability of endodontists. They observed that patients with root treated teeth were significantly higher in Toronto (39%) than in Saskatoon (26%). The prevalence of apical radiolucencies associated with root treated teeth was 44% in
Toronto and 51% in Saskatoon. There was a significant association between poor obturation density and poor radiographic quality of the restoration. Ten percent of the root treated teeth were associated with symptoms. Of these 50% were associated with periapical radiolucency. Fifty eight percent of teeth were obturated < 2 mm from the radiographic apex. Of these 36% were associated with periapical radiolucencies. Thirty percent of teeth were obturated short by > 2 mm from the radiographic apex. Of these
57% were associated with periapical radiolucencies. Twelve percent of teeth demonstrated apically extruded obturating material. Of these 61% were associated with periapical radiolucencies. Sixty percent of the obturated root canals had adequate obturation density. Of these 36% were associated with a periapical radiolucency. Forty percent of the obturated root canals contained inadequate obturation densities, of which
60% were associated with periapical radiolucencies. Radiographic quality of the coronal restoration was adequate in 42% of root treated teeth. Of these 62% were associated with periapical radiolucencies. Inadequate radiographic quality of the coronal
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Undergraduate curriculum for root canal therapy restoration was observed in 58% of cases. Of these 51% were associated with periapical radiolucencies. Post-retained restorations were present in 25% of the root treated teeth.
Of these 40% were associated with periapical radiolucencies. Thirty nine percent of the root treated teeth were obturated < 2 mm from the radiographic apex and with adequate density. Twenty one percent were obturated short by > 2 mm from the radiographic apex with inadequate density. Eighteen percent of the root treated teeth were obturated <
2 mm from the radiographic apex and had adequate coronal restoration and 37% were inadequately obturated and had inadequate coronal restoration. They could not find any significant difference in the incidence of apical lesions and root treated teeth performed by general dentists or endodontists. They concluded that the quality of both the root obturation and the coronal restoration had an impact on the periapical health of the root treated teeth. The impact of the coronal restoration was most critical when the quality of the root obturation was adequate. The results of their study demonstrated the need for improving the standards of root canal treatment and coronal restoration, to improve the outcome and benefit associated with endodontic treatment.
Hussey et al. (2003) investigated the quality of 183 completed anterior root canal treatments performed under the General Dental Services of the National Health Service in Northern Ireland. The radiographs of these cases were examined by three examiners for a series of criteria including: the quality of radiograph; root obturating material; quality of apical obturation; extent of obturation in the canal system; apical status and coronal seal. They reported that 54% of the radiographs were of poor clinical standard.
Sixty two percent of the root treated teeth were obturated < 2 mm from the radiographic
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Undergraduate curriculum for root canal therapy apex. Twenty four percent were obturated short by > 2 mm from the radiographic apex and 14% were associated with apically extruded obturating material. Thirty seven percent of the teeth contained poorly condensed obturating material apically and 50% were poorly condensed in the coronal two thirds of the canal system. Seventy one percent of the root treated teeth were associated with a periapical radiolucency. Of these
29% were obturated short by > 2 mm from the radiographic apex. Forty nine percent of the root canals had a good coronal seal and 32% had no coronal restoration when the post-obturation radiograph was taken.
They concluded that the quality of radiographs and the technical quality of root canal obturation in anterior teeth is less than optimal for the population investigated.
Postgraduate education may address some of these deficiencies (Table 1.1.1, 1.1.2).
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TABLE 1-1-1 STUDIES EVALUATING SUCCESS AND FAILURE OF ROOT CANAL TREATMENTS PERFORMED BY GENERAL DENTISTS
Included Excluded Follow-up Treatment outcome %
Author(s) LOCATION teeth teeth (year) success uncertain failure
Harty et al. Eastman Dental 1139 747 0.5-2 90 --- 10
(1970) Hospital
Adenubi & Eastman Dental 870 --- 0.5-5 88 5 7
Rule (1976) Hospital
Barbakow et al. Dental practitioners in 555 11 1-9 87 6 7
(1980) South Africa
Cvek et al. School of Dentistry, 54 --- 4 80 --- 20
(1982) Malmo
Smith et al. Eastman Dental 821 697 1-5 84 --- 16
(1993) Hospital
Peak (1994) Royal Air Force 136 --- 0.5-15 59 26 15
dental centre, UK
Friedman et al. Germany, USA, 378 108 0.5-1.5 78 16 6
(1995) Jerusalem
Tronstad et al. University of Oslo 1001 ------67 --- 33
(2000)
Peak et al. Royal Air Force 406 --- 1-3 57 28 15
(2001) dental centre, UK
Murakami et al. Japan 66 --- 0.1-20 88 8 5
(2002)
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TABLE 1-1-2 STUDIES INVESTIGATING THE QUALITY OF OBTURATION PERFORMED BY GENERAL DENTISTS
Root Quality of obturation % Author(s) Location treated short by > 2 mm from the < 2 mm from the over teeth radiographic apex radiographic apex obturation Eckerbom et al. (1987) Sweden 636 46 36 9 Imfeld (1991) Switzerland 406 64 36 --- De Cleen et al. (1993) Holland 97 49 49 2 Ray & Trope (1995) USA 985 50 PO 50 --- Saunders et al. (1997) UK 472 39 39 8 Weiger et al. (1997) Germany 215 50 42 8 Sidaravicius et al. (1999) Norway 320 53 IO 22 AO 25 De Moor et al. (2000) Belgium 312 47 43 3 Kirkevang et al. (2000) Denmark 773 40 IO 60 AO --- Heling et al. (2001) Jerusalem 319 30 53 10 Kirkevang et al. (2001b) Denmark 1728 52 IO 48 AO --- Boucher et al. (2002) France 1021 79 IO 21 --- Hommez et al. (2002) Belgium 745 53 42 5 Lupi-Pegurier et al. (2002) France 1429 55 39 6 Murakami et al. (2002) Japan 66 32 56 12 Boltacz-Rzepkowska & Poland 282 39 49 12 Pawlicka (2003) Dugas et al. (2003) Canada 383 30 58 12 Hussey et al. (2003) Northern 183 24 62 14 Ireland AO = adequate obturation, within 3 mm from the radiographic apex or flush to the radiographic apex. IO = inadequate obturation, short by > 3 mm from the radiographic apex or apically extruded PO = poor obturation presence of voids or short by > 2 mm from the radiographic apex
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Irrigation, Microbiology, Smear layer
1.2.1 INTRODUCTION
Root canal treatment (RCT) is a common dental procedure, usually undertaken with the aim of retaining teeth in which the pulp has become irreversibly infected or necrotic.
The procedure includes the removal of pulp tissue and heavily infected dentine surrounding it. This process is usually affected by mechanical debridement in the presence of an irrigating solution. Irrigation has an important role during endodontic treatment to help lubricate canal walls, soften dentine, remove debris and the smear layer. During the last several years endodontics has progressed to the point where treatment is less traumatic for the patient and less stressful for the dentist. However, although the use of nickel titanium rotary instruments has allowed us to gain time during endodontic treatment, it can also tempt us to neglect one of the main objectives of endodontics, that being the "cleaning" on which Dr. Herbert Schilder (1974) has emphasized since he insisted on "cleaning and shaping". It may be more appropriate to say, "Shaping for cleaning".
The concept of chemo mechanical debridement is not new and has been discussed by early workers in the field (Stewart 1955, Grossman 1955, Coolidge 1958). However, the importance of the use of an irrigant during non-surgical root canal treatment has frequently been neglected both during instruction of dental students and later in the clinical practice of endodontics. During and following shaping and cleaning, the canal should be irrigated to wash out fragments of pulp tissue and dentinal shavings that have
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Irrigation, Microbiology, Smear layer accumulated. Much debris and organic tissue, which are present more often than one realizes, are removed by the flushing action of the irrigating solutions. Irrigation may also be used to wash out food debris when the canal has been left open for drainage during the acute stage of a dentoalveolar abscess. Bystrom & Sundqvist (1981) demonstrated that mechanical instrumentation and irrigation with saline alone significantly reduced the number of bacteria but that bacteria remained in the canal systems in half the cases even after four separate treatments. They concluded that the supporting action of a disinfectant is necessary for successful elimination of microorganisms from root canals (Bystrom & Sundqvist 1985). Ram (1977) showed in his study that frequent irrigation of the canal is mandatory and irrigation is more complete in properly enlarged canals.
Penetration of the irrigant is more effective in canals with larger diameters than in smaller apical constrictions (Senia et al.1971).
Through the years, different irrigating solutions have been investigated such as a stream of hot water (140 to 176º F) discharged from an insulated syringe (Prader 1947).
Physiological saline solution (Baker et al.1975), a 30% solution of urea (Blechman &
Cohen 1951), urea peroxide solution in glycerine (Stewart 1969), a solution of chloramines (Coolidge & Kesel 1956), sodium hypochlorite (NaOCl) and sodium hypochlorite in conjunction with ethylenediaminotetraacetic acid (EDTA).
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1.2.2 PROPERTIES OF AN IDEAL IRRIGANT
An ideal irrigant will aid in both the debridement and disinfection of the root canal system, ideally with sustained antimicrobial action (Torabinejad et al. 2002,
Machnick et al.2003)
The following are the properties of an ideal irrigant:
1. Tissue or debris solvent. In regions inaccessible to instruments, the irrigant
could dissolve or disrupt soft tissue or hard tissue remnants to allow their
removal (Senia et al.1971, Rosenfeld et al. 1978, Baumgartner & Cuenin 1992).
2. Toxicity. The irrigant should be non-injurious to periradicular tissues. It should
also be non-antigenic, non-carcinogenic and cause no damage to the structure of
the dentine (Reeh & Messer 1989).
3. Low surface tension. This property promotes flow into tubules and into
inaccessible areas (Abou-Rass & Patonai 1982, Berutti et al.1997, Torabinejad et
al. 2003).
4. Lubricant. Lubrication helps instruments to slide down the canal.
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5. Removal of smear layer. The smear layer is a layer of microcrystalline and
organic particle debris spread on the walls after canal preparation. This smear
layer is organised into a superficial loose layer and a deeper adherent layer. The
superficial layer contains the majority of the micro-organisms found in
contaminated root canal systems. The smear layer should be removed completely
to allow antimicrobial agents to penetrate into the dentinal tubules (Orstavik &
Haapasalo 1990, Torabinejad et al. 2002).
1.2.2.1 SODIUM HYPOCHLORITE
Sodium hypochlorite in various concentrations is the most widely advocated endodontic irrigant. Sodium hypochlorite is inexpensive, readily available, easily used and is usually rated highly in research studies. It was used initially in medicine by Dakin in 1915 as a wound disinfectant on the battlefields of World War 1 and has been credited with saving many lives that might otherwise have been lost to gangrenous infection. Dakin’s solution was effective due to its ability to dissolve necrotic tissue at the edge of the battle wounds thereby exposing healthy wound extremities that were more likely to heal thereby preventing gangrene. It had only minor inflammatory effects on the adjacent vital tissue.
Sodium hypochlorite has been used as an irrigant in dentistry since Walker recommended its use in the treatment of pulpless teeth in 1936.
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1.2.2.1.1 SODIUM HYPOCHLORITE PROPERTIES
The worldwide use of sodium hypochlorite as a root canal irrigating solution is due mainly to its efficacy in pulpal dissolution and its antimicrobial activity. A less concentrated solution, such as 1% sodium hypochlorite, presents acceptable biological compatibility. Pécora et al. (1999) reported that sodium hypochlorite exhibited a dynamic balance as is shown by the reaction:
+ ⎯ + ⎯ NaOCl + H2O ↔ NaOH + HOCl ↔ Na + OH + H + OCl
The chemical reactions with organic tissue (Pecora et al. 1999, Spano et al. 2001) and sodium hypochlorite are shown as follows:
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Interpreting these chemical reactions, it can be observed that sodium hypochlorite acts as an organic and fat solvent degrading fatty acids, transforming them into fatty acid salts
(soap) and glycerol (alcohol), that reduces the surface tension of the remaining solution (
Scheme 1 : Saponification).
Sodium hypochlorite neutralizes amino acids forming water and salt (Scheme 2: neutralization reaction). With the exit of hydroxyl ions, there is a reduction of pH and formation of more hypochlorous acid, a substance present in sodium hypochlorite solution. When in contact with organic tissue it acts as a solvent, releasing chlorine that, combined with the protein amino group, forms chloramines (scheme 3: Chloramination reaction). Hypochlorous acid (HOCl-) and hypochlorite ions (OCl-) lead to amino acid degradation and hydrolysis.
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The chloramination reaction between chlorine and the amino group (NH) forms chloramines that interfere with cell metabolism. Chlorine (strong oxidant) presents antimicrobial action inhibiting bacterial enzymes leading to an irreversible oxidation of
SH groups (sulphydryl group) of essential bacterial enzymes.
Its antimicrobial mechanism of action can be observed verifying its physico-chemical characteristics and its reaction with organic tissue. Considering knowledge of pH processes and isolated activities in essential enzymatic sites, such as those in the membrane, it is enlightening to associate sodium hypochlorite (high pH, over 11), to harmful biological effects on bacterial cells in order to explain one part of its mechanism of action. Estrela et al. (1994) studied the biological effect of pH on the enzymatic activity of anaerobic bacteria. Enzymatic sites are located in the cytoplasmic membrane which is responsible for essential functions such as metabolism, cellular division and growth. It also takes part in the latter stages of cellular wall formation, biosynthesis of lipids, transport of electrons and oxidative phosphorylation.
The amino acid chloramination reaction (i.e. reaction 3) forming chloramine interferes with cellular metabolism. Oxidation promotes irreversible bacterial enzymatic inhibition replacing hydrogen with chlorine. This enzyme inactivation can be observed in the reaction of chlorine with amino groups (NH2-) and an irreversible oxidation of sulphydryl groups (SH) of bacterial enzymes. Thus, sodium hypochlorite combines antimicrobial activity with an action on bacterial essential enzymatic sites promoting irreversible inactivation originated by hydroxyl ions and chloramination action.
Dissolution of organic tissue can be verified in the saponification reaction when sodium
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Irrigation, Microbiology, Smear layer hypochlorite degrades fatty acids and lipids resulting in soap and glycerol. Some physico-chemical characteristics must be mentioned. Grossman and Meiman (1941) observed its pulp tissue dissolution capacity and reported that a 5% sodium hypochlorite solution dissolves this tissue in 20 min to 2 h. The dissolution of bovine pulp tissue by sodium hypochlorite (0.5, 1.0, 2.5 and 5.0%) has been studied in vitro under different conditions (Santos et al. 2006, Spano et al. 2001).
Sodium hypochlorite in higher concentrations is more irritant while in lower concentrations (0.5% to1%) it is biocompatible (Holland et al. 1992). For a substance to be biocompatible it must present no or only a small tissue reaction at all time periods.
A moderate or intense tissue reaction has been observed at 7 days which decreases in intensity with time until reaching a non-significant tissue reaction at 60 days (Costa
2001).
Higher concentrations, up to 6 % solutions are significantly more effective at dissolving tissue than lower concentrations (Miller et al. 2004). Abou-Rass & Oglesby (1981) showed that the best solvent effect was obtained with a 5.25 % solution at 60°C.
Several studies have demonstrated the efficacy of various concentrations of NaOCl in reducing bacterial growth. Estrela et al. (2003) demonstrated in vitro the antimicrobial effectiveness of 1% NaOCl, 2 % chlorhexidine (CHX), 1% Ca (OH) 2 solution and Ca
(OH) 2 solution with a detergent. NaOCl had the best antimicrobial effectiveness for all microorganisms at all times. CHX was effective for S.aureus, E. faecalis and C. albicans at all times but ineffective for P.aeruginosa, B. subtilis and the mixed culture of the microorganisms. Ca (OH) 2 gave the worst results.
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Buck et al. (2001) analyzed the detoxification of endodoxin by endodontic irrigants
(CHX, NaOCl, CHX chlorine, ethanol, EDTA, water) and Ca(OH)2 and reported that the biologically active portion of endotoxin, lipid A, is hydrolyzed by highly alkaline chemicals, namely Ca(OH)2 or a mixture of CHX, sodium hypochlorite and ethanol
EDTA, NaOCl, CHX and CHX chloride. Ethanol and water (control) showed little or no detoxifying ability for lipid A.
Vianna et al. (2006) concluded that NaOCl had a higher capacity to kill microorganisms and also had the ability to remove cells from the canal.
Sodium hypochlorite is the most frequently used endodontic irrigating solution, however, it is known to have a cytotoxic effect (Tanomaru filho et al.2002). Berber et al.
(2006) evaluated the efficacy of 0.5 %, 2.5% and 5.25% sodium hypochlorite (NaOCl) as intracanal irrigants associated with hand and rotary instrumentation techniques against Enterococcus faecalis within root canal and dentinal tubules. They concluded that, especially at higher concentrations NaOCl was able to disinfect the dentinal tubules independent of the canal preparation technique used.
Enterococcus faecalis is the most commonly isolated species from the canals of teeth presenting with post treatment diseases (Peciuliene et al. 2001). Pinheiro et al. a, b
(2003) found E. faecalis in 52.94% of canals with bacterial growth. This microorganism has demonstrated the capacity to survive in an environment in which there are scant available nutrients and in which commensality with other bacteria is minimal (Sundqvist et al. 1998).
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Enterococcus faecalis can invade dentinal tubules (Ørstavik & Haapasalo 1990) and it is therefore probable that cells within dentinal tubules surviving chemo-mechanical instrumentation and intracanal medication could colonize the tubules and reinfect the obturated root canal (Kreft et al. 1992). However, dentinal tubules contain an appreciable amount of unmineralized collagen and it has been established that dentinal tubule invasion by oral streptococci is associated with cell adhesion to collagen and a collagen-induced morphological growth response (Love et al. 1997). Love (2001) demonstrated that oral bacteria involved in dental caries and endodontic disease are able to gain nourishment from tissue fluids. This may account for the presence of streptococci and enterococci cases with post-treatment disease (Sundqvist et al. 1998,
Pinheiro et al. 2003), and suggests that tissue fluid from the periodontal ligament within radicular dentinal tubules or the filled root canal helps them to survive. Also, alveolar bone bathing the root of the tooth may provide nutrition to bacteria.
Among the procedures involved in the control of endodontic infection, irrigation is an important aspect in eliminating microorganisms from the root canal system. Intracanal cleaning and disinfecting procedures are highly dependent on the mechanical and chemical effects of the irrigants. Irrigant solutions in different concentrations with antimicrobial activity have been used during biomechanical instrumentation, particularly sodium hypochlorite (NaOCl). To date, NaOCl is the most commonly employed root canal irrigant, but no general agreement exists regarding its optimal concentration, which usually ranges from 0.5% to 5.25%. Its antimicrobial property is proportional to the drug concentration (Gomes et al. 2001, Vianna et al. 2004), as well as its toxicity
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The bactericidal ability of NaOCl results from the formation of hypochlorous acid
(HOCl) which, when in contact with organic debris exerts its effects by oxidizing sulphydryl groups within bacterial enzyme systems, thereby disrupting the metabolism of the microorganism (Siqueira et al. 1997) resulting in the killing of the bacterial cells
(Baumgartner & Cuenin 1992).
1.2.2.2 ETHYLENEDIAMINE TETRAACETIC ACID (EDTA)
EDTA is a weak acid and is a chelator that reacts with calcium ions in the hydroxyapatite crystals of the dentine to produce a metallic chelate. Removal of calcium ions from the dentine softens the dentinal tissue, especially the hydroxyapatite-rich peritubular dentine and increases the diameter of exposed dentinal tubules. This effect is also believed to be self-limiting (Goldberg & Spielberg 1982). However, it has recently been shown to cause erosion of the dentinal tubules following irrigation with NaOCl
(Torabinejad et al. 2003). An added benefit of EDTA is its antibacterial property that has been demonstrated to be as effective as sodium hypochlorite against black pigmented anaerobes and facultative bacteria in the agar diffusion test model (Siqueira et al. 2000). Other closely related chelating solutions include REDTA and EGTA.
REDTA is a commercial EDTA preparation comprising EDTA, cetyl-trimethyl- ammonium bromide, sodium hydroxide and distilled water and has very similar properties to EDTA. Ethylene glycol-bis tetraacetic acid (EGTA) is not as corrosive as
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EDTA however it is also not as effective in removing the smear layer. A commercial product called Smear clear containing 17% EDTA, cetrimide and proprietary surfactants is also available. EDTA can also be used as a final flush to open up the dentinal tubules thus allowing an increasing number of lateral canals to be filled (Villegas et al. 2002).
Several studies have shown that the use of a combination of sodium hypochlorite (2.5-
5%) and EDTA (10-17%) is particularly effective in the removal of organic and inorganic debris (Goldman et al. 1982, Baumgartner & Mader 1987)
1.2.2.3 CHLORHEXIDINE (CHX)
Chlorhexidine gluconate has shown promise as an endodontic irrigant (Jeansonne &
White 1994, White et al. 1997). It is a cationic bisbiguanide with optimal antimicrobial action ranging from pH 5.5 to 7.0. It has a broad spectrum of activity against Gram- positive and Gram-negative bacteria, bacteria spores, lipophilic viruses, yeasts and dermatophytes. It is bacteriostatic in low doses and bactericidal in higher doses
(Leonardo et al. 1999). Its antimicrobial properties are thought to result from disruption of the bacterial cytoplasmic membrane causing leakage of intracellular contents. An added advantage of chlorhexidine gluconate is its substantivity or residual action (White et al. 1997).
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Gomes et al. (2001) evaluated the effectiveness of various concentrations of chlorhexidine gluconate, 1% and 2% and 5.25 % NaOCl against E. faecalis in a broth dilution model. All irrigants were effective in killing the bacteria tested but at different times. Other studies have found chlorhexidine to be a useful antimicrobial agent but less effective than higher concentrations of sodium hypochlorite (Siqueira et al. 2000, Spratt et al. 2001).
1.2.2.4 ELECTROCHEMICALLY ACTIVATED WATER (ECA)
Recently new technology has been introduced in a hospital setting specifically aimed at destroying biofilms on endoscopes and in waterlines. The same technology is now available for use in dental surgery water lines and involves the production of an irrigant known as ‘Electrochemical activated water’ or ‘ Oxidative potential water’ (Marais &
Brozel 1999, Marais 2000, Solovyeva & Dummer 2000). These solutions are produced from tap water and saline solution using a flow-through electrolysis module (FEM). The
FEM contains the anode, made from titanium and coated with ruthenium-oxide, iridium and platinum, and the cathode made from titanium coated with pyro-carbon and glass carbon (Leonov 1997). A diaphragm consisting of ultra-filtration, electro-catalytic ceramics on a bed of zirconium, yttrium, aluminium and niobium-oxides separates the anode and cathode. Two types of ECA solution are produced. Anolyte has a high oxidation potential (plus 400 to plus 1200 millivolts). Catholyte is an alkaline solution
(pH 7- 12) with a high reduction potential (minus 80 to minus 900 millivolts). Catholyte is reputed to have a strong cleaning or detergent effect. Both these solutions remain in
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The antimicrobial nature of the anolyte was reported to be 99.999% effective at killing
Mycobacterium tuberculosis, M avium- intracellulare, M chelonae, Escherichia coli,
Enterococcus faecalis, Pseudomonas aeruginosa, Bacillus subtilis varniger spores, methicillin resistant Staphylococus aureus, Candida albicans, poliovirus type2 and human immunodeficiency virus ( HIV-1). This was accomplished in the relatively short time period of 2 min (Selkon et al. 1999, Shetty et al. 1999).
Marais (1998) undertook a scanning electron microscope study to evaluate smear layer removal using ECA (catholyte followed by anolyte) and NaOCl (3.5 %) as root canal irrigant. ECA produced surfaces that appeared (visually) as clean as those for the NaOCl group. It was concluded that ECA removed the smear layer from some surfaces of the canals. The research of Hata et al. (1996) and Serper et al. (2001) reported on the effectiveness of so-called oxidative potential water (OPW) as a root canal irrigant. The solutions are generated by electrolysing saline solution, a process no different to that used in the commercial production of sodium hypochlorite (Frais et al. 2001). The difference however is that the solution accumulating at the anode is harvested as the anolyte and that at the cathode as the catholyte. These solutions display properties that are dependent upon the strength of the initial saline solution, the applied potential difference and the rate of generation.
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The technology that allows harvesting of the respective solutions resides in the design of the anode and the cathode and originates either in Russia (electrochemically activated water) or Japan (oxidative potential water) (Marais 2000).
Although the solutions are named differently, the principles of manufacture are probably the same. The endodontic literature on the use of this technology is sparse but shows early promise. The solutions from both technologies have been tested for their ability to debride root canals (Marais 2000, Solovyeva & Dummer 2000, Hata et al. 2001), remove smear layer (Hata et al. 1996, Serper et al. 2001), kill bacteria (Horiba et al.
1999, Marais & Brozel 1999, Marais & Williams 2001, Prince et al. 2002) and bacterial spores (Loshon et al. 2001), with favourable results whilst showing biocompatibility with vital systems ( Petrushanko & Lobyshev 2001, Serper et al. 2001).
Anolyte and catholyte solutions generated from one such technology (Radical Waters
Halfway House 1685, S. Africa) have shown promise as antibacterial agents against laboratory grown single species biofilm models (Ghori et al. 2002). Such solutions have been recommended as suitable for removing biofilms in dental unit water lines (Marais
& Brozel 1999) and have even been marketed for this purpose (Walker et al. 2003).
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Gulabivala et al. (2004) undertook a study to test the effectiveness of electrochemically activated aqueous solutions in the debridement of Enterococcus faecalis biofilms in root canals of extracted teeth. Irrigant groups included neutral anolyte (NA) (pH6.5), acidic anolyte (AA) (pH 3.0), catholyte (C) (pH 11.5) and C alternated with neutral anolyte
(C/NA). Phosphate-buffered saline (PBS) with and without ultrasonication formed negative and NaOCl (3%) positive control groups.
The authors concluded that all but two groups (AA and C) were significantly different from their PBS controls. There was a significant difference between the C/NA groups with and without ultrasonication but not between other combinations. NA (U) and AA
(U) were the most effective test solutions but NaOCl (3%) gave by far the highest bacterial kills.
Martin & Gallagher (2005) demonstrated the efficacy of super-oxidised water (Optident/ sterilox) in the decontamination of dental unit water lines. They concluded that super- oxidised water was successful in the removal of bacteria from dental unit water supplies.
Complete removal required treatment with a purge phase of concentrated disinfectant and a maintenance phase of at least two weeks. Super-oxidised water is a solution of sodium chloride which has been electrolysed by passage over titanium electrodes at 9 amps. The product that is produced has a pH of 5.0-6.5, an oxidation potential of > 950 mv and is mainly hyopchlorous acid at a concentration of approximately 144 mg L-1 .
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1.2.2.5 PHOTO ACTIVATED DISINFECTION (PAD™)
Disinfection of root canals with laser irradiation of pre-tagged microorganisms has recently attracted some attention in the endodontic literature (Sarkar & Wilson 1993,
Seal et al. 2002). The principle on which it operates is that photosensitising molecules attach to the membrane of the bacteria. Irradiation with light at a specific wavelength, matched to the peak absorption of the photosensitise, leads to the production of singlet oxygen, which causes the bacterial cell wall to rupture killing the bacteria (Burns et al.
1993).
Extensive laboratory studies have shown that an important aspect of this system is that the two components when used independently of one another produce no effect on bacteria or on normal tissue. It is only the combination of photosensitiser and light which produces the effect on the bacteria (Burns et al. 1993, Williams et al. 2003,
2004).
Bonsor et al. A, B (2006) investigated the microbiological effect of photo-activated disinfection as an adjunct to normal root canal disinfection in vivo. They concluded that the PAD system offered a means of destroying bacteria which remained after using a conventional irrigant in endodontic therapy.
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1.2.2.6 ENDOX SYSTEM (LYSIS S.R.I, NOVA MILANESE, ITALY)
This can sterilize the root canal by emitting high- frequency electrical impulses. The manufacturer has claimed that Endox could completely eliminate the pulp and bacteria from the entire root canal system, including the lateral canals (Endox Endodontic system). In addition to claimingto having the advantage of reducing treatment time and safety, Endox seems to be popular among dentists in Germany, Italy, and Spain (Haffner et al. 1999).
1.2.2.7 MTAD ( BIOPURE®)
This recently introduced irrigant from Tulsa Dentsply, USA, was first marketed in
2005. It is a mixture of tetracycline, citric acid, and Tween 80 detergent (Polysorbate-
80) (MTAD) and was designed to be used as a final root canal rinse before obturation
(Torabinejad et al. 2003). Polysorbate-80 is a nonionic surfactant and emulsifier derived from sorbitol. It lowers surface tension thereby facilitating the penetration of the irrigant into the canal system. Due to its low pH, citric acid is an effective chelating agent removing the smear layer at concentrations of 10%, 25%, and 50% (Baumgartner et al.
1984). Citric acid has also been shown to demonstrate antibacterial properties against anaerobic bacteria isolated from infected root canals (Georgopoulou et al. 1994).
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Bio Pure® MTAD® is biocompatible (Zhang et al. 2003) and has been shown to remove the smear layer following irrigation with sodium hypochlorite while maintaining the integrity of the dentinal tubules (Torabinejad et al. 2003). MTAD has been shown to bind to dentine, a property believed to result from the affinity of doxycycline for dentine that may contribute to the substantivity to the solution (Beltz et al. 2003).
A major disadvantage of MTAD is its lack of tissue dissolving properties (Beltz et al.
2003) and therefore it must be used in conjunction with sodium hypochlorite.
Torabinejad et al. (2003) investigated the ability of MTAD to kill the microorganism E. faecalis that is frequently associated with refractory retreatment cases and compared its efficacy to that of NaOCl and EDTA. Their results suggested that BioPure® MTAD® was as effective as 5.25 % sodium hypochlorite. However, a study undertaken by
Dunavant et al. (2006) showed that the BioPure® MTAD® was completely ineffective against E. faecalis. Nevertheless, it seems that MTAD has some advantages over conventional irrigants and solutions used in root canal treatment. For example, MTAD is effective in removing the smear layer along the whole length of the canal (Torabinejad et al. 2003) and in removing organic and inorganic debris (Beltz et al. 2003). It also did not produce any signs of erosion or physical changes in dentine (Machnick et al. 2003).
1.2.2.8 LASERS
The use of lasers for various endodontic applications has been investigated since 1971
(Kimura et al. 2000). Different types of lasers have been investigated for their efficacy in root canal shaping and sterilization, removal of the smear layer and debris and sealing of dentinal tubules in the root canal wall. Lasers using carbon dioxide or krypton
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(Er:YAG); and erbium with chromiumyttrium- scandium-gallium-garnet (Er,Cr:YSGG).
Multiple drawbacks have prevented the widespread use of lasers in clinical endodontics.
For example, the carbon dioxide laser could not be delivered into the root canal system through a suitable fiber optic system and the Nd:YAG laser was poorly absorbed by the dentine (Khabbaz et al. 2004). Furthermore, the excessive heat generated by these lasers is deemed to be the major limiting factor against clinical acceptance in endodontic treatment (Kimura et al. 2000). The American Association of Endodontists has warned that the heat could potentially damage the periodontium or char the root canal dentine
(Position statement 2000).
Both Er:YAG 65 and Nd:YAG (Levy 1992) lasers have also been used to shape root canals. Generally, after laser irradiation, root canal walls can be rough and uneven
(Kimura et al. 2000). Consequently, improvements in the fiber tip and in the delivery method are necessary. In addition, its effectiveness at removing smear layer and debris has been demonstrated (Yamazaki et al. 2001, Ishizaki et al. 2004).
Eldeniz et al. (2007) compared the efficacy of a standard NaOCl irrigation procedure with that of Er,Cr:YSGG laser irradiation in contaminated root canals having small and large apical foramina. Their conclusion was that in teeth with straight roots the
Er,Cr:YSGG laser reduced the viable microbial population in root canals with small and large apical foramina but did not eradicate all bacteria. Three percent NaOCl inhibited the growth of E. faecalis and effectively sterilized all root canals.
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Although the Waterlaser has been granted approval for use on hard tissues (i.e. teeth) by the United States Food and Drug Administration it seems that selecting the correct laser setting is paramount to avoid causing any collateral damage to the surrounding tissues
(Kimura et al. 2000).
1.2.2.9 OZONE
Ozone has been recognized as a powerful sterilizing agent which can destroy bacteria, viruses and odours. Ozone is present around us in small quantities as a natural material but is well-known for its presence above us in the outer atmosphere. When oxygen (O2) rises to the upper atmosphere and is exposed to the sun’s ultraviolet rays, that oxygen is naturally turned into ozone (O3). This forms the protective ‘‘ozone layer’’ that filters out
UV radiation but because ozone is heavier than air it naturally falls back to earth, where it is said to naturally purify air and water. Ozone also occurs commonly in nature as a result of lightning strikes during thunderstorms and waterfalls. Ozone has a recognizable smell, which we also associate with photocopiers and laser printers. The odour is generally detectable by the human nose at concentrations between 0.02 and 0.05 ppm or approximately 1% of the recommended 15 min exposure level. Ozone is a respiratory irritant and following inhalation it can cause dryness in the mouth and throat, headache, chest restriction and coughing (McDonnell et al. 1983).
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Ozone acts as a hazardous air pollutant exacerbating asthma (Leikauf 2002), as well as causing lung damage (Menzel 1984). Ozone is a toxic gas at high concentrations and can be fatal (50 ppm for 60 min) with current recommended safety limits of 0.06 ppm for 8 h per day, 5 days a week or 0.3 ppm for 15 min while 120 ppb negatively affects the airway. It has been suggested that there may be no safe threshold level for ozone.The application of ozone gas has been advocated for use in dentistry for the sterilizing of cavities, root canals, periodontal pockets and herpetic lesions (Baysan & Lynch 2005,
2006). Much of the published work to date has been in relation to its antimicrobial effects (Baysan et al. 2000) and caries (Holmes 2003, Baysan & Lynch 2004, 2007,
Huth et al. 2005) although some consider that there is a lack of evidence in support of the application of ozone gas to the surface of decayed teeth stopping or reversing the decay process (Cochrane). Gaseous ozone has been shown to have an antibacterial effect on Enterococcus faecalis although less effective than NaOCl (Hems et al. 2005) but the dose of ozone used was very low.
Ozonated water has also been shown to be useful (Nagayoshi et al. 2004a). Extra-oral use in dentistry has been promising and Murakami et al. (2002) have shown that ozone, when used as a denture cleaner, is effective against Methycillin Resistant
Staphylococcus Aureus (MRSA) and viruses. However, some of the uses of ozone in medicine remain controversial (Bocci 1999, 2004). Recent reports question its
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Irrigation, Microbiology, Smear layer therapeutic effect although the recent Department of Health advice (Rickard et al. 2004) suggesting that ozone is of ‘‘no benefit and do not use’’ has been withdrawn. Current
National Institute of Clinical Excellence (NICE) guidelines (NICE report 2005) advises against using ozone alone in the treatment of caries in general dental practice within the
NHS except as part of an approved clinical trial. Any therapeutic use of ozone must be coupled with an awareness of the risks. However, one major disadvantage is that ozone is stable only for a short period of time and decomposes to form molecular oxygen which is metabolized by aquatic life (Kaplan & Pesce 1996).
Evacuation of ozone from the oral cavity remains a key concern, both from the point of view of exposure received by the patient and the dentist. CurOzone USA Inc. (Ontario,
Canada) developed the HealOzone with Professor Edward Lynch which is now distributed by Kavo Dental (Kavo GmbH, Biberach, Germany) for use in dentistry which can deliver relatively high concentrations of ozone (2100 ppm 0.052%, v/v in air at a rate of 10.25 ml/s, 615 cc/min).
The system has a built-in suction scavenging system designed to create a seal around the applicator tip. This permits ozone application only when coupled with a scavenging system. This makes it readily useable on occlusal, buccal and lingual/palatal cavities.
However, if a seal cannot be achieved then the HealOzone will not operate and this can limit its use. For example, applying ozone to approximal lesions or into a periodontal pocket is difficult and there are anecdotal reports that clinicians are modifying the applicator to extend its use into other areas of the mouth.
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More recently the Ozi-cure (PO Box 68992, Centurion, South Africa) has been launched in some markets (South Africa), which uses lower concentrations of ozone. While this increases its clinical application due to a simple delivery system there are concerns about the safety of patients and clinical staff (Miller & Hodson 2007). The absence of a built- in evacuation system makes it essential that high volume aspiration is used appropriately to provide this function.
Ozone is used externally also in the form of ozonylated olive or sunflower oils.
Ozonised sunflower oil (Oleozón) has been shown to have antimicrobial effects against viruses, bacteria and fungi (Sechi et al. 2001).
1.2.2.9.1 THE USE OF OZONE IN ENDODONTIC TREATMENT
The prevention and therapeutic effects of ozone in medicine has been well established
(Bocci 1996). It has also been tested in medicine to decontaminate hospital side rooms
(Dyas et al. 1983) and in auto-haemotherapy (Bocci 1992).
In the dental field ozone has been advocated for treatment of gum infections, during surgery, for failed implant cases (Sandhaus a, b, c 1969) and to treat root caries (Baysan et al. 2000, Baysan & Lynch 2004, 2007). Root canal treatment has also used ozone
(Deltour et al. 1970, Chahverdiani & Thadj-Bakhche 1976) and it has potential application in reducing bacterial counts in dental unit water delivery systems (Filippi et al .1991). To date, there have been several studies evaluating the efficiency of ozone as a root canal disinfectant. Hems et al. (2005) investigated the antibacterial effectiveness
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Its antibacterial efficacy was not comparable with that of NaOCl under the test conditions used. However the dose used was only 0.68 mg L-1 ( 0.68 ppm).
However Estrela et al. (2007) later reported that the irrigation of infected human root canals with ozonated water, 2.5% NaOCl, 2% chlorhexidine and the application of gaseous ozone for 20 min were not sufficient to inactivate E. faecalis.
The safety of the ozone application has been investigated in in-vitro and in-vivo studies
(Baysan & lynch 2006, Miller & Hodson 2007). The tightly fitting design of the cup against the lesions and the suction procedure in the ozone delivery system provided a good seal thereby preventing any noticeable leakage of ozone gas. The maximum detectable levels of ozone around the cup were within EU and FDA regulations (US environmental 1995, US Food & Drug 2004).
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1.2.2 MICROFLORA OF THE INFECTED ROOT CANAL
1.2.2.1 INTRODUCTION
Bacteria may enter the root canal system directly via carious lesions or via pulp exposure following trauma. However, many infections of the pulp occur as a result of supra- or sub- gingival bacteria penetrating exposed dentine, enamel- dentine cracks, and around restorations and the invading dentinal tubules (Pashley 1990, Love 1996, Peters et al. 2001). Almost all bacteria recovered from the root canal systems of teeth belong to the oral microflora (Sundqvist 1976) and various factors such as nutritional supply, oxygen tension and bacterial interaction influence the development of the root canal flora (Sundqvist 1992).
Most of the oxygen sensitive members of the root canal micro-flora are not readily cultured without strict application of anaerobic methods (Carlsson 1997). Utilizing strictly anaerobic sampling techniques it has been shown that in addition to streptococci, lactobacilli and actinomyces, obligatory anaerobic species of fusobacterium, peptostreptococcus, eubacterium, pro-porphyromonas dominate the established root canal microflora (Gomes et al. 2004).
Other microorganisms such as yeasts, candida and saccharomyces (Lana et al. 2001) and spirochetes, e.g. treponema (Jung et al. 2000, Rocas et al. 2001) have also been recovered from an infected root canal. Recently the use of molecular techniques to
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Once bacteria gain access into the root canal system, they invade radicular dentinal tubules and may be responsible for persistent root canal infection (Ørstavik & Haapasalo
1990). Shovelton (1964) examined histologically 97 extracted clinically non-vital teeth and found that 61 of the teeth showed bacterial penetration of the radicular dentinal tubules. The numbers of tubules containing bacteria were highly variable from tooth to tooth and among sections of an individual tooth. The depth of penetration by bacteria into the tubules was also found to be variable. It was noted that the presence of bacteria within the tubules was related to the clinical history of the tooth, such that chronic infections had more bacterial invasion and that tubule invasion did not occur immediately after the bacteria appeared in the root canal.
Peters et al. (2001) demonstrated that the flora recovered from mid-root radicular dentine of teeth with apical periodontitis of endodontic origin was similar to previous studies. Before bacteria can invade the human body they must first colonize the host by undergoing a series of interactive events. Firstly, bacteria must adhere to the host tissue.
Initially this is by a loose physical association of the organism to the surface of a tissue that allows stronger and more permanent bonds to be established through binding of microbial cell surface adhesions to complementary host surface receptors.
Once the microbial cells are bound, they must be able to utilize available nutrients, compete or co-operate with other species in the immediate environment and contend
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1.2.2.2 MICROBIOLOGICAL ASPECTS OF PERSISTENT PERIAPICAL DISEASE
Persistent periapical pathology subsequent to endodontic treatment is because of intra- radicular infection (Nair et al. 1990), extraradicular infection, or other pathology. a true cyst (Nair 1998, Nair et al. 1990)
Intra- radicular infection is the most common cause of persistent pathology and the reasons for infection are numerous including lack of coronal seal, missed canals, insufficient debridement and disinfection of the root canal system and therapy resistant bacteria. Unlike primary root canal infections, which are typically mixed consisting of between two and eight bacterial species with obligate anaerobic bacteria dominating the microflora and streptococci making up a significant proportion of the facultative species, the root canal flora from failed cases is primarily Gram-positive facultative anaerobes and consists of 1–2 species per canal. The most frequently cultivable microorganisms include bacterial species from enterococcus, streptococcus, peptostreptococcus and actinomyces (Molander et al.1998, Sundqvist et al.1998). In addition, molecular analysis of refractory endodontic cases has demonstrated the ability to detect the presence of uncultivable bacteria such as Dialister (Rolph et al. 2001, Siqueira & Rocas 2004).
Additionally, yeasts, notably C. albicans, have been isolated from cases of endodontic
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(Sundqvist et al. 1998, Peciuliene et al. 2001). For bacteria to be involved in the pathogenesis and maintenance of persistent apical periodontitis, they must be able to survive in the inhospitable environment of the obturated root canal where the nutrient supply is limited.
Studies have shown that E. faecalis is able to withstand a high alkaline environment such as the one generated by calcium hydroxide (Haapasalo & Ørstavik 1987) and this appears to be related to a cell proton-pump that is necessary for its survival at high pH
(Evans et al. 2002). In addition, under starved conditions, it shows resistance to sodium hypochlorite (LaPlace et al. 1997), heat, hydrogen peroxide, acid, and ethanol (Giard et al. 1996). E. faecalis can also survive extended periods of starvation in water (Hartke et al. 1998) and within water filled dentinal tubules (Ørstavik & Haapasalo 1990) and human serum (Love 2001) which likely reflects the nutritional supply within nonvital radicular dentinal tubules. Additionally, Enterococci possess a number of virulence factors that permit adherence to host cells and extracellular matrix and facilitate tissue invasion.
It has been demonstrated that dentinal tubule invasion and adhesion to collagen by S. mutans or S gordonii were inhibited by human serum, suggesting a protective mechanism of serum. In contrast, cells of E. faecalis maintained their ability to invade dentine and adhere to collagen in the presence of serum. It was suggested that following
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It has been projected that more than 99% of microorganisms observed in nature cannot be cultivated using established techniques (Amann et al. 1995) and in the case of the oral flora, only about 50% of the approximately 700 species present in the oral cavity are cultivable.
1.2.2.3 TYPES OF ENDODONTIC INFECTION
There are different types of endodontic infections, which are usually associated with different clinical conditions. The root canal infection is the primary cause of acute or chronic periradicular diseases. Secondary or chronic periradicular lesions, can result in persistent symptoms, exudation, or the failure of the endodontic treatment (Siqueira
1997).
1.2.2.3.1 PRIMARY ROOT CANAL INFECTION
Primary root canal infection is caused by microorganisms colonizing the necrotic pulp tissue. In general, primary infections are mixed and predominated by anaerobic bacteria.
Recent evidence indicates that bacteria can change their behaviour and hence become virulent because of environmental stresses generated by conditions such as starvation, population density, pH, temperature and iron availability (Finlay & Falkow 1989, 1997).
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1.2.2.3.2 SECONDARY ROOT CANAL INFECTION
Secondary intraradicular infection is caused by microorganisms that were not present in the primary infection and have penetrated the root canal systems during treatment, between appointments, or after the conclusion of the endodontic treatment (Siqueira
1997).
1.2.2.4 REQUIREMENTS FOR AN ENDODONTIC PATHOGEN
The following properties are required for a given microorganism to establish itself in the root canal system and to further participate in the pathogenesis of periradicular disease
(Siqueira 2002):
1. The microorganism must be present in sufficient number to initiate and maintain
the periradicular disease.
2. The microorganism must possess an array of virulence factors which should be
expressed during root canal infection.
3. The root canal environment must permit the survival and growth of the
microorganism and provide signals or cues that stimulate the expression of
virulence genes.
4. The microorganism must be spatially located in the root canal system in such a
way that it or its virulence factors can gain access to the periradicular tissues.
5. The host must mount a defence strategy at the periradicular tissues, inhibiting the
spread of the infection.
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6. Inhibiting microorganisms must be absent or present in low numbers in the root
canal environment.
In previous studies, bacterial samples were removed using paper points (Moshonov et al.1995, Ramskőld et al. 1997), by rinsing (Hardee et al. 1994, Folwaczny et al. 2002,
Schoop et al. 2002), or by immersion in culture broth (Zakariasen et al.1986) or physiological saline solution (Moritz et al. 2000, Schoop et al. 2004) and scraping of the canal walls (Peters et al.2001, Eldeniz et al.2007).
1.2.2.2 HISTORY OF ENDODONTIC FLORA
More than a century ago in the 19th century Miller (1894) demonstrated the presence of several distinct types of bacteria in the necrotic dental pulp. Miller stated that there was a large diversity of endodontic microflora, but not all of them could be detected by culture. Thus, the essential role of microorganisms in the aetiology of apical periodontitis remained vague for many years until Kakehashi et al. 1965 demonstrated that no apical periodontitis developed in germ-free rats when their molar-pulps were kept exposed to the oral cavity, as compared with control rats with a conventional oral microflora in which massive periapical radiolucencies occurred.
1.2.2.3 CAUSES OF ENDODONTIC FAILURES
It is commonly acknowledged that most endodontic treatment failure occurs when treatment procedures have not met satisfactory standards for control and elimination of infection (Nair et al.1990, Lin et al.1992). Root canal treatment usually fails when treatment falls short of acceptable standards (Seltzer et al. 1963, Sundqvist et al. 1998).
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The reason why many teeth do not respond to root canal treatment is because of procedural errors that prevent the control and prevention of intracanal endodontic infection (Siqueira& Lopes 1999). Procedural errors such as broken instruments, perforation, overfilling, under filling, ledges do not jeopardize the outcome of endodontic treatment unless a concomitant infection is present. Nevertheless, scientific evidence indicates that there are factors including microbial factors, comprising extraradicular and /or intraradicular infections, and intrinsic or extrinsic nonmicrobial factors which results in failure even when the treatment has been followed to the highest technical standards (Nair et al.. 1990a, Nair et al.. 1990b, Sjőgren 1996, Nair et al.
1999).
1.2.2.3.1 MICROBIAL FACTORS 1.2.2.3.1.1 INTRARADICULAR INFECTION
Microorganisms colonizing the root canal system play an essential role in the pathogenesis of periradicular lesions. Kakehashi et al. (1965) exposed the dental pulps of conventional and germ-free rats to the oral cavity and reported that pulp necrosis and periradicular lesions developed only in conventional rats with an oral microbiota. In a study of monkey teeth, Möller et al. (1981) demonstrated that only devitalized pulps that were infected induced periradicular lesions, whereas devitalized and uninfected pulps showed absence of pathological changes in the periradicular tissues. Sundqvist (1976) confirmed the important role of bacteria in periradicular lesions in a study using human teeth, in which bacteria were only found in root canals of pulpless teeth with
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Irrigation, Microbiology, Smear layer periradicular bone destruction. The chances of a favourable outcome with root canal treatment are significantly higher if infection is eradicated effectively before the root canal system is obturated. However, if microorganisms persist in the root canal at the time of root filling or if they penetrate into the canal after filling, there is a higher risk that the treatment will fail (Byström et al. 1987, Sjögren et al. 1997).
To survive in the root-filled canal, microorganisms must withstand intracanal disinfecting measures and adapt to an environment in which there are few available nutrients. Therefore, the few microbial species that have such ability may be involved in the failure of root canal treatment. Bacteria located in areas such as isthmuses, ramifications, deltas, irregularities and dentinal tubules may sometimes be unaffected by endodontic disinfection procedures (Lin et al. 1991, Siqueira et al. 1996, Siqueira &
Uzeda 1996).
The microbiota associated with failed cases differs markedly from that reported in untreated teeth (primary root canal infection). Whereas the latter is typically a mixed infection, in which gram-negative anaerobic rods are dominant, the former is usually composed of one or a few bacterial species, generally gram-positive bacteria, with no apparent predominance of facultatives anaerobes. Möller (1966), after examining failed cases, reported a mean of 1.6 bacterial species per root canal. Anaerobic bacteria corresponded to 51% of the isolates. Enterococcus faecalis was found in 29% of the cases. Sundqvist et al. (1998) observed a mean of 1.3 bacterial species per canal and
42% of the recovered strains were anaerobic bacteria. E. faecalis was detected in 38% of the infected root canals. Whilst this facultative bacteria is restricted to a few cases of
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Irrigation, Microbiology, Smear layer primary root canal infections, usually in low numbers, it is frequently isolated from secondary and/or persistent root canal infections, usually as the single species of microorganism. E. faecalis strains have been demonstrated to be extremely resistant to several medicaments, including calcium hydroxide (Siqueira & Uzeda 1996, Siqueira &
Lopes 1999). Therefore, when E. faecalis is established in the root canal, its eradication by conventional means may be extremely difficult (Molander et al. 1998).
Yeast-like microorganisms have also been found in root canals of obturated teeth in which treatment has failed (Nair et al. 1990a). This suggests that they may be therapy- resistant. In fact, it has been demonstrated that Candida spp. are resistant to some medicaments commonly used in endodontics (Waltimo et al. a, b 1999). The microbiota associated with poorly treated teeth is more likely to contain a greater number of microbial species, predominated by anaerobes, and be similar to that found in untreated teeth (primary infections) (Sundqvist et al. 1998, Sundqvist & Figdor 1998). This probably occurs because the microorganisms causing the initial infection persisted in the canal after inadequate cleaning of the root canal system.
1.2.2.3.1.2 EXTRARADICULAR INFECTION
The development of periradicular lesions creates a barrier within the body to prevent further spread of microorganisms.
Bone tissue is resorbed and substituted by a granulomatous tissue containing defence elements, such as cells (phagocytes) and molecules (antibodies and complement
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Irrigation, Microbiology, Smear layer molecules) (Siqueira 1997). A dense wall composed of polymorphonuclear leucocytes, or less frequently an epithelial plug, is usually present at the apical foramen, blocking the egress of microorganisms into the periradicular tissues (Nair 1987).
Recently, considerable interest has been generated regarding the potential role of extraradicular persistent microorganisms in the failure of the root canal treatment.
Cultural and microscopic studies have reported the occurrence of extraradicular infections in both treated and untreated root canals (Tronstad et al. 1987, Tronstad et al.
1990, Lomçali et al. 1996).
1.2.2.3.2 MICROBIAL INVOLVEMENT IN SPECIAL SITUATIONS 1.2.2.3.2.1 OVERFILLING
It has been claimed that the success rate of the root canal treatment is decreased in cases of overfilling (Strindberg 1956, Engström et al. 1964). The toxicity of root canal filling materials has been considered to play an important role in this regard (Muruzábal et al.
1966). Conversely, it has been reported that the apical extent of root canal fillings has no correlation with treatment failure (Lin et al. 1992). Most of the materials used in root canal obturation are either biocompatible or show cytotoxicity only prior to setting
(Barbosa et al. 1993, Spangberg 1998, Lopes & Siqueira 1999). Apart from the paraformaldehyde-containing materials, sealer toxicity is significantly reduced or even eliminated after setting.
Therefore, it is highly improbable that most of the contemporary endodontic materials are able to maintain a periradicular inflammation in the absence of a concomitant endodontic infection.
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This statement is reinforced by the high success rate of treatment in teeth without periradicular lesions even in cases of overfilling (Lin et al. 1992, Sjögren et al. 1997).
Initially, microorganisms may be either absent or present in low numbers in these cases
(Sundqvist 1976, Siqueira 1997). Obviously, overfilling should be prevented as often as possible since undesirable postoperative complications such as flare-ups can develop usually when a large amount of filling material extrudes through the apical foramen. It is well known that overinstrumentation usually precedes overfilling. In teeth with infected necrotic pulps overinstrumentation induces the displacement of infected dentine or debris into the periradicular tissues.
1.2.2.3.2.2 CORONAL SEALING
It has been stated that coronal leakage may be an important cause of failure of endodontic treatment (Saunders & Saunders 1994). There are some situations in which obturated root canals may be contaminated from the oral cavity. leakage through the temporary or permanent restorative material, breakdown, fracture or loss of the temporary/permanent restoration, fracture of the tooth structure, recurrent decay exposing the root canal filling material, or delay in the placement of permanent restorations (Siqueira et al. 1999). In such circumstances, if root canal obturation does not impede saliva leakage, microorganisms may invade and recolonize the root canal system. If microbial cells and their products reach the periradicular tissues, they can induce and/or perpetuate periradicular disease. Recontamination of the root canal system by coronal leakage will occur through sealer dissolution by saliva percolation of saliva
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Irrigation, Microbiology, Smear layer in the interface between sealer and root canal walls particularly if a smear layer is present and/or between sealer and gutta-percha (Siqueira et al. 1999). In addition, voids and other minor flaws in the obturation, which often are not detected radiographically, may be responsible for the rapid recontamination of the root canal system.
Taken together, some studies (Torabinejad et al.1991, Siqueira et al. 1999) have revealed that, regardless of the obturation technique or filling material employed, entire recontamination of the root canal can occur after a short period of microbial challenge.
Once the coronal seal is lost, microorganisms, their products and other irritants from saliva may reach the periradicular tissues via lateral canals or apical foramina’s, and thereby jeopardize the outcome of root canal treatment. Clinically, it is impossible to determine whether the entire root canal system is recontaminated after exposure to saliva.
1.2.2.3.2.3 NONMICROBIAL FACTORS
Although most of the cases of root canal treatment failure are associated with intraradicular and/or extraradicular infections, it has been suggested that some cases can fail because of intrinsic or extrinsic nonmicrobial factors. In these cases, no microorganisms can be found and failures have been attributed to a foreign body reaction in the periradicular tissues.
One study reported a therapy-resistant lesion, which was surgically removed and diagnosed as a periradicular cyst by light and electron microscopy (Nair et al. 1993). A great number of cholesterol crystals were observed in the connective tissue around the
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Irrigation, Microbiology, Smear layer cystic epithelial lining. Since microorganisms were not detected, the investigators attributed the failure to a foreign body reaction against cholesterol crystals. Cholesterol crystals are believed to be precipitated and accumulate as they are released from disintegrating host cells, including erythrocytes, lymphocytes, plasma cells and macrophages
1.2.2.4 SUCCESS OF ENDODONTIC THERAPY
During preparation of root canals, the mechanical action of instruments and chemical action of irrigants occurs simultaneously, promoting cleaning and disinfection of the root canal system (Barbizam et al. 2002, Baratto-Filho et al. 2004, Albrecht et al.
.2004). While the instruments shape and widen the root canals, the irrigating solutions act by dissolving the organic tissue (vital or necrotic) and removing debris and microorganisms (Hülsmann et al. 2003, Weiger et al. 2002). The pool of dentine chips, pulp remnants and other particles that remain loosely stuck within the intracanal space after biomechanical preparation in areas that were not accurately cleaned by action of chemical solutions and endodontic files is generally called debris (Rödig et al. 2002,
Hülsmann et al. 2003).
1.2.2.5 SMEAR LAYER
The amorphous structure composed of dentine debris, organic material and microorganisms that is produced by mechanical instrumentation and adhere to the root canal walls obstructing the dentinal tubule openings constitutes the smear layer (Siqueira et al. 1997, Hülsmann et al. 2003).
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Boyde and his group in 1963 were the first to explain the presence of a layer of grinding debris on tooth surfaces. They coined the term ‘smear layer’(Boyde et al. 1963) to describe the layer of cutting debris that remains on top of any calcified tissue when it is cut with a hand instrument or rotary bur. Eick et al. (1970) were the first to characterize the chemical composition and particle size of the constituents of the smear layer.
Diamond & Carrel (1984) described the composition of the smear layer from which they were formed. Thus, smear layers on deep dentine may contain fragments of amputated odontoblast processes, cytoplasmic and organelle enzymes, lamina limitans (Thomas
1985), pieces of organic and inorganic dentine matrix and perhaps fragments of predentine depending upon where in the tooth the smear layer is formed.
Mader et al. (1984) reported that during the creation of smear layers, microscopic cutting debris is forced into dentinal tubules for varying distances thereby creating what have been term‘smear plugs’. Smear plugs can only be created if the cutting debris particles are smaller than the diameter of the tubules being cut. In superficial dentine, this means the particles must have a diameter less than 0.8 µ m. Deep dentine tubules are
2.5- 3 µm in diameter and can accommodate larger particles of cutting debris
(Garberoglio & Brännstrőm 1976). Most smear layers are created under conditions that generate either high temperature (Friskopp & Larsson 1985) or high shear forces
(Pashley 1989) which lead to denaturation (loss of banding) of surface collagen (Bowen et al. 1984). While this may increase the solubility and enzymatic susceptibility of the organic phase of the smear layer, it may lower the solubility of the inorganic phase if the constituent particles of the smear layer are coated with gelatinized collagen.
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Duke & Lindemuth (1990) investigated the fact that the smear layers created on sclerotic dentine appeared more acid resistant than smear layers created on normal dentine because many tubules in sclerotic dentine are filled with acid-resistant crystals of whitlockite or other less soluble forms of calcium phosphate. The smear layer was absent from specimens of demineralised teeth examined by light microscopy because the smear layer is dissolved during demineralization. When examined in undemineralized specimens by scanning electron microscopy (SEM) the smear layer looks like an amorphous, relatively smooth, featureless surface. The presence and absence of the smear layer is of interest not only to restorative dentists, but to endodontists as well.
Whenever dentine is filed, a smear is produced on its surface. If a smear layer containing bacteria or bacterial products were allowed to remain within the pulp chamber or root canals, it might provide a reservoir of potential irritants.
The removal of the smear layer from the dentine lining the pulp chamber and root canals has been the subject of numerous investigations. McComb & Smith (1975) indicated that most standard instrumentation techniques produced a canal wall that was smeared and often packed with debris. Goldman et al. (1982) recommended alternate use of sodium hypochlorite (NaOCl) and EDTA to remove smeared dentine. The NaOCl removed the organic material, including the collagenous matrix of dentine and EDTA removed the mineralized dentine, thereby exposing more collagen. This permits better adaptation of obturating material and sealers to the dentine and increases the tensile strength of plastic posts (Goldman et al. 1984 a, b).
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1.2.2.6 SCANNING ELECTRON MICROSCOPY 1.2.2.6.1 HISTORY
The introduction of the first commercially available scanning electron microscope
(SEM) in 1965 sparked wide interest in the use of this instrument in investigating various biological problems. This interest has continually broadened to the present day and has already resulted in the accumulation of a large and significant literature on the subject. Enough has been learned so far to indicate that as an information-gathering device the SEM is now clearly the equal of the light microscope (LM) and the conventional transmission electron microscope (TEM).
To date, the main advantage of the SEM to the biologist has been its ability to record quickly and accurately in three dimensions the surface features of tissues and cells.
1.2.2.6.2 TYPE OF ELECTRON MICROSCOPES
The most common type of electron microscope is called the conventional scanning electron microscope (CSEM), and its associated technique has a long and distinguished record in the field of biomaterials. CSEM offers unique advantages such as high resolution and large depth of field.To overcome the limitations of CSEM, a second type of SEM called the environmental scanning electron microscope (ESEM) has been developed. The first commercial version of this product was made by the ElectroScan
Corporation (Wilmington, MS, USA; later purchased by FEI/Philips Electron Optics).
In recent years, ESEM has begun to make an impact across the diverse fields of
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Irrigation, Microbiology, Smear layer materials science and this an expansion can be evidenced from the increased range of applications over a short span of time (Danilatos 1993b). The major advantage of ESEM is that hydrated and non-conducting samples, such as biological tissues and (bacterial) cells, can be imaged without prior dehydration or conductive coating. ESEM differs therefore from CSEM in two crucial aspects. First, instead of the sample being held under a high vacuum, a gaseous pressure is maintained in the specimen chamber whilst imaging is performed although the electron gun itself is kept at standard pressures of around 10). The second major difference between ESEM and CSEM is that insulators no longer need to be coated with a metallic layer before imaging. Since gas is present in the chamber, a mechanism exists to help dissipate the build-up of charge injected by the incident electron beam. Technically, ESEM is based on the integration of efficient differential pumping with a new design of electron-optics and detection systems. A final type of EM, identified as the transmission electron microscope (TEM), offers unique properties such as high resolution. TEM involves the irradiation of whole specimens or ultra-thin sections (Bancroft & Stevens 1996) using electron beam energies in the range of 60–350 keV.
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1.2.2.7 REMOVAL OF THE SMEAR LAYER 1.2.2.7.1 INTRODUCTION
Mader et al. (1984) in a scanning electron microscope (SEM) investigation of root canal walls was able to measure the thickness of the smear layer and the depth of its penetration into the dentinal tubules. Evans & Simon (1986) injected thermo-plasticized gutta-percha into canals after smear layer removal and concluded that the presence or absence of the smear layer had no significant effect on the apical seal. Smear layer removal is controversial regarding the effect of the smear layer on the quality of instrumentation and obturation. Several investigators have found that the smear layer itself may be infected and may protect the bacteria already present in the dentinal tubules (McComb& Smith 1975, Brannstrőm 1984, Pashley 1984). Indeed, some studies that investigated the removal of the smear layer concluded that a better seal was achieved when the smear layer was removed (Kennedy et al. 1986, Cergneux et al.
1987, Taylor et al. 1997, Clark-Holke et al. 2003, Cobankara et al. 2004). Other studies have suggested that removing the smear layer increases dentine permeability and might impair the sealing ability, and even allow bacteria to grow inside the dentinal tubules
(Pashley et al. 1981, Drake et al. 1994, Galvan et al. 1994, Love 1996).
Two review articles on the clinical implications of the smear layer in endodontics have confirmed the uncertainty and debate relating to the removal of smear layer before filling (Sen et al. 1995, Torabinejad et al. 2002). More recently Saleh et al. (2007) carried out a study to investigate the effect of the smear layer on the penetration of bacteria along different root canal filling materials and to examine the dentine/sealer and
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Irrigation, Microbiology, Smear layer sealer/core material interfaces for the presence of bacteria. They concluded that the removal of the smear layer did not impair bacterial penetration along root canal fillings.
A comparison of the sealers revealed no difference except that AH performed better than
RS in the absence of the smear layer.
Gulabivala et al. (2005) discussed the effects of mechanical and chemical procedures including the removal of the smear layer on the seal and stated that the mechanisms leading to successful root canal treatment remained to be determined.
The smear layer’s presence plays a significant part in an increase or decrease in apical leakage. Its absence makes the dentine more conductive to a better and closer adaptation of the gutta percha to the canal wall. Eighty per cent of obturated teeth will leak after 96 hours regardless of the presence or removal of the smear layer (Goldman 1986). With the smear layer intact, apical leakage will be significantly increased. Without the smear layer the leakage will still occur but at a decreased rate (Kennedy et al. 1986). Removal of the smear layer can be undertaken by chemical removal, mechanical removal, and laser removal as describe subsequently.
1.2.2.7.2 CHEMICAL REMOVAL
The components of the smear layer are very small particles with a large surface-mass ratio, which makes them very soluble in acids (Pashley 1992). As a result of this characteristic, acid has been used to remove the smear layer. McComb and Smith (1975) were the first investigators to show that REDTA (a commercial brand of EDTA) could remove the smear layer. Goldman et al. (1982) showed that when used alone, REDTA removed the inorganic portion and left an organic layer intact in the tubules To remove
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Irrigation, Microbiology, Smear layer this organic layer, another solvent was needed. Sodium hypochlorite (NaOCl) has been shown to be very effective for this purpose. When used alone, NaOCl can dissolve pulpal remnants. However, many studies have shown its ineffectiveness in removing the entire smear layer when used alone. Brent et al.( 2005) quantified the volume of 17 % ethylene diamine tetra-acetic acid (EDTA) needed to efficiently remove the smear layer after rotary instrumentation and to determine if additional irrigation had any effect on debris removal. They demonstrated that 1 ml of EDTA with a contact time of 1 min was just as effective as 10 ml in removing the smear layer.
Sharma & Shivanna (2002) compared the removal of smear layer by manual instrumentation of ‘K’ files versus nickel titanium rotary instruments with irrigation with
3 % NaOCl. They concluded that the removal of the smear layer was better by nickel titanium rotary instruments than conventional ‘K’ files and smear layer removal was better with light speed nickel titanium instruments as compared to Profile and Hero 642 instruments.
Prabhu et al. (2003) concluded that the NaOCl failed to remove the smear layer while the ability of maleic acid was significantly better than EDTA. Goldman et al. (1982)
Yamada et al. (1983) and Baumgartner & Mader (1987) showed that alternating the use of EDTA and NaOCl was an effective method for smear layer removal. Correr et al.
(2006) using scanning electron microscopy evaluated the alterations of etched deciduous dentine when exposed to different time and concentrations of sodium hypochlorite
(NaOCl).
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They reported that the NaOCl action produced significant changes in the etched deciduous dentine. The higher NaOCl concentration the lower the time required to completely removing the collagen fibrils network in deciduous dentine.
O’Connell et al. (2000) compared the ability of various salts of EDTA to remove the smear layer. They showed that all salts of EDTA were capable of removing the smear layer from the coronal two thirds of root canals. In addition, they reported that tetrasodium salt pH-adjusted with HCl is less expensive and just as effective as the more commonly used disodium EDTA. Goldberg &Abramovich (1977) added a quaternary ammonium bromide (Cetavlon) to EDTA to reduce its surface tension. This solution was called EDTAC. This addition increased the wetting effect on the canal wall and permitted deeper penetration of the solution into irregularities. This combination shown by Goldberg & Spielberg (1982) to be very effective in smear layer removal, reaching its peak effect at 15 minutes and increases the diameter of the opened dentinal tubules.
Tetracyclines including tetracycline-HCl, minocycline and doxycycline are broad- spectrum antibiotics that are effective against a wide range of microorganisms. Genco et al. (1978) have suggested that tetracyclines significantly enhance healing after surgical periodontal therapy. Tetracyclines have many unique properties in addition to their antimicrobial effects. They have a low pH in concentrated solution and thus can act as a calcium chelator, and they can cause enamel and root surface demineralization (Bjorvatn
1982).
Marques et al. (2006) evaluated by scanning electron microscopy (SEM), smear layer removal and quantified, by atomic absorption spectrophotometry, the amount of calcium
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Irrigation, Microbiology, Smear layer ion present in the chelating solutions after their use. Sixteen extracted canines were instrumented using the step-back technique and were assigned to 3 groups according to the irrigating solution used: G1: 1 mL 17% EDTAC between each file; G2: 1 mL 17%
CDTA; G3: 1 mL 17% EGTA. Freidman’s test was used for statistical analysis of SEM values and showed that canals irrigated with 17% EDTAC and 17% CDTA had significantly less smear layer throughout the canals than 17% EGTA (p<0.01).
1.2.2.7.3 ULTRASONIC REMOVAL
The activation of endodontic files by ultrasonic energy has been shown in some studies to be effective in both cleaning and shaping of root canal systems. Cunningham &
Martin (1982) showed that canals which were cleaned and shaped with ultrasonic instrumentation were significantly cleaner than those instrumented with conventional instrumentation.
Cameron (1983) produced a debris-free canal with the use of a 3% NaOCl solution combined with ultrasonic instrumentation for 5 minutes after conventional canal instrumentation. The mechanism of action for debris removal was described as acoustic streaming by Ahmad et al. (1987). When sonic or ultrasonic files are used in curved canals they may bind, restricting their vibratory motion and cleaning efficiency.
Walmsley &Williams (1989) concluded that using 3 min of sonic or ultrasonic irrigation in each canal of a molar with four canals would add 12 min to the endodontic procedure.
Guerisoli et al. (2002) evaluated the use of ultrasonics to remove the smear layer and found it necessary to use 15% EDTAC with either distilled water or 1% NaOCl to achieve the desired result.
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The scanning electron microscope has been used to compare the smear layer removal capability of ethylenediamine tetra-acetic acid (EDTA) application with passive ultrasonic and cotton wrapped on reamer activation. When the techniques were compared, the cotton wrapped on reamer agitation method was as successful as the ultrasonic activation of the files. Although all groups had significantly higher smear layer scores at the apical as compared to the coronal sections, no significant differences were recorded (Tinaz et al. 2006).
1.2.2.7.4 LASER REMOVAL
Laser technology has the potential to aid in endodontic treatment (Stabholz et al. 2004).
It has been suggested that apart from the improved removal of debris and smear layer, dental lasers could provide greater accessibility to formerly unreachable parts of the tubular network of the root canal system because of their enhanced penetration into dentinal tissues (Vaarkamp et al. 1995, Klinke et al. 1997).
Takeda et al. (1998, 1999) found that lasers could be used to vaporize tissues in the main canal, remove the smear layer and eliminate the residual tissue in the apical portion of the root canals. Several investigators (Dederich et al. 1984, Moshonov et al. 1995) have reported that the effectiveness of lasers depends on many factors including the power level, the duration of exposure, the absorption of light in the tissue, the geometry of the root canal and the tip-to-target distance. Dederich et al. 1984 and Tewfik et al. 1993 used variants of the neodymium-yttrium-aluminum-garnet laser and reported a range of findings from no change or disruption of the smear layer to actual melting and recrystallization of the dentine.
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1.2.2.7.5 SMEAR CLEAN™
Gambarini (1999) reported that the cleaning of the root canals can be significantly improved once the shaping procedure is completed (the ‘shaping and cleaning’ concept).
Upon completion of instrumentation, root canal diameters are considered to have been adequately enlarged with a funnel-form shape that provides easier and superior penetration of the irrigant into the apical portions.
Gambarini (2004) evaluated the canal debridement using a scanning electron microscope
(SEM) by using K3 NiTi endodontic instruments in a crown-down instrumentation technique. The results of the study showed that K3 rotary instrumentation followed by a specific final irrigation sequence produced efficient canal debridement. The use of
Smear Clean was therefore found to be effective and its use advocated.
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ozone
1.3.1 INTRODUCTION
Ozone is one of nature’s most powerful oxidants and is reactive towards many bio molecules. In the Earth’s biosphere, the role of ozone is controversial. Ozone can be produced either by ultra-violet rays of the sun, or artificially by an ozone generator. It has been used in water purification and sewage treatment and is now being applied to treat patients with inflammatory bowel disorders (specifically ulcerative colitis, cohn’s disease and chronic bacterial diarrhoea), cancer, stroke and AIDS in Europe and the
U.S.A (Buckley et al. 1975). Ozone also acts as a disinfectant, and has the unique feature of decomposing to a harmless, non-toxic and environmentally safe molecule
(oxygen). To date, many studies have been conducted using ozone for oral and dental application (Table 1.3.1.1).
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TABLE 1-3-1-1 STUDIES EVALUATE THE USE OF OZONE
Author Study Title Sample Ozone Dose Result Name Type
Estrela et Antimicrobial efficacy of 30 human 7 g h-1 ozone Inactivation of the E.Faecalis al. (2007) ozonated water, gaseous maxillary flow rate (1.2%) after 72h ozone, sodium hypochlorite anterior and chlorhexidine in infected teeth human root canals Miller and Assessment of the safety of Ozi-cure and 100 and 2100 ± HealOzone was safe to use Hodson two ozone delivery devices HealOzone 10% ppm (2007) Johansson Ozone air levels contiguous a Flat metal 2100 ppm ± The heal ozone delivery Elisabeth dental ozone gas delivery surface and 10% system is a safe system et al. system on buccal with low ozone leakage level in air (2007) and occlusal tooth surface Huth et al. Effects of ozone on oral cells Human oral Gaseous ozone Aqueous ozone has less cytotoxicity than (2006) compared with established epithelial and 4x106 µg m-3 gaseous ozone antimicrobials gingival aqueous ozone fibroblasts 1.25-20 µg m-1 Estrela et Antimicrobial potential of Staphylococc 7 g/h ozone Addition of ozone to a ultrasonic cleaning al. (2006) ozone n an ultrasonic cleaning us aureus flow rate (1.2 system resulted in antibacterial action system againt Staphylococcus %) against Staphylococcus aureus aureus 1 Grootveld High Resolution H NMR Saliva Ozone 2100 O3 produced oxidation of pyruvate, et al. nvestigations of the oxidative samples ppm ± 10 % at lactate, carbohydrates, methionine (2006) consumpation of salivary from 12 615 cc/min and urea. Moreover, minor O3 – biomolecules by ozone: healthy applied for 10s indued modifications included the oxidation Relevence to the theraputic volunteers trimethylamine and 3-D- hydroxybutyrate applications of this agent in clinical dentistry
Polydorou Antibacterial effect of an S.mutans 2100 ppm ozone 80m s application of ozone et al. ozone device and in 32 human ± 5% at a flow is a very promising therapy (2006) comparsion with two dentin- molar rate of 615 cc for eliminating residual microorganisms in bonding systems min-1 deep cavities 40 and 80 s
Arita et Microbiocidal efficacy of C.albicans Ozonated water Nonexistence of viable C.albicans. Inaddition al. (2005) ozonated water against (2 or 4mg/l) for ultrasonication Candida albicans adhering to 1 min had a strong effect on the viability of C.albicans acrylic denture plates
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Nagayoshi Antimicrobial effect of Enterococcus 4 mg/L of Significant decrease of CFU et al. ozonated water on bacteria Faecalis and ozonated water when the bacterial cells were (2004 b) invading dentinal tubules Streptococcu (O3 aq), 4 mg/L treated with ozonated water s Mutans of O3 aq with and the number of CFU remaining ultrasonication in specimens treated by ozonated water with sonication was nearly the same as with NaOCl
Nagayoshi Efficacy of ozone on survival Streptococcu Ozonated water Ozonated water was effective et al. and permeability of oral s salivarius (4mg/l) for 10, for killing gram-positive (2004 a) microorganisms and 30, 60 or 120 s and gram-negative oral Sreptococcus microorganisms and oral c.albicans in pure culture sanguis
1.3.2 OZONE DELIVERY SYSTEM
1.3.2.1 INTRODUCTION
Ozone (O3) is the agent of choice for the disinfection of public water supplies in the
U.S.A. The reason for the preferential application of O3 here is primarily to remove iron and manganese ion discolorations, and to avoid adverse tastes and odours (O’ Donovan,
1965). However, one major disadvantage is that O3 is stable for only a short period of time and decomposes to form molecular oxygen which is utilised by aquatic life (Rilling and Viebahn, 1987) and hence it disappears very quickly from the system (Kaplan et al.
1996). Consequently, it is impossible to maintain a residual level of ozone in a water distribution system. However, Burleson et al. (1975) found that the application of a simultaneous treatment of O3 with sonication to be more effective in a bactericidal treatment process designed for the disinfection of waste water. Sonication reduced or altered oxidisable organic material as measured by biological oxygen demand and
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ozone chemical oxygen demand determinations and therefore the O3 demand of the secondary effluent was also reduced (Guinvarc'h 1959). This may also enhance the O3-mediated inactivation of microorganisms by ozone via dissipation of particulate organic material and clusters of bacteria a process facilitating their exposure to the oxidant (Morris 1971).
With pre-treated water, ozone can kill bacteria by rapidly rupturing their cell membranes
(within 2 s). Chlorine, on the other hand, simply diffuses into the cell and requires 30 min to achieve bacteriocidal effects. The rate of lysis is dependent upon the ozone level.
Higher ozone concentrations are used for highly contaminated systems, whereas lower concentrations are used for maintenance. Following O3-mediated lysis of the microorganisms, the cytoplasmic constituents are oxidised by this agent, which is then removed by UV irradiation at a wavelength of 254 nm. Ozone has also been employed commercially to remove trace organic contaminants from water. However, high levels of
O3 were found to be insufficient for disinfection in view of the limited solubility of this gas in water and adverse toxicological problems arising from the employment of such high concentrations (Guinvarc’h 1959).
Humans are continually exposed to O3 during their daily lives, a phenomenon which may raise some doubts about the harmful health effects of this reactive oxygen species
(ROS). Occupational exposure to O3 can be by electric arc welding, mercury vapour lamps, laser printers, some office photocopying equipment, X-ray generators and other high voltage electrical equipment, water purification processes and the employment of this oxidant for bleaching purposes (Dickermann et al. 1954, Burleson et al. 1975).
Bocci (1994) emphasised that the potential toxicity of O3 should not preclude its
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ozone employment for medical purposes. Certainly, carefully selected dose levels of this agent are of potential therapeutic value in the management of circulatory disorders, viral diseases and cancer. The permissible concentration of ozone, to which workers may be exposed, is 0.1 ppm over 24 hours. The short-term exposure limit was 0.3 ppm for 15 minutes. A concentration of 10 ppm ozone in air is generally accepted as “Immediately
Dangerous to Life or Health” (IDLH).
Gliner et al. (1979) investigated the effects of increasing concentrations of O3 (0.00,
0.25, 0.50 and 0.75 ppm) on visual and auditory attention tasks (vigilance performance).
Spectral and discriminant function analyses were performed on the EEG signals collected during the study. EEG signals were categorised between different O3 levels at rest, during each task performance and between task and non-task performance under ambient air conditions. Results showed that O3 at concentrations as high as 0.75 ppm did not alter the performance of visual and auditory tasks.
1.3.2.2 HISTORY OF OZONE
O3 was first discovered and named by C. F. Schonbein in 1840, and the utilisation of O3 in industrial environments has an impressive history. The Native Americans, for whom fishing was a central industry, recognised a correlation between a successful catch of fish and a strong odour released by the action of lightning following an electric storm.
Similarly, the ancient Greeks also noticed this odour, which they termed ‘ozein’. They preferentially fished subsequent to electric storms, a custom, which prevails today, since the upper layer of lake water is enriched with dioxygen. It should also be noted that
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ozone ozone in lake water arises from air diffusion in its upper layer rather than as a product arising from chemical reactions within the lake.
1.3.2.3 CHEMISTRY OF OZONE
O3 is produced by the photo dissociation (i.e. bond cleavage induced by light energy) of molecular O2 into activated oxygen atoms, which then react with further oxygen molecules. The two oxygen-oxygen bonds in the O3 molecule are of equal length and intermediate in nature between those of oxygen-oxygen single and double bonds
(Halliwell & Gutteridge 1989). In view of its powerful oxidising properties, O3 can attack many biomolecules such as the cysteine, methionine and the histidine residues of proteins.
Tyrosine residues in proteins can be cross-linked subsequent to the O3-mediated oxidation of their phenolic-OH groups, yielding O, O’-dityrosine, the oxygen-oxygen bond acting as a cross-linking unit. Oxidation of polyunsaturated fatty acids by O3 can lead to lipid peroxidation, a reaction system proceeding via the prior generation of
· ozonides. There is also evidence that O3 produces OH radicals in aqueous solution, which are an extremely reactive species that contribute to tissue injury (Hoppe et al.
1995).
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1.3.3 CLINICAL APPLICATIONS OF OZONE
O3 has the unique feature of decomposing to a harmless, non-toxic and environmentally safe material (oxygen). The first O3 generator was developed by Werner von Siemens in
Germany as early as 1857, and the first report of it being used therapeutically was for the purpose of purifying blood by C. Lender in 1870. In 1885, Dr. Charles J. Kenworthy first published important information regarding the medical applications of O3.
1.3.2.1 THE FOUR PRIMARY CURRENT METHODS OF ADMINISTERING MEDICAL OZONE ARE:
Autohaemotherapy. Autohaemotherapy involves the treatment of up to 200 ml of pre- isolated human blood with a gaseous mixture of oxygen and O3 and has been used since
1950 (Belianin & Shemelev 1994). There are two classes of autohaemotherapy. Major therapy involves the removal of approximately 200 ml of blood from a patient, adding
O3 and O2 to it and infusing the mixture back into the individual (Bocci 1992).
Heparin is required as an anticoagulant to prevent the blood from clotting. Minor autohaemotherapy involves the process of withdrawing only 5-10 ml of blood from patients for treatment with O3.
Many unrelated diseases such as acute and chronic viral diseases (Shiratori et al. 1993), neoplasia, vascular disorders such as obstructive arteriopathies, venous insufficiency and vascular degenerative diseases, ulcers and cutaneous infections have been treated with ozone. There are several mechanisms of autohaemotherapy by which ozonised blood is
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ozone claimed to improve the circulation and oxygenation of hypoxic tissues. CD4 cell count, and interleukin-2, gamma-interferon, beta-2-microglobulin, neopterin and p24 antigen activities were found to be unaffected by the application of O3 during the treatment of 10 patients with HIV infection (Bocci 1996a).
The effects of autohaemotherapy on the human hair cycle in 42 subjects suffering from adrogenetic alopecia were studied by Riva Sanseverino et al. (1995). The microscopic observation of hairs (trichogram) was carried out before and after autohaemotherapy according to a European Scientific Protocol the O3 dosage was 2500-3000 mg for each treatment and one cycle consisted of 16 treatments. The investigators concluded that there was a marked improvement in the hair cycle.
Rectal insufflation. O3 and O2 are administered as a rectal enema. The O2/O3 mixture is then absorbed through the large intestine (Leon et al. 1998).
Özmen et al. (1993) studied the peritoneal cavities of 240 rats following faecal-capsule implantation. Ozonylated saline proved to be an effective irrigating solution for reducing abscess formation in survivors when compared to normal saline solution, and saline-cephalothin irrigation in the treatment of faecal peritonitis.
Subsequently, Romero Valdes et al. (1993) reported that the least uncomfortable, most harmless and economically feasible manner of O3 administration was rectal insufflation in the treatment of 72 non-diabetic patients with obliterate atherosclerosis, rather than the endovenous and intramuscular methods of employing O3 and conventional medical treatment (control group). Daily doses of O3 ranging from 2.7 to 30 mg were employed in the treatment of intractable diarrhoea associated with AIDS.
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O3 “bagging”. This involves having an airtight bag placed around the area to be treated.
A mixture of O3 and O2 is pumped into the bag and absorbed through the skin (Church
1980). It was first used in Germany as a bactericidal agent, particulary on staphylococcal, Streptococcal and protean infections and had employed been in the treatment of open wounds.
Ozonylated olive or sunflower oils. O3 is also utilised externally in the form of ozonylated olive or sunflower oils. In this respect, medical treatment with ozone is claimed to be safe, therapeutically beneficial, and cost-effective. Ozonised sunflower oil
(Oleozón) of concentration ranging from 1.18 to 9.5 mg/ml-1 , has shown antimicrobial effects against viruses, bacteria and fungi (Sechi et al. 2001). Oleozón is a substance produced by the reaction of ozone with unsaturated fatty acids present in sunflower oil.
This reaction occurs almost exclusively with carbon-carbon double bonds and produces several compounds such as ozonides and hydrogen peroxide (Santrock 1992).
1.3.3 POTENTIAL APPLICATIONS OF OZONE TREATMENT IN DENTISTRY
The effect of ozone as an antimicrobial agent was established before the beginning of the previous century and it was suggested that it be used for the disinfection of working surfaces in hospitals and dental clinics. Early reports described the use of ozone for the sterilisation of instruments used for endodontic treatment with this therapeutic agent being applied for the disinfection of the root canal system (Haimovici et al. 1970).
Antimicrobial activity of ozonised water on bacterial suspensions and contaminated materials was basically dependant on the concentration and the time of exposure on
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ozone buccal microflora and were tested after rinsing with ozonated water. After successive rinses a substantial reduction in the number of colonies of bacteria was found. This effect was more pronounced on the flora of the hands. The antimicrobial activity lasted for 20 minutes in open water and then decreased substantially after 30 minutes (Minguez et al. 1990).
Denture disinfection was one of the fields that drew attention to the applications of the potent abilities of ozone to be tested in dentistry. It was considered as clinically appropriate because of its strong disinfecting and deodorising power and high biological safety.
The microbiocidal effect of gaseous ozone was found to be more effective compared with ozonated water when tested against oral microorganisms such as C.albicans
(Oizumi et al.1998). Therefore, it was suggested its use for the disinfection of dentures was significantly reduced after using 10-ppm ozonated water for variable treatment times (Murakami et al. 1996).
Ozone had little influence on oxidation compared with acid-electrolyse. A 10 ppm concentration of ozone in water used in denture a cleaner was found to be effective against methicilline-resistant Staphylococcus aureus (MRSA) and T1 phage (Suzuki et al. 1999).
Ozone was first proposed for the treatment of dental unit waterlines in the last decade.
The microbial effect of O3 on dental treatment units lasted longer when compared to the conventional methods such as hydrogen peroxide/ silver ion solutions in-vivo and in- vitro. Under the precondition that the dental chair had been thoroughly sanitised, the
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ozone system showed a good disinfecting effect (Filippi et al. 1991). Pseudomonas aeruginosa, a potentially pathogenic microorganisms frequently found in dental treatment units was eliminated after O3 treatment (10 µg O3/ml water).
Furthermore, there was no evidence of air pollution related to the use of ozone in the treatment area and no ozone detected in water taken from units. Later, ozone was tested with variable concentrations through the water lines. The 5-minute application achieved sterile water. The biofilm in the tube walls was removed after a 15-minute application and flushing (Al Shorman et al. 2002).
The effect of ozone on cariogenic bacteria was studied (Baysan et al. 2000). Root carious lesions were chosen to be exposed to ozonised water with concentrations of
0.069 or 0.138 ml of ozone equal to 10 and 20-second exposure times. A significant reduction was observed in the mean total microbial counts in the ozone-treated groups with either a 10-second or 20-second application time compared with the control groups.
Saliva-coated glass beads inoculated with S. mutans and S. sobrinus were exposed to 10 s of ozone gas. There was a significant reduction in the ozone-treated samples for S. mutans and S. sobrinus compared with the control samples. It was concluded that the treatment was an effective, quick, conservative and simple method to kill micro- organisms.
Other studies on ozone treatment have been performed in a clinical trial of 214 lesions
(Baysan & Lynch 2002). These were treated with ozone, ozone and fissure sealant, fissure sealant only and controls. There were significant results in terms of clinical criteria detected within the lesions in the treatment group in terms of the number of
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ozone lesions which became hard (64.9% of the lesions in the treatment group compared to
7.5% in the control group). A further reduction in DIAGNOdent readings was present.
In the fissure sealant groups, these showed better results in the ozone treatment group where 68.5% of the sealants were retentive whilst the retention was 38.5% in the control group.
Safety of the design of the cup and handpiece system was tested during the application of ozone on teeth with primary root caries for 10 and 20 second treatments. The detector was kept around 2 mm from the edge of the cup. Levels of ozone within the patients’ mouths were lower than the recommended EU and FDA regulation for ozone concentration permissible in the air (Baysan & Lynch 2001).
The High field Proton Nuclear Magnetic Resonance spectroscopy (1H NMR) system for the analysis of biomolecules allowed for the effect of ozone treatment to be tested on the biomolecules in plaque, saliva and root carious lesions (Grootveld et al. 2001, Lynch et al. 2001, 2002). Results had demonstrated the powerful oxidative ability of ozone gas in the concentration proposed and the consumption of biomolecules essential for the process of demineralisation of lesions to occur. Amongst these molecules are formic and pyruvic acids; K(a) = 1.77 x 10-4 and 3.20 x 10-3 mol/dm3, respectively. These were proven to contribute substantially to the decreased pH values associated with active carious lesions in root caries. By doing so, the precipitation of minerals was inhibited
(Silwood et al. 1999). Pyruvic acid was found to be oxidised by ozone to form acetate and carbon dioxide compounds associated with higher pH values (Lynch et al. 2002).
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Abu-Naba’a (2003) assessing the effect of ozone on fissure caries of permanent teeth showed that ozone treatment produced significant remineralisation in lesions in the treatment group regardless of lesion type or location. All age groups benefited from the treatment.
Oral medicine and oral surgery had their share of ozone use as well. Cellulitis has been treated with an ozone solution (Kiniapina & Durnovo 1996) as well as gingivitis in adult subjects (Brauner 1991) .
Ozonised water applied on a daily basis accelerated the healing rate of oral mucosa noticeable within the first two postoperative days and under the influence of O3, more wounds were closed after seven days and cell proliferation commenced earlier. It was concluded that the use of O3 was completely safe since ozone dissipated very quickly in water. In addition, the influence of ozone led to a higher expression of cytokines that were important for wound healing, especially TGF-â 1, an important substance for regulation and coordination in the initial wound healing phase. TGF-â 1 had a marked influence on cell proliferation, chemotaxis (monocytes and fibroblasts), angiogenesis, synthesis of extra cellular matrix and collagen synthesis. Ozonated water was found to be effective in the dental surgery where it was reported to promote haemostasis, enhance local oxygen supply and inhibit bacterial proliferation. Therefore, ozone can be potentially have application following during dental surgery or following tooth extraction.
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Ozonated water has lots of applications in oral medicine and oral surgery. It is acts as a haemostatic and anti-inflammatory agent after tooth extraction, enhances local oxygen supply and inhibits bacterial proliferation. The application of ozonised water
(concentration 11-12 μg ozone/ml water), clearly showed anacceleration of wound healing within the first 48 hours, resulting in earlier epithelial woundclosure after 7 days
(p < 0.01) (Filippi 2001). A study by Homutinnikova and Durnovo (1999) aimed to determine the efficiency of ozone therapy (ozonised 0.9% NaCL solution at 102-196 mg/1 ozone locally at 237 mg/1 ozone concentration) in the treatment of the open fractures of the mandible (p < 0.01). A study in prophylaxis of posttraumatic inflammatory complications showed that ozone therapy method was a perfect method of conservative therapy of open fractures of the mandible and in preventing the development of inflammatory complications by stabilization of membrane lipid peroxidation processes in the body as well as in the oral cavity.
Huth et al. (2005) investigated, with a randomized controlled clinical study, the effect of ozone on non-cavitated initial occlusal fissure caries compared with untreated contra- lateral control lesions (split mouth) considering the patient's current caries risk. Forty- one patients with 57 pairs of lesions were enrolled in the study. Gaseous ozone
(HealOzone) was applied once for 40 seconds to the randomly assigned test molar of each pair without the use of remineralizing solutions. After 3 months, explorative data analysis revealed that the ozone-treated lesions showed significantly more caries reversal or reduced caries progression than the untreated control lesions within the group of patients at high current caries risk (P= 0.035). There was no statistical significance
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ozone examining the whole study population. They concluded that ozone application significantly improved non-cavitated initial fissure caries in patients at high caries risk over a 3-month period.
Polydorou et al. (2006) evaluated the antibacterial activity of two different application times of an ozone-generating device on a tooth cavity model. In addition, the antibacterial activity of ozone was compared with that of two dentine bonding agents.
They concluded that an 80 s application of ozone with the HealOzone device was a very promising therapy for eliminating residual microorganisms in deep cavities and therefore of potentially increasing the clinical success of restorations. However, the antimicrobial potential of 60 seconds ozone gas was assessed in an in-vitro study and compared with Photodynamic Therapy (PDT); (methylene blue in combination with or without a diode soft laser, and a soft laser alone) and antimicrobial solutions (2% chlorhexidine or in 0.5 and 5% hypochlorite solution) (Muller et al. 2007). Their result showed that only the 5% hypochlorite solution was able to totally eliminate the microorganisms in the biofilm. The observed reduction of viable counts by vacuum- ozone application and PDT was less than one log10 step. They concluded that under the conditions of the current study, gasiform ozone and PDT had a minimal effect on the viability of microorganisms organized in a cariogenic biofilm. However, they did not bubble the ozone into the biofilm unlike the application method on caries where the ozone tip is placed against the carious surface thereby fushing ozone into the lesion.
Also the biofilm contained growth media full of reducants which would have formed a redox reaction with the ozone before the ozone could have killed the bacteria.
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1.3.4 EFFECT OF OZONE ON BOND STRENGTH AND SURFACE HARDNESS OF DENTAL BONDING MATERIALS
Schmidlin et al. (2005) evaluated the influence of a direct high-dose gaseous ozone application, 2100 ppm for 60 seconds, on dentine and enamel shear bond strength to composite. That study showed that a high-dose of ozone gas for 60 seconds did not affect the shear bond strength value of bovine enamel and dentine samples to composite resin. In contrast, bleaching using H2O2 resulted in significant decreased bond strength
(p < 0.05) on enamel specimens.
Celiberti et al. (2006) investigated the effect of a 40 seconds ozone application on sealant tag length and microleakage was evaluated on intact and prepared sound molar fissures. The results indicated that ozone did not influence the enamel physical properties and neither enhanced nor was harmful to the sealing ability. Prepared fissures exhibited a statistically significantly lower microleakage compared to intact fissures.
They concluded that Ozone dehydrate enamel and consequently enhance its microhardness, which was reversible. It was also reported that the application of ozone, for 10 seconds to restorative materials, did not significantly affect the surface hardness of the materials tested (p = 0.15), (without ozone -116.4 N, with ozone -128.6 N)
(Campbell et al. 2003). It was also reported that the predominant failure mode in all treatment groups was adhesive between resin and teeth.
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1.3.5 OZONE IN ENDODONTICS
A study by Brunel et al. (1965) showed that ozone could be used for sterilization of
endodontic instruments. Ozone also was used as a local therapeutic agent applied for
the disinfection of the root canal system after pulp disease (Haimovici et al. 1970)
and root canal treatment (Deltour et al. 1970, Chahverdiani & Thadj-Bakhche 1976).
Ozone is known to act as a strong antimicrobial agent against bacteria, fungi and
viruses. Nagayoshi et al. (2004a) suggested that ozonated water (4 mg/l) for 10
seconds was effective in killing gram-positive and gram-negative oral
microorganisms and oral Candida albicans in pure culture and had strong
bactericidal activity against the bacteria in plaque biofilm (p < 0.01) and suggested
that the application of ozone may be useful for endodontic therapy. Ozonated water
had nearly the same antimicrobial activity as 2.5% NaOCl during irrigation,
especially when combined with sonication and showed a low level of toxicity against
cultured cells (Nagayoshi et al. 2004b) .
Ozone is a selective oxidant and affects only certain compounds but when it
dissolves in water, it becomes highly unstable and rapidly decomposes through a
complex series of chain reactions (Hoigne & Bader 1975, Shin et al. 1999).
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1.3.5.1 EFFECT OF OZONE ON ORAL MICROORGANISMS
Current studies have investigated the effect of ozone on oral microorganisms. In a study undertaken by Kamali et al. (2003), a strip mutans was placed in a subject’s mouth and rolled on the tongue. A part of the surface of the tongue was treated with ozone for 20 seconds. The result of this study showed a significant difference (P=0.022) in numbers of mutans streptococci in saliva and plaque before and after ozone treatment and also showed that ozone effectively kills the great majority of the microorganisms.
Another study undertaken to investigate the efficiency of an ozone delivery system on lactobacilli in saliva proved that ozone had an influence in the significant reduction of the growth of lactobacilli. The study concluded that ozone had antimicrobial effects on lactobacilli in saliva (Hedberg et al. 2003).
Hems et al. (2005) evaluated the potential of ozone as an antibacterial agent using
Enterococcus Faecalis as the test species. Ozone had an antibacterial effect on planktonic E. Faecalis cells and those suspended in fluid, but little effect when embedded in biofilms.
Huth et al. (2006) investigated in an in vitro study whether gaseous (4 x 106 µg/ml) or aqueous (1.25-20 µg/ml) ozone exerted any toxic effects on human oral epithelial
(BHY) cell and gingival fibroblast (HGF-1) cells compared with established antiseptics
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ozone and one clinically applied topical antimicrobial (metronidazole) by using several independent biochemical techniques. The aqueous form of ozone, as a potential antiseptic agent, showed less cytotoxicity than gaseous ozone or established antimicrobials under most conditions. Therefore, aqueous ozone fulfils optimal cell biological characteristics in terms of biocompatibility for oral application. In dentistry, the cytotoxicity of antimicrobials is clinically relevant only if contact with resident oral cells takes place. Cytotoxicity is not relevant when applying ozone gas onto carious tooth hard substance via a sealing suction system as a prerequisite to avoid inhalation.
For root canal disinfection, cytotoxicity is relevant owing to probable contact with cells in the apical region. Nonetheless, ozone gas has performed well compared with the established endodontic irrigants (CHX 2%; NaOCl 5.25%, 2.25%; H2O2 3%), which show equal or even higher cytotoxic potentials than ozone.
In addition, it is also possible that the ozone gas applied into the moist root canal, as currently performed with the HealOzone device (KaVo), dissolves in canal fluids thereby resulting in aqueous ozone which then comes into contact with tissues. In contrast to ozone gas, aqueous ozone revealed essentially no toxic effects, demonstrating a higher biocompatibility than even CHX 0.2% (BHY), not to mention the high cytotoxicity of NaOCl and H2O2. The latter findings may be relevant in assessing the usefulness of ozone for root canal disinfection, adjunctive periodontal treatment or as a caries-preventive mouth rinse (Huth et al. 2007).
Chang et al. (2003) concluded that the ozone killed all Enterococcus Faecalis when its concentration in suspension was 106 or lower even at exposure times of only 10 seconds.
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However, Estrela et al. (2007) investigated that the irrigation of infected human root canals with ozonated water (a constant 50 mL/ min1 flow for 20 min) 2.5% NaOCl, 2% chlorhexidine and the application of gaseous ozone for 20 min was not sufficient to inactivate E. faecalis. However, the gaseous O3 was not bubbled in as recommended and the agaseous O3 dose was low.
Estrela et al. (2006) evaluated the antimicrobial potential of ozone applied to 3 different solutions in an ultrasonic cleaning system against Staphylococcus aureus. They concluded that the application of ozone in an ultrasonic cleaning sustem containing either sterile distilled water, vinegar or sterile distilled water + Endozime A W pluzs showed antibacterial activity against S. aureus.
Broadwater et al. (1973) showed that the ozone, in relatively low concentrations, is an effective bactericide against both vegetative cells and spores of three bacterial species
(Escherichia coli, Bacillus cereus, and Bacillus megaterium).
Recently, there is growing concern regarding the quality of water that exits in Dental
Unit Waterlines (DUWs). The numbers of micro-organisms that have been found in water samples collected from dental units may exceed current limits for water quality and are perceived as a potential health risk to patients and dental personnel (Williams et al. 1993, Putnins et al. 2001, Lee et al. 2001). O3 has successfully been employed for the treatment of dental unit water lines since the 1990s. The microbial effect of O3 on dental treatment units lasted longer when compared to the conventional methods such as hydrogen peroxide/silver ion solutions in- vivo and in- vitro (Filippi et al. 1991; Filippi
1997a, 1998).
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Filippi (1997a) tested the effect of ozone on Pseudomonas aeruginosa, a potentially pathogenic micro-organism, which is frequently found in dental treatment units. After
O3 treatment (10 µg O3/ml water = 10 ppm), there were no micro-organisms detected in water. Furthermore, there was no evidence of air pollution related to the use of ozone in the treatment area and no ozone detected in water taken from DUWs.
Subsequently, ozonated water was considered to be an alternative to a sterile isotonic solution for oral rinsing during dental surgery, or following tooth extraction processes
(Filippi 1997b, 1999b). Filippi (2001) showed that ozonised water (5-10 µg ozone/ml water) applied on a daily basis can accelerate the healing rate of oral mucosa. The effect was observed on the first two postoperative days. Between the second and seventh post- operative day, there were no further effects observed related to ozone. However, this author stated that the effect observed in the first 48 h, modified the final wound closure so that under the influence of O3 more wounds were closed after seven days and cell proliferation commenced earlier. It was concluded that the use of O3 was completely safe since ozone dissipated very quickly in water.
O3 is approximately 10 times more soluble in water than oxygen. Mixed into pyrogen- free water, the half-life of O3 is 9 to 10 h (at pH 7 and 20°C), and at 0°C this value is doubled.
Ozonated water was found to be effective in the dental surgery where it is reported to promote haemostasis, enhance the local oxygen supply and inhibit bacterial proliferation
(Filippi 1997b).
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A denture cleaner using O3 bubbles (O3 concentration approximately 10 ppm) was considered as clinically appropriate in view of its strong disinfecting and deodorising power, and high biological safety (Murakami et al. 1996).
The effectiveness of this cleaner against C. albicans was investigated and levels of this microbe were found to decrease to about 1/10 of their initial value after 30 min, and to
1/103 after a 60 min. period of exposure. Subsequently, the antimicrobial effect of gaseous ozone either with water or without water on S. mutans (strain IID 973),
Staphylococcus aureus (strain 209-P) and C. albicans (strain LAM 14322) for disinfecting dentures was investigated (Oizumi et al. 1998).
When the ozone injection method was used, the numbers of cells for all three strains decreased to 1/105 at 1 min and they were below the detection limit after 3 min. In contrast, when ozonated water at 1 ppm and 3 ppm was used, C. albicans decreased to
1/10. In addition, the ozone production level which was required to prepare 1 ppm ozonated water was 700 mg/h, whilst the ozone generator required only 20 mg/h of ozone to produce the same amount of ozonated water.
Several studies investigated the effect of ozone on the carious lesion. The result of
Holmes (2003) showed that at 18 months of recall visits, 87 (100%) of ozone-treated
PRCL's had arrested, whilst in the control group, 32 lesions (37%) of the PRCL's had worsened from hard to soft (p < 0.01), 54 (62%) PRCL's remained hard and only one of the control PRCL's had reversed (p < 0.01). He concluded that non-cavitated primary root caries can be arrested non-operatively with ozone and remineralising products.
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Baysan & Lynch (2007) carried out a longitudinal study to assess the safety and efficacy of ozone either with or without a root sealant for the management of leathery root caries.
The results of this longitudinal study revealed that at the 6 month recall, 78 patients completed. There were no observed adverse events. 38.1% of lesions became hard in the ozone only group, whilst none of the lesions became hard in the control group (p <
0.001).
Baysan & Beighton (2007) undertook a study to assess the ability of ozone to kill micro- organisms associated with non-cavitated occlusal caries. The occlusal surfaces were treated with ozone (n = 53) or air (n = 49) for 40 s, and the underlying infected dentine was exposed. There was no significant difference between the number of bacteria recovered from the ozone-treated and the control sites (p > 0.1). Treatment of the exposed dentine with ozone resulted in a significant (p = 0.044) reduction in bacterial counts. Ozone treatment of non-cavitated occlusal lesions for 40 s failed to significantly reduce the numbers of viable bacteria in infected dentine beneath the non cavitated fissures. However, ozone is only recommended to treat 1mm of infected dentine unlike that used in this study.. The authors were attemting to treat relatively dry caries while is not recommended as ozone is very soluble in moisture. The methods of applying the ozone was not used according to the recommended techniques. Ozone is not recommended for treating infected dentine beneath non cavitated fissures. Thus, they suggest that the ozone should be applied for a longer time, more than 40 seconds to reach deep lesions and that the antimicrobial effect could be achieved in such experiments with application of ozonated H2O.
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However, this study was flawed as stated above and also the clinical measurement for recording the severty of the lesions was not a validated methods. Ozone gas was reported to significantly reduce the number of bacteria in small lesions (1 mm2 ) while in larger lesions the effect were much smaller or non-existent (Baysan & Lynch 2004).
This study by Baysan & Beighton (2007) were trying to achieve too much.
1.3.6 SAFETY OF OZONE
O3 is often found in ambient air at levels exceeding the National Air Quality Standard in the U.S.A, of 0.12 ppm averaged over a period of 1 h (United States Environmental
Protection Agency, 1997). Recently, Brown (1999) found that small emissions of nitrogen dioxide, O3 and formaldehyde were generated by a dry-process photocopier in a controlled room. In maintenance, construction and cleaning departments, high exposures to O3 have been observed (Teschke et al. 1999). Interestingly, artists are also susceptible to the occupational exposure to O3 in their daily lives (Lesser & Weiss
1995). O3 is a major component of environmental photochemical smog and can exert toxic effects on erythrocytes, the lungs and other organs after prolonged exposure
(Rahman et al. 1991). However, there is evidence that nature produces and uses this reactive oxygen species, together with nitric oxide (Moncada et al. 1991) for microbial purposes and possibly for killing infected and neoplastic cells.
Bocci (1992) suggested that treating human blood with low O3 concentrations for the management of vascular disorders, chronic viral and autoimmune diseases can actually
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ozone activate cells of the immune system and exert beneficial effects. However, it should be noted that O3 concentrations and the time of exposure to this agent need to be considered. Furthermore, Bocci (1994) reported that human blood treated with the correct dose of O3 can minimise the formation of free radicals and convert oxidants to less toxic species as ozonated autohaemotherapy stimulates the increase of cellular anti- oxidant enzymes such as superoxidine dismutase (Bocci, 1996b) and glutathione peroxidase (Hernández et al. 1995) and this effect inhibits the oxidative stress.
These interesting phenomena of oxidative stress adaptation may explain why ozonated autohaemotherapy is claimed to have a therapeutic effect on ischaemic, degenerative, autoimmune diseases and possibly on cancer where a persistent oxidative stress has been noted as a factor which favours the progression of invasion and metastasis (Toyokuni et al. 1995).
Al-Dalain et al. (2001a) also highlighted the protective effects of O3 by means of oxidative preconditioning, stimulating and/or preserving the endogenous antioxidant systems related to diabetes mellitus. In this study, O3 treatment improved glycemic control and prevented oxidative stress related to diabetes mellitus and its complications.
Ozone protective effects on antioxidant endogenous defence improved glucose metabolism in diabetic patients.
O3 has also been used in the U.S. food processing industry (Whistler & Sheldon 1989).
Indeed, Moore et al. (2000) indicated that low levels of ozone have a significant bacteriocidal effect on the microorganisms that are responsible for causing common foodborne illnesses and infections.
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These authors concluded that the efficacy of O3 coupled with its relatively low running costs, known deodorising properties, lack of environmentally sensitive residues and its ability to kill resistant bacteria should lead to an increase in the use of ozone as a disinfectant.
It has been estimated that over ten million people primarily in Germany, Russia, Italy, the former Soviet Union and Cuba have been given bio-oxidative therapies over the past seventy years to treat over fifty different medical diseases (Bocci 1994). They include heart and blood vessel diseases, lung diseases, infectious diseases and immune-related disorders. For many years, O3 had a very limited application in buildings for the elimination of microorganisms. However, it is now accepted as a good odour eliminator in bars, restaurants, kitchens, and homes (Smet & Van Langenhove 1998). It is curently estimated that more than 30,000 dentists use ozone in their daily practice.
1.3.7 CONCLUSION
The modern development of ozone’s application to medicine began in the 1950s in
Europe and gradually spread throughout this continent and then to Australia, Israel,
Cuba, Brazil and Columbia. In World War I, O3 was used to treat wounds and other infections. Over 6000 physicians worldwide routinely use O3 in their medical practices.
Research concerning the anti-microbial efficacy of ozone has continued over the last twenty years and has conclusively shown the ability of both gaseous and dissolved ozone to eliminate a wide range of bacteria, bacterial spores and viruses (Katzeneleson
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1974, Vaughan 1987, Whistler & Sheldon 1989). However, although the oxidative modification of essential biomolecules is primarily responsible for the biocidal actions of ozone, cellular DNA may also be damaged when concentrations of this oxidant at levels greater than those permitted by the European Union are employed.
Treatment with ozone has many advantages including:
♥ Less need to use local anaesthesia when treating caries, which could eliminate any pain or the numb feeling from the anaesthetic.
♥ Less need to drill the tooth by conventional burs and this would reduce noise and vibration associated with drilling.
♥ O3 treatment is a painless procedure.
♥ It is less time-consuming than conventional methods so there is no need for a patient to keep their mouth open for long periods.
Disadvantages
The cycle of oxygen and ozone is just like the cycle of water in nature. Ozone is also created by waterfalls, the oceans’ surf and during thunder and lighting storms with concentration levels triple the allowable limit, as set by EPA. Ozone created electronically or through ultra-violet light converts molecules of Oxygen (02) into molecules of Ozone (03). This is sometimes referred to as activated oxygen, triatomic form of oxygen or pure air.
Being an unstable gas, ozone's life span ranges from 20 to 80 or 90 minutes, depending mainly on the temperature. After completing its job, it reverts back to oxygen. This means ozone has to be produced on site. Ozone is second only to fluorine as the most
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ozone powerful oxidant in the world. It is the most powerful, natural air and water sanitizer readily available. Ozone will break down chemicals into their basic naturally-occurring component parts. After time they are eventually broken down into water, carbon dioxide, sulfur, nitrogen and oxygen.
Ozone decays rapidly at high pH and warm temperatures.
The initial cost of ozonation equipment is high.
Daily changes in ambient O3 exposure are linked to premature mortality, even at very low pollution levels. These findings, coupled with a greater relative risk of ozone in the summer versus the winter, demonstrate that geographic and seasonal heterogeneity in ozone relative risk should be anticipated, but that the observed relationship between ozone and mortality should be considered for future regulatory impact analyses (Levy et al. 2005). Bell et al (2006) found strong evidence of this relationship between O3 exposure and mortality when they used data that included only O3 levels nearing background concentrations, which typically range from 10 to 25 ppb. Therefore, any anthropogenic contribution to ambient O3, however slight, still presents an increased risk for premature mortality.
The same chemical properties that allow high concentrations of ozone to react with organic material outside the body give it the ability to react with similar organic material that makes up the body, and potentially cause harmful health consequences. When inhaled, ozone can damage the lungs (Ozone & Your Health). Relatively low amounts can cause chest pain, coughing, shortness of breath and throat irritation. Ozone may also worsen chronic respiratory diseases such as asthma and compromise the ability of the
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ozone body to fight respiratory infections. People vary widely in their susceptibility to ozone.
Healthy people, as well as those with respiratory difficulty, can experience breathing problems when exposed to ozone. Exercise during exposure to ozone causes a greater amount of ozone to be inhaled, and increases the risk of harmful respiratory effects.
Recovery from the harmful effects can occur following short-term exposure to low levels of ozone, but health effects may become more damaging and recovery less certain at higher levels or from longer exposures (US EPA, 1996a and 1996b).
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1.4.1 INTRODUCTION
The basic aim of root canal treatment is to relieve pain and infection through the removal both mechanically and chemically of the irritants from the infected root canals followed by obturation the root canal system to eliminate or reduce the ingress of microorganisms. Studies by Möller et al. (1981) and Peters et al. (2002) have implicated anaerobic bacteria as one of the most important causes of periradicular inflammation and endodontic pain. Hence, the incidence of postoperative and flare-up pain and swelling are significantly lower if infection is eradicated effectively when the root canal is obturated (Sjőgren et al.1997).
Pain is a common symptom, bringing many patients to the dental surgery. Despite its prevalence, however, it can present the most challenging diagnostic and treatment planning dilemmas faced by dentists in everyday practice.
1.4.1.1 DEFINITION
Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential damage or described in terms of such damage (Merskey 1994).
Endodontic pain is acute and the management of acute pain in dentistry is important, as the association of dentistry with pain has been shown to lead to apprehension about future dental care (Dionne & Gordon 1994). A study by Leclaire et al. (1988) on endodontic fear of adult patients showed that dental treatment procedures like root canal therapy and oral surgery treatment were categorized in the high anxiety category, which
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Postoperative pain comprised 22 % of those surveyed. However, 43.9 % of the subjects reported a decrease in fearfulness following root canal therapy. Scott & Hirshaman (1982) suggested that the association of root canal therapy with pain could be due to antecedent experiences or preconceptions based on negative comments from the mass media, relatives or friends.
Preshaw et al. (2000) reported that some patients with dental pain self medicated for extended periods of up to 6 months rather than seek dental treatment as a cure.
The term flare-up is used commonly to describe the development of pain and or swelling which commences a few hours or days after root canal procedures and is of significant severity to require an unscheduled visit for emergency treatment (Siqueira et al. 2002).
The reported prevalence of postobturation pain ranges widely from 0% (at 30 days) to
65% (at 1 day) (Fox et al. 1970, O’Keefe 1976, Mulhern et al. 1982, Direnzo et al.
2002).
Pain after endodontic treatment is thought to be related to a periapical inflammatory response secondary to one or more of the following factors namely instrumentation, the introduction of medications and or debris into the periapical tissues and severing of vital neural and pulpal tissues (Georgopoulou et al. 1986).
Persistent pain associated with teeth after non-surgical or surgical endodontic treatment has been used as an indicator of treatment failure (Rahbaran et al. 2001, Hoskinson et al.
2002). Although postoperative pain associated with root canal therapy is a poor indicator of long-term success (Taintor et al. 1981), the occurrence and the control of pain are of clinical interest to dentists and their patients. Certain factors such as preoperative pain
(Siqueira et al. 2002), number of appointments (Roane et al.1983, Albashaireh &
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Alnegrish 1998, Eleazer & Eleazer 1998), use of intracanal medications (Abbott 1990) and tooth localization (Alacam & Tinaz 2002) may predispose to the development of postoperative pain and flare-ups.
One-appointment root canal treatment is generally considered to be efficient, but the more important questions concerning the incidence of postoperative pain and prognosis for long-term healing remain unanswered. The majority of research to date has shown either no significant difference in postoperative pain when one visit root canal treatment is compared with multiple-visit treatment (Walton & Fouad 1992, Mulhern et al. 1982,
Oliet 1983) or less pain with one visit treatment (Roane et al. 1983, Albashaireh & Al negrish 1998, Eleazer & Eleazer 1998). However, many of these studies were retrospective studies or prospective studies without adequate controls or randomization.
Prospective, randomized studies are generally believed to provide the highest level of support for evidence-based clinical practice, but these are currently leading in this key area of endodontic treatment.
1.4.2 TYPES OF ENDODONTIC PAIN
Pain in endodontics not only involves the acute pulpal and periapical pain prior to initiating root canal therapy, but also post-endodontic pain. Post endodontic pain in turn can be classified as general post-appointment pain and pain due to flare-up which is a more severe nature (Morse et al. 1990).
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1.4.2.1 PREOPERATIVE PAIN
Preoperative pain is an acute pain and may arise from irreversible pulpitis of the vital or necrotic pulp, or from an acute exacerbation of chronic apical periodontitis. It is characterised by the spontaneous occurrence of pain. It presents clinically as a throbbing pain with tenderness of the tooth on percussion indicating a reduced pain threshold to mechanical stimuli. The two major groups of nociceptive afferent nerver fibres innervating the pulp tissue and periapical tissues and bone are the A delta fibres and C fibres (Gluskin & Goon 1994).
Pain associated with pulpal inflammation is also often characterised by a prolonged periods of hyperalgesia. Innocuous stimuli often produce a prolonged painful reaction.
This is in part due to the sustained actions of the peripheral inflammatory mediators that are thought to interact in the development of a local positive feedback cycle and to plasticity changes in the CNS (central hyperalgesia) (Gluskin & Goon 1994).
1.4.2.2 POSTOPERATIVE PAIN
Several mechanisms have been projected as the causative factors for pain after root canal therapy. This includes an acute inflammatory response from the periapical tissues due to mechanical, chemical or microbial origin.
Various endodontic procedures that result in pain include instrumentation of the canal, intra-canal medicaments, irrigation and obturation (Genet et al. 1987, Torabinejad et al.
1994). Incomplete instrumentation of the canal is another reason for postoperative pain.
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This is due to the necrotic remnants that disrupt the equilibrium and cause overgrowth of some microbial species leading to an acute exacerbation. In addition, the introduction of new organisms into the root canal during treatment due to a break in the aseptic chain may also be a cause of postoperative pain of microbial origin (Sj gren et al. 1991).
1.4.2.3 FLARE-UP PAIN
A flare-up phenomenon can be characterised by severe pain, tenderness of the tooth and swelling. The incidence of flare-ups is about 3-15%. Flare-ups cause the occurrence of moderate to severe pain during the course of root canal therapy. An additional symptom is intra or extra oral swelling of varying degrees from localized to diffuse with a rare occurrence of complications such as Ludwig’s angina (Harrington & Natkin 1992). This occurrence is upsetting to both the patient and the dentist. The prompt and effective treatment of flare-ups will enhance the positive attitude among patients towards dental treatment and ensure the well being and comfort of the patient (Gluskin & Goon 1994).
1.4.3 PROGNOSTIC FACTORS ASSOCIATED WITH INCIDENCE OF PAIN 1.4.3.1 PREOPERATIVE PAIN, VITALITY AND PERIAPICAL PATHOLOGY
The following clinical studies have assessed the interrelation between preoperative pain, inter-appointment pain and postoperative pain. Harrison et al. (1983b) and Torabinejad et al. (1994) conducted a two part prospective study with 236 and 588 patients respectively. The strength of the studies was in their proper cohort study design. The same groups of people were followed over time and the data collected and followed prospectively.
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Harrison et al. (1983a) assessed only asymptomatic teeth referred for endodontic treatment for the presence of inter-appointment pain and found that 55.5% had no inter- appointment pain, 28.8% had mild pain and 15.7% had moderate to severe pain. Pain assessment was by a validated verbal rating scale (VRS).
Torabinejed et al. (1994) performed a study using consecutive endodontic patients to assess the effectiveness of various medications on the incidence of postoperative pain and found a statistically significant association between pre and postoperative pain. The incidence of moderate to severe postoperative pain was 5.83% while 22.4% experienced inter-appointment pain. The results indicated that root canal instrumentation and obturation reduced pain.
Genet et al. (1987) investigated 13 preoperative factors related to postoperative pain using stringent inclusion and exclusion criteria. Out of 803 patients requiring endodontic treatment from 1980-82 only 443 teeth were used for the study. The study design was rigorous as the operators, who were from several different clinics, were calibrated.
Patients with factors that may have influenced the incidence of pain were excluded, for example, patients who were on systemic medication or antibiotics. In addition, 95% of the questionnaires were returned which improved the validity of the treatment results.
Pain assessment was by a validated Verbal Rating Scale (VRS). Since cases with swelling and exudation were excluded in the inter-appointment stage, the overall incidence of postoperative pain differed from the original data. Thirty percent of the patients experienced moderate to severe inter-appointment pain of which 7 % had severe
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Postoperative pain pain and 23 % moderate pain.
The incidence decreased to 22 % overall after obturation indicating the effectiveness of the root canal procedures of instrumentation and obturation. The study also found that only the combined presence of preoperative pain and a non-vital tooth (symptomatic non-vital teeth) was a prognostic factor in predicting postoperative pain.
The strength of this study was its rigorous methodology with a large sample size and proper cohort study design. Hence, the validity of the results is good when the prognostic factors are assessed in relation to postoperative pain.
1.4.3.2 SINGLE VERSUS MULTIPLE SESSION ENDODONTIC TREATMENT
Albashaireh & Alnegrish (1998) in a comparative prospective study over 30 days used a single operator to avoid operator dependent variability thus improving the rigour of the study. Experienced and skilled operators were less likely to compromise the outcome of treatment by performing procedural errors. The sample comprised 291 patients who were assigned consecutively and included patients without pain. No mention was made of periapical tooth status. Pain was assessed by the verbal rating scale and classified as mild, moderate or severe. A significantly higher incidence of post-obturation pain was found in the multiple visit groups i.e. 38% when compared to the single visit group at 27
% within a 24-hr observation period (p < 0.01). Non-vital teeth had a significantly greater incidence of post-obturation pain when compared to vital teeth in the ratio of
41% versus 9% (p < 0.005).
With respect to flare-up incidence of pain and or swelling with single and multiple visits endodontic therapy Walton & Fouad (1992) conducted a comparative prospective study
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Postoperative pain on the incidence and factors related to endodontic inter-appointment flare-ups. Operators ranging from undergraduates to graduates and no intra-canal medicaments were used.
Endodontic treatment of 946 patients resulted in an incidence of (3.17 %) of flare-ups.
Flare-ups were positively correlated with more severe presenting symptoms, painful non-vital teeth with periapical pathology and patients taking analgesics. Fewer flare-ups occurred following obturation. There was no association between flare-ups and the number of treatment sessions indicating that single visit root canal treatments did not result in a higher flare-up rate than treatments performed in multiple visits.
Eleazer & Eleazer (1998) conducted a retrospective study on 432 necrotic molar teeth with periapical radiolucencey from 1991-1996 and reported similar results. Eight percent of flare-ups occurred in two visits versus 3% for one visit indicating an advantage of single visit endodontics.
Fox et al. (1970) in a private practice clinical study treated 291 consecutively patients with single visit endodontics and found more pain associated with teeth without radiolucencey or periapical pathology. The difference was statistically significant at the
5% level using the Chi square test. Vital or non-vital teeth had little effect on postoperative pain.
Pain assessment was either categorised as spontaneous or pericementitis / percussion pain. Severe spontaneous pain was seen in 2% of patients and pain from severe pericementitis in 5%. This classification differed from other studies but gave an indication of the overall percentage of pain experienced.
In another private practice clinical study using single and multiple visit techniques on
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264 teeth, Oliet (1983) similarly found that the magnitude and frequency of pain did not differ significantly between the two techniques. There was no statistically significant difference between vital and non-vital teeth.
1.4.4 PROGNOSTIC FACTORS ASSOCIATED WITH FLARE-UP INCIDENCE
Torabinejad et al. (1988) in a retrospective study analysed the data of 2000 patients from five geographically separate endodontic offices and found that for asymptomatic non- vital teeth (with or without periapical pathosis), the incidence of flare-up pain and swelling that required non-scheduled office visits and palliative treatment exceeded 20
%. Non-vital teeth without periapical pathology and preoperative pain had the highest incidence. The advantage in this study, though retrospective, is the large sample size, which is critical for a clinical study involving many variables as it decreases bias and improves the ability of generalising the results to a larger endodontic population.
The limitation of this study was due to the retrospective cross sectional nature of the design of the study, which resulted in over-interpretation of data.
Siqueira et al. (2002) conducted a prospective study of 627 teeth and assessed the flare- up incidence of non-vital teeth with or without a periapical lesion, treated by undergraduate students and found that the incidence was low at 1.8 %. The low incidence was surprising since undergraduate students conducted the RCT. It was possible that the specialist saw cases that are a lot more complicated and retreatment cases. The selection process may thus have biased the results. The lower incidence of pain was claimed to be associated with the intra-canal medicament variable of the calcium hydroxide/camphorated monochlorophenol combination paste used.
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However, there was an overall incidence of 48 % inter-appointment pain. The results showed that postoperative pain was significantly associated with symptomatic teeth without periapical lesions, as in the Genet et al. (1987) study.
1.4.5 PROGNOSTIC FACTORS AND SUCCESS OF ENDODONTIC TREATMENT
Chugal et al. (2001) in a well designed study assessed the biologic and diagnostic variables in an historical prospective cohort study. A prognostic study of 441 root canal treatments in 200 teeth was conducted over a period of 5 years (1998-1992). The strength of this study was in its proper cohort study design. The same groups of people were followed over time and the data followed prospectively, which is ideal for understanding the cause of a disease and the risk factors. The potential problem with the cohort design is maintaining calibrated observers and the risk of subject dropout. Recall bias may also have influenced the significant and conclusion of the study.
Smith et al. (1993) in another study with 821 patients, assessed the prognostic factors of sex, age, preoperative vitality and periapical pathology in a five year retrospective study from 1970-1982. The overall success rate was 84.29%. Vital teeth had a 6.7% higher success compared to non-vital teeth (P < 0.03%) and teeth without periapical pathology had a 7.5% higher success when compared to teeth with periapical changes.
Hence, though single session treatment of non-vital teeth with periapical pathology did not seem to influence postoperative pain or the incidence of flare-up, long term follow up studies of non-vital teeth with periapical pathology have been shown to have a
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Postoperative pain statistically significant lower success rate versus that of vital teeth (Smith et al. 1993).
1.4.6 AETIOLOGY OF ENDODONTIC PAIN
A complex interaction of multiple mechanisms is though to be involved in the pathological changes associated with the formation of acute and chronic periapical lesions resulting in pain and swelling. Studies have indicated that pulpal and periapical pain is due to a multi-microbial infection of the dental pulp, which triggers the inflammatory response, eliciting a host defence reaction and ultimately leading to bone loss at the periradicular tissues (Nair et al. 1996, Abou-Rass & Bogen 1998).
Abou-Rass & Bogen (1998) reported the incidence of anaerobes in infected root canals of up to 90%. They investigated the microorganisms of closed periapical lesions refractory to root canal treatment. Thirteen referenced lesions were selected from 70 patients with endodontic surgical indications. Samples taken at the apex yielded microorganisms comprising 63.6% obligate anaerobes and 36.4% facultative anaerobes.
In addition, a study by Peters et al. (2002) reported 81 specific combinations of anaerobic bacteria in the root canal. Microbial associations between species were determined by computing the odds ratio of detecting one species in the presence of another species. Changes in the physical and chemical environment may contribute to the population shifts of the flora, the development of clinical signs and symptoms, or to apical bone destruction. Aseptic methodology, experimental controls, use of single operator and bacteriological sampling with an aseptic techniques enhanced the rigour of the study and therefore the validity of the results.
The dynamic role of the microbial flora to clinical symptoms in various types of root
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Postoperative pain canal infections have also been studied by various authors. Yoshida et al. (1987) found that all patients who had percussion pain had positive cultures and that anaerobes predominated in these cultures i.e. in 78%. Bacteroides species were commonly found in clinically acute cases and the results suggested that lack of clinical symptoms related to low bacterial growth in the root canal and periapical region. In asymptomatic cases only
7 out of 12 cases, exhibited positive cultures (58%). However, as only 36 cases were included, further studies should be undertaken to validate the findings. Symptoms such as pain, swelling, sinus tract formation and foul odour were also found to be associated with the presence of anaerobes in the study by Gomes et al. (1996).
Siren et al. (1997) investigated the relationship between bacteriological findings and root canal treatment procedures. Bacteriological samples were received from general practitioners across Finland and diagnosed at the laboratory of Helsinki University.
Though the reliability of retrospective collected information must be regarded with caution, the strength of the study was the high level of a sepsis maintained throughout the treatment. In addition, the questionnaire return rate was high thus improving the validity of the results. Enteric bacteria were associated with 55 % of the teeth that were open to the oral environment, those that had increased number of appointments and in retreatment cases. It also important to note that the Enterococci have been shown to be the most difficult organism to eradicate from the infected root canals and have been implicated in persistent root canal infections with pain and retreatment (Molander et al.1998, Sundqvist et al. 1998). This may help explain why well-treated cases may yet show resistance to endodontic therapy with persistence of apical periodontitis (Siqueira
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& Lopes 1999).
1.4.7 METHODS FOR ASSESSMENT OF THE POST-OBTURATION PAIN
Pain in a tooth site of neurogenic origin has been reported in the literature (Marbach et al.1982, Campbell et al.1990). In addition epidemiological studies (Marbach et al.1982,
Berge 2002) have investigated the prevalence of chronic neuropathic pain after dental treatment.
The study by Marbach et al. (1982) was conducted by a single endodontist who mailed questionnaires to patients one month following nonsurgical endodontic treatment. Only female patients were included in their analyses because the male sample was considered too small. Of the 256 female patients assessed, twenty (9%) reported persistent pain during the period of the survey but only eleven female patients attended for clinical and radiographic examination to exclude an odontogenic cause of pain. Of the eleven patients, eight (3% of 256 female patients) were diagnosed with ‘phantom toothache’.
Campbell et al. (1990) undertook a similar survey of patients who had undergone surgical endodontic treatment two years previously and found that 59 (5%) of the 118 patients suffered from chronic pain that divided equally into two groups namely post- traumatic stress dysaesthesia (absence of pain preoperatively) (PTD) and phantom tooth pain (PTP) (presence of pain preoperatively). In contrast, Berge (2002) found none of the 1035 patients in their survey suffered from chronic neuropathic pain following surgical removal of third molar teeth 5–6 years previously.
A recent study by Polycarpou et al. (2005) aimed to determine the prevalence of
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Postoperative pain persistent pain following endodontic treatment, and (ii) to evaluate the association between the prevalence of persistent pain after ‘successful’ endodontic treatment and potential risk factors. They concluded that the presence and duration of preoperative pain from the tooth site (lasting at least three months), a positive history of previous chronic pain experience or painful treatment in the orofacial region and female gender were important risk factors associated with persistent pain after successful endodontic treatment.
The visual analogue scale (VAS) is considered to be a valid and reliable ratio scale for measurement of pain (Bodian et al. 2001, Direnzo et al. 2002, Ng et al. 2004). The severity of pain is recorded on a visual analogue scale of 0-5 or 0-10 or 0-100. The
McGill pain questionnaire (Melzack 1975) and the graded chronic pain scale (Von Korff et al. 1992) have also been used.
Siqueira et al. (2002) undertook a prospective study to evaluate the incidence of postoperative pain after root canal procedures based on an antimicrobial strategy. The root canal procedures used in this study to control root canal infections showed a small incidence of postoperative pain, particularly flare-ups, even when treatment was performed by inexperienced undergraduate dental students. There was also no difference regarding the incidence of postoperative pain between treatment and retreatment.
Ehrmann et al. (2003) investigated the relationship of postoperative pain to three different medicaments placed in the root canal after a complete biomechanical debridement of the root canal system in patients presenting for emergency relief of pain in a prospective randomized clinical trial using a visual pain analogue scale (0 -100).
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Painful teeth with acute apical periodontitis that had been dressed with Ledermix paste a mixture of corticosteroid and antibiotics gave rise to less pain than that experienced by patients who had adressing of calcium hydroxide or no dressing at all.
Al-Negrish and Habahbeh (2006) claimed that there was no statistically significant difference in flare up rate in asymptomatic endodontically treated non vital maxillary central incisors between single and two appointment endodontic procedures and between a 2 and 7 days postobturation period. The rate of postobturation flare up in asymptomatic endodontically treated non-vital maxillary central incisors was 11.6% and
3.6% after 2 and 7 days respectively.
Oliet (1983) showed no significant difference in postoperative pain and healing when comparing single-visit root canal treatment (RCT) versus multiple visit endodontic procedures when proper diagnosis, case selection and skilled treatment were performed.
A study by Soltanoff (1978) yielded similar results in regards to postoperative pain and healing. In addition, Fava (1991) observed no significant difference in the incidence of postoperative pain between non-vital teeth treated in one or two visits. However, in other studies the rates of endodontic flare-ups were reported to be more following multiple visits than for single visits (Imura & Zuolo 1995, Eleazer & Eleazer 1998). Albashaireh
& Alnegrish (1998) reported that the pain was significantly higher in the multiple-visit
RCT group and significantly associated with the treatment of the non-vital pulp.
Fox et al. (1970) reported that 90% of single visit treatments produced little or no spontaneous pain while only 1% of patient has experienced slight pain over a one-week follow up period. Oginni & Udoye (2004) reported higher incidences of post-obturation
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Postoperative pain pain and flare-ups following the single visit procedures. However, single visit endodontic therapy has been shown to be a safe and effective alternative to multiple visit treatment, especially in communities where patients default after the first appointment at which pain is relieved.
1.4.8 EFFICACY OF VARIOUS TREATMENT PROTOCOLS FOR ENDODONTIC PAIN 1.4.8.1 EFFICACY OF INTRA-CANAL MEDICAMENT
One major controversy in root canal treatment is whether a thorough debridement of the necrotic tissue, bacteria and inflammatory products in the canal is sufficient for relieving pain and swelling, or whether intra-canal medicaments and irrigant or the use of antibiotics and steroids are necessary to achieve the desired alleviation of symptoms.
The use of root canal medicaments as an adjunct to controlling bacterial contamination between appointments has been a routine practice and said to control infection and reduce inter-appointment pain (Sj gren et al. 1991, Siqueira et al. 2002).
Although an antibacterial intra-canal medicament would be the treatment of choice method of removing the residual bacteria that cause inflammation and resultant endodontic pain, many of these medicaments have been shown to be irritant and highly toxic.
The need for intra-canal medicaments and their effectiveness in achieving total sterility have been questioned in several papers (Massilomani et al. 1981).
Harrison et al. (1981) conducted a clinical experimental study to determine the incidence and degree of inter-appointment pain associated with the combined use of intra-canal
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Postoperative pain medicaments that have a potential for toxicity. Formocresol and camphorated parachlorophenol (CPC) were tested against water, which formed the control.Out of the
245 cases treated 17.6% had slight pain and 5.7% needed palliative treatment. Statistical analysis showed no significant relationship between the incidence or degree of inter- appointment pain and the combination of chemical agents used in the study.
Several in-vitro studies have also been conducted to study the antibacterial effects of intra-canal medicaments. For example, Ohara et al. (1993) studied the antibacterial effects of some commonly used medicaments against six selected anaerobic bacteria often found in infected root canals. They tested the vapours of formocresol, cresatin, iodine potassium iodide, camphorated parachlorophenol, eugenol and glutaraldehyde experimentally using agar plates streaked with bacteria. Formocresol was found to be superior in its antimicrobial effect compared to other medicaments.
It is however, difficult to draw conclusions based on these in-vitro studies with isolated bacteria as the effect of direct contact of medicaments may differ from in vivo studies
(Niom 1988) and many are subject to other variables such as the immunological component from the host environment (Seltzer & Naidorf 1985). In addition, what is effective against an organism in an in vitro study may not be effective against a mixed infection or when used in vivo. The shorter duration of action also negates the rationale for their use in prevention of bacterial growth and re-infection from coronal or apical regions. Hence, the introduction and use of filling materials that carry risks such as diffusion of vapours into the periapical tissues must therefore be avoided as long as their alleged benefits are unsubstantiated as shown in the studies by Messer et al. (1994).
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1.4.8.2 ROLE OF CALCIUM HYDROXIDE
To investigate the antibacterial activity of calcium hydroxide, Sj gren et al. (1991) evaluated its effectiveness when used as an intra-canal medicament for 10 minutes and for 7 days. Bacteria were initially present in all 30 single rooted teeth. Following root canal instrumentation, ultrasonic filing and irrigation, bacteria were present in 15 of the
30 canals. Enterococcus Faecalis was the facultative anaerobic bacteria isolated in this study. There was a significant reduction in the media regarding number of bacterial cells when calcium hydroxide dressing was in place for 7 days versus 10 minutes.
However, in the study by Sundqvist et al. (1998), enterococci like Enterococcus
Faecalis appeared to be highly resistant to medicaments used during treatment including calcium hydroxide. Enterococcus Faecalis was isolated in 38 % of teeth with failed endodontic treatment.
Other studies like Peters et al. (2002) compared single-visit root canal treatments without the use of intra-canal medicaments with two-visit treatment using intracanal medicaments. The hypothesis for single visit root canal treatment was that instrumentation and irrigation alone decreased the number of bacteria in the canal. The low number of bacteria left in the canal is claimed to be below the threshold to sustain the inflammation periapically and are killed due to lack of space and nutrition after effective obturation of the canals (Peters et al. 1995).
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However, in a study by Sj gren et al. (1997) using strict anaerobic techniques to assess the influence of infection at the time of root filling on the outcome of endodontic treatment of teeth with apical periodontitis, it was found that the presence of infection at the time of obturation significantly reduced the success rate. Single- visit root canal treatment was completed in 55 single rooted teeth and followed up annually for up to 5 years. It was found that complete periapical healing occurred in 94 % of cases that yielded a negative culture prior to root filling whereas the success rate of treatment was just 68% when the culture was positive prior to root filling. This study indicated that elimination of bacteria from infected root canals resulted in a higher success rate.
However, clinically it is impossible to predict which 32 % of teeth treated using a single visit approach would result in failure as bacterial culture is not practiced in most dental clinics.
Weiger et al. (1998) in their studies advocated the use of calcium hydroxide as an intra- canal medicament to control bacterial infection and to prevent its associated symptoms of pain and swelling.
1.4.8.3 ROLE OF INTRA-CANAL IRRIGANT
As is clear from the previous studies, microbial persistence in the root canal system has been determined as one of the most important causes of endodontic failure and flare-up resulting in severe pain or swelling. Studies have shown the existence of bio-film, smear layer and bacterial organism’s presence in the apical third of the dentinal tubules (Nair et
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Postoperative pain al. 1987 and Tronstad et al. 1990).
Since calcium hydroxide has a questionable role in removal of all bacteria from the dentinal tubules and especially bacteria that are present in the apical third of the dentinal tubules, treatment strategies should ideally be directed towards medicaments that penetrate the dentinal tubules and eliminate the infection and associated pain or swelling
(Siqueira & Lopes 1999).
The rationale for the use of an irrigant especially in non-vital teeth is to allow for their effect on the bacteria inside the dentinal tubules that are protected from the host defense cells, chemico-mechanical preparation and systemically administered drugs.
Current techniques in the root canal treatment support the preparation of the access of the root canal with a flare, thus allowing the irrigant to reach the apex (Reddy & Hicks
1998).
Sodium hypochlorite (NaOCl) is the most widely accepted and used irrigant in root canal treatment (Trepagnier et al. 1977). There is however controversy regarding its effective antibacterial concentration and its role in removal of smear layer. For example
D’Arcangelo et al. (1999) in an in-vitro study compared the antimicrobial effect of
NaOCl in various concentration to new generation irrigants like chlorhexidine (CHX) and cetrimide on the microorganisms frequently found in the canal i.e., obligate anaerobes, facultative aerobes, anaerobes and microarophiles. Contact time was 10, 20 or 30 minutes. All irrigants had a strong bacteriocidal effect on the tested strains.
Trepagnier et al. (1977) in a quantitative study showed NaOCl to be a powerful tissue solvent in a concentration of either 2.5% or 0.5% concentrations as an in-vitro
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The effective concentration of NaOCl for dissolving the necrotic tissue is also controversial. Lower concentrations of NaOCl appear to be effective when combined with a pre-treatment using calcium hydroxide and ultrasonic irrigation.
Turkun et al. (1997) conducted an in-vitro study with 40 extracted single rooted teeth and evaluated the efficacy of calcium hydroxide pre-treatment as an intra-canal medicament for 24 hours in 1 group and for 7 days in another group. A scanning electron microscope was used for a detailed evaluation of the cleanliness of the root canal. This increased the rigour of the study as histological evaluation enabled detection of organic tissue remnants. The studies found that the pre-treatment of the root canal for
24 hours enhanced the tissue dissolving and cleansing efficacy of 0.5 % NaOCl irrigating solution using an ultrasonic method. The effect was comparable to that of 5 % sodium hypochlorite, which has been shown to be toxic in several studies (Tanomaru
Filho et al. 2002).
Currently the debate is whether the smear layer should be removed to allow effective penetration of sodium hypochlorite into the resultant patent dentinal tubules to reach the bacteria present within. Smear layer removal is also believed to allow closer adaptation of the root canal filling materials to the dentinal wall. The combination of sodium hypochlorite and EDTA as intra-canal irrigants has become standard practice and an important supplement to the biomechanical preparation of the root canal. The antibacterial and necrotic tissue dissolving property of sodium hypochlorite together with its effect on the smear layer when combined with EDTA, aids in removing both the
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The aim is to create a cleaner dentinal surface allowing closer adaptation of root filling material and reducing the number and ingress of bacteria thus preventing the occurrence of flare-ups leading to severe pain and or swelling (Goldberg & Abramovich 1977,
Behrend et al. 1996).
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1.5.1 INTRODUCTION
The objective of root canal treatment is to clean and shape the canal system to eliminate necrotic material, microorganisms and canal irregularities and to facilitate the placement of a permanent root filling (Schilder1974). The ideal preparation for a root canal is a continuously tapered funnel shape with the smallest diameter at the apex and the widest diameter at the canal orifice (Schilder & Yee 1984). The shape can be achieved either by hand or by mechanical preparation and is readily produced in straight canals. However, cleaning and shaping of narrow and curved canals with stainless steel instruments can be difficult and may not provide the optimal shape (Weine et al. 1975).
Many reports have described the tendency of root canal preparation techniques to cause canal transportation and other procedural problems such as ledge formation, apical perforation and mid-root perforation. These complications may compromise the long- term success of treatment by failing to eliminate infection of the root canal system and making obturation more difficult (Weine et al. 1975, El-Deeb & Boraas 1985, Al-Omari et al. 1992 a, b).
Traditionally, the hand instruments used in root canal shaping have been made of stainless steel, but these instruments lack flexibility particularly in the larger size and can sometimes lead to technical errors (Serene et al. 1995) resulting in a decreased success rate of endodontic treatment. These errors may be in part be due to the nature and limitations of stainless steel instruments. It is perhaps surprising that little
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Various instrumentation techniques and endodontic instruments have been introduced in an attempt to reduce these problems and aim at providing the optimum shaped root canal preparation. The unique properties of nickel-titanium alloy, such as flexibility, have allowed the development of nickel titanium endodontic instruments in order to overcome the limitations of stainless steel alloy instruments (Walia et al. 1988).
Rotary nickel-titanium instruments have been shown to prepare the root canal rapidly and maintain the canal shape and working length with few aberrations during root canal preparation (Thompson & Dummer 1997a,b,c,d,e,f, 1998 a,b,c,d, 2000 a,b, Bryant et al.
1998 a,b).
Numerous studies have shown the ability of several new rotary nickel-titanium instruments to maintain the original canal curvature and to produce a well-tapered root canal form adequate for obturation (Song et al. 2004). The instruments are available in various designs that differ in tip and taper design, rake angles, helical angles, pitch and presence of radial lands. Many new systems are on the market (Table 1.5.1).
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TABLE 1-5-1 OVERVIEW OF DIFFERENT EXISTING NITI ROTARY SYSTEMS
GT Rotary Files
Hero 642
K3
Lightspeed
Mc XIM / NT files
Mity Roto 360º
Naviflex
Profile
ProTaper
Quantec
1.5.2 THE USE OF NITI IN ENDODONTIC TREATMENT
Civjan et al. (1975) was the first to suggest the use of NiTi in endodontic treatment. The research group felt that the characteristic of 60 Nitinol would be suitable for the manufacture of tough, non-dulling, corrosion resistant hand or rotary cutting instruments. The uses of larger diameter handles were advocated if flexibility of the file itself was thought to be a problem. The corrosion resistance of the material also suggested its use for the manufacture of root canal points.
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1.5.3 SUMMARY OF NICKEL- TITANIUM ALLOY
Nickel-titanium appears to be the material currently in vogue for the construction of root canal instruments. They have the complimentary characteristic of super-elasticity and flexibility and claim to be able to shape the root canals with any degree of curvature.
The composition of the NiTi alloy itself and the manufacturing process used in the construction of endodontic instruments appears to be critical in order for the desired characteristics of these instruments to be achieved. Clearly, other factors are involved such as instrument design which compound the influences of the alloy itself with other factors such as cross-sectional shape and blade angle. These make it difficult to ascertain the advantages and disadvantages over one system of instruments over another.
NiTi alloys appear to be as biocompatible as stainless steel probably due to the presence of a TiO2 coating. NiTi can be autoclaved without a significant release of metal ions.
Indeed an increase in the TiO2 layer as a result of autoclaving improves the surface hardness and corrosion resistance of the alloy.
Potential problems could be associated with the use of nickel-titanium alloys as nickel ions are thought to be toxic to humans. About 10 % of females are sensitised to nickel generally due to the wearing of jewellery or metal on clothing (Burrows 1986).
Moffa et al. (1983) in a retrospective study found that there was a highly significant difference between males and females in relation to nickel. They reported a 4.8 times relative risk of nickel sensitivity in females between the ages 25-44 than in other age groups with a positive correlation with pierced ears. For all age groups, sensitivity to
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Nickel-Titanium alloys chromium was 4.1% in females and 1.5% in males. There was no correlation between the incidence of sensitivity to either nickel or chromium and the presence of dental prostheses containing these metals.
The corrosion resistance of root canal instruments could be improved by mechanically polishing the surface, thereby decreasing the potential release of Ni ions.
The range of application for nickel- titanium alloys is expanding rapidly. It appears that its shape memory or super elasticity effects can be utilised for different applications. one of the greatest developments in a commercial sense for the use of Nitinol was the introduction of hydraulic pipe couplings for use in military aircraft and ships (Duerig
1990). NiTi orthodontic wires take advantage of the shape memory effects that imparts a constancy of stress to the dental arch.
1.5.2 CANAL PREPARATION WITH ROTARY AND HAND NICKEL-TITANIUM
Esposito and Cunningham (1995) attributed the difficulty, which they experienced in instrumenting the smaller NiTi rotary instruments to working length (without exceeding the recommended apical pressures) to the less aggressive flute design in these instruments up to size 35. However, full working length could be reached with the more aggressively designed size 40 NiTi rotary file. Due to the flexibility of nickel- titanium instruments, it appeared that the degree to which anticurvature filing and flaring could be accomplished was greatly reduced.
Zakariasen et al. (1996a) compared the shapes of canals prepared by hand filing with a step-back technique using Hedstrom files alone, Hedstrom along with Rispisonic files in a sonic air 1500 headpiece and with radical taper. They assessed apical transportation,
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Significantly, more ledging were created using Hedstrom and Rispisonic filing than with the other groups, although the ledging was not severe. All of the other preparation techniques were successful in producing satisfactory canal shapes.
Kavanagh & Lumley (1998) evaluated canal preparation of 30 maxillary molars using either rotary NiTi profile .04 Taper series 29 instruments, Profile .04 and .06 Taper with orifice openers or Profile hand instrumentation with .02 Taper and Gates Glidden drills.
There was no significant difference between the techniques for canal transportation in any region. They felt that the canal shape was improved using increased taper files.
Schäfer & Lau (1999) investigated the cutting efficiency and the effects of instrumentation on curved canal shape of both stainless-steel and nickel- titanium non- standardized profile series 29 hand instruments and stainless-steel flexoreamear. It seemed that flexible stainless-steel instruments with no cutting tips were superior to the nonstandardized profile series 29 instruments with regard to cutting efficiency and instrumentation of curved canals.
Bramante & Betti (2000) reported that the Ni-Ti instruments used with EDTA were less effective in maintaining the original path of curved canals.
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Peters et al. (2001) compared the effects of four preparation techniques (Ni-Ti K-files,
Light-speed instruments, Profile.04 and GT rotary instruments) on canal volume and surface area using three-dimensionally reconstructed root canals in extracted human maxillary molars. In addition µCT data was used to describe morphometric parameters related to the four preparation techniques. There were few differences between the four- canal instrumentation techniques used due to limitations of the µCT system.
Pettiette et al. (2001) reported that the Nickel-titanium 0.02 hand files maintained the original canal shape better than similar stainless-steel K-files (SS-K) thus indicating that maintaining the original canal shape after instrumentation leads to a better prognosis of endodontic treatment.
Szep et al. (2001) investigated the efficacy and safety of six different NiTi engine-driven instruments used in a torque-controlled engine device and nickel-titanium hand and stainless steel hand instruments in preparation of curved canals. All instruments tested tended to straighten the original canal curvature. The shortest instrumentation time and the best-tapered form of the canal in the middle part of the curvature was achieved using
ProFile.04 and prototype d instruments. A large number of instruments fractured, particularly in the case of prototypes and a 2, but not with hand instrumentation.
Peters et al. (2003) investigated the physical parameters for ProTaper NiTi rotary instruments whilst preparing curved canals in maxillary molars in vitro. No fracture of
ProTaper occurred when a glide path was present. Nevertheless, there was a significant positive correlations between canal geometry and physical parameters during shaping.
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Inexperienced operators achieved better canal preparations with rotary Ni-Ti instruments than with manual stainless steel files. However, rotary preparation was associated with significantly more fractures (Sonntag et al. 2003).
Song et al. (2004) reported that the GT hand files and NiTi flex files remained better centered and produced significantly less transportation in curved canals than SS K-files.
Comparison of hand stainless steel and nickel titanium rotary instrumentation (NiTi Flex
Master files (VDW, Munich,Germany) indicated that the original curvature was significantly better maintained with automated FlexMaster files than with hand instruments (Schäfer et al. 2004).
Some authors have attempted to evaluate the number of bacteria extruded apically from extracted teeth ex vivo after canal instrumentation using the two engine-driven techniques utilizing nickel-titanium instruments (ProTaper and System GT). There was no significant difference in the number of extruded bacteria between the ProTaper and
System GT engine-driven systems (P > 0.05) (Er et al. 2005).
Guelzow et al. (2005) compared ex vivo various parameters of root canal preparation using a manual technique and six different rotary nickel–titanium (Ni–Ti) instruments
(FlexMaster, System GT, HERO 642, K3, ProTaper, and RaCe). All Ni–Ti systems maintained the canal curvature, were associated with fewer instrument fractures, and were more rapid than a standardized manual technique. Instrument fractures occurred with ProTaper in three root canals, whilst preparation with System GT, HERO 642, K3 and the manual technique resulted in only one fracture each.
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ProTaper instruments created more regular canal diameters. Whilst Ni–Ti instruments prepared canals more rapidly than the manual technique, the shortest time for instrumentation was achieved with System GT.
Bürklein & Schäfer (2006) compared the shaping ability of Mtwo rotary nickel-titanium instruments in simulated curved canals and in curved canals of extracted teeth when set into permanent rotation with two different torque-limited automated devices. Both systems respected original root canal curvature well and were safe, indicating that the
Mtwo direct handpiece is suitable for preparing curved root canals with the Mtwo instruments.
Jodway & Hülsmann (2006) evaluated and compared several parameters of curved root canal preparation using two different Ni-Ti systems: NiTi-TEE (Sjo¨ding Sendoline,
Kista, Sweden) and K3 (Sybron Endo, Orange County, CA, USA). Fifty extracted mandibular molars with mesial root canal curvatures ranging from 20 to 40 degree were divided into two groups. In one group, 50 root canals were instrumented using NiTi-TEE files to an apical size 30; 0.04 taper, in the other group, 50 root canals were prepared with K3 instruments to an apical size 45; 02 taper. Both systems used a crown down manner, with copious NaOCl (3%) irrigation and a chelating agent (Calcinase Slide, lege artis, Dettenhausen, Germany), employing torque-controlled motors
Both systems maintained original canal curvature well and were safe to use. Whilst debridement of canals was considered satisfactory, both systems failed to remove the smear layer sufficiently. For smear layer, NiTi-TEE and K3 only received good scores (I
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Nickel-Titanium alloys and II) in 38.7% and 40% of canal wall specimens, respectively. For both parameters, no significant differences were found between groups.
File fractures did not occur, but loss of working length was observed in one case following the preparation with NiTi-TEE and in three cases during K3 instrumentation.
Yang et al. (2006) compared the shaping ability of progressive versus constant taper shaft designed instruments in simulated root canals. Simulated L- and S-shaped resin canals were prepared by ProTaper (progressive taper) and high elasticity in rotation 642
(Hero 642) (constant taper) instruments (n ¼ 10 canals in each case).
ProTaper and Hero 642 instruments prepared curved canals rapidly, maintained working length well and were relatively safe without creating perforations and danger zones. In both canal types, Hero 642 instruments maintained the original canal curvature better, and had a better centering ability in curved canals because of its constant taper design.
The taper prepared by Hero 642 instruments in the coronal part of the canal was generally poor. The K3 file (SybronEndo, West Collins, CA, USA) is a rotary instrument with a radial land relief in combination with a positive rake angle, a flattened noncutting tip and an asymmetrical constant tapered active file design with variable helical flute angle and variable core diameter (Bergmans et al. 2003).
These features are claimed to enhance cutting- efficiency, debris removal and file guidance and strength.
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Ayar & Love (2004) compared the shaping ability of Profile and K3 rotary Ni-Ti instruments when used in a variable tip sequence in simulated curved root canals with different curvature and radius. Both rotary nickel-titanium instruments prepared well- shaped root canals with minimal canal transportation.
Ankrum et al. (2004) reported that there was no significant difference between the tapered rotary nickel-titanium systems (ProTaper, Profile and K3). However, with regards to instrument breakage there were significantly more distorted files in the Profile group when compared with the ProTaper group.
Yoshimine et al. (2005) reported that the nickel-titanium file system including less tapered, more flexible instruments, like K3 and Race should be used in the apical preparation of canals with a complicated curvature
Troian et al. (2006) evaluated, by scanning electron microscopy, the deformation and fracture of NiTi RaCe and K3 size25, 0.04 taper instruments. A significant difference was found between the two systems in deformation and fracture of size 25, 0.04 taper instruments. Overall, K3 instruments had more favourable results than RaCe instruments.
Deformation and fracture was not observed for the K3 size 25, 0.04 taper instruments and wear was not obvious after five uses. Simulated canals with smaller curvature radius led to more fractures of RaCe instruments.
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1.5.3 CANAL PREPARATION METHODS 1.5.3.1 INTRODUCTION
One of the aims of root canal preparation is to achieve a progressively and uniformly conical shape within the canal. However, this may not always be possible in canals that do not have a circular morphology. One of the greatest concerns of the endodontist is the cleaning, shaping and disinfection of the root canal. According to Schilder (1974), this leads to a tapered conical form from the crown to the apex, simulating the original root canal and permitting complete filling of the root canal system.
Complications such as transportation, blockage, ledge formation and root perforation become more frequent and consequential. Many techniques have been introduced in an attempt to reduce the creation of these complications. Molven (1970) concluded that the ability to shape dentine is not only dependent upon the technique of operation but also on the design of the instrument. Roane et al. (1985) proposed the use of a K-type file with a file with a triangular cross-section and a modified tip. They concluded that a file with a triangular cross-section had increased flexibility because of decreased cross- sectional area and that a modified tip produced less transportation and ledging of the canal.
Ciucchi et al. (1990) reported that the use of modified instruments eliminated ledging and transportation effects often seen with conventional rotating instruments used in curved canals. The use of modified tip instruments prevented apical misadventures and preserved the flow of the preparations in contrast to the undesirable ledging and gouging that are frequently observed when using conventional tipped instruments.
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1.5.3.2 STANDARDIZED PREPARATION
This is classic technique investigated by Ingle (1961). The desired result is the creation of a preparation that has the same size, shape and taper as achieved by standardized instruments. This technique is difficult even in an ideal anatomical situation and almost impossible in curved canals (Haga 1968, Schneider 1971).
1.5.3.3 FLARING TECHNIQUES
This is a tapered preparation, using a step-back or crown-down technique or a combination of the two.
• Clem (1969) first described step-back (also known as flaring or serial
preparation). This technique creates a smoother flow and a more tapered
preparation from an apical to coronal direction. The step-back technique is
superior over the standardized preparation techniques and the step-back
technique with stainless steel instruments is widely taught and used (Bolanos &
Jensen 1980, Cailleteau & Mullaney 1997).
• Goerig et al. (1982) described a step-down (also known as crown-down)
radicular access. The objective of this techniques is to keep the apical preparation
as small as practical (but well debrided) with an increasing taper throughout the
canal. In addition, the final apical preparation should be at or close to the original
canal position.
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Advantage of the crown-down techniques:
1) The vast majority of microorganisms and pulpal tissues are removed
early during cleaning and shaping, thereby reducing the potential for
extruding material into the periapical area.
2) Instruments pass unhindered into the apical area once the coronal two-
thirds are enlarged. Apical shaping is completed quickly and efficiently.
3) The methodology allows for better penetration of the irrigant.
4) It’s a biologically ideal shaping method because of its control over the
movement of contents.
However, the technique seems aggressive because larger instruments are used before smaller ones. All instruments must have the ability to follow curvature and not form undesirable outcomes like transportation, ledges and blockages.
Roane (1998) proposed combining the crown-down technique with a file possessing tip guidance as one of its features. He reported that aberrations in canal shape after instrumentation were significantly reduced and instrument breakage was minimized by this combination. He deduced that shaping is accomplished primarily with the tip of each instrument and lighter loads are produced on the files.
Although irrigation is improved using the crown-down techniques, larger apical preparations allowed adequate mechanical and chemical debridement of the canal. Haga
(1968) demonstrated that for mesial canals of mandibular molars, a number 50 ISO size is required for complete debridement.
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Sabala & Biggs (1991) advocated a designed preparation that enlarges molar canals to size 45, 1mm short of the foramen. However, Kerekess & Tronstad (1977) suggested that at a level of 1 mm from the root apex, instrument sizes required to achieve a circular shape range between file size 30 and 60 for various buccal and mesial canals of maxillary and mandibular molars.
Dulaimi & Al-Hashimi (2005) compared the influence of various root canal preparation techniques on spreader penetration depth and load required during lateral condensation with gutta-percha and sealer. They concluded that the step-back canal preparation technique with Gates-Glidden drills was associated with the least difference between initial spreader penetration and the working length and was not significantly different to the hybrid technique.
The crown-down pressureless canal preparation technique was associated with the greatest difference between the initial spreader penetration and the working length.
However, it was not significantly different when compared with the step-back without the use of Gates-Glidden burs.
• Crown-Down
The ‘crown-down pressureless’ techniques (Morgan & Montgomery 1984) and the step- down technique (Goerig et al. 1982) are modifications of the step-back technique.
Crown-down, step-down, and step-back procedures produce a similar outcome, resulting in a flaring preparation with small apical enlargement. Like the step-back, these techniques are particularly useful in fine curved canals of maxillary and mandibular molars. Advocates propose that the canals will be somewhat debrided before the
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• Passive Step-Back
The passive step-back technique uses a combination of hand instruments (files) and flare before apical root canal preparation.
The passive step-back technique provides an unforceful and gradual enlargement of canals in an apical-coronal direction. In addition it is applicable to every root canal type, is easy to master, reduces procedural accidents and is convenient for both operator and patient.
The crown down or step down technique with rotary instruments is advocated by the manufacturers for the shaping of canals with rotary NiTi files. The main disadvantage of this recommendation is the possibility of instrument separation. To reduce the frequency of this procedural accident, coronal flaring as recommended for the passive step-back technique used before rotary instruments is used to shape the apical portion of the canal.
This flaring enhances irrigation of the apical third and helps removes irritants. In addition, the use of this technique before the use of rotary instruments creates straighter line access to the apical canal and less transportation during apical preparation with rotary instruments (Torabinejad 1994). This procedure reduces the chances for instrument separation, packing debris, ledging, straightening the apical portion of the canal and root perforation.
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• Balanced forces
The balanced forces use an altered instrument design (Roane 1985). The files used have a modified tip that is noncutting. Canal preparation involves counterclockwise rotation combined with apical pressure. These techniques cause less transportation (Sepic et al.
1989, Charles & Charles 1998).
1.5.4 WORKING LENGTH DETERMINATION
The apical limit of root canal instrumentation is still a very controversial topic in endodontics (Cailleteau & Mullaney 1997, Negishi et al. 2005). The possibility of damage to apical and periapical tissues has supported the principle of the working length staying short of the radiographic apex (Ricucci 1998, Schaeffer et al. 2005, Holland et al. 2005). Although some authors still advocate that it is possible to establish, by tactile sensibility, the CDJ (cementodentinal junction) limit as the ideal point where root canal preparation should end, it has been demonstrated that this procedure leads to several errors (Vanni et al. 2005). Different working lengths have been proposed, but the most widely accepted approach seems to be choosing a working length of 1 mm coronal to the root apex.
Currently, the role of microorganisms in pulpal and periapical diseases is well known, and anaerobic bacteria are recognized as important pathogens. Despite the divergences concerning their percentage, the predominance of anaerobic microorganisms in the apical third is a common trait in most studies (Baumgartner & Falkler 1991, Wayman et al. 1992). This understanding has brought about important changes for endodontic therapy. This means that, in many cases, the endodontic treatment should not be limited
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Although there is a recent trend to accept this approach in some cases of teeth with periapical lesions, in fact the apical limit of instrumentation in teeth with necrotic and vital pulps is still a source of discussion and controversy in endodontics.
In cases of periapical lesions, recognizing the presence of microorganisms in the cemental canal (Baumgartner & Falkler 1991) and even in the lesion itself (Wayman et al. 1992), has contributed to spread the acceptance of cleaning and debridement of the apical foramen during root canal instrumentation. Nevertheless, the possible existence of a vital pulp stump in cases of a necrotic pulp without a periapical lesion has precluded the full acceptation of these procedures by endodontists and researchers.
On the other hand, the major concern during root canal therapy of teeth with vital pulp has been to preserve the vitality of the pulp. For this reason, several authors have recommended that the working length should be determined 1-2 mm short of the radiographic root apex (Ricucci & Langeland 1998, Ricucci 1998).
1.5.4.1 METHODS OF CANAL LENGTH DETERMINATION
In endodontic treatment, the determination of the working length comprises one of the most critical steps and is still difficult to achieve under clinical circumstances (Inoue &
Skinner 1985).
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1.5.4.1.1 RADIOGRAPHIC TECHNIQUE
Radiography is the traditional method of obtaining information on the anatomy of the root canal and its surrounding tissue (Forsberg 1987).The exact determination is achieved using hand instruments and the subsequent translation with the assistance of gauges (Katz et al. 1991). However, radiography is sensitive both in its exposure and in interpretation. Goldman et al. (1972) examined 253 cases and found agreement among observers in less than half the cases with the most disagreement being found in maxillary molars.
A single radiograph is but a two-dimensional shadow of a three-dimensional object. For maximum information, the third dimension must be visualized and interpreted (Walton
1973). Distance from a reference point to the radiographic apex is determined precisely.
This establishes the distance from the apex at which the canal is to be prepared and obturated (Stein & Corcoran 1992).
As a result of the hazards of radiation (Katz et al. 1991, Pendlebury et al. 2004), the technical problems associated with radiographic techniques (Heling & Karmon 1976,
Forsberg 1987a) and the need to avoid over-instrumentation beyond the canal terminus
(ElAyouti et al. 2002). Electronic root canal length measuring devices were advocated.
These have been widely studied in-vitro using different mediums, such as agar, gelatin, or alginate (Aurelio et al. 1983, Donnelly 1993, Tinaz et al. 2002), and in the presence of various canal fluids (Weiger et al.1999). In a study by Huang (1987), it was concluded that the principle of electronic root canal measurement is purely a physical
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Nickel-Titanium alloys phenomenon. When the electrode passes through the narrow apical foramen, the foramen produces a significant electrical resistant gradient that is constant except when the canal is filled with electrolytes or the apical foramen is too large.
1.5.4.1.2 ELECTRONIC APEX LOCATORS
Electronic apex locators (EALs) reduce the number of radiographs required, and are recommended to complement and assist radiographic methods of working length determination. Moreover, they can indicate cases where the apical foramen is some distance from the radiographic apex and might be helpful in detecting root canal perforations (Gordon & Chandler 2004). In 1962, Sunada developed the first apex locator (first-generation apex locators) based on the assumption that there is a constant resistance of 6.5 kU at a defined current (amperage) between the periodontal membrane and oral mucosa. The device worked with direct current. The apex was located as soon as the resistance determined with a probe (hand instrument) corresponded to the device’s integrated resistance of 6.5 kU (Huang 1987). The apical constriction was determined from the difference between the two reading (Pilot & Pitts 1997).
Kobayashi & Suda (1994) improved this idea of relative impedance measurement and introduced the ‘ratio method’ in 1991, creating an impedance quotient instead of a difference. The description of this principle initiated the development of the latest endometric devices.
160
Literature Review 1.5
Nickel-Titanium alloys
The third generation was similar to the second, but it used multiple frequencies to determine distance from the end of the canal. This provided even more information that could be used to compensate automatically for various canal conditions. Research performed on third-generation devices have shown that accurate measurements could be obtained even in the presence of electrolytes with an accuracy of between 85% and 95%
(Frank & Torabinejad 1993, Kobayashi 1995). Modern EALs determine the working length by measuring impedance with different frequencies between the file tip and the canal fluid. The impedance is small at the apical constriction and has a higher value at the major foramen (Hoer & Attin 2004). However, Nguyen et al. (1996) reported that file size did not affect the accuracy of EALs. Lengths measured with size15 instruments, compared with lengths obtained using the size comparable with the diameter of the root canal, were the same as or less than 0.5 mm different (Felippe & Soares 1994).
There was many types of electronic root canal length measurement devices (Table
1.5.2).
161
Literature Review 1.5
Nickel-Titanium alloys
TABLE 1-5-2 CLASSIFICATION OF ELECTRONIC ROOT CANAL LENGTH MEASUREMENT DEVICES
Type Name Manufacturer Resistance-based ERCLMDs Endodontic Meter® Parkell Inc., New York, NY, USA Endometer® Faramatron 4® Apex Finder®
Low frequency oscillation Sono-Explorer® Hayashi Dental Supply, Tokyo, Sono-Explorer Mark II® Japan
High frequency devices (capacitance-based Endocater® Hygenic Corp., Akron, OH, USA devices) Elements™ Diagnostic unit SybronEndo, Orange, CA, USA Capacitance and resistance look-up table No commercial model Voltage gradient (difference in impedance available with three nodes)
Two frequencies, impedance difference Apit® Osada, Tokyo, Japan Apex pointer® MicroMega, Besanc¸on, France Root ZX® J. Morita Co., Kyoto, Japan
Impedance ratio (Quotient) Justy II Parkell Inc., New York, NY, USA Endy 5000 Parkell Inc., New York, NY, USA
Multifrequency Endo Analyzer® (8005) SybronEndo, Orange, CA, USA AFA Apex Finder® (7005) SybronEndo, Orange, CA, USA
Unknown Foramatron® D10
Apex locators are most helpful in placement of the first length determination file.
Without a locator, the working length must be estimated from a preoperative radiograph.
To confirm the accuracy of the apex locators, the file is left at the indicated position and exposed radiographically. When used in conjunction with a radiograph, the locator is a most effective adjunct (Fouad et al. 1990).
The Elements™ Diagnostic Unit is a fourth-generation apex locator. Impedance, in fourth-generation units, is broken down into its primary components (resistance and
162
Literature Review 1.5
Nickel-Titanium alloys capacitance) and measured directly and independently during use. This eliminates erroneous readings from different combinations of these properties that can provide the same impedance reading. In other words, there has to be two combinations of resistance and capacitance giving the same impedance, so that there are two different situations that would give the same feedback and, thus, the same location reading within the canal.
The Elements™ Diagnostic Unit also uses multiple frequencies to compensate for canal conditions and does not make any calculations internally, as in third-generation units.
Instead, all combinations of capacitance and resistance are calculated and loaded into a matrix database within the unit, making the displayed information much more stable.
1.5.4.1.3 TACTILE SENSATION
The experienced clinician develops a keen tactile sense and gains considerable information from the passage of an instrument through the root canal. Once radicular access has removed dentinal interference from the coronal third of a canal, the observant clinician can detect a sudden rise of resistance as a file approaches the apex. The awareness of an apex can be enhanced by use of a file diameter that is equal or slightly larger than the constrictors. But in most instances, this is unreliable (Stabholz et al. 1995). Many apical regions do not in fact have a constriction but even those that do are at variable distances from the apical foramen.
163
Literature Review 1.5
Nickel-Titanium alloys
1.5.4.1.4 PAPER POINT EVALUATION
Once the preparation is complete, a paper point may yield more than a dry canal.
After the canal is rendered dry, an additional paper point may be used to seek out apical moisture or bleeding. A bloody or moist tip suggests an overextended preparation or seepage of fluids into the canal. Moreover, it indicates that the foramen has been passed or the apex perforated during preparation.
1.5.5 SUMMARY
Different techniques has been used and advocated for determining working length, including radiographic (conventional or digital), electronic and tactile methods.
However, none are entirely accurate or infallible (Katz et al. 1991).
Wrbas et al. (2007) verified in an in vivo study that the use of electronic apex locators was a reliable method for determining working length.
Studies by Haffner et al. (2005) recommend the combined application of radiographs and electronic apex locators preferably using the following sequence: (1) radiograph for diagnostic reason (2) electronic root canal length determination and (3) radiography for confirmation of electronically determined working length.
164
AIMS OF THE STUDY
1) To review the literature to identify the main causes of failure of RCT.
2) To assess the quality of first and second root canal fillings performed by
undergraduates.
3) To assess the ability of irrigant solutions to remove the smear layer using an
SEM study.
4) To assess the effect of ozone treatment on microorganisms in root canal systems
and to assess the ability of using ozone to kill a strain of Enterococcus Faecalis
in an in-vitro study.
5) To assess the immediate effect of ozone treatment delivered into NaOCl on
microorganisms in root canal systems in an in-vivo study and compare with
NaOCl and air.
6) To evaluate the postoperative pain experience of subjects having RCT with and
without ozone.
7) To assess the practicalities of delivering ozone into prepared root canals.
8) To asses, radiographic x-rays from baselines in order to determine if the x-rays
still been normal.
9) To assess the effect of the use of ozone into NaOCl on periapical radiolucencies
after 6 months.
165
HYPOTHESIS
The second root canal filling (RCT) performed by undergraduates should be equal to or better than the first root canal filling. Ozone treatment can reduce some possible causes of RCT failure as measured by a reduction in postoperative pain after RCT, reduced microorganisms and reduced E. faecalis after irrigation and more removal of the smear layer. Ozone gas can be easily delivered into root canals and can significantly reduce periapical radiolucencies at 6 months.
166
Introduction 2.1
2.1 QUALITY OF THE FIRST ROOT CANAL TREATMENT PERFORMED BY UNDERGRADUATE STUDENTS.
2.1.1 INTRODUCTION
Radiographs are essential in all phases of endodontic therapy. They contribute to the diagnosis and the various treatment phases and help evaluate the success or failure of treatment. The literature reveals that the paralleling technique in endodontic radiographs is superior to the bisecting angle techniques (Gound et al.1994), its routine use in endodontic practice ranges from 26.3% (Chandler & Koshy 2002) to 41.7% of dentists
(Saunders et al. 1999).
Endodontology is the branch of dental science concerned with the study of the form, function and health of injuries to and diseases of the dental pulp and periradicular region, and their treatment. The aetiology and diagnosis of dental pain and disease are integral parts of endodontic practice.
The scope of the special area of dental practice known as endodontics is defined by the educational requirements for the training of a dentist as described by the European
Society of Endodontology (ESE 1992). Endodontic treatment encompasses procedures that are designed to maintain the health of all or part of the pulp. When the pulp is diseased or injured, treatment is aimed at preserving normal periradicular tissues.
When pulpal diseases has spread to the periradicular tissues, treatment is aimed at restoring them to health. This is usually done by root canal treatment, occasionally in combination with endodontic surgery.
184 Introduction 2.1
The British Endodontic Society (BES) in 1983 published guidelines for root canal
treatment. These guidelines were revised in 1990, and after discussions with the
European Society of Endodontology, these guidelines were published (ESE 1994).
In many countries, endodontics comes under the discipline of conservative dentistry. In
a number of European countries, endodontics is not recognised as a speciality but the
consensus is that endodontics should be taught in clinical areas dedicated to that
purpose. It is important that students should have adequate experience in the treatment
of endodontic emergencies.
Success of root canal treatment has been shown to range between 53% and 94%
(Jokinen et al. 1978, Lazarski et al. 2001). There is evidence that the technical qualities
of root canal fillings completed in general dental practice is less than ideal (De Moor et
al. 2000, Saunders et al. 1997, Loftus et al. 2005).
There have been several studies undertaken to evaluate the success and failure rate of
root canal treatment performed by undergraduates (Table 2.1.1).
185
Introduction 2.1
TABLE 2-1-1 STUDIES EVALUATING ENDODONTIC TREATMENTS PERFORMED BY UNDERGRADUATES AT DIFFERENT DENTAL SCHOOLS
Author(s) Dental School Investigated Observation Treatment outcome cases period/year Success Uncertain Failure Engstrom et al. Royal School of 306 t 4-5 76.8% 6.5% 16.7% (1964) Dentistry, Stockholm Grossman et al. University of 432 t 1-5 89.9% 0.7% 9.5% (1964) Pennsylvania Heling & Tamshe School of Dental 198 t 1-5 75.3% --- 24.7% (1970) Medicine, Jerusalem Heling & Shapira School of Dental 118 t 1-5 78% --- 22% (1978) Medicine, Jerusalem Jokinen et al. (1978) University of 1782 t 2-7 53% 13% 34% Helsinki Heling & School of Dental 127 t 1-16 81% --- 19% Kischinovsky (1979) Medicine, Jerusalem Kerekes & Tronstad University of Oslo 501 r 0.5-5 91% 4% 5% (1979) Swartz (1983) West Virginia 1007 t 1-10 87.8% --- 12.2% University Molven & Halse University of Bergen 526 r 10-17 79.5% --- 20.5% (1988) Sjogren et al. (1990) University of Umea 849 r 8-10 91% --- 9% Orstavik (1996) University of Oslo 732 t 1-4 88% --- 12% Benenati & Khajotia University of 894 t 0.5-7 62% 28.9% 6.6% 2.5% (2002) Oklahoma success acceptable Molven et al. (2002) University of Bergen 265 r 10-17 95.1% --- 4.9 r = endodontically treated roots t = endodontically treated teeth
186
Introduction 2.1
There is no question that the public's acceptance of endodontic treatment is on the rise.
In 1995/1996, over 1.2 million teeth were root filled in England and Wales under the
regulations of the General Dental Services (Dental Practice Board 1996). Of these, 29 %
were anterior teeth and 36 % molars. In the period 2004-2005 the Annual Report and
Digest of statistics of the Dental Practice Board showed that 907,148 adult root filling
treatments were performed within the NHS in England and Wales (Dental Practice
Board 2005). A large number of these treatment relied upon one or more intraoral
radiographs to assess root morphology and pathology. The American Dental Association
(ADA) in 1969 estimated that 6 million root canal fillings performed in the USA. In
1979, their estimate had risen to 17,390,000. The oral health status of Americans has
improved dramatically over the past twenty-five to thirty years, the mean number of
decayed, missing, or filled surface of teeth of U.S. children ages five to seventeen has
declined from 7.1 to 2.5. Approximately 55 percent of children five to seventeen have no
tooth decay in their permanent teeth. The mean number of teeth present in adults aged
eighteen to seventy four has trended upwards in all age groups. The percent of all adults
who are edentulous has fallen from 14.7 to 7.7 percent. The ADA now estimates that at
least 30 million root canals are filled annually in the United States. Also in surveys of
the general public in 1984 and 1986 by the Opinion Research Institute, 62% in 1986 said
they would choose root canal therapy over extraction, an increase of 10% since 1984
(Ingle & Bakland 1994).
187
Introduction 2.1
A study by Bjǿrondal & Reit (2004) concluded that an increase of root filled canals was
observed between 1977 and 2003 which was probably due to a reduction of the tooth
extraction rate and an increased treatment of multi-rooted teeth.
Root canal treatment (RCT) is an essential part of comprehensive quality dental care
(Chueh et al. 2003). The increased volume of root canal treatment completed in recent
years has mirrored the continuing rise in patient expectations. Furthermore, significant
developments in endodontic materials and equipment, changes in the canal preparation
techniques and a greater understanding of the associated disease and healing process has
been a further catalyst for expansion of endodontic care at the expense of tooth
extraction.
188
Material and Methods 2.1
2.1.2 MATERIAL AND METHODS
Postoperative periapical radiographs were obtained from the records of patients who had received dental treatment at the School of Dentistry, Queen’s University, Belfast,
Northern Ireland. These cases had been treated by 3rd year undergraduate students in the period from 1993-2002.
From the dental records unit, the administrative personnel were asked to collect all files generated between the years 1993 and 2002. Radiographs were retrieved and the method of viewing the radiographs was standardized.
Radiographs were examined in a darkened room using an illuminated viewer box with
2.5x magnification whilst surrounded by a black card to exclude peripheral light emanating from the box. All root canal treatments were performed by third year undergraduate students using a step-back preparation and lateral condensation technique.
For each root filled tooth, periapical radiographs were examined. The subjective quality of each radiograph was assessed on a simple three point scale, as suggested by the
National Radiological Protection Board Guidelines (1994) (Table 2.1.2).
189
Material and Methods 2.1
TABLE 2-1-2 SUBJECTIVE QUALITY RATING OF RADIOGRAPHS
Rating Quality Basis 1 Excellent No errors of preparation, exposure, positioning, processing or film handling 2 Diagnostically acceptable Some errors of preparation, exposure, positioning, processing or film handling, but do not detract from diagnostic utility of the radiograph 3 Unacceptable Errors of preparation, exposure, positioning, processing or film handling, which renders the radiograph diagnostically unacceptable
The following criteria were assessed:
The quality of the root filling in the apical third, quality of remaining root filling, root filling relationship to apex, periapical condition and coronal seal (Table 2.1.3, Table
2.1.4, Table 2.1.5, Table 2.1.6 and Table 2.1.7).
The aim of this study was to assess radiographically the quality of the first root filling performed on patients by junior clinical dental students attending the Queen's
University, Belfast, Northern Ireland.
2.1.2.1 STATISTICAL ANALYSIS
Statistical analysis of the data was performed using the SPSS Win Version 12.0 package program (Chicago, IL, USA).
When assessing the radiographs it is important to be able to establish correlation between examiners throughout the study. This was measured using a kappa score. In the present study, three examiners assessed all the radiographs. The data collected was collated and a final assessment was agreed between the examiners. An initial calibration was performed during a pilot study.
190
Material and Methods 2.1
TABLE 2-1-3 RATING OF QUALITY OF APICAL ROOT FILLING-DENSITY AND LATERAL FILL Score Variable Definition
1 Yes Complete root filling to the
apical third
2 No Presence of visible canal space
within and around the root filling
material
8 Unreadable Film has technical problems
TABLE 2-1-4 RATING OF QUALITY OF REMAINING ROOT FILLING-DENSITY AND LATERAL FILL
Score Variable Definition
1 Yes Complete root filling up to
coronal level
2 No Presence of visible space within
and around the root filling
material
8 Unreadable Film has technical problems
191
Material and Methods 2.1
TABLE 2-1-5 RATING OF QUALITY OF ROOT FILLING-RELATIONSHIP TO APEX
Score Definition
1 The root filling material is within 2mm from the radiographic
apex, within the root canal system
2 The root filling material is greater than 2mm from the
radiographic apex, within the root canal system
3 The root filling material is beyond the radiographic apex
8 The film is unreadable due to technical problems
TABLE 2-1-6 RATING OF PERIAPICAL CONDITION
Score Definition
1 Normal periapical area without clear evidence of
periapical widening
2 Periapical widening extending less than 2mm
vertically beyond the end of the apex
3 Periapical radiolucency,extending 2mm or more
vertically beyond the apex
8 Film unreadable due to technical problem
192
Material and Methods 2.1
TABLE 2-1-7 RATING OF CORONAL SEAL Score Definition
1 Presence of coronal restoration, sound
radiographically at the periphery
2 Presence of coronal restoration, unsound
radiographically (show voids, caries, inadequate
seal)
8 Film unreadable for technical problem
9 Unscorable (missing restoration)
193
Results 2.1
2.1.3 RESULTS
Seventy one percent of the radiographs were considered clinically excellent, 23% considered diagnostically acceptable while 6% had major technical problems making interpretation impossible.
All teeth were filled with gutta-percha and sealer and there was no evidence of fractured instruments. Kappa readings for the three examiners in this calibration ranged from
0.35-0.65.
Thirty percent of the treatments had no postoperative periapical radiographs. These radiographs are the means by which undergraduates achieve credit to fulfil the clinical requirement and thus they should have a vested interest in providing the film.
Sixty nine percent of the cases were root filled to within 2mm of the radiographic apex with the remainder being either filled short (24%) or beyond (5%) the apex.
Twenty two percent of teeth had inadequately condensed apical material and 19% of teeth were assessed as being poorly condensed in the rest of the canal. Overall 67% of the radiographs had no apical radiolucency.
Seventeen percent had a radiolucency extending less than 2mm from the apex, while
12% extended more than 2mm from the apex. Eight percent of the RCTs showed an absence of a coronal restoration, while 80% of the RCTs showed the presence of a
194
Results 2.1 coronal restoration which was radiographically sound at the periphery and 11% revealed a coronal restoration which was radiographically unsound. Examples of radiographs examined in this study are shown in (Figs 2.1.1 and 2.1.2)
FIGURE 2-1-1 WELL-SHAPED AND OBTURATED ROOT CANALS USING GUTTA-PERCHA SEALER AND LATERAL COMPACTION
FIGURE 2-1-2 IMPROPER ROOT CANAL OBTURATION THAT LACK PROPER CANAL SHAPE, IN ADDITION TO POORLY COMPACTED ROOT CANAL FILLINGS
195
Discussion 2.1
2.1.4 DISCUSSION
The material used in the study consisted of periapical radiographs of patients who had received root canal treatment at the School of Dentistry, Queen's University Belfast,
Northern Ireland. All treatment had been performed by third year undergraduate dental student between 1993 and 2002. All periapical radiographs used in thus study were taken during routine RCT procedures within a dental student practice and were not taken especially for this study. Panoramic radiographs were not used for this study as it has been shown that they provide less inter-examiner reliability (Flint et al. 1998). De Cleen et al. (1993) reported that a large number of teeth could not be categorized due to difficulties in reading panoramic view radiographs.
Rohlin et al. (1991) reported that when comparing three groups of observers, kappa values for intra-examiner agreement were higher for periapical radiographs than for panoramic radiographs. According to the European Society of Endodontology (1994), the assessment of endodontic treatment requires clinical as well as radiographic follow- up at regular intervals. The radiographic evidence of success is the presence of a normal periodontal ligament space around the root. If radiographs reveal that a lesion has remained the same or has only slightly diminished in size, the treatment is not considered a success (ESE 1994).
196
Discussion 2.1
The criteria used to assess the quality of the root canal fillings were similar to those used
by Hussey et al. (2003). To evaluate the periapical radiographs, two examiners
calibrated a number of radiographs independently following strict and clear criteria.
There was a strong correlation between the examiners throughout the study
(kappa=0.65).
The percentage of radiographs assessed as excellent, acceptable or unacceptable were
71, 23, and 6% respectively. These results compare favourably with recent studies
undertaken on the assessment of radiographs from general practitioners.
The study by Hussey et al. (2003) used similar criteria and reported a much higher
percentage (54%) of radiographs having major problems of which only 46% were
excellent. This may be because most of the post obturation radiographs were taken at the
end of treatment by qualified radiologists. This result fulfils the NRPB guidelines
(2001), which state that the minimum target for ‘rating 1’ should be not less than 70%.
It is obvious in this study, that the quality of the apical root filling was lower than the
quality of the rest of the obturated canal.
It is generally accepted that the apical limit for instrumentation and obturation of the
root canal system is ideally the narrowest portion of the canal.
197
Discussion 2.1
The apical foramen is usually located at the end of the anatomic root during root
formation. The apical foramen is smaller and more eccentric during tooth development.
Studies have shown that the biological apical foramen or dentinocementum junction is
generally located 0.5 to 1.0mm or more short of the anatomic apex (Palmer et al. 1971,
Grossman 1974, Cohen et al. 1988, Ricucci 1998).
The radiographic apex is defined as the anatomical end of the root as seen on the
radiograph, while the apical foramen is the region where the canal leaves the root canal
surface next to the periodontal ligament (American Association of Endodontics 1984).
Internal to the foramen is the apical constriction, i.e. the area of the apical portion of the
root canal which has the narrowest diameter. It often coincidental with the cemento-
dentinal junction (Kuttler 1955, American Association of Endodontists 1984).
Kuttler stated that the distance from the apical constriction to the apical foramen was
approximately 0.5 mm in younger age groups, and 0.7mm in older age groups. This
natural constriction where the dentine meets cementum appears to be the ideal location
for development of an apical seal for the root filling material (Coolidge 1929, Orban
1930 as cited in Olson et al. (1991).
Sixty nine percent of the canals were considered to be obturated to within 2 mm of the
radiographic apex while only 5% went beyond the apex and 24% were more than 2 mm
beyond the radiographic apex.
198
Discussion 2.1
Although it is difficult to compare these result with other studies, the percentage of root
fillings that had adequate length were superior when compared with those reported by
Peak et al. (2001) who evaluated the root canal treatment performed by the Royal Air
Force Dental practitioners. They found the percentages of satisfactory, short or
overfilled canals to be 50, 32 and 18% respectively (Chueh et al. 2003) .Barrieshi-
Nusair et al. (2004) also undertook a study to evaluate radiographically the technical
standard of root canal treatment performed by undergraduate dental students at the
Dental Teaching Centre in Jordan and found 61% of roots fillings as acceptable while
34.5% were short and 4.2% were overfilled.
Lynch & Burke (2006) reported 63% of root filling were classified as acceptable.
However, Smith et al. (1993) reported a much higher percentage 74.7% of acceptable
root filling, while short and overfilling were reported in 14.1 and 11.2% of cases
respectively.
A recent study by Er et al. (2006) evaluated the radiographic quality of root fillings
performed by undergraduate students at a dental faculty in Turkey and reported the
percentage of root fillings with adequate length as being 69.6 %, with 13 % over-filled
and 17.4 % under filled.
A large number of studies have demonstrated that the success rate in endodontic therapy
is significantly influenced by the presence or absence of a pre-treatment radiographic
lesion.
199
Discussion 2.1
Teeth with an apical radiolucencey may show up to a 20% lower success rate than teeth
without such lesions (Sjögren et al.1990).
One must acknowledge that poor obturation is not the only cause of clinical root canal
failure. Lesser quality root fillings only facilitate the process of bacterial infection more
easily.
The origin of these bacteria cannot always be determined. Lin et al. (1991) suggesting
that they are probably from the following sources:
1- From the bacteria, originally present in the infected root canal or introduced into the
canal by poor endodontic treatment procedures.
2- Through a defective seal in the crown and canal space or exposed root dentinal
tubules, thus the importance of good quality obturation and a sound coronal seal.
3- Rarely the seed in the canal space through anachoresis i.e. seeding of organisms
directly into the pulp via the pulpal blood supply during bacteraemia.
Although there is controversy in defining the factors influencing the success of RCT,
three factors are largely acknowledged: the technical quality of root canal obturation,
periapical status prior to treatment and the length of the observation period (Friedman
1998). For the first two, radiology is close to being the only feasible evaluation method.
As periapical biopsies are difficult to obtain, radiography and the examination of clinical
symptoms are the means to assess the outcome of the RCT (Nicholls 1963, Reit 1987,
ESE 1994).
200
Discussion 2.1
The scoring of the periapical condition showed 67% had no apical radiolucency, with
12% of the cases having a radiolucency greater than 2mm from the apex.
The prepared root canal should be tapered from the crown with the smallest diameter at
the apical foramen and the largest at the orifice to allow effective irrigation and filling.
Many instruments have been recommended but only a few seem to be capable of
achieving these primary objectives of root canal preparation consistently (Schäfer et al.
2006) and no voids should be seen between the root filling and canal walls. The quality
of filling should be assessed with a radiograph that shows the root apex with preferably
at least 2 mm of periapical region clearly identifiable (ESE 1994).
It is essential, following root canal treatment, that the canal system is protected from
subsequent leakage as much as possible (Saunders & Saunders 1994). They concluded
that the coronal leakage is an important cause of failure of root canal treatment. In the
present study 80% appeared to show a radiographically sound coronal restoration.
Working length estimations were achieved by exposing radiographs of a file of pre-
determined length in the root canal system. All of the root canals in this sample were
prepared using a step-back preparation and cold lateral condensations are the standard
techniques. Cailleteau & Mulluney (1997) reported that this technique was then the most
widely taught and used technique in the United States Dental schools. This technique is
useful when teaching undergraduate students and it is indicated in straight to moderately
curved canals (Carrotte 2003).
201
Discussion 2.1
Root canal procedures at the Royal Victoria Hospital, School of Dentistry, are combined
with Conservative Dentistry and are carried out in a multidisciplinary clinic.
Important adjuncts in modern endodontic treatment, such as nickel-titanium rotary
instruments and electronic apex locators were not used during treatment of the cases that
were included in this study. It has been demonstrated that Ni-Ti rotary instruments
shape the root canal better than conventional instruments with fewer procedural errors
and reduced treatment time (Thompson & Dummer 1997, Park 2001, Sonntag et
al.2003). Furthermore, electronic apex locators are claimed to be more reliable than
radiographs to identify the working length of the root canal (Pratten & McDonald 1996).
Therefore, their use could have been beneficial in minimizing the risk of procedural
errors. Finally, the use of patency files has been proposed to prevent the occurrence of
preparation errors. However, this concept was not used during the treatment of the cases
that were evaluated.
202
Conclusion 2.1
2.1.5 CONCLUSION
This methodology was useful for qualitative assessment of RCT. Sixty-seven percent of these RCT’s were radiographically successful, in spite of several shortcomings in the techniques used and the inexperience of the students.
203
Introduction 2.2
2.2 QUALITY OF THE SECOND ROOT CANAL TREATMENT PERFORMED BY UNDERGRADUATE STUDENTS.
2.2.1 INTRODUCTION
Optimal prognosis for root canal treatment is dependent on the successful elimination of microorganisms from the infected root canals (Bystrom et al.1987, Sjögren et al. 1990,
Sjögren et al.1997). To optimize successful outcome the focus of endodontic treatment is directed at disinfection through chemomechanical debridement and biomechanical preparation, followed by a quality obturation of the root canal system. Finally, it is necessary to preserve the remaining tooth structure by timely placement of an appropriate perment restoration. However, the methods used to determine the technical outcome of endodontic treatment have been mostly based on radiographic evaluation
(Buckley & Spangberg 1995, Saunders et al. 1997)
Endodontic treatment plays a very important role in providing patients with high quality comprehensive dental care. It is therefore the responsibility of teachers within dental schools to prepare their students to implement the guidelines and recommended standards in root canal debridement, shaping and obturation (ESE 1994, General Dental
Council 2002). Root canal treatment usually fails when treatment falls short of acceptable standards (Sjögren 1996, Qualtrough et al. 1999).
204
Introduction 2.2
According to the European Society of Endodontology (1994), appropriate treatment includes, in addition to root canal preparation and filling, the exposure of preoperative radiographs, determination of the working length and radiographic control of the quality of the filling.
Several studies indicate that the root fillings placed within 0-2 mm of the radiographic apex were associated with less post-treatment disease than those that were filled greater than 2 mm from the radiographic apex or those that were overfilled (Peak et al. 2001,
Boltacz-Rzepkowska & Paw-licka 2003).
The increased volume of root canal treatment completed in recent years has mirrored the continuing rise in patient expectations. Furthermore, significant developments in endodontic materials and equipment, changes in the canal preparation techniques and a greater understanding of the associated disease and healing process has been a further catalyst for expansion of endodontic care at the expense of tooth extraction.
The work in section study 2.1 of this thesis showed that 67% of first root canal fillings performed by undergraduate students were radiographically successful, in spite of the clinical inexperience of the students.
The aims of this study were to evaluate the quality of the second root canal filling performed by undergraduate students and to compare this to their first root canal filling.
It was hypothesised that there would be no difference between the first and second root canal fillings performed by undergraduate students.
205
Material and Methods 2.2
2.2.2 MATERIAL AND METHODS
This study was based on third year undergraduate dental students carrying out their
second RCT in the School of Dentistry, Queen’s University Belfast in the period from
1993-2002. Student records revealed patients who had completed RCT undertaken by
third year students. Radiographs were selected of patients who were the second patients
treated for root canal treatment by individual students.
Ninety one second RCT periapical radiographs showing completed anterior, single RCT
were examined and compared with 139 first RCT periapical radiographs. The methods
of viewing the radiographs were standardized. Examination was in a darkened room
using an illuminated viewer box with 2.5x magnification. The radiographs were
surrounded by a black card which was adjusted to block off ambient light emanating
from the viewer.
The initial variable was to assess the quality of each radiograph using the National
Radiological Protection Broad Guidelines (NRPB. Guidelines on radiology standards for
primary dental care, as used in Table 2.1.2 in study 2.1 (Document of the NRPB, 5.No.3,
1994).
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Material and Methods 2.2
In a systematic way other variables were assessed, starting with the root filling material,
the presence of any fractured instruments, the density of the root filling both apically
and coronally, the relationship of the root filling to the tooth apex, the periapical
condition and evidence of a coronal seal. The evaluation was undertaken by two
calibrated examiners and where conflict was noted a consensus was obtained with a third
calibrated examiner.
2.2.2.1 STATISTICAL ANALYSIS
Statistical analysis of the data was performed using the SPSS Win version 12.0 package
program. Chi-square analysis was used to assess if statistically significant differences
occured between the quality of the first and second root canal fillings performed by
undergraduates. A p value equal to or less than 0.05 was considered statistically
significant.
207
Results 2.2
2.2.3 RESULTS
The study included second and first postoperative periapical radiographs showing
completed anterior, single RCT’s performed by undergraduate dental students in the
School of Dentistry, Queen’s University Belfast.
Under the NRPB guideline, 86% of the radiographs of the second RCT’s were assessed
as clinically excellent, with 13% considered to be imperfect but still of some diagnostic
use.
When comparing the treatment for two postoperative first and second radiographs there
was a significant difference between the two radiographs. This suggests that the
radiographs were of a higher standard postoperatively for the second case. The overall
results for the two radiographs are summarized in Table 2.2.1.
TABLE 2-2-1 PROPORTION OF GRADES 1, 2 AND 3 FOR THE RADIOGRAPHS FROM THE 1ST AND 2ND RCT’S. THERE WAS A SIGNIFICANT DIFFERENCE OVERALL (CHI-SQUARE OF 6.503, DF =2, P ≤ 0.05).
Radiographs Total 1st RCT 2nd RCT Radiographic Excellent Count 99 67 166 quality % 71.2% 85.9% 76.5% Acceptable Count 32 10 42 % 23.0% 12.8% 19.4% Unacceptable Count 8 1 9 % 5.8% 1.3% 4.1% Total Count 139 78 217 % 100.0% 100.0% 100.0%
208
Results 2.2
Gutta percha was the obturation material used in all cases. There was no evidence of
fractured instruments performed within the canal system of any teeth.
All root canal treatment were carried out by third year undergraduate dental students
included rubber dam isolation, standard step-back preparation with 0.5% sodium
hypochlorite as the irrigant and a cold lateral condensation technique.
The root canal system was examined for the quality of apical root filling, looking at both
filling density and lateral fill within the apical third of the root canal. If there was the
presence of any visible canal space within or around the root filling material, this was
judged as a poor quality RCT.
The quality of the filling was then assessed for the rest of the canal up to the coronal
level. Results showed that 79% of the teeth were judged to have well condensed fillings
in the apical third of the canal, with 70% of canals being well condensed in the coronal
area. There was no significant overall difference between the radiographs of the first and
second RCT’s in terms of the quality of the apical root filling. The P-values for these
comparisons was P = 0.73.
The next aspect of the quality of the root fillings was to look at the relationship to the
apex of the tooth. All radiographs of poor quality were excluded from the study.
Overall, 61% of the teeth were filled to within 2 mm of the radiographic apex with the
remainder being either filled short (27%) or beyond the apex (12%) (Table 2.2.2).
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Results 2.2
TABLE 2-2-2 QUALITY OF ROOT CANAL FILLINGS IN RELATION TO THE APEX
Radiograph 1st RCT 2nd RCT Total Quality of root ≤2mm Count 96 46 142 filling % 70.6% 61.3% 67.3% relationship-to ≥2mm Count 33 20 53 apex % 24.3% 26.7% 25.1% Beyond Count 7 9 16 % 5.1% 12.0% 7.6% Total Count 136 75 211 % 100.0% 100.0% 100.0%
Eighty four percent of radiographs showed the presence of a coronal restoration which
appeared to be radiographically sound at the periphery, with 16% showing the presence
of a coronal restoration which appeared to be radiographically unsound. The overall
results for the two radiographs are summarized in Table 2.2.3. There was no significant
difference between the groups.
210
Results 2.2
TABLE 2-2-3 QUALITY OF THE CORONAL SEAL
Radiographs 1st RCT 2nd RCT Total Coronal seal Sound Count 111 57 168 % 88.1% 83.8% 86.6% Unsound Count 15 11 26 % 11.9% 16.2% 13.4% Total Count 126 68 194 % 100.0% 100.0% 100.0%
211
Discussion 2.2
2.2.4 DISCUSSION
The materials used in this investigation consisted of a sample of dental records and
periapical radiographs of patients who had received RCT from junior undergraduate
students at the School of Dentistry, Queen’s University Belfast.
The criteria used to assess the quality of root canal fillings were similar to those used by
Buckley and Spangberg (1995) which was originally adopted and modified from Odesjo
et al. (1990) and Petersson et al. (1991) and were similar to those used in study 2.1.
Controversy exists about whether the quality of care is better assessed by focusing on
the process of care or on the resulting outcome. Practice guidelines carry the inherent
assumption that adequate procedures affects the treatment outcome positively (Bader &
Shugars 1995).
The material of choice for obturation is currently gutta-percha combined with a sealer
(Dummer 1991). Cold lateral condensation of gutta-percha is a commonly taught
method of root canal filling and is widely used by dental practitioners (Peak et al. 2001,
Levitan et al. 2003).
To evaluate the periapical radiographs, two examiners calibrated a number of
radiographs independently following strict and clear criteria. There was strong
correlation between the examiners throughout the study (kappa=0.65).
The first variable measured was the subjective quality rating of the radiograph in terms
of diagnostic value. The results show that 76.5% of all the radiographs were considered
to be clinically excellent (rating 1). This fulfils the NRPB guidelines but it is obvious in
212
Discussion 2.2
this study that the second RCT radiographs had a higher excellent percentage rating
(85.9%) than the radiographs of the first RCT.
Radiology has played an important role in evaluating of the success of root canal
treatment. The quality of the radiograph is dependent on the x-ray source, the film type,
the projection in the mouth and the way that the film is processed (Preece & Jensen
1983). Vande voorde and Bjorndahl (1969) in a study of 101 extracted anterior teeth
found that the actual tooth length was magnified by 5.4 per cent using the right-angled
paralleling technique. They concluded that right –angled parallel radiographs can
consistently serve as a reliable guide when predetermining a tooth's working length for
RCT. Forsberg (1987) reported that the results of his study were in accordance with
others previously documented, in that the paralleling principle technique reproduces the
total length of the tooth more consistently than the bisecting angle technique.
The root filling is considered satisfactory if there is no lumen apical to the root filling
and no void in the apical part. Both the density and length of the root filling is taken into
account. In the present study, 77.9% were considered to have a well condensed filling in
the apical third of the canal with 77% of canals beings well condensed in the coronal
area.
Step-back preparation and cold lateral condensation are the standard techniques that are
taught to the undergraduate dental student. Cailleteau and Mulluney (1997) stated that
this technique is the most widely taught and used technique in the United States Dental
Schools. All teeth were filled with gutta-percha and sealer and there was no evidence of
fractured instruments remaining in situ in the present study.
213
Discussion 2.2
Dummer (1991) indicated that a more consistent pattern of teaching had evolved, and
that the step back preparation technique and lateral condensation of gutta-percha were
universally accepted. At that time few schools had introduced contemporary approaches
towards canal preparation and filling.
Poorly condensed root fillings and overfilled canals were strongly associated with the
presence of apical periodontitis (Petersson et al. 1986). It is important to emphasize that
a periapical lesion dose not always indicate failure of RCT but it can facilitate the
introduction of microorganisms and their by-products into the root canal which in turn
can produce disease. Nevertheless, there are some cases in which the treatment has
followed the highest technical standards and yet failure results. Scientific evidence
indicates that some factors may be associated with the unsatisfactory outcome of well
treated cases. They include microbial factors, comprising extra-radicular and / or intra-
radicular infections, and intrinsic or extrinsic nonmicrobial factors (Nair et al. 1990,
Sundqvist et al. 1998, Nair et al. 1999).
There was no significant difference in coronal sealing between the two sets of
radiographs. Overall quality of the coronal restoration was 86.6%. It has been stated that
coronal leakage may be an important cause of failure of endodontic treatment (Saunders
& Saunders 1994).
Recontamination of the root canal system by coronal leakage will occur through sealer
dissolution by saliva in the interface between sealer and root canal walls particularly if
the smear layer is present and / or between sealer and gutta-percha (Siqueira & Lopes
1999). In addition voids and other minor flaws in the obturation, which often are not
214
Discussion 2.2
detected radiographically, may be responsible for the rapid recontamination of the root
canal system.
A large number of studies have demonstrated that the success rate in endodontic therapy
is significantly influenced by the presence or absence of a pre-treatment radiographic
lesion. Teeth with an apical radiolucency may show up to 20% lower success rate than
teeth without such lesions (Benenati & Khajotia 2002).
Although there is controversy in defining the factors influencing the success of RCT,
three factors are largely acknowledged as being important. These are: the technical
quality of root canal obturation, periapical status prior to treatment and the length of the
observation period (Friedman 1998). For the first two factors, radiology is close to being
the only feasible evaluation method.
As periapical biopsies are difficult to obtain, radiography and the examination of clinical
symptoms are the means to assess the outcome of the RCT (Reit 1987, Qualtrough et al.
1999).
In the present study, there was no significant difference in the quality of the first and
second root canal fillings performed by undergraduate dental students. The result
reflects that the students have reached a plateau in their learning.
Qualtrough and Dummer (1997) determined the current pattern of undergraduate
endodontic teaching within the Dental Schools of the UK. Data was gathered by
questionnaires from all 14 undergraduate dental schools and supplemented with further
detailed enquiries where necessary. The study confirmed that a number of endodontics
topics were either not included or were covered only briefly. However, the average time
215
Discussion 2.2
devoted to the preclinical instruction of RCT in the first clinical year had increased from
14 to 24 hours with additional time provided in subsequent years by the majority of
dental schools. In most instances, staff teaching Endodontology in the UK have no
specialist training.
Cruz et al. (2000) evaluated the pattern of undergraduate endodontic teaching in the
Philippine Dental Schools. The result of this study demonstrated that there is a need to
review endodontic teaching in the majority of the Philippine Dental Schools to ensure
that the course content and curriculum employed by all schools meet specified standards
and that appropriate measures should be considered to enhance the learning experience
of students.
Long-term clinical and radiographic follow up is essential for the assessment of
endodontic treatment outcomes. Although the process of periapical healing may often be
diagnosed radiographically at the 1-year recall, individual cases may take up to 4 years
for complete healing of periapical lesions (Orstavik 1996).
Most studies of periapical lesions show that between 75% and 95% are complications
resulting from pulpal necrosis and that the majority would respond to conservative root
canal treatment (Kuc et al. 2000, Peters & Lau 2003). For example, in 70% of cases
(Murphy et al.1991) healing of these periapical radiolucencies occurred at least 12
months after nonsurgical root canal treatment.
216
Conclusion 2.2
2.2.5 CONCLUSION
There was no statistically significant improvement in the quality of the second root canal
filling when compared radiographically with the first clinical attempt of RCT. It could
be suggested that the standard of teaching pre-clinically allowed the students to be
competent to carry out RCT on a real patient.
The fact that the quality did not improve with the second root canal filling supports
competency training. It suggests that the students have reached a plateau in their
learning. Further investigation is indicated to examine the factors contributing to failures
in different postoperative periods.
217
Introduction 3.1
3.1 EFFICACY OF SOME IRRIGANTS TO REMOVE THE SMEAR LAYER IN ROOT CANALS: AN SEM STUDY.
3.1.1 INTRODUCTION Several studies have shown that current methods of cleaning and shaping root canals can produce a smear layer that covers the canal walls (McComb & Smith 1975, Pashley
1992). This thin amorphous structure is composed of both inorganic and organic substances, which include fragments of odontoblastic processes, microorganisms and necrotic material that adheres to the root canal walls. Obstruction to the openings of the dentine tubules results. This in turn hampers the entry of medicaments to the dentinal tubules and root canal system (Karagöz-kucukay & Bayirli 1994).
Different solutions have been used to remove the smear layer. These include various organic acids, ultrasonic instruments and laser treatment. Sodium hypochlorite (NaOCl), in a 0.5 % - 5.25% concentration is an irrigant solution widely used in root canal therapy because of its bactericidal properties and ability to dissolve organic tissue (Yamada et al.
1983, Baumgartner& Mader 1987).
The dissolution of organic tissues by sodium hypochlorite solutions is based on the action of chlorite over the proteins, forming chloramines, which are soluble in water.
This reaction is directly proportional to the active chlorite concentration present in the solution (Moorer & Wesselink 1982). However, NaOCl has been claimed to be ineffective in removing the smear layer (Prati et al. 1994).
218
Introduction 3.1
NaOCl also weakens dentine by reducing its flexural strength and resilience, thereby rendering the tooth more susceptible to deformation and possibly to fracture when used in a high concentrations 5 % (Grigoratos et al. 2001, Sim et al. 2001). The principles of current root canal therapy, which have existed for almost a century, have a failure rate of about 16% (Lewsey et al. 2001). There is therefore a need to develop new and more effective treatment strategies, with corresponding antibacterial irrigants, that are milder in their action on vital tissue and debride the dentine surface without weakening its structure (O’ Driscoll et al. 2002).
A novel irrigant termed electrochemical activated water (Marais 2000) or oxidative potential water (Hata et al. 1996, 2001) has been employed with some success. The solution accumulating at the anode is harvested as the anolyte and that the cathode as the catholyte.
Sterilox is a biocide liquid made by electrolysis of a dilute saline solution within a proprietary electrochemical cell (Tapper et al. 1998). It is highly microbiocidal when freshly generated.
Sterilox is a super oxidizing water with an oxidation-reduction potential of > 950 mV and containing a mixture of oxidizing compounds including hypochlorous acid.
The presence of various reactive species, such as oxygen and chlorine based radicals, has been reported to contribute to the antimicrobial action of sterilox (Shetty et al. 1999,
Zinkevich et al. 2000).
All sterilox preparations have pH values of about 6.3 and available free chlorine levels of about 240 mg 1-1.
219
Introduction 3.1
Super-oxidised water has a high bactericidal activity against a range of bacteria including Legionella and Mycobacteria spp (Shetty et al. 1999).
It is well known that ozone, in the gaseous or aqueous phase, can kill bacteria, fungi, and viruses (Kim et al. 1999). Within dentistry, ozone has been advocated for the treatment of root caries (Baysan et al. 2000) and in root canal treatment (Deltour et al. 1970,
Chahverdiani & Thadj-Bakhche 1976, Hems et al. 2005).
However, we are not aware of any reports on the efficacy of ozonated NaOCl to remove the smear layer.
The purpose of this study was to evaluate through Scanning Electron Microscopy (SEM) the removal of the smear layer from the root canal walls prepared and irrigated with
0.5% sodium hypochlorite, water, saline or sterilox and with either air, or ozone bubbled into the irrigant.
220
Material and Methods 3.1
3.1.2 MATERIAL AND METHODS:
Eighty freshly extracted human mandibular first premolar teeth, with a single canal,
were selected after being examined radiographically with a periapical intraoral film
(Kodak, New York, USA) in both mesiodistal and buccolingual views, to confirm root
canal patency and the absence of complicated root canal anatomy. Prior to access cavity
preparation, all teeth were immersed in saline for 72 h - 96 h.
The teeth were externally cleaned with curettes, the crowns were removed at the
cementoenamel junction using diamond fissure burs and the crowns were discarded.
Before preparation, the roots were randomly divided into seven experimental groups of
10 roots each, and one control group of 10 roots.
The experimental groups were irrigated as follows:
Group 1: 1 ml of 0.5% NaOCl used for two minutes and then air was bubbled into the
NaOCl from the Healozone tip for 10 seconds between each instrument use.
Group 2: 1 ml of 0.5 % NaOCl applied for two minutes and ozone bubbled in for 10
seconds after each instrumentation.
Group 3: 1 ml of distilled water used for two minutes and then air was bubbled into the
water from the Healozone tip for 10 seconds between each instrument size.
Group 4: 1 ml of distilled water used for two minutes and ozone bubbled in for 10
seconds after each instrumentation.
Group 5: 1 ml of sterile physiological saline solution used for 2 minutes and then air was
bubbled into the saline from the Healozone tip for 10 seconds between each instrument
size.
221
Material and Methods 3.1
Group 6: 1 ml of sterile physiological saline solution applied for 2 minutes and ozone
bubbled in for 10 seconds after each instrumentation.
Group 7: 1 ml of Sterilox (Anolyte) used for two minutes and then air was bubbled into
the sterilox from the Healozone tip for 10 seconds between each instrument use.
Group 8: 1 ml of Sterilox (Anolyte) used for two minutes and ozone bubbled in for
10 seconds after each instrument.
The working length of each root canal was established as 1mm short of the radiographic
apex with a size 15 K- type root canal file. A size 10 K-type root canal file was inserted
through each root canal apex to establish patency. The root canal was cleaned and
shaped to a size 40 K-type root canal file at the working length and flared using a step-
back preparation technique
The apical third was shaped with sizes 20, 25, 30, 35 and 40 K-files using a push-pull
motion. Then step-back preparation from 45 to 60 K-files, was undertaken by shortening
each size by 1mm of the preceding instrument.
Irrigation was performed after each instrument with 10 ml of the previously reported
solution for each tooth obeying the already mentioned protocols. An endodontic syringe
with a 30 gauge endodontic irrigating needle (corresponding to instrument size 35) was
used to deliver the solutions.
The needle was placed as far as possible into the canal without binding. One ml of
distilled water was used before the first instrument was used in each tooth. Canals were
kept flooded with irrigant during the instrumentation phase.
222
Material and Methods 3.1
The root canals were finally irrigated with 3 ml of distilled water to remove any
precipitate that may have formed from the test irrigant.
The unit for the generation of the super-oxidised water, Sterilox (Optident, IIkley,
Yorkhire), consisted of a generator attached to a saline solution reservoir.
Ozone or air was produced by a device with attachments specifically designed for
endodontic treatment (HealOzone, KaVo, Germany) and the operator doing the
procedure was blinded to which was being applied. A second operator switched the
system to deliver either air or ozone and recorded this in a file which remained sealed
until the analysis was completed.
Biomechanical preparations were performed according to conventional step back
preparation using K flex files (Kerr Corporation, Germany). After the root canal
preparation, the canals were dried with paper points (Ultradent Products Inc). Sectioning
and splitting of the root was achieved using either a slow speed diamond saw blade
(Buehler, Lake Bluff, Illinois, USA) or with a steel chisel shearing through a sharp
groove made on the external root surfaces. The teeth were split in half to expose the root
canal and the roots mounted on stubs.
The specimens were then dehydrated and coated with gold using an ion sputter
technique and immediately examined for SEM evaluation (JSM-6500F; JEOL Ltd,
Tokyo, Japan).
The specimens were viewed in the coronal, middle and apical thirds of the root. Each
canal was evaluated at various magnifications, from x 500 to x 4,000, to show varying
levels of detail. Two representative areas for each group were photographed from the
223
Material and Methods 3.1
scanning electron microscope at x 4,000 magnification and another 2 at x 500
magnification and 2 at x 1000 magnification , 2 at x 2000 magnification and 2 at x 3000
magnification. The photographs were studied for the presence of a smear layer.
The specimens were coded, based on the irrigation group, in a blinded manner. Two
investigators scored the presence or absence of a smear layer on the surface of the root
canal according to the criteria used by Takeda et al. 1998, whilst assessing all 60 SEM’s
for each region in each group. The most representative category was chosen.
0 - No smear layer, open dentinal tubules, smear layer completely removed.
1- Thin smear layer covering the surface, outline of dentinal tubules and the location of
the tubule indicated by a crack.
2- Moderate smear layer, outlines of dentinal tubules observable, removed in some
areas.
3- Heavy smear layer with outlines of tubules obliterated.
3.1.2.1 STATISTICAL ANALYSIS
Statistical analyses by means of non-parametric statistics using the Kruskal Wallis test to
determine if there were significant differences between the groups.
The Mann-Whitney U test was used to confirm any significant difference between pairs
of groups (P< 0.05).
224
Results 3.1
3.1.3 RESULTS
The results are presented by a descriptive analysis of the events, and the statistical
analysis of the categorical determination of smear layer removal on the dentine.
Description of events
Group 1 (NaOCl)
SEM analysis of specimens irrigated with 0.5 % NaOCl for 2 minutes and then air was
bubbled into the NaOCl from the Healozone tip for 10 seconds after each file showed in
the coronal third, several open dentinal tubules, which were regularly distributed (Fig
3.1.1).
FIGURE 3-1-1 CORONAL THIRD OF A SAMPLE IRRIGATED WITH 0.5% NAOCL SHOWING PERITUBULAR AND INTERTUBULAR SURFACE DENTINE WHICH APPEARED SMOOTH AND FLAT. INDIVIDUAL ORIFICES OF DENTINAL TUBULES WERE CLEARLY OBSERVED (ORIGINAL MAGNIFICATION X 4000)
225
Results 3.1
FIGURE 3-1-2 MIDDLE THIRD OF ROOT CANAL IRRIGATED WITH 0.5% NAOCL SHOWING SOME AREAS OF SMEAR LAYER AND SEVERAL OPEN TUBULE ORIFICES
In the middle third, a smear layer partly remained on the root canal face (Fig 3.1.2). And
in some cases, a moderate smear layer could be observed in the openings of the dentinal
tubules in the apical one third (Fig 3.1.3).
226
Results 3.1
FIGURE 3-1-3 AT THE APICAL THIRD REGION OF A SAMPLE IRRIGATED WITH 0.5% NAOCL HAD PULPAL REMNANTS PRESENT WITH COLLAGENOUS MATRIX SPREAD ALONG THE ROOT CANAL WALLS AND SOME SMEAR LAYER IS SHOWN (ORIGINAL MAGNIFICATION X 4000)
Group 2 (NaOCl and Ozone)
These specimens were treated with 0.5% NaOCl and ozone bubbled in it for 10 seconds
after each file. The smear layer was almost totally removed, in the coronal, middle and
apical thirds, revealing the collagen network of the intertubular dentine around enlarged
tubule openings (Figs. 3.1.4, 3.1.5, 3.1.6).
227
Results 3.1
FIGURE 3-1-4 CORONAL THIRD OF ROOT CANAL IRRIGATED WITH 0.5% NAOCL AND OZONE BUBBLED IN FOR 10 SECONDS AFTER EACH FILE. EROSION OF PERITUBULAR AND INTERTUBULAR DENTINE WAS OBSERVED, WITH IRREGULARLY ENLARGED DENTINAL TUBULES (ORIGINAL MAGNIFICATION TOP, X 4000, BOTTOM X 500)
228
Results 3.1
FIGURE 3-1-5 MIDDLE THIRD OF ROOT CANAL IRRIGATED WITH NAOCL AND OZONE BUBBLED IN FOR 10 SECONDS SHOWING CLEAN, EXPOSED DENTINAL TUBULES, SOME DEBRIS WAS OBSERVED (ORIGINAL MAGNIFICATION X 500, X 1000, X 4000)
229
Results 3.1
FIGURE 3-1-6 SOME SPECIMENS IRRIGATED WITH NAOCL AND HAD OZONE BUBBLED IN FOR 10 SECONDS SHOWED A MODERATE SMEAR LAYER IN LOCALISED AREAS IN THE APICAL THIRD. EXCESSIVE EROSION HAS LED TO CONJUGATION OF TWO OR MORE DENTINAL TUBULES (ORIGINAL MAGNIFICATION X 1500, X 1000, X 4000)
230
Results 3.1
Group 3 (Distilled water)
The SEM observations of the specimens treated with distilled water are shown. The
smear layer was predominantly smooth with a few areas of irregularity and the presence
of loose debris was observed in all samples (Figs 3.1.7, 3.1.8). However, in some
specimens, the opening of dentinal tubules could be observed in the apical third of the
tooth (Fig 3.1.9).
FIGURE 3-1-7 CORONAL THIRD OF ROOT CANAL. SURFACE TOTALLY COVERED BY A THICK SMEAR LAYER AND TUBULE ORIFICES ARE BLOCKED (ORIGINAL MAGNIFICATION X 4000)
231
Results 3.1
FIGURE 3-1-8 MIDDLE THIRD SHOWING HEAVY SMEAR LAYER AND EXTENSIVE AMOUNTS OF LOOSE DEBRIS (ORIGINAL MAGNIFICATION X 2000)
FIGURE 3-1-9 SPECIMEN IRRIGATED WITH DISTILLED WATER. APICAL THIRD OF CANAL WALL SHOWING A MODERATE SMEAR LAYER (X 4000)
232
Results 3.1
Group 4 (Distilled water and ozone)
The specimens which were irrigated with distilled water and had ozone applied for 10
seconds after each instrumentation are shown. In some cases, a moderate smear layer
could be observed with some opening of dentinal tubules in the apical third (Fig 3.1.10).
In the coronal and middle third, a large number of dentinal tubules were visible (Figs
3.1.11, 3.1.12).
FIGURE 3-1-10 SPECIMENS IRRIGATED WITH DISTILLED WATER AND OZONE BUBBLED IN FOR 10 SECONDS AFTER EACH FILE. THE ROOT CANAL WALLS SHOWED, AT THE APICAL THIRD, A MODERATE SMEAR LAYER ON THE OPENINGS OF THE DENTINAL TUBULES
233
Results 3.1
FIGURE 3-1-11 SPECIMEN IN THE MIDDLE THIRD WHERE DENTINAL TUBULES WERE CLEARLY OBSERVED WITH VISIBLE SMEAR LAYER
FIGURE 3-1-12 AT THE CORONAL THIRD, THE DENTINAL TUBULES WERE CLEARLY OBSERVED AND SOME SMEAR LAYER WAS VISIBLE (ORIGINAL MAGNIFICATION X 4000)
234
Results 3.1
Group 5 (Control)
Specimens irrigated with physiological saline solution were almost completely covered
with a smear layer on the coronal, middle and apical one third as shown in (coronal Fig
3.1.13, middle Fig 3.1.14, apical Fig 3.1.15).
FIGURE 3-1-13 PRESENCE OF SMEAR LAYER ON THE SURFACE OF THE CORONAL THIRD OF A ROOT CANAL IRRIGATED WITH PHYSIOLOGICAL SALINE
235
Results 3.1
FIGURE 3-1-14 MIDDLE THIRD SHOWING A SMOOTH AND SLIGHTLY POROUS SMEAR LAYER WITH FULLY OR PARTIALLY BLOCKED TUBULES EVENLY DISTRIBUTED THROUGHOUT THE SURFACE AND WITH SOME LOOSE DEBRIS
FIGURE 3-1-15 APICAL THIRD OF THE ROOT CANAL INSTRUMENTED AND IRRIGATED WITH SALINE. THE SMEAR LAYER COVERED THE DENTINAL TUBULES
236
Results 3.1
Group 6 (Saline and Ozone)
SEM observations of irrigation with saline and ozone are shown. The smear layer in the
coronal, middle and apical one-third was moderately removed with few openings of
dentinal tubules (Figs 3.1.16, 3.1.17, 3.1.18).
FIGURE 3-1-16 MIDDLE THIRD OF THE ROOT CANAL IRRIGATED WITH SALINE AND OZONE BUBBLED IN FOR 10 SECONDS. LARGE AREAS OF THIN SMEAR LAYER WITH FULLY OR PARTIALLY BLOCKED TUBULE ORIFICES ARE SHOWN
237
Results 3.1
FIGURE 3-1-17 CORONAL THIRD SPECIMENS IRRIGATED WITH SALINE AND OZONE BUBBLED IN FOR 10 SECONDS SHOWING A MODERATE SMEAR LAYER REMAINING ON THE SURFACE OF THE ROOT CANAL
FIGURE 3-1-18 IN THE APICAL THIRD THE SPECIMENS IRRIGATED WITH SALINE AND OZONE BUBBLED IN FOR 10 SECONDS SHOWED A THIN SMEAR LAYER COVERING THE SURFACE, WITH A FEW DENTINAL TUBULES CLEARLY VISIBLE
238
Results 3.1
Group 7 (Sterilox)
In the specimens irrigated with Sterilox (pH 6.7), the smear layer was smooth and
slightly porous (Figs 3.1.20, 3.1.21). However, in some cases, the coronal third showed a
clean area of smear layer with openings of the dentinal tubules seen (Fig 3.1.19).
FIGURE 3-1-19 SPECIMEN IN THE CORONAL THIRD AFTER STERILOX IRRIGATION SHOWING CLEAN ROOT CANAL WALLS WITH CONSIDERABLE SMEAR LAYER MISSING (ORIGINAL MAGNIFICATION X 4000)
239
Results 3.1
FIGURE 3-1-20 SMEAR LAYER COVERING THE DENTINE WALL AND SOME OF EXPOSED DENTINE TUBULES IN THE MIDDLE REGION TREATED BY STERILOX IRRIGATION (ORIGINAL MAGNIFICATION X 4000)
FIGURE 3-1-21 SPECIMEN IN THE APICAL THIRD TREATED WITH STERILOX SHOWING THE ROOT CANAL COVERED WITH A HEAVY SMEAR LAYER AND DEBRIS WITH VERY FEW EXPOSED DENTINAL TUBULES (ORIGINAL MAGNIFICATION X 1000, X 4000)
240
Results 3.1
Group 8 (Sterilox and Ozone)
When ozone was used in conjunction with sterilox, the root canal walls showed no
smear layer but open dentinal tubules in the coronal and middle third (Figs 3.1.22,
3.1.23). However, in the apical one-third, a smear layer remained on the root canal
surface (Fig 3.1.24).
FIGURE 3-1-22 CORONAL THIRD OF ROOT CANAL IRRIGATED WITH STERILOX AND OZONE BUBBLED IN FOR 10 SECONDS AFTER EACH FILE. THIS RESULTED IN OPEN DENTINAL TUBULES AND REMOVAL OF THE SMEAR LAYER. SCATTERED LOOSE DENTINE DEBRIS IS PRESENT IN SOME AREAS
241
Results 3.1
FIGURE 3-1-23 MIDDLE THIRD OF ROOT CANAL IRRIGATED WITH STERILOX AND OZONE BUBBLED IN FOR 10 SECONDS AFTER EACH FILE. INDIVIDUAL ORIFICES OF DENTINAL TUBULES ARE CLEARLY OBSERVED, WITH LOOSE DENTINE DEBRIS ALSO PRESENT
FIGURE 3-1-24 PRESENCE OF THE SMEAR LAYER ON THE SURFACE OF THE APICAL THIRD OF A ROOT CANAL IRRIGATED WITH STERILOX AND OZONE BUBBLED IN FOR 10 SECONDS. PARTIALLY BLOCKED TUBULES ARE LIGHTLY DISTRIBUTED THROUGH THE SURFACE (ORIGINAL MAGNIFICATION X 4000)
242
Results 3.1
Statistical analysis showed a significant difference in cleanliness of the smear layer
between group 5 (control) and groups 1, 2 and 4 in the coronal, whilst there was a
significant difference between group 5 and groups 2, 4 and 8 in the middle and apical
third of the root canal there is significant difference in group 5 and 2 and 8. However,
there was no significant difference between group 5 and groups 3, 6, and 7. Moreover a
statistical significant difference (p<0.05) was detected between groups 5 and 4 in the
coronal third and middle thirds (Figs 3.1.25, 3.1.26 and 3.1.27).
12 10 8 Score 6 3 4 2 2 1 0
) 0 (1) 3) 5) 6) l ( ( ( (8 C e ter er (4) ine n ox a at i il NaO W Sal Sal Sterilox (7) Ster ed ated NaOCl (2) ated W at ed n o nat z zon o O O Ozon z O Irrigation Group
FIGURE 3-1-25 DISTRIBUTION OF SCORES AMONG THE GROUPS IN THE CORONAL THIRD
243
Results 3.1
12 10 8 Score 6 3 4 2 2 1 0
) 0 (1) 3) 5) 6) l ( ( ( (8 C e ter er (4) ine n ox a at i il NaO W Sal Sal Sterilox (7) Ster ed ated NaOCl (2) ated W at ed n o nat z zon o O O Ozon z O Irrigation Group
FIGURE 3-1-26 FREQUENCY OF SCORES IN THE EXPERIMENTAL GROUPS IN THE MIDDLE ONE THIRD
12 10 8 Score 6 3 4 2 2 1 0
) 0 (1) 3) 5) 6) l ( ( ( (8 C e ter er (4) ine n ox a at i il NaO W Sal Sal Sterilox (7) Ster ed ated NaOCl (2) ated W at ed n o nat z zon o O O Ozon z O Irrigation Group
FIGURE 3-1-27 DISTRIBUTION OF SCORES AMONG THE GROUPS IN THE APICAL ONE THIRD
244
Results 3.1
The result of the Kruskal-Wallis test revealed that there was a statistically significant
difference between all the groups in the coronal, middle and apical third of the root canal
(p < 0.05) Table 3.1.1.
TABLE 3-1-1 P VALUES- STATISTICAL SIGNIFICANT DIFFERENCE BETWEEN THE CORONAL, MIDDLE AND APICAL THIRDS OF THE ROOT CANAL (SIGNIFICANT IN BOLD)
Coronal third Middle third Apical third Chi-square 27.056 21.873 29.155 Significant 0.000 0.003 0.000
To confirm the significant differences between the groups 28 comparative statistical
analyses were carried out between the groups using the Mann-Whitney test. The
statistical significant of the differences between all eight groups is summarized in Table
3.1.2. The ozonated NaOCl (Group 2) was more significant in the removal of the smear
layer from the coronal, middle and apical third of the root canal. The second best group
was the ozonated sterilox (Group 8) which was effective in removing the smear layer
from the middle and apical part on the root canal as well as NaOCl (Group 1) was
effective in removing the smear layer from the coronal compared to saline (Group 5).
245
Results 3.1
TABLE 3-1-2 RESULT OF THE MANN-WHITNEY TEST COMPARING SMEAR LAYER REMOVAL IN EACH GROUP (STATISTICALLY SIGNIFICANT DIFFERENCE IN BOLD)
Groups Coronal Middle Apical 1 and 2 0.02 0.005 0.002 1 and 3 0 0.004 0.012 1 and 4 0.582 0.263 1 1 and 5 0 0.006 0.012 1 and 6 0.019 0.628 1 1 and 7 0.211 0.628 1 1 and 8 0.37 0.014 0.122 2 and 3 0 0 0 2 and 4 0.001 0.057 0.001 2 and 5 0 0 0 2 and 6 0 0.002 0.004 2 and 7 0 0.002 0.001 2 and 8 0.303 1 0.12 3 and 4 0.001 0.001 0.042 3 and 5 0.871 0.885 1 3 and 6 0.036 0.036 0.012 3 and 7 0.001 0.036 0.042 3 and 8 0 0 0.002 4 and 5 0.001 0.001 0.024 4 and 6 0.054 0.054 0.65 4 and 7 1 0.054 1 4 and 8 0.057 0.141 0.062 5 and 6 0.056 0.023 0.005 5 and 7 0.001 0.023 0.023 5 and 8 0 0 0 6 and 7 0.087 1 0.65 6 and 8 0.002 0.005 0.224 7 and 8 0.011 0.005 0.062
246
Discussion 3.1.4
3.1.4 DISCUSSION
Whether the smear layer should be preserved or eliminated during instrumentation is
still a subject of controversy. Kennedy et al. (1986) reported that with the smear layer
intact, apical leakage was significantly increased. The smear layers presence plays a
significant role in apical leakage; its absence makes dentine more conductive to better
and closer adaptation of the gutta-percha to the canal wall (Baumgartner & Mader
1987). Evans & Simon (1986) however showed that the smear layer had no significant
effect on apical microleakage. A recent study showed that no statistically significant
difference in glucose penetration or fluid transportation was observed along the 4 mm
apical root filling, with gutta-percha and AH 26, whether or not the smear layer was
removed prior to filling (Shemesh et al. 2006). It has been suggested by some authors
that keeping the smear layer may block the dentinal tubules and limit bacterial or toxin
penetration by altering the dentinal permeability (Pashley et al. 1981, Safavi et al. 1990).
The bactericidal potential of sodium hypochlorite (NaOCl) is not in doubt (Siqueira et
al. 1997) but the fact that it is highly toxic to human tissues is of concern (Spangberg et
al.1973, Pashley et al. 1985).
Concern about this potentially dangerous side effect has led to the recommendation that
irrigating needles should be placed passively in the canal in order to prevent apical
extrusion (Brown et al.1995).
247
Discussion 3.1.4
Various chemicals have been used to remove the smear layer; such as different
formulations of EDTA, acetic acid, citric acid, polyacrylic acid and tannic acid (Mc
Comb & Smith 1975, Torabinejad et al. 2002).
The finding of the present study confirms previous reports that NaOCl is not always
very effective in removing the smear layer when used alone. Reports have indicated that
the use of EDTA and NaOCl together could be an effective method of smear layer
removal (Baumgartner & Mader 1987, Calt & Serper 2000). Sodium hypochlorite did
not remove all the smear layer in the middle and apical one-third of the root canal in the
present study. Morgan & Baumgartner (1997) reported that the quantity of smear layer
removed by an irrigation material was directly related to its pH and the time of
application. Siqueira et al. (2000) found no difference in the antibacterial effect of 1%,
2.5% and 5.2% NaOCl. They suggested that copious irrigation with NaOCl may
maintain a chlorine reserve that is sufficient to eliminate bacterial cells and compensate
for the effect of concentration.
Yamada et al. (1983) showed that the most efficient final irrigation for removing
superficial debris was with 2.25% NaOCl solution. In the present study, 0.5% NaOCl
solution was used which was shown, in a previous study, to be the lowest concentration
effective in dissolution of the pulp tissue (Spano et al. 2001).
248
Discussion 3.1.4
Byström & Sundqvist (1985) showed no antibacterial difference between 0.5 % and 5 %
NaOCl solutions. Heling & Chandler (1998) analyzed the antimicrobial effect of irrigant
combinations within dentinal tubules and concluded that 0.12 % CHX and 1 % NaOCl
were similarly effective.
In this work, it was verified that there was no difference in the preparation of the
specimens for SEM using either a saw or a chisel. (Fig 3.1.28, 3.1.29).
FIGURE 3-1-28 MIDDLE THIRD OF ROOT CANAL IRRIGATED WITH NAOCL AND OZONE BUBBLED IN IT FOR 10 SECONDS. THIS SHOWS CLEAN, EXPOSED DENTINAL TUBULES BUT WITH SOME DEBRIS AND SOME LOCALISED SMEAR LAYER. THIS SPECIMEN WAS PREPARED FOR SEM USING A SAW
249
Discussion 3.1.4
FIGURE 3-1-29 MIDDLE THIRD OF ROOT CANAL IRRIGATED WITH NAOCL AND OZONE BUBBLED IN IT FOR 10 SECONDS. THIS SHOW CLEAN, EXPOSED DENTINAL TUBULES BUT WITH SOME DEBRIS. THIS SPECIMEN WAS PREPARED FOR SEM USING A CHISEL
Another finding of the present study revealed that the use of NaOCl with ozone was
more significant in removal of the smear layer than the NaOCl only in the middle and
apical third of the root canal compared to the control group.
The oxidizing ability of ozone, an allotropic form of oxygen, has been known to be
effective in the inactivation of pathogenic microorganisms. The use of ozone may be
justified as a new option as an irrigating agent with antimicrobial action. The
antimicrobial effect of ozone results from oxidation of microbial cellular components.
Ozone is a highly reactive form of oxygen that is generated by passing oxygen through
high voltage (Tortora et al. 1998). Oxidation is the removal of electrons from an atom or
molecule, a reaction that often produces energy. A number of biological oxidations
involve the loss of hydrogen atoms (dehydrogenation reaction). Oxygen is essential for
the survival of cells that follow aerobic metabolism, although it has a considerable toxic
effect on microareophiles and anaerobic bacteria. Aerobic respiration involves ATP
250
Discussion 3.1.4
generation at specific sites in the electron transport chain via oxidative phosphorylation
(the final electron acceptors include oxygen). Although aerobic bacteria contain a
variety of enzymes that protect them from oxygen toxicity, microaerophilic and
anaerobic bacteria are devoid of these protective mechanisms.
The final electron acceptors in anaerobic respiration include inorganic substrate-sulphate
ions, nitrate ions and carbonate ions. Oxygen is not used in the fermentation process.
Anaerobic bacteria use organic compounds as final oxygen acceptors during its energetic
metabolism (Gould & Chamberlaine 1995).
It is generally accepted that oxidation mediated by ozone destroys the cell walls and
cytoplasmic membranes of bacteria and fungi (Yamayoshi & Tatsumi 1993). After the
membrane is damaged by oxidation, its permeability increases and ozone molecules can
readily enter the cells (Bünning & Hempel 1996), causing the microorganism to die.
NaOCl is useful because:
a) Ozonated NaOCl releases hypochlorous acid which reacts with
insoluble proteins to form soluble polypeptides, amino acids and
assorted by-products
b) NaOCl acts as an organic and fat solvent, degrading fatty acids and
transforming them into fatty acid salts and glycerol thus reducing the
surface tension of the residual solution.
c) The chloramines produced interfere with cell metabolism and cause
destruction of cell walls and cytoplasmic membranes of
microorganisms.
251
Discussion 3.1.4
Irrigation with distilled water or saline is effective in eliminating loose debris from the
coronal and middle thirds of the root canal, but they have little effect on the smear layer
(Walker & del Rio 1991).
An evaluation of the smear layer integrity demonstrated that neither distilled water or
saline was effective in its removal. However, in some specimens, openings of the
dentinal tubules was observed in the apical third by irrigation by distilled water
compared to saline (pH 7.4). This may be associated with the acidity of the distilled
water which was (pH 5.7).
Yang & Bae (2002) claimed that in the efficacy of removing the smear layer there was
no significant difference between saline irrigation and NaOCl.
The sodium hypochlorite solution application produces a significant and complex
alteration on the micromorphology of deciduous dentine. The higher the concentration
of the solution the lower can be the time for the application of the solution for the
complete removal of the collagen fibrils (Correr et al. 2006).
Methods for producing electrochemically activated water have been developed and used
extensively in Russia and Japan. As an antimicrobial agent, electrochemically activated
water have been used for many applications, such as irrigating root canals,
supplementing distilled water in dental unit water lines, decontaminating food products
and surfaces and disinfecting medical equipment (Marais 2000, Solovyeva & Dummer
2000, Russell 2003, Marais & Williams 2001, Gulabivala et al. 2004 , Deza et al. 2005).
Electrochemically activated water (ECA) cleaned the root canal wall surfaces in a
significant way, removing the smear layer in large areas. The result of this study
252
Discussion 3.1.4
confirms previous reports that irrigation with electrochemically activated solutions
provide efficient cleaning of root canal walls and may be an alternative to NaOCl in
conventional root canal treatment (Solovyeva & Dummer 2000). In most specimens in
the study, irrigation with Sterilox and ozone resulted in removal of the smear layer in the
coronal and middle third areas of the root canal only.
It has been demonstrated that ECA is deemed harmless to humans; even when patients
drink considerable quantities of ECA and indeed open wounds been washed with it
(Leonov 1997, Bakhir 1997). The sterilox technology device consist of two solutions,
the solution accumulating at the anode is harvested as the anolyte.
This possess an odour akin to bleach. The catholyte dose not possess an obvious smell
but has a soapy feel (Marais 2000). Gulabivala et al. (2004) demonstrated that
electrochemically activated anolyte solution (especially when ultrasonicated), has
potential as a root canal irrigant even if it is not as potent as 3% NaOCl. The potentially
reduced toxicity and less dentine weakening effect may prove to be advantageous.
Prince et al. (2002) reported on the ability of a commercially produced biocide
(Aquabox system, Steribox technologies Ltd, Abingdon, UK) to control Legionella spp.
and heterotrophic bacteria in industrial cooling towers. The ability of Sterilox®
(electrochemically activated water (Sterilox Technologies, Sterilox Medical Ltd,
Yardley, PA, USA) to kill Bacillus subtitles spores has been shown (Loshon et al. 2001).
Ozone is useful for endodontic disinfection and as an additional source of free radicals.
Ozone leads to lipid peroxidation.
253
Discussion 3.1.4
A recent study by Marending et al. (2007) reported that the concentration dependent
hypochlorite effect on the mechanical dentine properties with the dissolution of organic
dentine component, immersion of root dentine in 5 ml of 1% NaOCl at 37 ºC did not
cause a significant drop in their elastic modulus or flexural strength compared to the 5%
and 9% hypochlorite reduced elastic modules and flexural strength by half, also both
carbon and nitrogen content were significantly reduced by those concentration.
A recent study evaluated the influence of a direct high-dose gaseous ozone application,
2100 ppm for 60 seconds, on dentine and enamel shear bond strength to composite. A
high-dose of ozone gas for 60 seconds did not affect the shear bond strength value of
bovine enamel and dentine samples to composite resin. In contrast, bleaching using
H2O2 resulted in significant decreased bond strength (p < 0.05) on enamel specimens
(Schmidlin et al. 2005). Controversy use the HealOzone treatment alone had a tendency
to weaken the shear bond strength of glass ionomers bonded to bovine enamel, but this
was eliminated by the use of ozone reductants (aqua, sodium fluoride xylitol, citric
acid). The group subjected to ozone exhibited lower values of shear bond strength than
that of the group subjected to ozone and reductants liquid (Czarnecka et al. 2004).
It was also reported that the application of ozone, for 10 seconds to restorative materials,
did not significantly affect the surface hardness of the materials tested (p = 0.15),
(without ozone -116.4 N, with ozone -128.6 N) (Campbell et al. 2003).
254
Discussion 3.1.4
Ideally, an irrigation solution is expected to remove the smear layer with as low of a
toxicity as possible. Normally, as the concentration of a solution is increased, unwanted
cytotoxic effect are produced.
Oxidative potential water is accepted to be safe for patients to hold in the oral cavity,
due to its ability to lose the high oxidation -reduction potential and low pH upon to light
and / or organic substance (Hata et al. 1996).
The present study demonstrated that ozonated NaOCl was more significant in removal
of the smear layer from all the root canal parts (coronal, middle and apical) and the
second best groups was ozonated sterilox for removing the smear layer from the middle
and apical thirds of the canals. Ozonated water (group 4) shown favorable result in
removal of the smear layer from the coronal and middle thirds of the canals, as well as
NaOCl are in favourable results for removing the smear layer from the coronal parts.
Irrigation, via a syringe, particularly with a large volume of irrigation, created an
effective fluid flow and circulation in the canal system. The addition of ozone to these
established irrigants in root canals leads to a trend in an improved and more intensive
smear layer removal but in some groups, this was not significant.
255
Conclusion 3.1.5
3.1.5 CONCLUSION
Under the limitations of this study, it was concluded that irrigation of ozonated NaOCl
(Group 2) was most significant in smear layer removal compared to groups 3, 4, 5, 6 and
7. The second best groups were ozonated sterilox (Group 8) for removal of the smear
layer. Ozonated water (Group 4) and NaOCl (Group 1) also showed favourable results in
removal the smear layer. The additional of ozone to some established irrigants led to
more smear layer removal.
256
Introduction 3.2
3.2 ANTIMICROBIAL EFFECT OF OZONE ON MICROORGANISMS IN AN IN- VITRO STUDY. A PILOT STUDY
3.2.1 INTRODUCTION
Infection is a cause of apical periodontitis and the dominant cause of failure of root canal
treatment. Bacteria present in obturated root canals may be denied access to nutrients
and die, or they may survive and ultimately proliferate. They may be killed by root
filling materials (Orstavik 1988, Heling & Chandler 1998). However, the prognosis for
successful root canal treatment is significantly improved if the root canal is free of
bacteria when obturated (Heling & Shapira 1978). The key objective at all stages of
therapy is therefore the elimination of microorganisms.
During hand preparation of canals using saline the number of bacteria present is reduced
significantly, but not such that negative cultures are achieved during one appointment
(Bystrom & Sundqvist 1981). Hence an antibacterial irrigating solution is used, most
commonly sodium hypochlorite (NaOCl) in concentrations ranging from 0.5% to 5.25%.
This chemical oxidant exhibits powerful antimicrobial activity and is an excellent
solvent of necrotic tissue. However, it is highly irritating to periapical tissues especially
at high concentrations (Becking 1991, Ercan et al. 2004).
Ideally, an intracanal medicament should be able to neutralize the virulence of
microorganisms and pathogenic factors, such as proteins, enzymes, toxins, aggregation
substances and induce a host response that favours periapical tissue healing.
257
Introduction 3.2
Nevertheless, studies have revealed that the chemomechanical preparation perse is not
sufficient to predictably render root canals bacteria-free, with about 40–50% of the
prepared canals still containing cultivable bacteria (Bystrom & Sundqvist 1985, Shuping
et al. 2000).
E. faecalis is a gram-positive facultative anaerobe found among the commensally
microflora of the human intestinal tract. Although the prevalence of E. faecalis in root
canals was already reported in 1959 (Winkler & Amerongen 1959), this bacterium has
recently attracted the attention of dental researchers because it has been isolated
frequently from dentine caries and from infected root canals (Siqueira & Uzeda 1996,
Siren et al. 1997, Nakajo et al. 2004). Furthermore, E. faecalis, which possesses various
survival and virulence factors (Stuart et al. 2006), is a major pathogen in the aetiology of
apical periodontitis after root canal treatment. Many studies have reported the existence
of E. faecalis in root-filled teeth with apical periodontitis (Sundqvist et al. 1998,
Siqueira & Rocas 2004, Rocas et al. 2004).
Vivacqua-Gomes et al. (2005) assess the presence of E. faecalis after root canal
treatment in single or multiple visits in an ex vivo model. They projected that neither
single- nor multiple-visit root canal treatment ex vivo, eliminated E. faecalis completely
from dentinal tubules. Up to 60 days after root filling, E. faecalis remained viable inside
dentinal tubules. When no sealer was used, E. faecalis presented a higher growth rate.
258
Introduction 3.2
The use of ozonated water for treatment of endodontic infections has been suggested
(Hems et al. 2005). Ozone is used for disinfection as well as removing discolouration,
and to avoid adverse tastes and odours of public water supplies in the U.S.A (Fonseca et
al. 2001).
A study by Nagayoshi et al (2004a) demonstrated that ozonated water (4 mg/l) for 10
seconds was effective in killing gram-positive and gram-negative oral microorganisms
and oral Candida albicans in pure culture and had strong bactericidal activity against the
bacteria in plaque biofilm (p < 0.01). Also Arita et al (2005) found that aqueous ozone
(2-4 mg/l for 1 min.) reduced the number of Candida albicans on denture plates
significantly (p < 0.01).
Recently, a number of studies have been undertaken on the effects of ozone on treating
dental caries and the reduction of oral microorganisms (Abu-Naba 2003, Nagayoshi et
al. 2004, Arita et al. 2005, Dahnhardt et al. 2006, Estrela et al. 2007).
The present study aimed to evaluate if ozone treatment had any effect on
microorganisms in the root canal system in vitro and to assess if ozone could kill a strain
of E. faecalis in vitro.
259
Material and Methods 3.2.2
3.2.2 MATERIAL AND METHODS
The present study used the in-vitro model originally described by Chang et al. 2003 with
some modification. Enterococcal identification was performed using colonial
morphology, oxygen tolerance, Gram-staining characteristics and rapid ID 32 STREP
(Bio Merieux, Marcyl’Etoile, France).
3.2.2.1 TEST ORGANISMS
E. faecalis was cultured overnight on blood agar plates. A suspension of the
microorganisms was made up to an approximate concentration of 108/ml using
McFarland Standards in Phosphate Buffered Saline (PBS). Serial dilutions to 107, 106,
105 and 104/ml were made. From these 50 μl of each concentrate were pipetted into a
well of a microtitre plate. In group A, the 50 μl in each well was treated with ozone
from the HealOzone unit at different exposure times. Ozone was delivered into the cup
closely adapted to the bottom of the plate for either10s, 20s, 40s, 60s or 120s through the
special needle adapted to the hand piece with the Heal Ozone™ device.
In-group B, 50 μl in each well was treated subsequently with 40 μl of 0.5% NaOCl
pipetted into each well followed by the use of the HealOzone exactly as in group A
except that only air was delivered with no ozone.
The inactivation of NaOCl next was accomplished by the addition of 10 μl of 5% of
sterile sodium thiosulphate pipetted into each well.
In group C, exactly the method used in group A was used but only air was delivered
from the HealOzone as in group B.
260
Material and Methods 3.2.2
Samples were taken from the well, spiral-plated and incubated at 35°C for 5 days. A
count of the colony forming units (C.F.U.) was performed using the spread-plate
method.
3.2.2.2 OZONE APPLICATION
The system used was the HealOzone (KaVo Dental, Biberach, Germany) (Figs 3-2-1, 3-
2-2 and 3-2-3). The HealOzone is a self-contained device that produces ozone at a fixed
concentration of 2100 p.p.m. ozone ± 10 % at a flow rate of 102.5 cc min-1 in the
endodontic mode and has the facility for research purposes to be set to deliver air
without any ozone.
The setting to deliver air or ozone was done by a second person who recorded this
separately and therefore the other operator was blinded, as was the patient in the later
clinical trials in this thesis.
3.2.2.3 STATISTICAL ANALYSES
The SPSS (Statistical Package for Social Sciences), version 14 was used to analyse the
data.
The descriptive statistics, including the median, minimum and maximum values were
calculated for the treatment groups. The correlation tests were performed using the non-
parametric Spearman’s correlation coefficient. The Mann-Whitney test was used to
determine whether significant difference existed between the treatment groups. The level
of significant was measured using the Exact sign test (p < 0.05).
261
Material and Methods 3.2.2
FIGURE 3-2-1 HEALOZONE UNIT (KAVO, GERMANY) DELIVERY CAPABILITY OF OZONE: 2,100-PPM CONC OF OZONE, 102.5 CCS /MIN FLOW RATE
262
Material and Methods 3.2.2
FIGURE 3-2-2 HEALOZONE (KAVO) HANDPIECE USED FOR OZONE DELIVERY WITH DIFFERENT DISPOSABLE REMOVABLE SILICONE CUPS
263
Material and Methods 3.2.2
FIGURE 3-2-3 THE NEEDLE (KAVO) TO DELIVER OZONE INTO ROOT CANALS
264
Result 3.2.3
3.2.3 RESULTS
To examine antimicrobial activity, E. faecalis was exposed to several exposure times of
both gaseous ozone or air or NaOCl and air as shown in Fig 3-2-3-1. Air had no
significant effect at any time interval. Both gaseous ozone and NaOCl had a significant
antimicrobial effect against E. faecalis in the 10s group compared to air.
In contrast, all of E. faecalis were killed by gaseous ozone in the 60s and 120s groups at
the concentration of 5.8 x 106 and lower. Moreover, ozone had the ability to kill E.
faecalis at 120s at a concentration of 5.9 x 107 and at 40s in a concentration of 5.9 x 104.
However, E. faecalis was detected in this latter 40s treated NaOCl with air group
although they were dramatically reduced in numbers. NaOCl killed all the E. faecalis in
the 60s and 120s group at the concentration of 5.9 x 104 and NaOCl had the ability to
kill all the E. faecalis at 120s in the concentrations of 5.9 x 105 and 5.8 x 106 . It takes
more time for NaOCl and air to achieve complete elimination of E. faecalis than with
the use of ozone gas as shown in Table 3-2-3-1.
265
Result 3.2.3
TABLE 3-2-3-1 ANTIMICROBIAL EFFICACY OF MEDICATION
Base line (Bacterial Irrigation Exposure Time concentration) Groups 10s 20s 40s 60s 120s Ozone 5x 107 5x 106 5x 104 500 5 6.6 x 108 NaOCl 6 x 107 5 x 107 5 x 105 5 x 103 5 x 102 with air Air 6 x10 8 5.5 x 108 7 x 107 6 x 107 5.1 x 107 Ozone 5.5 x 106 5 x 105 5 x 103 20 0 5.9 x 107 NaOCl 5 x 107 5 x 105 5 x 102 30 10 with air Air 5.7 x 107 5.3 x 107 5 x 107 5.1 x 107 5 x 107 Ozone 4 x 105 5 x 104 3 x 103 0 0 5.8 x 106 NaOCl 5 x 105 4.5 x 104 3.5 x 103 20 0 with air Air 5.5 x 106 5.3 x 106 5.1 x 106 5 x 106 4 x 106 Ozone 5 x 103 4 x 103 4 x 102 0 0 5.9 x 105 NaOCl 4 x 104 3.4 x 103 2 x 103 3.3 x 102 0 with air Air 5.9 x 105 5.8 x 105 5.5 x 105 5 x 105 4.2 x 105 Ozone 5 x 102 3 x 102 0 0 0 5.9 x 104 NaOCl 4 x 103 4 x 102 5 0 0 with air Air 5.8 x 104 5.6 x 104 5 x 104 4.8 x 104 4.3 x 104
266
Result 3.2.3
100
80
Ozone 60 NaOCl Air 40
Bacterial reduction (%) 20
0 Baseline 10s 20s 40s 60s 120s Exposure time
FIGURE 3-2-3-1 MEDIAN LEVEL OF C.F.U. REMAINING AFTER DIFFERENT EXPOSURE TIMES (IN SECONDS) TO OZONE, NAOCL WITH AIR OR AIR
To compare the antimicrobial activity of gaseous ozone and the NaOCl disinfectant and
the exposure time, the non-parametric Spearman’s rank analysis correlation was used.
There was a statistically significant inverse association between the exposure time and
the colony count in both the gaseous ozone (rs = -0.98, P = 0.005) and NaOCl with air
groups (rs = -1.00, P=0.001). Therefore, it can be concluded that the colony count
reduced with increasing exposure time for both gaseous ozone and the NaOCl groups.
267
Result 3.2.3
The Mann-Whitney test showed there was no statistically significant difference between
the ozone and the NaOCl treated groups. However, there was a significant difference
between the ozone or NaOCl versus air (Table 3-2-3-2).
TABLE 3-2-3-2 DESCRIPTIVE STATISTICS BETWEEN THE TREATMENT GROUPS
Irrigation Exposure Time Groups 10s 20s 40s 60s 120s Mann- Ozone vs. 0.421 0.841 0.548 0.690 1 Whitney test NaOCl Ozone vs. 0.008 0.008 0.008 0.008 0.008 Air NaOCl vs. 0.008 0.008 0.008 0.008 0.008 Air Statistically significant difference in bold.
The result of the Kruskal-Wallis test in Table 3-2-3-3 showed that there was a
significant difference among the treatment groups.
TABLE 3-2-3-3 DESCRIPTIVE STATISTIC FOR THE TREATMENT GROUPS
Irrigation Exposure Time Groups 10s 20s 40s 60s 120s Kruskal- Ozone Wallis test NaOCl Air 0.001 0.002 0.001 0.001 0.001
Statistically significant difference in bold.
268
Discussion 3.2.4
3.2.4 DISCUSSION
These results need to be interpreted with caution as the microorganisms in the NaOCl
group were effectively diluted in volume by 50% with the addition of the NaOCl and
sodium thiosulphate. This would have made it appear that the NaOCl was more effective
than it actually was.
It has been reported that ozone, in the gaseous or aqueous phases has strong oxidizing
powers with a reliable microbial effect (Broadwater et al. 1973, Nagayoshi et al. 2004,
Arita et al. 2005). Ozone destroys the cell walls and cytoplasmic membranes of bacteria
and fungi by oxidation (Bocci et al. 1993, Yamayoshi and Tatsumi 1993). After the
membrane is damaged by oxidation, its permeability increases and ozone molecules can
readily enter the cell, causing the microorganisms to die (Bűnning and Hempel 1996).
Since the efficacy of disinfectants is usually evaluated on the basis of the reduction of
cultivable microorganisms, in the present study we examined the microbicidal activity of
gaseous ozone produced by the HealOzone device system and 0.5% NaOCl and air
against E. faecalis at different exposure times and our results were consistent with those
of previous studies (Nagayoshi et al. 2004, Polydorou et al.2006). When E.Faecalis was
treated with gaseous ozone, we found a trend to decrease in the number of CFU of these
bacteria including at the 10 seconds application time. Air had no effect.
In the current study, ozone revealed a favourable result in the short time of 10s
compared with NaOCl which was already diluted 100%, which explains how ozone can
work in a short time whilst the NaOCl needs more time to work.
269
Discussion 3.2.4
Many studies have shown that chemomechanical methods are not able to entirely clean
the root canal space. Among root canal preparation techniques, ultrasonic
instrumentation with NaOCl produced a better cleanliness of the root canal walls
(Panighi & Jacquot 1995).
No toxicity to periapical tissues is an important requirement of endodontic irrigants.
As mentioned earlier although NaOCl has a strong antimicrobial activity it can corrode
dental equipment and can damage periapical and other oral tissues especially at high
concentrations (2.5% and 5.25%) (Gatot et al. 1991, Heling et al. 2001).
Sodium hypochlorite is the most commonly employed root canal irrigant, but no general
agreement exists regarding the optimal concentration to be used, which might range
from 0.5% to 5.25%. Within this range, its antimicrobial activity increases
proportionally (Vianna et al. 2004). However, its toxicity also increases as a trade-off
between possible toxic side effects and antimicrobial activity, and therefore a low
strength concentration was used in these studies which is probably the most common
concentration used in dental practices.
Nagayoshi et al. (2004) found that 2.5% NaOCl damaged the L-929 mouse fibroblast
cell when compared with ozonated water. This low cytotoxicity of ozonated water may
be caused by a rapid degradation of ozone just after contact with organic compounds,
and is one of its major environmental advantages.
In the current study, ozone kills all E. faecalis when its concentration in suspension is
5.8 × 106 ml and lower, at an exposure time ≥ 60s. However, Chang et al. (2003)
reported that ozone killed all E. faecalis when its concentration in suspension was
270
Discussion 3.2.4
106/ml and lower, even at an exposure times of only 10s. However, the differences are
explained by the fact that he used full flow rates i.e. x 615 cc/ min, whilst in the current
study the flow rates in the endo mode was 6 times less i.e. 102.5 cc/ min and therefore
he used 6 times the dose of ozone.
In dentistry, the cytotoxicity of antimicrobials is clinically relevant only if contact with
resident oral cells takes place. Cytotoxicity is not significant when applying ozone gas
onto non-pulp exposed carious tooth substance via a sealing suction system as a
prerequisite to avoid inhalation. For root canal disinfection, cytotoxicity is relevant
owing to probable contact with cells in the apical region. In a study by Huth et al.
(2006), ozone gas performed well compared with the established endodontic irrigants
(CHX 2%; NaOCl 5.25% and 2.25%; H2O2 3%), which showed equal or even higher
cytotoxicity potential than ozone.
In addition, it is also possible that the ozone gas applied into the moist root canal, as
currently performed with the HealOzone device (KaVo), dissolves in canal fluids,
thereby resulting in aqueous ozone that is exposed to tissues.
In contrast to ozone gas, aqueous ozone revealed essentially no toxic effects,
demonstrating a higher biocompatibility than even CHX 0.2% , not to mention the high
cytotoxicity of NaOCl and H2O2. The latter findings may be relevant in assessing the
usefulness of ozone for endodontic disinfection, adjunctive periodontal treatment or as a
caries-preventive mouth rinse. A study showed that an 80 second application of ozone
with the HealOzone device is a very promising therapy for eliminating residual
microorganisms in deep cavities and therefore of potentially increasing the clinical
271
Discussion 3.2.4
success of restorations. A 40 second application of ozone was found to reduce
significantly the numbers of S. mutans, but not to the extent of the other treatments
(Polydorou et al. 2006).
However, in the present study an application of ozone for 60 seconds significantly
eliminated all the E. faecalis, whilst NaOCl killed all E. faecalis within a 120 second
period. Spratt et al. (2001) studied the bactericidal effect of 2.25 % NaOCl, 0.2 %
chlorhexidine, 10% iodine or phosphate-buffered saline on single species of biofilms,
(Prevotella intermedia, Peptostreptococcus micros, Streptococcus intermedius,
Fusobacterium nucleatum and E. faecalis) derived from a range of root canal isolates.
They concluded that the efficacy of a particular agent was dependent on the nature of the
organism in the biofilm and on the contact time. NaOCl was generally the most effective
agent tested followed by iodine. However, the clinical effectiveness of these agents must
be regarded in the light of the complexity of root canal anatomy and polymicrobial
nature of root canal infections Abdullah et al. (2005) evaluated and compared the
efficacy of 3% NaOCl, 10% povidone iodine, 0.2% chlorhexidine, 17% EDTA and
calcium hydroxide on a clinical isolate of E. faecalis grown as a biofilm or planktonic
suspension phenotype. The difference in gradients of bacterial killing amongst the
biofilm, planktonic suspension or pellet presentation was significant and dependent upon
the agent, except for NaOCl and calcium hydroxide, in which no difference could be
detected. NaOCl was the most effective agent and achieved 100% kill for all
presentations of after a 2-minute contact time. The result of this study supports this
finding that the NaOCl kill all the E. faecalis at 2 minutes (120 seconds).
272
Discussion 3.2.4
Studies have shown that the magnitude of the antimicrobial efficacy of a medicament
can be influenced by the methodology, microbial characteristics in the biofilm, exposure
time and concentration of the substance tested (Spratt et al. 2001, Estrela et al. 2003).
The antimicrobial effect of NaOCl, by direct contact on E. faecalis occurred after 2
minutes (Estrela et al. 2003, Abdullah et al. 2005).
The findings of this investigation are consistent with those of previous studies that
showed bacterial persistence after use of potent irrigants in endodontic infections
(Bystrom et al. 1985, Sjogren et al. 1991, Estrela et al. 2004, Nair et al. 2005).
The results of the present study differ from those of other recent studies (Estrela et al.
2007, Hems et al. 2005), which is due to differences in methodologies, particularly the
irrigation dose of ozone and the contact time.
Estrela et al. (2007) evaluated ozonated water, gaseous ozone, sodium hypochlorite and
chlorhexidine in human root canals infected with E. Faecalis. The irrigation of infected
human root canals with ozonated water, 2.5 % NaOCl, 2 % chlorhexidine and the
application of gaseous ozone for 20 seconds were not sufficient to inactivate E. Faecalis.
Hems et al. (2005) evaluated the potential of ozone as an antibacterial agent using E.
faecalis as the target species. Ozone was produced by a custom-made bench top
generator and its solubility in water was determined by ultraviolet (258 nm)
spectrophotometric analysis of the solution through which ozone was sparged for
different periods. Ozone demand-free water was used as a reference. The ozone
concentration was only 0.68 mg L-1 (0.68 ppm) and it was produced after exposure for 30
seconds. The results showed that biofilms incubated for 240s with ozonated water
273
Discussion 3.2.4
showed no significant reduction in cell viability attributable to ozone alone, whereas no
viable cells were detected with NaOCl over the same time. Gaseous ozone applied for
300s had no effect on these biofilms. Ozone had an antibacterial effect on planktonic E.
faecalis cells and those suspended in fluid, but little effect was observed when the
microorganism was embedded in biofilms which was not surprising considering the low
dose of ozone used.
It is important to take into consideration that root canal infection is not a random event,
as observed by Sundqvist & Fidgor (2003) in a recent study about the survival of
endodontic pathogens.
The type and combination of microbial microbiota are developed in response to the
surrounding environment. Factors that influence whether species shall die or survive
include the particular ecological niche, nutrition, anaerobiosis, pH and competition with
other microorganisms.
Our results are in agreement with the results of Bezrukova et al. (2005) that the use of
ozone results in a reduction of microorganisms. Bezrukova carried out a study to assess
the ozone for use in RCT using the polymerase chain reaction (PCR) techniques. The
high efficacy of ozone therapy is revealed. The findings demonstrate the reduction in the
number of the micro-organisms in root canal: Actinobacillus actinomycetemcomitans
from 31.25% to 10.21%; Bacteriodes forsythus from 68.75% to 15.50%; Treponema
denticola from 37.5% to 11.4%; Porphyromonas gingivalis from 56.25% to 45%; and
Prevotella intermedia from 16% to 0%.
274
Discussion 3.2.4
One cannot directly extrapolate to the human situation from the results of this
experiment but the use of ozone as an endodontic irrigant shows promise. Further
research is essential to investigate the applicability of ozone in the clinical situation.
275
Conclusion 3.2.5
3.2.5 CONCLUSIONS
The irrigation of root canals with gaseous ozone or sodium hypochlorite with air for 120
seconds kills all E. faecalis, when its concentration in suspension is 104/ml. Air had no
significant effect.
Sodium hypochlorite was not effective in reducing the number E. faecalis in the lower
time of application of 10s, it takes more time to reduce the number of the
microorganisms.
The application of ozone gas for a period of 10 to 120 seconds was capable of reducing
the number of E. faecalis more than NaOCl and air and total eradication of E. faecalis
occurred after ozone treatment with an exposure time of ≥ 40 seconds when the starting
bacterial concentration was 5.9 x 104 for 40s and 5.8 x 106 for 60 or 120s.
276
(Study 4)
4. ANTIMICROBIAL ASPECTS, POSTOPERATIVE PAIN INCIDENCE AND PRACTICALITIES OF IRRIGATION WITH AND WITHOUT OZONE: A CLINICAL STUDY
This study consisted of two components. The first component assessed the antimicrobial effect of ozone treatment on microorganisms in root canal systems and determination of the practicalities of delivering ozone in-vivo into prepared root canals. This study also investigated the use of an ozone delivery system into the root canal especially related to the incidence of post-obturation pain.
Prior to commencement of the in vivo studies, ethical approval was obtained from the
Research Ethics Committee, Government of Dubai, Rashid Hospital, Department of
Health and Medical Services and Ministry of Health, U.A.E (Appendices).
4.1 STUDY POPULATION
All participants were recruited from patients on a waiting list who were attending the dental clinic for root canal treatment. Each subject had given his or her informed written consent for both root canal and ozone treatments to be undertaken.
Root canals were sampled from 100 patients (42 males and 58 females). One tooth per patient was selected. The age of the subjects ranged from 17 to 50 years (Mean ±
Standard Deviation = 31 ± 9).
The patients were randomly divided into two treatment groups, using random number tables.
277
(Study 4)
4.2 TREATMENT GROUPS
Group A (control group). The root canal was irrigated with 1 ml of 0.5% sodium hypochlorite for 30s after the use of each instrument in each canal. The root canal irrigation procedure was performed using a disposable syringe with a 30-gauge irrigating needle.
Air was then delivered from the Healozone device at an exposure time of 10 seconds into each canal after the final rinse.
A switch of the Healozone system allows for the unit to function apparently as normal but to only deliver air in order to blind the patient and the operator and this was done and recorded by a second operator.
Group B (study group). The root canal was irrigated with 1 ml of 0.5% sodium hypochlorite for 30s after the use of each instrument in each canal. The root canal irrigation procedure was performed using a disposable syringe with a 30-gauge irrigating needle. Ozone was delivered from the HealOzoneTm device at an exposure time of 10 seconds into each canal after the final rinse with 1 ml of 0.5% NaOCl in group B.
Overdoses of ozone were prevented as the ozone dose is designed to be maintained by the device by a constant voltage of the generator and the constant air flow through it.
Lower doses could be possible if there is failure to regularly change desiccants especially if extra humidity is present in the air. A new desiccant was used each morning before use. The HealOzoneTm device was calibrated from KaVo before starting this study.
278
(Study 4)
4.3 INCLUSION AND EXCLUSION CRITERIA
The following were the criteria for the inclusion of subjects in this clinical study:
• Male or female > 17 years of age.
• Presence of enough coronal tissues for adequate isolation of the tooth with rubber
dam.
• All involved teeth were to be root canal treated, in a one visit procedure.
• All selected teeth were single rooted.
• No swelling.
• Written Informed Consent (IC) for this protocol had to be obtained prior to study
enrolment. Each subject was required to sign and date the IC form prior to their
participation after being explained the clinical procedure and risks involved and
clarifying all questions raised by the patient.
The following were the criteria for the exclusion of subjects in this clinical study:
• Prior endodontic treatment on the involved tooth.
• Patient with a diagnosis of diabetes or any immunocompromising disease (such as
thyroid disease, cardiac disease, kidney disease, Cohn’s disease, depression).
• Pregnancy
• No antibiotics having been taken within 3 months
• Sterility controls taken of the operation field demonstrated growth of bacteria.
279
(Study 4)
4.4 SAMPLE SIZE CALCULATION
The power calculation was based on having a study using 72 patients (36 per group) having pre-operative colony counts to have an 80% power to detect a difference in microorganisms eradication rates of 60% on one treatment versus 25% on the other treatment using a significance set at the 5% level (Fig 4.1).
This calculation assumes that the post-operative colony count is categorised as either zero (eradication) or non-zero (no eradication). In fact, the actual analysis will compare the percentage reduction in colony counts between treatments. It is anticipated that such an analysis will provide more power than the analysis based purely on a comparison of eradication rates.
280
(Study 4)
FIGURE 4-1 STATISTICAL METHODS FOR RATES AND PROPORTIONS 2ND ED, WILEY, 1981. PP.38-45
281
Introduction 4.1
4.1 TO INVESTIGATE SODIUM HYPOCHLORITE WITH AND WITHOUT THE USE OF OZONE AS AN ANTIMICROBIAL AGENT IN RCT IRRIGATION.
4.1.1 INTRODUCTION
Apical periodontitis is an infectious disease caused by microorganisms infecting the dental root canal. Participating microorganisms can have been involved in the early stages of pulp tissue invasion, which culminated in inflammation and further necrosis, or they can be latecomers that took advantage of the environmental conditions in the root canal after pulp necrosis. Studies using culture-dependent and culture- independent techniques indicated that primary root canal infections are characterized by a mixed population conspicuously dominated by anaerobic bacteria, with the number of bacterial cells per canal varying from less than 102 to about 108 (Sundqvist 1976, Siqueira &
Rocas 2005, Vianna et al. 2006, Sakamoto et al. 2007).
Currently, the objective of treatment of root canals of both deciduous and permanent teeth with pulp necrosis and chronic periapical lesions is not only the elimination of bacteria, but also the inactivation of endotoxins, especially the inactivation of lipid A which is the most damaging part of endotoxins. This is not accomplished with intracanal dressings which only kill residual bacteria.
According to Dwyer and Torabinejad (1981), substances that are highly alkaline, such as
NaOH, detoxify lipopolysaccharide (LPS). However, these substances are considered irritant to the periapical tissues.
282
Introduction 4.1
Sodium hypochlorite (bleach solution) is a cytotoxic agent (Gatot et al. 1991, Gernhardt et al. 2004). When it comes into contact with vital tissue, it causes haemolysis, ulceration, inhibits neutrophil migration and damages endothelial and fibroblast cells
(Gatot et al. 1991).
A study by Witton et al. (2005) showed that the sodium hypochlorite extrusion can cause facial nerve weakness in addition to other soft tissue damage. Early recognition of this problem and prompt management may reduce further complications.
Research has shown that irrigation with solutions is fundamental for the cleaning of root canals (Leonardo et al. 2001). However, this can temporary and limited because, even at high concentrations, sodium hypochlorite does not neutralize a large number of endotoxins (Buttler & Crawford1982). Even if sodium hypochlorite (NaOCl) eliminated all of the microbiota in the main root canal, it does not act effectively in the entire extension of the dentinal tubules, even when associated with chelating or tensoactive substances (Berutti et al.1997) or other antibacterial agents such as chlorhexidine or hydrogen peroxide (Heling & Chandler 1998).
Ozone treatment is being considered as an alternative management strategy. The powerful ability of ozone to inactivate microorganisms has led to its use in water disinfection and there is growing evidence that it can be employed as a useful therapeutic agent in both dentistry and medicine. It has been reported that ozone, in either the gaseous or aqueous phases, has a strong oxidizing power with a reliable microbiocidal effect (Broadwater et al. 1973, Restaino et al. 1995). Baysan et al. (2000) found a significant reduction in S. mutans and S. sobrinus in ozone treated samples compared with control samples.
283
Introduction 4.1
Previous studies (Bocci et al. 1993, Yamayoshi & Tatsumi 1993) suggested that ozone treatment killed microorganisms via a mechanism involving the rupture of their membranes. Baysan & Lynch (2004) found, in their study, that ozone treatment dramatically reduced the total number of microorganisms and reversed most of the root carious lesions.
One of the major environmental advantages of ozone is its low cytotoxicity, which, in clinical situations, can be caused by a rapid degradation of ozone just after contact with organic compounds (Nagayoshi et al. 2004).
Classic bacteriological studies were performed using stainless-steel hand instruments with a filing or reaming motion (Bystrom & Sundqvist 1985). The disinfection efficacy should, therefore become one of the considerations in the development of new instrumentation techniques to be used in root canal therapy. For example, studies by
Kerekes and Tronstad (1977 a, b) describing the morphology of apical root canal anatomy and the standardized instrumentation technique, concluded that to achieve adequate debridement and root end preparation the use of larger files than those commonly used in practice today was necessary. Soon after the introduction of nickel- titanium (NiTi) endodontic hand instruments in 1988, NiTi rotary instrumentation became popular (Walia et al. 1988).
In modern endodontic practice, there is a move towards the use of engine-driven rotary instrumentation with NiTi files. Many clinicians argue that this form of instrumentation allows for easier production of standardized root canal preparations, thereby yielding superior debridement, in part because of the NiTi instruments flexibility. The removal of
284
Introduction 4.1 bacteria by NiTi instrumentation was evaluated in previous studies (Dalton et al. 1998 and Shuping et al. 2000). The results from Dalton et al.1998 mirrored those of Byström and Sundqvist (1981). They found a significant bacterial reduction. In addition, no significant difference was found between the instrumentation with either stainless steel hand files or rotary NiTi instrumentation.
There is no data regarding the use of ozone as a root canal irrigant in in-vivo studies.
Thus, the objective of this study was to evaluate the antibacterial activity of two different irrigation solutions, NaOCl with air or ozonated NaOCl used for root canal irrigation.
285
Material and Methods 4.1
4.1.2 MATERIAL AND METHODS
4.1.2 EQUIPMENT USED
4.1.2.1 OZONE DELIVERY SYSTEM
In this study, an ozone delivery system (HealOzoneTm, KaVo) was employed (Fig 4.1.
2.1.1). The ozone delivery system is a portable apparatus with an ozone generator for the treatment of caries and endodontic treatment and delivers ozone at a concentration of
2,100 ppm ± 10%. The vacuum pump pulls air through the generator at 102.5 cc/min to supply ozone to the root canal and purges the system of ozone after ozone treatment. A disposable removable silicone cup (diameters ranging between 5 and 8 mm), is attached to the handpiece to provide the gas and enclosing a selected area of the tooth to the gas through the tips. The tightly fitting cup seals the selected area on the tooth to prevent the escape of ozone. The ozone is drawn out of the sealing cup through an ozone neutraliser that converts the ozone back to oxygen. A suction system then removes any possible remaining ozone whilst the cup is still adapted to the tooth, (the suction system passes the gas from the delivery system through manganese (II) ions) (Fig 4.1.2.1.2 and
Fig 4.1.2.1.3). The HealOzoneTm was modified so that a second operator could set the unit to deliver only air with no ozone which allowed the in vitro and in vivo studies to be fully blinded.
286
Material and Methods 4.1
FIGURE 4-1-2-1-1 OZONE DELIVERY SYSTEM
287
Material and Methods 4.1
FIGURE 2.5.3 THE HEAD OF THE HANDPIECE DELIVERING OZONE, WITH THE
FIGURE 4-1-2-1-2 THE HEAD OF THE HANDPIECE DELIVERING OZONE, WITH THE OPENING FOR THE OZONE GAS THROUGH A NEEDLE
288
Material and Methods 4.1
FIGURE 4-1-2-1-3 HANDPIECE WITH A CUP
289
Material and Methods 4.1
4.1.2.2 APEX LOCATOR ELEMENTS DIAGNOSTIC UNIT
This is a fourth-generation electronic apex locator that measures both resistance and capacitance as the file is advanced. The reading obtained initially can be verified again by a second measurement after the instrumentation is finalized and sometimes can be confirmed with a bleeding/moisture point measurement obtained with paper points (Fig
4.1.2.2.1).
FIGURE 4-1-2-2-1 APEX LOCATOR ELEMENTS DIAGNOSTIC UNIT
290
Material and Methods 4.1
3 4.1.2.3 K TCM ENDO MOTOR WITH W&H HANDPIECE
3 FIGURE 4-1-2-3-1 TCM ENDO III MOTOR WITH HANDPIECE FOR K FILES
291
Material and Methods 4.1
4.1.3 CLINICAL PROCEDURE
All clinical procedures were carried out by one operator. Preoperative periapical radiographs using size DF-58 (Kodak Ultra-speed, New York, USA), were taken and endodontic diagnosis was established. After local anaesthesia using (EcoCaine 2% with vasoconstrictor (Novocol pharmaceutical of Canada, Inc Cambridge, Canada) and isolation of the tooth by rubber dam (Coltene, Langenau, Germany), the operative sites were disinfected with 30% hydrogen peroxide and a 5% iodine tincture in accordance with the protocol advocated by Mőller (1966). The sterility of the operation field was checked after inactivation of the iodine with 5% sodium thiosulphate solution (Gomes et al. 2004).
A swab sample was taken from the surface and streaked on to blood agar plates to test for disinfection. This sample was designated sample 1 which as coded as (D1).
An access cavity was prepared with a sterile high-speed diamond bur (# 010/012,
Hauptstrasse, Switzerland) using irrigation with sterile physiological saline.
The access cavity was disinfected with the same protocol as above and the sterility again checked by taking a swab sample of the cavity surface and streaking it onto a blood agar plate. All subsequent procedures was performed aseptically.
292
Material and Methods 4.1
After accessing the pulp chamber and subsequent pre-chemomechanical microbial sampling, the pulp chamber was thoroughly cleaned with either 0.5 % NaOCl with air or with ozonated NaOCl. A k-file of size 10 or 15 (FFDM, PNEUMAT, Bourges,
France) was placed to the full length of the root canal being calculated from the pre- operative radiograph (Fig 4.1.3.1).
FIGURE 4-1-3-1 PREOPERATIVE RADIOGRAPH TO ASSESS THE ROOT CANAL LENGTH
293
Material and Methods 4.1
3 FIGURE 4-1-3-2 MEASUREMENT OF THE WORKING LENGTH OF THE K FILE BEFORE STARTING THE PROCEDURE
The initial 3 mm of the canal were prepared using Gates-Glidden burs (GGB) sizes 4, 3 and 2 (SIMFRA, Paris). Each Gates-Glidden burs progressed only in the straight coronal portion of the root canals by 1mm.
After using each GGB, the canals were irrigated with 1 ml 0.5 % of sodium hypochlorite to help flush out the accumulated debris.
The rest of the coronal two-thirds of each canal were prepared using rotary files K3
(Sybron Endo, Orange County, CA, USA) (Fig 4.1.3.2), used with its compatible K3
TCM torque-controlled motor (Kerr, Karlsruhe, Germany) and an 18:1 reduction handpiece (W& H, Buermoos, Austria).
294
Material and Methods 4.1
The torque setting was three (according to the manufacturer) and the rotational speed was 350 r.p.m. Instruments were advanced apically in a gentle pecking motion until the first sign of resistance was felt.
The following 10 instruments were chosen to create a crown-down sequence (Fig
4.1.3.3):
• Coronal Preparation
Size 25; 0.10 taper: orifice shaper
Size 25; 0.08 taper: orifice shaper 1/3–2/3 of estimated working length.
The working length (WL) was checked with a radiograph after inserting a file in the canal to the estimated working length which was confirmed by the electronic apex locator (Elements Diagnostic Unit). In addition, the working length was checked again later with a gutta-percha master cone-fit radiograph when that stage of the procedure was reached.
295
Material and Methods 4.1
K3 file
3 FIGURE 4-1-3-3 K FILES
With the working length obtained, a glide path for subsequent K3 files was created to a size 15 K file to the working length. In other words, the canal was instrumented with K files to a 15 K file to the working length before the K3 file was used. Subsequently, the
K3 files was used in a crown down fashion to the WL (proceeding in 1 mm increments) size 30; 0.06 taper, size 30; 0.04 taper, size 25; 0.06 taper, size 25; 0.04 taper and size
20; 0.04 taper to the full WL.
• The apical preparation used sizes 25– 35; 0.04 taper to the full WL. The total
number of instruments used was 10.
After completion of the mechanical preparation with K3, in both treatment groups a
second sample was taken and labelled (D2).
296
Material and Methods 4.1
3 4.1.3.1 K SYSTEM FEATURES
The K3 canal shaping files are available with a fixed taper of .02, .04 or .06. The .02 tapered K3 files are available in 15-45 tip sizes and 21, 25 and 30 mm lengths. The .04 and .06 tapered K3 files are available in 15-60 tip sizes and 21, 25 and 30 mm lengths. In addition, K3 shaping files have recently been introduced with tapers of .08, .10 and .12.
These instruments can be used as canal shaping files, orifice openers, and deep body shaping files. They are available in a fixed 25 tip size and 17, 21 and 25 mm lengths.
The K3 (Figure 4.1.3.4) has a slightly positive rake angle providing the effective cutting that the file possesses.
Positive rake angle Wide radial land
Radial land relief
3 FIGURE 4-1-3-4 CROSS SECTION OF K WITH VARIOUS FEATURES APPROPRIATELY LABELED
297
Material and Methods 4.1
Recent study by Sonntag et al. (2007) examine the result of rotary root canal preparation with the nickel-titanium (NiTi) systems K3, ProTaper and Mtwo. They found that no significant differences were found in the preparation length, transportation or taper. The three systems tested, K3, Mtwo and ProTaper, achieved good preparation results.
In summary, the suggested techniques for using K3 instrument are as follows:
1. Coronal Third Shaping
When the orifices are located, they are initially enlarged with the K3 Shaper. Larger canals (distal roots of lower molars, palatal canals of upper molars) will require the .12
Shaper. Medium canals (upper second bicuspids, upper central incisors) will require the
.10 Shaper. Smaller canals will require the .08 Shaper for initial coronal third enlargement. In small canals, after the .08 Shaper has been used, the operator can go back and subsequently insert the .12 and .10 files successively to further open the orifice. The shaper files are used with light resistance, which is usually about 3 mm to 4 mm apically or until resistance is met.
2. Middle Third Shaping
If the Shaper advances easily, a glide path may not always be required in the middle third. Many times, the shaper alone used in succession (.12 followed by .10 and .08) which will reach the junction of the middle and apical thirds, and the .06 and .04 files as described below are unnecessary. If a glide path is required at this level, after initially scouting the canal with a #6-10 K file to the junction of the middle and apical thirds, a middle third glide path is created by instrumenting up to a #15 K file before using the
K3. Then, a .06 /40 K3 (or the appropriate Shaper) can often be inserted to the mid root
298
Material and Methods 4.1 or beyond after the middle third glide path has been created. The apical third should not be entered at this point. If the.06/40 K3 will not progress to the junction of the middle and apical thirds, a smaller .06 tapered K3 (or Shaper) can be used. The .06 K3 files are used in decreasing tip sizes until the middle and apical third junction is reached.
Specifically, a .06/40 is used first, followed by a .06/35, .06/30 until the middle and apical third junction is reached. Recapitulation and irrigation are alternated after every file. In some narrow canals, .04 tapered files are used as described above for the .06 instruments.
3. Apical Third Shaping
Initial exploration of the apical third can be thought of as a process of discovery.
Because of the diversity of apical anatomy, (multiplanar curvatures, fins, isthmuses, cul- de-sacs, etc), a delicate touch is required to ascertain a road map to the clinical realities present in this most challenging canal space. Entering the apical third too quickly risks a myriad of iatrogenic events (potentially causing ledges, perforations, apical zipping, etc), all of which diminish the possibility of endodontic success. Adequate patience, time and a gentle touch are required in the apical third. Apical curvatures, calcifications, patency, and ease of negotiation must be carefully evaluated with #6 through #10 K files before engaging a K3 file in this region.
One of the attributes of the K3 system is the option to introduce the .02/15 or .02/20 after glide path creation. The .02/15 and .02/20 can further accentuate and define the glide path, as well as accelerate its creation and to make way for subsequent K3 files used in a crown down manner. Specifically, after a glide path has been created by hand files to a
15-20 K file, insertion of the .02/15 and .02/20 can often, with a gentle motion, reach
299
Material and Methods 4.1 true working length. When used to true working length, this refines the glide path and opens the canal more efficiently for subsequent K3 use.
After the .02/15 and .02/20 K3 ‘s, subsequent K3 files are then introduced in a crown down sequence, varying either the tip size (with subsequently smaller K3 tip sizes of the same taper) or varying the taper (mixing the tapers of the instruments as the tip size diminishes). Regardless of whether the tip size or taper is varied, K3 files are inserted from larger to smaller tip sizes in a coronal to apical direction until true working length is reached. Each subsequently smaller taper and/or tip size, entered in the sequence recommended, will reach a deeper apical level in the canal. Varying the tip size, .06 K3 files are generally inserted from a 40 tip size, (or larger) to a 20 or 15 tip size (canal size, curvature, initial diameter of the apical foramen, and apical-curvature dependent), and the sequence is repeated until the desired apical diameter is achieved. When varying the tip size in smaller canals, the .04 K3 can be used in the same manner. Varying the tip size and/or taper ensures a crown down instrumentation as each successively smaller file advances further apically. Good clinical judgment is essential. Before deciding to what tip size and taper the master apical file should be instrumented, it is often necessary to
“gauge” the apex.
In other words, it is necessary to determine the apical diameter of the prepared canal. For example if a 20 K file resists displacement through the apical foramen at the true working length, then an appropriately tapered K3 25 or 30 tip size (canal-morphology dependent) can be used to finalize canal preparation. This technique allows shape to be created coronally to the foramen while maintaining its size, location, and patency.
300
Material and Methods 4.1
The 100 patients were randomly divided in two groups. In group A the root canals were irrigated with 1 ml of 0.5% sodium hypochlorite for 30 seconds after use of each instrument in each canal. The root canal irrigation procedure was performed using a disposable syringe and a 30-gauge irrigating needle. Ten seconds of air was then delivered from the HealOzoneTm unit in the same way as described for the use of ozone in group B below.
The inactivation of NaOCl next was accomplished with a rinse of 1 ml of sterile sodium thiosulphate for 1 minute using a 30-gauge irrigating needle and then the canal was filled using 1ml of saline solution before the post chemomechanical preparation sample was taken.
Specimens were taken for microbiological examination using sterile paper points
(Precise Dental Products LTD, Canoga Park, CA, USA) which were consecutively introduced into each canal to the total length calculated from the pre-operative radiographs. This was maintained for 3 minutes for sample collection and then pooled for each canal in a sterile tube containing 1 ml of reduced transport fluid (RTF) (Syed
&Loesche 1972) Table (4.1.1). The samples were transferred to the laboratory within one hour for microbiological processing. This sample was designated as D3.
The second group B was treated as in group A by irrigating the root canal with 1 ml of
0.5% sodium hypochlorite for 30 seconds after the use of each instrument in each canal.
The root canal irrigation procedure was performed using a disposable syringe and a 30- gauge irrigating needle. Ozone was then delivered from the HealOzoneTm at an exposure time of 10 seconds in each canal after the last delivery of the NaOCl in each canal in group B (Fig 4.1.3.5). Final rinse of 1 ml of sterile sodium thiosulphate for 1 minute
301
Material and Methods 4.1 using a 30-gauge irrigating needle and then the canal was filled using 1ml of saline solution before the post chemomechanical preparation sample was taken.
Ozone was delivered into the cup closely adapted to the tooth for 10 seconds, through the special needle adapted to the hand piece with the Healozone™ device after adjustment to the working length of each canal (1 mm from the radiographic apex). The suction system then removed any possible remaining ozone whilst the cup was still adapted to the tooth (the suction system passed the gas from the delivery system through manganese (II) ions (Fig 4.1.3.6).
FIGURE 4-1-3-5 PICTURE OF THE NEEDLE READY MOUNTED TO THE HEALOZONE HANDPIECE TO BE USED FOR OZONE DELIVERY (RIGHT) AND THE 30 GAUGE ENDODONTIC IRRIGATING NEEDLE
302
Material and Methods 4.1
FIGURE 4-1-3-6 OZONE OR AIR TREATMENT USING THE APPROPRIATE SILICONE CUP SIZE, SEALED AROUND THE TOOTH AND PREVIOUSLY TREATED WITH NAOCL. OZONE SAFELY DELIVERED THROUGH THE PROTOTYPE NEEDLE MOUNTED TO THE HEALOZONE HANDPIECE
303
Material and Methods 4.1
All teeth were obturated using lateral compaction of gutta-percha cones with Endofill sealer (Dentsply) and the access cavities were restored with 3 mm of Cavit ™ (3M
Dental product).
4.1.4 STATISTICAL ANALYSES
Post-operative microbiological counts from the study (group B) and control group
(group A) were expressed as a percentage reductions from pre-operative levels using the following equation:
Percentage reduction = Pre-operative – Postoperative x 100 Pre-operative
Statistical analyses of the data were conducted using the Mann-Whitney U test to determine the significance of differences observed between the study and control groups, (the threshold of significance was 0.05 for each study). All analyses were performed using the SPSS statistical package for Windows version 14.
Descriptive statistics were used to summarize the frequency distribution of the data.
Colony counts were summarized using medians and interquartile ranges because they showed a heavily skewed distribution.
304
Material and Methods 4.1
4.1.5 MICROBIOLOGICAL ANALYSES
All root canals samples were sent to the adjacent microbiology laboratory for processing within 1 hour of sampling. Transport tubes were incubated at 37º C for 15 minutes and vigorously mixed for 20 to 30 seconds using a vortex mixer to facilitate the extraction of any microorganisms from the paper points and disperse any aggregates. Dilutions were performed by transferring 1 ml of the resulting suspensions into 9 ml of FAB. This process was repeated with a 10-fold dilution to 104. After decimal dilution with FAB,
100 µL aliquots, (for both group A and B) were prepared. First 50 µL of each dilution was inoculated on blood agar plates supplemented with 5% horse blood, 5 mg L-1 haemin and 1 mg L-1 menadione.
Plates were incubated anaerobically (80% N2, 10% H2, 10% CO2) for 5 to 7 days at 37º C
(Peters et al. 2002). Subsequently, 50 µL of each dilution was inoculated on brain heart infusion (BHI) agar plates supplemented with 5% sheep blood and incubated aerobically
(37ºC, air) for 24 . The total number of CFUs was then calculated.
305
Material and Methods 4.1
TABLE 4-1-1 COMPOSITION OF REDUCED TRANSPORT FLUID (RTF)A
Components Amount (ml)
1. Stock mineral salt solution no. 1b. .…………………………………..75 2. Stock mineral salt solution no. 2c...... 75 3. 0.1 M EDTA ...... ……10 4. 8% Na2CO3...... 5 5. 1% Dithiothreitol (freshly prepared)…………………………… ……20 6. Resazurin 0.1% (optional)...... ……….1 7. Distilled water...... ……….814
The RTF was prepared by membrane filter sterilization by using a membrane filter
(0.22-gm pore size) and dispensed into 16 x125 mm screwcap tubes (dilution tubes) and
18 x 150 mm test tubes (sample collection tubes). The pH of this medium was 8 ± 0.2 without adjustment, and it decreased to 7 in 48 hr in the anaerobic glove box atmosphere
(85% N., 10% H2, and 5% C02). b Contained 0.6% K2HPO4. c Contained 1.2% NaCl,
1.2% (NH4)2S04, 0.6%KH2PO4, and 0.25% MgSO4.
306
Result 4.1.3
4.1.3 RESULTS OF STUDY
Disinfection of the rubber dam, the crown and its surrounding area was tested before and after entry into the pulp chamber by taking swab samples (D1), which were plated on blood agar plates. Fifteen samples were positive for the presence of bacterial growths and were excluded from the study. Five samples (D2) showed negative results for bacterial growth after completion of the mechanical preparations using the rotary instrument K3 system and were excluded from the study. The remaining 80 samples showed positive results for sample D2 after completion of the mechanical preparation by the rotary K3 system and sample D3 was taken after using the irrigation treatment (Table
4.1.3.1 and Table 4.1.3.2).
The results in Table 4.1.3.3 shows that there was no statistically significant difference between the type of irrigation with the gender of the patient and or with type of the tooth involved in this study. However, there was a statistically significant difference between the irrigation groups and the tooth arch. The results in Table 4.1.3.4 showed that there was a relationship between the irrigation groups and the number of colony unit before the intervention of the treatment. Moreover, there was a statistically significant difference between the bacterial reduction and the type of the irrigation used.
The results of the Mann-Whitney U tests indicated that there was a statistically significant difference in the percentages of bacterial reduction between NaOCl with air and ozonated NaOCl (p=0.004).
307
Result 4.1.3
In the current study, the bacterial reduction in the NaOCl with air and ozonated NaOCl group ranged from 60% to 100% and 94.44 to 100%, respectively. However, in the ozonated NaOCl group 63% (27 cases) were bacteria free after chemomechanical preparation according to the culture technique, whilst only 37% (16 cases) were free of bacteria in the NaOCl with air group.
308
Result 4.1.3
TABLE 4-1-3-1 BACTERIAL GROWTH (CFU) AND PERCENTAGE REDUCTION DETERMINED FOR ROOT CANAL SAMPLES OF 38 TEETH, BEFORE AND AFTER CHEMO-MECHANICAL PREPARATION WITH NAOCL WITH AIR AS THE IRRIGATING SUBSTANCE
Sample Sex Before (D2) After (D3) % Reduction 1 Female 5.4×105 2×102 99.96 2 Female 1.1×102 0 100 3 Female 1.1×103 0 100 4 Male 1×105 0 100 6 Male 9.0×105 0 100 12 Male 1×105 0 100 13 Male 2.3×104 1×101 99.96 14 Female 5.0×105 3×102 99.94 15 Female 8.5×104 30 99.96 23 Female 500 30 94 28 Male 9.0×105 4×103 99.56 41 Male 3×105 0 100 43 Female 2.4×103 20 99.17 44 Female 3.3×104 0 100 45 Male 3×105 0 100 46 Female 1×104 10 99.9 47 Male 3×104 0 100 50 Female 3×105 2×102 99.93 55 Female 3×104 0 100 56 Male 3×105 0 100 57 Male 3×104 200 99.33 59 Male 20 0 100 60 Male 30 2 93.33 61 Male 300 50 83.33 62 Male 5 1 80 63 Male 70 3 95.71 64 Male 1.1×103 5 99.55 65 Female 1.1×104 20 99.82 66 Female 1.1×104 5 99.95 67 Female 20 0 100 68 Female 20 0 100 70 Female 30 5 83.33 73 Female 100 10 90 75 Female 500 200 60 76 Male 10 0 100 77 Male 3×104 0 100 79 Male 3.3×104 2×102 99.39 80 Male 9.0×105 3×103 99.67
309
Result 4.1.3
TABLE 4-1-3-2 BACTERIAL GROWTH (CFU) AND PERCENTAGE REDUCTION DETERMINED FOR ROOT CANAL SAMPLES OF 42 TEETH, BEFORE AND AFTER CHEMO-MECHANICAL PREPARATION WITH OZONATED NAOCL AS THE IRRIGATING SUBSTANCE
Sample Sex Before After % Reduction 5 Female 3×105 1×102 99.97 7 Male 1×105 0 100 8 Male 1×105 0 100 9 Female 3×105 1×102 99.97 10 Female 3×105 1×102 99.97 11 Female 1×103 20 98 16 Female 9×104 0 100 17 Female 1.1×105 0 100 18 Female 1.5×104 0 100 19 Female 2×105 0 100 20 Female 1×104 0 100 21 Female 1.1×105 20 99.98 22 Male 5 0 100 24 Female 1×103 30 97 25 Female 3.3×104 0 100 26 Female 2.4×104 0 100 27 Male 5 0 100 28 Male 8.8×105 2×102 99.98 29 Female 5 0 100 30 Female 9.0×105 5×104 94.44 31 Male 6.2×105 0 100 32 Male 4×105 0 100 33 Female 5.0×105 0 100 34 Male 8×105 0 100 35 Male 9.0×105 0 100 36 Female 5.4×105 5×102 99.91 37 Female 5×105 40 99.99 38 Female 4×104 20 99.95 39 Female 3×102 0 100 40 Male 4×105 0 100 42 Female 1.0×104 50 99.5 49 Female 3×104 3 99.99 51 Male 5 ×104 20 99.96 52 Female 1×105 0 100 53 Female 3×104 0 100 54 Female 3×103 0 100 58 Female 3×105 0 100 69 Male 30 0 100 71 Female 5.4×105 0 100 72 Male 5.4×105 0 100 74 Male 5.4×105 0 100 78 Female 9×104 30 99.97
310
Result 4.1.3
TABLE 4-1-3-3 COMPARISON OF GROUPS CHARACTERISTICS
Irrigation Solution (%) Significant differences Gender NaOCl with air (38) Ozonated NaOCl (42) Male 20 (53%) 14 (33%) p = 0.081 Female 18 (47%) 28 (67%) Tooth Type Anterior 18 (47%) 25 (60%) p = 0.276 (Incisors/canines) Premolars 20 (53 %) 17 (41%)
Tooth arch Upper arch 14 (37%) 31 (74%) p = 0.001 Lower arch 24 (63 %) 11 (26 %) Tooth side Right 26 (68%) 25 (60%) p = 0.408 Left 12 (32%) 17 (40%)
Values shows a significant difference in bold (p<0.05).
TABLE 4-1-3-4 MEDIAN VALUES FOR THE TREATMENT GROUPS
Irrigation Solution (%) Significant differences NaOCl with air (38) Ozonated NaOCl (42) Colony forming unit 17,000 (108-150,000) 100,000 (13,750- p = 0.014 before treatment. Median 500,000) (IQR) Colony forming unit after 4 (0-35) 0 (0-23) p = 0.120 treatment. Median (IQR) Bacterial reduction. 99.96 (99.29-100) 100 (99.97-100) p = 0.004 Median (IQR)
Values shows a significant difference in bold (p<0.05).
311
Discussion 4.1.4
4.1.4 DISCUSSION OF THE STUDY
It has been shown that ozone, in the gaseous or aqueous phase, can kill bacteria, fungi, and viruses (Kim et al.1999, Nagayoshi et al. 2004). The efficiency of disinfectants is usually evaluated based on a decrease in cultivable microorganisms as tested in this study (Camper & McFeters 1979).
Diligent antimicrobial treatment can occasionally fail to promote total eradication of bacteria from root canals, with consequent selection of the most resistant segment of the microbiota. In the present study, the degree of bacterial reduction, after applying NaOCl with air or ozonated NaOCl was assessed with quantification strategies.
For evaluating chemomechanical preparation, the bacterial load and the pre and post preparation values has been determined by cultures in many studies (Byström &
Sundqvist 1981, Peters et al. 2002, Vianna et al. 2006, Berber et al. 2006). These values are in accordance with the cell numbers that were determined by culture analysis in this study.
A culture-dependent approach was used in the present study because it is one of the most reliable methods of detecting viable bacteria, particularly when samples are taken immediately after antimicrobial treatment where viability may not be ascertained by most culture-independent methods (Siqueira & Rôças 2005). Furthermore, studies using cultures have shown a correlation between negative cultures and favorable treatment outcome (Sjögren et al. 1997, Waltimo et al. 2005). it is worth pointing out that the bacterial diversity and bacterial counts are usually underrepresented by culturing
312
Discussion 4.1.4 analysis. Also, because of limitations of sampling procedures, low sensitivity of the culturing techniques, and presence of as yet uncultivated bacteria, a negative culture does not imply sterility. Indeed, a negative culture usually means that cultivable bacterial populations were reduced to levels below the detection ability of culture- dependent methods, and that these levels can be compatible to periradicular tissue healing in most cases.
The current study showed that ozonated NaOCl was more effective in killing micro- organisms than NaOCl with air. The importance of obtaining a bacteria free root canal system before permanent root filling in order to achieve an optimal healing condition for the periapical tissues has been demonstrated (Fabricius et al. 2006 ).
The present study revealed that 43 (53.8%) of the 80 cases were free from bacteria after chemo-mechanical preparation of the root canal in vivo using 0.5% NaOCl with air or ozonated NaOCl (16 and 27 cases respectively).
The results of this study should be interpreted with caution however. Regrettably there was a significant difference in the colony count between the ozonated NaOCl and
NaOCl with air groups before the intervention was applied (P = 0.014). This causes concern about the validity of the randomisation since a difference between groups of this magnitude would only be expected by chance on 1 in 70 occasions. Since there was no indication that the randomisation was compromised, the most likely explanation is that the difference is due to chance.
Unfortunately, there is a significant difference between the allocation of the treatment groups and the tooth location in the upper or lower arch. These results should be also treated with the caution.
313
Discussion 4.1.4
Mechanical instrumentation alone can reduce bacteria from human root canals by approximately 50% (Byström & Sundqvist 1981). Auxiliary substances are necessary to aid the removal of microbiota in areas where instruments cannot reach (Lee et al. 1990).
Microorganisms can invade the dentinal tubules of teeth with vital and nonvital pulps, but the invasion is less severe with vital pulps because of the protective function of the pulp (Nagaoka et al.1995). Bacteria entering either the pulpal surface or periodontal surface of the root can exist within the dentinal tubules. If viable, these bacteria could act as reservoirs of infection (Buck et al.1999). Irrigation is presently the best method for the removal of tissue remnants and dentine debris during instrumentation (Spangberg
& Haapasalo 2002, Haapasalo et al. 2005).
Use of irrigating solutions provides gross debridement, lubrication, destruction of microbes and dissolution of tissues (Spangberg & Haapasalo 2002, Haapasalo et al.
2005).
NaOCl solutions has been used as the current irrigant of choice due to its antibacterial action and its ability to dissolve tissue (Byström & Sundqvist 1983, 1985, Moorer &
Wesselink 1982).
Sodium hypochlorite has a broad-spectrum antimicrobial activity, rapidly killing vegetative and spore-forming bacteria, fungi, protozoa, and viruses (Dychdala 1991,
Rutala & Weber 1997). Most oral bacteria are killed after a short time of contact with
NaOCl (Ohara et al. 1993, Vianna et al. 2004). Sodium hypochlorite exerts its antibacterial effect by inducing the irreversible oxidation of sulfhydryl groups of essential bacterial enzymes, resulting in disulfide linkages, with consequent disruption of the metabolic functions of the bacterial cell (Brooks et al. 1998). Sodium hypochlorite
314
Discussion 4.1.4 can also have deleterious effects on bacterial DNA, which involve the formation of chlorinated derivatives of nucleotide bases. In addition, NaOCl has been reported to disrupt membrane-associated activities (McDonnel & Russell 1999, Hugo & Russel
1998).
The choice of the ideal irrigant solution and its concentration is difficult to determine.
Byström & Sundqvist 1985 and Siqueira et al. 2000 in their clinical and laboratory studies did not demonstrate any significant difference in the antibacterial effect between
NaOCl of concentrations ranging from 0.5% to 5%. No further debris removal was seen with additional EDTA irrigation. One ml of EDTA was just as effective in removing the smear layer as 10 ml. A major advantage of EDTA over NaOCl is the action on the smear layer. EDTA was found to be effective in removing the smear layer (McComb &
Smith 1975, Goldberg & Abramovich 1977). However, it has been shown that EDTA is effective in removing the inorganic element but not the organic components (Goldman et al.1981). Yoshida et al. (1995) studied the effect of EDTA on removing the smear layer clinically. They found no bacteria in the canals irrigated with EDTA compared with that of saline irrigation. They concluded that because saline only removed the superficial bacteria, the remaining bacteria could repopulate the root canal. They further concluded that EDTA was successful in removing the smear layer and the bacteria.
The advantage of EDTA in removing the inorganic element of the smear layer and that of NaOCl in removing the organic components, has led to the adoption of a combination of the two irrigants to achieve patent dentinal tubules and a clean surface even in the apical portion of the root canal (Yamada et al. 1983, Serper et al. 2001).
Superior results have been reported when NaOCl is used as the last irrigant (Yamada et
315
Discussion 4.1.4 al.1983), however, this combination has been shown to alter the mineral content of the root dentine (Serper et al.2001).
Estrela et al. (2002) proposed the physico-chemical characteristics of NaOCl which are essential for the explanation of its mechanism of action. Saponification, the neutralization of amino acids and chloramination reactions that occur in the presence of microorganisms and organic tissue, aid the antimicrobial and tissue dissolution processes. Antimicrobial activity is related to bacterial essential enzymes promoting irreversible inactivation by hydroxyl ions and the chloramination reaction.
Sodium hypochlorite promotes biosynthetic alterations in cell metabolism, phospholipids destruction, and the formation of chloramines that interfere with cell metabolism by an oxidant action. The organic dissolution action can be observed in the
Saponification reaction when sodium hypochlorite destroys lipids and fatty acids resulting in soap and glycerol.
Alternative approaches to improve the effectiveness of NaOCl in the root canal system may involve the following:
1. An increase the temperature of the low-concentration NaOCl solution. This
appears to improve immediate tissue-dissolution capacity (Abou-Rass & Oglesbt
1981).
2. Passive ultrasonic irrigation (PUl) with sodium hypochlorite as the irrigant
removes the smear layer completely (Cameron 1983, Huque et al. 1998) or
partially from the root canal wall (Cheung & Stock 1993). There is substantial
evidence that negative cultures are consistently obtained after adequate
instrumentation and rinsing of the canals with NaOCl and EDTA, and the
316
Discussion 4.1.4
application of an intracanal microbial dressing (Byström et al.1985, Dalton et al.
1998, Shuping et al. 2000). Short intra-appointment application of a bactericidal
dressing has not so far resulted in a satisfactory reduction of root canal microbes
(Kvist et al. 2004). It was found that only 13 of the 46 (28%) teeth sampled were
culture-negative after instrumentation and saline irrigation.
There was no statistical difference between the outcomes of the instrumentation with
stainless steel hand files and NiTi rotary instruments (Dalton et al. 1998). A reduced
working time is made possible by the advent of rotary instruments made from (Ni-
Ti), which have a high degree of flexibility and can be used in a dental hand piece
rotating in the range of 200-300 r.p.m, allows for tapers and flute design to be
completed, difficult with stainless steel instruments.
In addition, the increased taper combined with Ni-Ti alloy, allows more predictable use of rotary methods to provide a consistent canal shape (Short et al. 1997). Kum et al.
(2006) claimed that the use of the K3 rotary system generated less formation of smear on root canal walls compared to the ProFile system in the selected apical third area of curved root canals.
Schafer & Florek (2003) showed that K3 instruments prepared curved canals rapidly with minimal transportation towards the outer aspect of the curve.
In the present study all the root canal preparations was performed by the K3 rotary instrument in a crown down technique. The greatest number of microorganisms in the root canal lie in the coronal third (Shovelton 1964). Initial preparation of this section of the root canal system helps to reduce the number of microorganisms that may be pushed apically. Secondly, early flaring of the coronal part of the preparation may improve
317
Discussion 4.1.4 instrument control during preparation of the apical third of the canal (Goerig et al.
1982). In our study, we noticed the same ease of preparation.
Jodway & Hülsmann (2006) stated that the K3 system maintained the original canal curvature and is therefore safe to use. Preflaring of the cervical and middle thirds improved the deterimination of the anatomical diameter at the working length and the type of instrument played a major role in this procedure (Barroso et al. 2005). In view of the great anatomical complexity of the root canal system, particularly of molars (Perrini et al. 1991), the ecological organization of the flora is to protect seeile biofilms
(Costerton et al. 2003).
Nair et al. (2005) concluded that 14 of the 16-instrumented root canal treated mandibular molars showed residual infection of the mesial roots after instrumentation, and irrigation with NaOCl in a one- visit treatment. The infectious agents were mostly located in the uninstrumented recesses of the main canal the isthmus communicating between them and in accessory canals.
The findings of this study showed that after the use of ozonated sodium hypochlorite resulted in reduced bacterial levels after chemomechanical preparation. There was a statistically significant difference between the treatment groups (P= 0.011).
Siqueira et al. (2007) revealed no significant difference when comparing the antibacterial effects of 2.5% NaOCl and 0.12% chlorhexidine used as irrigants during the treatment of infected canals.
318
Discussion 4.1.4
Several studies have demonstrated the antibacterial effect of ozone (Broadwater et al.
1973, Lezcano et al. 1999, 2001, Baysan et al. 2000, Abu-Naba’a 2003, Estrela et al.
2006, Polydorou et al. 2006).
Ozone kills microorganisms when its concentration in suspension is 106/ ml and lower, even at exposure times of only 10 seconds (Chang et al. 2003). Hems et al. (2005) showed that ozone had an antibacterial effect on planktonic E. Faecalis cells and those suspended in fluid, but little effect when embedded in biofilms. But the dose of ozone used was very low.
Barder et al. (2006) studied the efficacy of various concentrations of NaOCl (0.5%,
2.5% and 5.25%) and instrumentation techniques in reducing E. faecalis within root canals and dentinal tubules. They found no difference between concentrations in cleaning the root canal and only at higher concentrations was NaOCl able to disinfect the dentinal tubules independent of the canal preparation techniques used.
Ozonated NaOCl was produced by bubbling NaOCl with ozone using a closed ended silicone cup through a needle mounted on the HealOzone hand piece and attached to the ozone delivery nozzle. Two ozone modes appear on the HealOzone device which are: caries (Setting 1; time of ozone application) and endodontic (setting 2; time of ozone application) the setting 2 was used in this study.
319
Discussion 4.1.4
In this study ozonated NaOCl:
a) Releases hypochlorous acid which reacted with insoluble proteins to form
soluble polypeptides, amino acids and assorted by-products.
b) Acts as an organic and fat solvent, degrading fatty acids and transforming
them into fatty acid salts and glycerol thus reducing the surface tension of
the residual solution.
c) The chloramines produced interference in cell metabolism and caused
destruction of cell walls and cytoplasmic membranes of micro-organisms.
d) Ozonation of NaOCl in a negative pressure differential environment as
created by HealOzone should help reduce apical extrusion of irrigants.
Ozone is a strong oxidizer of cell walls and cytoplasmatic membranes of
bacteria and is considered to be one of the best bacteriocidal, antiviral and
antifungal agents (Bocci 2006). Oxidation promotes irreversible bacterial
enzymatic inhibition. This enzyme inactivation can be observed in the
- reaction of ozone with amino groups (NH2 ) and an irreversible oxidation
of sulphydryl groups (SH) of bacterial enzymes.
It is generally accepted that oxidation due to ozone induces the destruction of cell walls and cytoplasmic membrane of microorganisms and that differences in the sensitivity to ozonated water are probably due to differences in the structure of their cell walls
(Yamayoshi & Tatsumi 1993).
Huth et al. (2006) investigated whether gaseous ozone and aqueous ozone exerted any cytotoxic effects on human oral epithelial (BHY) cells and gingival fibroblast (HGF-1) cells compared with established antiseptics [chlorhexidine digluconate (CHX) 2%,
320
Discussion 4.1.4
0.2%; sodium hypochlorite (NaOCl) 5.25%, 2.25%; hydrogen peroxide (H2O2) 3%], exposure time was 1 minute and was compared with the antimicrobial, metronidazole, over 24 hours.
They found that the aqueous form of ozone, as a potential antiseptic agent, showed less cytotoxicity than gaseous ozone or established antimicrobials under most conditions.
Therefore, aqueous ozone fulfils optimal cell biological characteristics in terms of biocompatibility for oral application.
Arita et al (2005) found that aqueous ozone (2-4 mg/l for 1 min.) reduced the number of
Candida albicans on denture plates significantly (p < 0.01).
A study by Nagayoshi et al (2004a) demonstrated that ozonated water (4 mg/l) for 10 seconds was effective in killing gram-positive and gram-negative oral microorganisms and oral Candida albicans in pure culture and had strong bactericidal activity against the bacteria in plaque biofilm (p < 0.01). and their suggested that ozonated water application may be useful for endodontic therapy . After overnight incubation of single-species biofilms of S. mutans and S. sobrinus, the application of 2100 ppm of ozone for 10 seconds killed > 99% of bacteria (Baysan et al.2000).
The antimicrobial potential of 60 seconds ozone gas was assessed in an in-vitro study and compared with Photodynamic Therapy (PDT); (methylene blue in combination with or without a diode soft laser, and a soft laser alone) and antimicrobial solutions (2% chlorhexidine or in 0.5 and 5% hypochlorite solution) (Muller et al. 2007). Their result showed that only the 5% hypochlorite solution was able to totally eliminate the microorganisms in the biofilm. The observed reduction of viable counts by vacuum- ozone application and PDT was less than one log10 step. They concluded that under the
321
Discussion 4.1.4 conditions of the current study, gasiform ozone and PDT had a minimal effect on the viability of microorganisms organized in a cariogenic biofilm. However, they did not bubble the ozone into the biofilm unlike the application method on caries where the ozone tip is placed against the caries surface thereby flushing ozone into the lesion. Also the biofilm contained growth media full of reductants which would have formed a redox reaction with the ozone before the ozone could have killed the bacteria.
The accurate determination of root canal length is one of the important factors that can influence the outcome of root canal treatment (Seltzer et al. 1963, Smith et al. 1993,
Ricucci & Langeland 1998). It is widely accepted that root canal instrumentation and filling should be terminated at the apical constriction, where the periodontal ligament begins and the pulp ends (Kuttler 1955, Christie & Peikoff 1980, Dunlap et al. 1998,
Ricucci & Langeland 1998, Gordon & Chandler 2004). The effect of irrigating solutions on EALs has been evaluated previously (Fouad et al. 1993, Jenkins et al. 2001, Meares
& Steiman 2002). Many clinical studies have determined the accuracy of the EALs with radiographic techniques (Busch et al. 1976, Trope et al. 1985, Kaufman et al. 1989).
The position of the apical constriction cannot be accurately determined by radiographs
(Dummer et al. 1984, Ricucci 1998). Several reports have shown that the location of the apical constriction varies, usually in a range of 0.5–3.0 mm from the radiographic apex
(Kuttler 1955, Green 1960). In addition, in-vivo radiographic assessment of instrument position alone has been shown to be arbitrary (Chunn et al. 1981) and results from such studies can be questioned.
322
Discussion 4.1.4
In a recent study, Williams et al. (2006) reported that when the instrument was short, it was actually closer to the apical foramen than it appeared radiographically.
When the instrument was long, it was actually longer than it appeared radiographically.
In the present study the working length were measured with K-files using both radiographic x-ray and with an electronic apex locator (Elements-Dignostic (Sybron
Endo, Sybron Dental, Orange, CA).
The ozone apparatus tested is an electrical medical appliance. According to the manufacturer the pathway for the ozone is under negative pressure, which means that tha ozone generator is shut down if an incomplete seal occurs during treatment. After the ozone treatment is completed, only air is supplied through the system. Slippage of the resin cup from the teeth can occur easily during different clinical situations due to limited accessibility of the target tooth or non-cooperating patients.
Millar and Hodson (2007) compared the safety of two ozone delivery systems, the Ozi- cure and the Healozone, regarding the leakage. The Ozi-cure apparatus allowed high levels of ozone to build up in absence of suction, with a peak level of 1.22 ppm. No high ozone levels were detected when using the Healozone, even without additional suction.
The ozone sensor used in that study was accurate in the detection of ozone between 0-20 ppm.
In the current study, the delivery of ozone was carried out in a convenient way, without any incident report recorded.
Although bacterial reduction after chemomechanical preparation was significant in quantitative terms, 15 (35.7%) of 42 cases treated with ozonated NaOCl and 22 (57.8 %) of 38 cases treated with NaOCl with air were still positive for the presence of cultivable
323
Discussion 4.1.4 bacteria. These figures are within the range reported by other studies (Table 4.1.4.1).
The impact of persisting bacteria on treatment outcome is predictable. Although some cases of apical periodontitis lesions can even heal when bacteria are found in the canal at the root-canal filling stage (Sjögren et al. 1997, Fabricius et al. 2006). It has been demonstrated that the outcome of the endodontic treatment is significantly influenced by the presence of bacteria in the canals at the time of filling (Waltimo et al. 2005). The findings of this study and the other studies listed in Table 4.1.4.1 with regard to the antimicrobial effectiveness of chemomechanical procedures reinforce the need for using additional or alternative antimicrobial strategies to predictably render root canals free of cultivable bacteria before filling.
Our finding indicated that the whole protocol succeeded in rendering the root canals free of bacteria in only 43 of 80 cases (53.8%). The results of this study showed that the ozone delivery system functioned successfully in all cases, with the seal always easy to achieve. Further research on the follow-up of these cases is necessary. Addition studies are required to validate the current in vivo results in more clinical situations.
324
Discussion 4.1.4
TABLE 4-1-4-1 DATA FROM DIFFERENT CLINICAL STUDIES, SHOWING THE INCIDENCE OF POSITIVE CULTURES
Study Irrigation Positive cultures* Byström & Sundqvist 0.5% sodium hypochlorite 13/15 (86.7%) (1983) Byström & Sundqvist 0.5% sodium hypochlorite 12/20 (60%) (1985) Sjögren et al. (1997) 0.5% sodium hypochlorite 22/55 (40%) Kvist et al. (2004) 0.5% sodium hypochlorite 58/94 (61.7%) Siqueira et al. (2007) 2.5% sodium hypochlorite 10/16 (62.5%)
Shuping et al. (2000) 1.25% sodium hypochlorite 15/41 (36.6%)
Peters et al. (2002) 2% sodium hypochlorite 10/42 (23.8%) Vianna et al. (2006) 2.5% sodium hypochlorite 4/16 (25%) Ercan et al. (2004) 5.25% sodium hypochlorite 4/15 (26.7%) This study 0.5% sodium hypochlorite 22/38 (57.8%) with air
0.5% sodium hypochlorite 15/42 (35.7%) with ozone
*Number of cases positive for bacteria in post treatment samples/No. of cases positive for bacteria in initial samples.
325
Conclusion 4.1.5
4.1.5 CONCLUSION
Ozone treatment has important potential clinical uses, particularly from the point of view
of reducing the number of microorganisms.
Furthermore, we found that both the irrigant groups had the ability to reduce the number
of microorganisms. In addition, ozonated NaOCl had a strong significant antibacterial
activity. Moreover, the use of ozone has led to significantly fewer microorganisms in the
canal systems.
The use of ozone in root canal therapy was carried out in a convenient way and was able
to get a seal around the treatment tooth in an easy way. This new approach is simple to
use.
326
Introduction 4.2.1
4.2 INFLUENCES OF OZONE TREATMENT ON POST-OPERATIVE PAIN AFTER RCT IN-VIVO.
4.2.1 INTRODUCTION
Until recently, the most accepted technique of undertaking endodontic treatment
required multiple visit procedures. Most schools also concentrated upon teaching the
multi-visit concept. However, it has recently been reported that the procedure of single
visit treatment is advocated by at least 70% of schools in all geographical areas
(Qualtrough et al. 1999).
Some of the problems of root canal treatment are postobturation pain and inter-
appointment pain and swelling. Although these complications in most cases do not last
long, they could be a source of embarrassment to the dentist and annoyance for the
patient. More so if the tooth was symptom less before the commencement of treatment.
A literature review revealed varied opinions on the incidence and severity of post-
obturation pain. Some authors reported slightly more post-obturation pain following
single visit than with multiple visit procedures (Clem 1970, Soltanoff 1978).
Others found no significant differences in the post-obturation pain experienced by
patients following single or multiple visit treatment procedures (O' Keefe 1976).
O'Keefe (1976) however proposed a correlation between pre-treatment pain and post-
obturation discomfort. The rate of endodontic flare-ups was reported to be more frequent
following multiple visits than for the single visit (Albashaireh & Alnegrish 1998).
327
Introduction 4.2.1
Imura & Zuolo (1995) also reported a positive correlation between flare-ups and
multiple appointment retreatment cases, peri-radicular pain prior to treatment and
presence of radiolucent lesions. They reported no correlation between post-obturation
flare-ups and the status of the pulp. However, Sim (1997) reported a significantly higher
incidence of flare-ups in necrotic teeth than in vital teeth (p = 0.01). Fox et al. (1970) in
their study showed that female patients had more postoperative pain than did males.
Factors such as age, bacteriologic status, tooth position and type of filling material
showed no clear effect upon post-operative results.
Futhermore, persistent pain associated with teeth after non-surgical or surgical
endodontic treatment has been used as an indicator of treatment failure (Hoskinson et
al.2002). However, pain may be experienced in a tooth or adjacent site in the absence of
clinical or radiographic signs of dental disease. The ability to predict its prevalence and
forewarn the patient may go some way towards enabling coping strategies. It has been
used as an outcome measure to justify single as opposed to multiple-visit root canal
treatment (Mulhern et al.1982, Albashaireh & Alnegrish 1998).
The aim of the present study was to investigate the use of an ozone delivery system in
single visit root canal treatment especially related to the incidence of post-obturation
pain.
328
Material and Methods 4.2.2
4.2.2 MATERIAL AND METHODS
This study was undertaken between April 2006 and Jan 2007 in the UAE. One hundred
patients consented to participate and were included for analyses in this study. All the
root canal treatment was performed by one operator in a single visit.
The following criteria were used for the inclusion of subjects this clinical study:
• Male or female > 17 years of age.
• Presence of enough coronal tooth tissue for adequate isolation of the tooth with
rubber dam.
• All involved teeth were treated endodontically, in one visit.
• No swelling.
• Written subject Informed Consent (IC) for this protocol had been obtained prior to
the study enrolment. Each subject was required to sign and date the IC form prior to
their participation and after explaining the clinical procedure and risks involved and
clarifying all questions raised by the patient.
The following criteria were used for the exclusion of subjects in this clinical study:
• No prior endodontic treatment on the involved tooth.
• Patient with a diagnosis of diabetes or any immunocompromising disease (such as
thyroid disease, cardiac disease, kidney disease, Cohn’s disease, depression).
• Pregnancy.
• No previous antibiotics in the preceding 3 months.
• Sterility controls taken of the operation field should demonstrate no growth of
bacteria.
329
Material and Methods 4.2.2
The protocol and informed consent forms were approved by the Research Ethics
Committee, Government of Dubai, Rashid Hospital, Department of Health and medical
services and Ministry of Health U.A.E. Preoperative diagnostic information was
obtained. Nonvital teeth were included in the study. The pulp vitality was tested by an
electric pulp tester (Sybron Endo Vitality scanner Model 2006, Kerr, Italy) in
combination with the presence of pulpal haemorrhage (Fig 4.2.2.1).
FIGURE 4-2-2-1 VITALITY SCANNER
330
Material and Methods 4.2.2
For each patient the data gathering were recorded by one operator (Table 4.2.2.1). The
presence and severity of pain over the 1st, 2nd, 7th and 30th day were recorded by the
patient. All teeth were filled using lateral compaction of gutta-percha cones with
Endofill sealer (Dentsply) and the access cavities were restored with 3 mm of Cavit ™
(3M).
At the beginning of each review appointment, patients were asked about the occurrence
of postoperative pain. The level of discomfort was rated as follows: no pain, mild pain,
which was recognizable but not discomforting, moderate pain, which was discomforting
but bearable (analgesics, if used, were effective in relieving pain) and severe pain, which
was difficult to bear (analgesics, if used, were ineffective in relieving pain). Cases with
severe postoperative pain and/or the occurrence of swelling were classified as flare-ups
and treated accordingly. Patients had pain levels recorded in the presence of the clinician
to ensure that they understood the instructions.
All the 100 patients were treated as in study 4.1.
Follow-up examination after 30 days and 6 months consisted of history taking, clinical
and radiographic examination at 6 months recall. All subjects were interviewed and
examined by two operators. During the interview, the patients personal, medical and
dental details as well as the preoperative pain history were confirmed. A detailed pain
interview was conducted on patients presenting with pain on review. Extra-oral
examination included palpation of the masticatory, neck and shoulder muscles for
comparative tenderness, and palpation of the temporomandibular joint. The tooth
331
Material and Methods 4.2.2
adjacent and opposing the tooth under investigation were also examined in order to
exclude them as causes of pain. All the pre-operative and follow-up postoperative
periapical radiographs were calibrated as the same assessment criteria used in study 2.1
Table 2.1.6.
TABLE 4-2-2-1 DATA RECORDED FOR EACH CASE
Preoperative data Age and gender Tooth type Preoperative clinical signs and symptoms associated with the tooth studied History of pain (before and within 24 h) Intra-operative data Irrigant used (Ozonated NaOCl or NaOCl with air) Post-obturation pain Presence and intensity of pain in the first 24h and also in the second 24h Presence and intensity of pain in the 7th day Presence and intensity of pain in the 30th day
4.2.2.2 STATISTICAL ANALYSIS
The overall incidence of postoperative discomfort was recorded and expressed as a
percentage of the total number of patients evaluated. The incidence of postoperative pain
was calculated for each study variable. Data were statistically analyzed using the
Fisher’s exact test and the Mann-Whitney U test. All analyses were performed using the
SPSS statistical package for Windows version 14. The significant level was set at 0.05
(2-tailed).
332
Result 4.2.3
4.2.3 RESULTS OF THE STUDY
Some level of postoperative pain (mild - severe) occurred in 25% of the cases in the first
day (i.e. 0-24 hours) after complete chemo-mechanical preparation with NaOCl with air
or ozonated NaOCl as the irrigant substances. In the second day the occurrence of mild
pain was found in only 2.5% of the cases. These results are shown in Table 4.2.3.1 and
Figure 4.2.3.1. The results in Table 4.2.3.1 show that there were a substantial percentage
of patients who experienced different levels of pain on the first day of treatment with
NaOCl with air and ozonated NaOCl. Indeed, 78% (n =33) of patients treated with
ozonated NaOCl reported having “no pain”, compared to 71% (n =27) of the patients
treated with the NaOCl and air.
Moreover, mild pain was reported by 12% (n= 5) of patients treated with ozonated
NaOCl and 3% (n =1) of all patients treated with NaOCl with air. Interestingly, 18% (n
= 7) of patients treated with NaOCl with air reported having “moderate pain”, compared
to only 5 % (n = 2) of patients treated with ozonated NaOCl. In addition, 8 % (n = 3) of
patients treated with NaOCl with air reported severe pain and 5% (n =2) of patients
treated with ozonated NaOCl had the same level of pain.
333
Result 4.2.3
TABLE 4-2-3-1 OCCURRENCES OF POSTOPERATIVE PAIN IN THE FIRST DAY
Level of Pain Irrigation Solution ( % ) Total of NaOCl Ozonated Patients with air NaOCl No Pain 27 (71%) 33 (78%) 60 (75%)
Mild 1 (3%) 5 (12%) 6 (8%)
Moderate 7 (18%) 2 (5%) 9 (11%)
Severe 3 (8%) 2 (5%) 5 (6%)
Total 38 42 80
90% 80% NaOCl with air 70% Ozonated NaOCl 60% 50% 40% 30% 20% 10% 0% No pain Mild Moderate Severe Pain Score
FIGURE 4-2-3-1 PERCENTAGES OF PAIN IN THE FIRST DAY WITH REGARD TO IRRIGATION GROUPS
334
Result 4.2.3
The result in Table 4.2.3.2 revealed that 5% (n= 2) of patients reported a mild level of
pain on the second day of treatment with NaOCl with air and none with ozonated
NaOCl. 100% (n= 42) of patients treated with ozonated NaOCl reported having “no
pain”, compared to 95 % (n= 36) of patients treated with NaOCl with air.
TABLE 4-2-3-2 OCCURRENCES OF POSTOPERATIVE PAIN IN THE SECOND DAY
Level of Pain Irrigation Solution ( % ) Total of NaOCl Ozonated Patients NaOCl No Pain 36 (95%) 42 (100%) 78 (97.5%)
Mild 2 (5%) 0 2 (2.5%)
Total 38 42 80
There was no pain in 75% and 97.5% of the cases on the first day and second day
respectively. With respect to the differences between the level of pain in the first or
second day of treatment and the type of irrigating solution, the Mann-Whitney and the
Fisher’s exact test revealed no statistically significant differences (Table 4.2.3.3).
335
Result 4.2.3
TABLE 4-2-3-3 RESULT OF THE APPROPRIATE TEST USED
Post-operative Day Irrigation solution No Pain % Mild Pain Moderate Pain Severe Pain Significance % % % 1st Day NaOCl 27 (71 ) 1 (3 ) 7 (18) 3 (8) Mann-Whitney U test P= 0.314 Ozonated NaOCl 33 (78) 5 (12) 2 (5) 2 (5) 2nd Day NaOCl 36 (95) 2 (5) 0 0 Fisher ‘s exact test p=0.22 Ozonated NaOCl 42 (100) 0 0 0
There was no pain on the 7th and 30th day in all cases (80 patients).
The incidence of postoperative pain is one of the major concerns when evaluating
endodontic treatment. The results of the Spearman’s rank analysis showed that there was
a positive correlation between the pain in the first day and the bacterial reduction i.e.
there was more pain with more eradication of bacteria closer to 100% in both treatment
groups NaOCl with air (rs = 0.32, p = 0.054) and Ozonated NaOCl (rs = 0.37, p = 0.015).
The result of the Mann-Whitney U test (p<0.05) in the current study verified that there
was a significant difference in the experience of pain in the 1st day and the gender of the
patients (p = 0.001). Moreover, there was no statistically significant difference in pain
score before the interventions of treatment between men and women (p = 0.908).
Figure 4-2-3-2 showed that more male patients experienced pain, ranging from mild to
severe in the first day than the female patients.
Table 4-2-3-4 illustrated the percent of male and female patients who experienced
postoperative pain in the first day. With regards to gender, 19% (n=15) of male patients
experienced postoperative pain ranging from mild to severe in the first day compared to
only 6% (n =5) of female patients. Seventy-five percent (n = 60) of all patients reported
336
Result 4.2.3
no pain in the first day postoperatively while 25% (n = 20) of all patients experienced
pain postoperative following the single visit procedures.
TABLE 4-2-3-4 COMPARISON BETWEEN GENDERS ON THE LEVEL OF PAIN IN THE FIRST DAY POSTOPERATIVELY
Pain Score Male (n=34) Female (n=46) Total (n=80)
No Pain 19 (23.8%) 41(51.3%) 60 (75%)
Mild Pain 5 (6.3%) 1 (1.3%) 6 (7.5%)
Moderate Pain 7 (8.8%) 2 (2.5%) 9 (11.3%)
Severe Pain 3 (3.8%) 2 (2.5%) 5 (6.3%)
Surprisingly, there was no statistically significant difference between tooth types
(anterior or premolar) and the level of pain in the first day (p = 0.389) or second day (p=
0.799). Moreover, there was no significant difference between the level of pain and the
location (upper or lower jaw) of the treated tooth in the first day (p=0.432), or in the
second day (p=0.107). The results also, revealed no significant differences between the
level of pain and the treated side of the tooth (right or left) in the first day (p= 0.540), or
in the second day (p =0.280).
337
Result 4.2.3
50 Gender Male Female
40
30
20 51.25%
10 23.75%
8.75% 6.25% 2.5% 3.75% 2.5% 0 1.25% No Pain Mild Pain Moderate Pain Severe Pain Pain Score on First Day
FIGURE 4-2-3-2 COMPARISON BETWEEN GENDER ON THE LEVEL OF PAIN
The results of the Spearman’s Rank Correlation Coefficient showed that there was a
statistically significant positive correlation between pre-operative and post-operative
pain at first day (rs =0.472, p = 0.001). In this study the results of the Spearman’s rank
correlation coefficient found no evidence of association between the pre-operative
radiolucency and post-operative pain at first day (rs = 0.136, p =0.229).
338
Result 4.2.3
The result of the Mann-Whitney test showed that there was no statistically significant
difference in the changes of the x-ray scores and the treatment groups (p = 0.78). The
following test done only with cases who had normal x-rays at the being of treatment,
revealed that there was no statistically significant differences in percentage of bacterial
reduction between treatments groups NaOCl with air (p = 0.652) or ozonated NaOCl (p=
0.515) in the review periods at 6 months.
Comparison of the treatment groups are summarized in Table 4.2.3.5. An interesting
finding was that the two (2.5%) cases that had the worst x-ray result were also not sterile
after irrigation in the NaOCl group. Moreover, in the ozonated NaOCl group 39 (48.8%)
of the cases which had periapical radiolucencies became normal.
A graphical method was used to summarize the correlation between the bacterial
reduction in both treatment groups and the score of the x-rays (Fig 4.2.3.3). In the
ozonated NaOCl groups, 12 cases out of 15 which were non-sterile after irrigation had
an improvement in the x-ray score at the 6 months recall, whilst 16 cases out of 22
which were non-sterile after irrigation improved in the x-ray score with treatment of
NaOCl at 6 month recall.
The two cases, which got worse were both with x-ray score of 1 at baseline and were 2
at 6 months recall. Whilst in the ozonated NaOCl group no cases got worse.
339
Result 4.2.3
X-rays scores of the treatment groups related to the bacterial reduction
FIGURE 4-2-3-3 HISTOGRAM OF THE IRRIGATION GROUPS (NAOCL WITH AIR AND OZONATED NAOCL) BETWEEN BACTERIAL REDUCTION AND X-RAYS FINDINGS
340
Result 4.2.3
TABLE 4-2-3-5 CROSS TABULATION OF X-RAYS CHANGES WITH REGARDS TO IRRIGATION GROUPS
X-rays changed at 6 months periods Better Same (Abnormal to (Normal to Worse (Normal to Normal) Normal) Abnormal) Total irrigation NaOCl Count 30 6 2 38 % of Total 37.5% 7.5% 2.5% 47.5% Ozonated NaOCl Count 39 3 0 42 % of Total 48.8% 3.8% .0% 52.5% Total Count 69 9 2 80 % of Total 86.3% 11.3% 2.5% 100.0%
341
Discussion 4.2.4
4.2.4 DISCUSSION OF THE STUDY
The super elastic property of nickel-titanium, coupled with advanced file design, allows
safe and effective instrumentation using hand piece-driven files operated at low speeds.
However, all canal preparation techniques are reported to cause apical extrusion of
debris even when the file action is maintained short of the apical terminus (Genet et
al.1987). The difference is that some techniques extrude more debris than others. For
example, crown-down techniques, such as alternated rotation motion techniques have
been demonstrated to extrude a lesser amount of debris (Martin & Cunningham 1982,
Moore 1996).
Pekruhn (1981) demonstrated that single-visit endodontic therapy appears at least equal
in desirability to multiple-visit therapy from the point of view of painfulness to the
patient. Oliet (1983) showed no significant difference in postoperative pain and healing
when comparing single visit versus multiple visit endodontic procedures when proper
diagnosis, case selection and skilled treatment were performed. In addition, Fava (1991)
noted no significant difference in the incidence of postoperative pain between non- vital
teeth treated in one or two visits. There was no difference in postoperative pain between
patients treated in one appointment and patients treated in two appointments.
The majority of patients in both groups reported no pain or only minimal pain within 24
to 48 hours of treatment (Direnzo et al. 2002).
342
Discussion 4.2.4
However, in other studies the rate of endodontic flare-ups was reported to be greater
following multiple visits than for single visits (Imura & Zuolo 1995, Al bashaireh & Al
Negrish 1998). Oginni & Udoye (2004) reported a high incidence of postobturation pain
and flare-ups following single visit procedures (18.3%) compared to multiple visit
procedures (8.1%).
A recent study by Al Negrish & Habahbeh (2006) reported that there was no statistically
significant difference in the incidence and degree of postoperative pain between one and
two visit endodontic procedures.
Aqrabawi & Jamani (2006) undertook a study to evaluate the effect of the ProTaper
rotary NiTi instrumentation technique on post-treatment pain at different times when
compared with a step-back technique. Patients assessed post-treatment pain at 8, 24 and
48 hours as none, mild, moderate or severe. The results demonstrated that there was no
statistically significant difference in post-treatment pain between the two groups at any
time (P > 0.05).
Sathorn et al. (2007) undertook a systematic review to assess the evidence regarding
postoperative pain and flare-up of single- or multiple-visit root canal treatment. They
concluded that compelling evidence indicated a significantly different prevalence of
postoperative pain/flare-up of either single- or multiple-visit root canal treatment is
lacking.
Postoperative pain after non-surgical root canal treatment has been reported to range
from approximately 3% to more than 5% (Torabinejad et al. 1994, Albashaireh &
Alnegrish 1998).
343
Discussion 4.2.4
In the present study, 60 out of 80 (75%) patients reported no pain in the first post-
appointment day. The number increased to 78 (97.5%) for those who indicated no pain
on the second day. Again the number significantly increased to 80 (100%) of all patients
who had no pain on the seventh and thirtieth post-appointment day. In clinical terms,
these results indicate that the treatment procedures had been fully successful with
respect to the postoperative pain after 7 days in this study.
The occurrence of this level of pain (mild to severe), in patients after root canal
obturation in the first day (25%), is in agreement with Yesilsoy et al. (1988) who
reported a similar prevalence of pain experience by patients after root canal obturation at
25.3% in the first day and 2.5% in the second day. Other studies (Fox et al. 1970, Morse
et al. 1987, Ng et al. 2004) reported a higher percentage of pain (62, 43.3 and 40.2
respectively). This discrepancy could be attributed to differences in the preoperative
status of the teeth, treatment protocol and the level of pain severity included for analysis.
A major objective in root canal treatment is to obtain a clean root canal system. Dentine
chips, pulp tissue fragments, necrotic tissue, microorganisms and intracanal irrigants
may be extruded from the apical foramen during canal instrumentation. This is of
concern since material extruded from the apical foramen may be related to post
instrumentation pain or to a ‘flare-up’ (Seltzer & Naidorf 1985). Even though all
instrumentation techniques extrude some debris apically (Vande Visse & Brilliant 1975),
there are differences amongst them. Al-Omari & Dummer (1995) verified that
techniques involving a linear filing motion, such as the step-back technique, create a
greater mass of debris than those involving some sort of rotational action.
344
Discussion 4.2.4
Reddy & Hicks (1998) were the first to compare apical debris extrusion between hand
instrumentation and engine-driven nickel–titanium instruments. Comparing the mean
weights of apically extruded debris, they noted that the step-back instrumentation
techniques (Light Speed and Profile Series 29) and the balanced force technique
produced significantly more debris than the two engine-driven nickel–titanium methods.
Martin & Cunningham (1982) reported that endosonics extruded less debris and,
regardless of the method used, a smaller amount of debris was extruded when
instrumentation was restricted to the confines of the root canal. However, in a clinical
study the same authors did not find a significant difference in the incidence of post
instrumentation pain following endosonic or conventional hand instrumentation.
In the current study, root canal instrumentation with the (NiTi) K3 system was coupled
with crown-down techniques. K3 instruments (SybronEndo, West Collins, CA, USA)
had a slightly positive rake angle in combination with so called radial land relief and an
asymmetrical cross-sectional design and has been reported to respect original root canal
curvature well and be safe to use (Schäfer & Florek 2003, Schäfer et al. 2006). A crown-
down instrumentation sequence has been suggested for most of the rotary nickel-
titanium instruments, in which larger files precede smaller ones, which in turn progress,
further apically, which minimises the risk of instrument separation (Peters 2004).
During canal preparation, bacteria, pulp tissue debris and infected dentine particles may
be moved apically, often resulting in loss of working length if recapitulation is not
performed frequently or if it is ineffective (West & Roane 1998, Wu et al. 2000b). This
infected material may be pushed into the apical region beyond the original extent of
345
Discussion 4.2.4
preparation and even extruded through the foramen (Simon 1994, Wu et al. 2000b) with
a potentially negative influence on outcome (Simon 1994).
The bacteria and infected debris accumulating in this most apical portion of the root
canal may affect apical healing (Nair et al. 1990a, 1999, Simon 1994, West & Roane
1998). One suggested approach to solve the problem is to create a continuously tapering
root canal, the apical foramen, rather than the apical constriction, serving as the apical
end-point of preparation (West & Roane 1998, Buchanan 2000).
Another frequently used technique that is claimed can ‘clean’ the apical region is the
apical patency concept’ (Cailleteau & Mullaney 1997).
This concept involves the periodic use of a small file (size 10 or 15) placed
approximately 1 mm longer than the working length, in an attempt to push any debris
that has accumulated through the foramen and allow the irrigant solution to rinse the
entire apical portion.
An interesting finding is the number of patients experiencing symptoms after an
endodontic procedure. In this study, 25% of patient reported significant (mild to severe)
pain level in the first day. Post appointment, the number dropped, reaching only 2.5% on
the second day.
In clinical terms, these results indicate that the practitioner may need to prescribe an
adequate amount of analgesic medication to provide post- treatment pain relief.
Sim (1997) reported a significantly higher incidence of flare-ups in necrotic teeth than in
vital teeth (p = 0.01).
346
Discussion 4.2.4
The incidence of severe pain was relatively low five (6%) for the cases post-obturation
on the first day whilst the occurrence of mild pain post-obturation in the first and second
days was respectively 6 (8%) and 2 (2.5%) and only 11% had a moderate postoperative
pain in the first day.
Studies have reported that intracanal medication had no influence on the incidence of
postoperative pain (Trope 1990, Torabinejad et al.1998). Others have shown that the use
of an antimicrobial intracanal medication and sodium hypochlorite irrigation could
prevent postoperative pain (Harrison et al.1981).
The results of this investigation showed no significant difference regarding post-
treatment pain between the use of NaOCl with air or ozonated NaOCl irrigation solution
and level of pain before treatment and after the first and second day post-obturation (p >
0.05).
The results of the present study found a significant difference between the occurrence of
pain on the first day and the age of the participant. Our result reveals notable difference
between males and females reporting postoperative pain; in fact, the results showed that
male patients (44.1%) experienced more pain than female patients (10.8%). This finding
disagrees with other studies such as (Fox et al. 1970, Ng et al. 2004, Polycarpou et al.
2005) who reported that female patients had more postoperative pain than male patients
did.
This study’s result supported other studies showing that adult women had a lower pain
threshold and less pain tolerance compared to males (Ellermeier & Westphal 1995,
Fillingim et al. 1998, Riley et al. 1998, Iqbal et al. 2007). However, these results are in
347
Discussion 4.2.4
contrast to those reported by Lin et al. (2006) who did not find any significant effect of
gender on postoperative symptoms after endodontic surgery.
In the current study, it was not surprising that the NaOCl might have lead to pain, as it is
highly irritating to periapical tissues, especially at high concentrations (Ercan et al.
2004). However, the addition of ozone did not reveal any significant differences in the
level of pain.
Tooth type was not significantly associated with anticipated or experienced dental
procedure pain. The study investigated this aspect by comparing anterior teeth with
premolars. Also previous studies support that, tooth type has been reported to have no
association with endodontic interappointment pain (Harrison et al.1983a) or post-
obturation pain Yesilsoy et al. (1988).
The posterior teeth located in the mandibular arch, however, have been reported to be
significantly associated with higher levels of endodontic pain. Yesilsoy et al. (1988) felt
that their findings corroborated the impression held by many clinicians that mandibular
posterior teeth have more postobturation pain than do maxillary anterior teeth. This
difference may be related biologically to a greater number of canals and high frequency
of bifurcated root canals in mandibular posterior teeth (Stabholz et al. 1994).
Previous studies have shown that there is a strong positive correlation between pre-
operative and post-obturation pain (O’Keefe 1976, Genet et al. 1986, Oginni & Udoye
2004, Ng et al. 2004). The present study supports this correlation that there was a
statistically significant correlation between pre-operative and post-obturation pain (p =
0.001).
348
Discussion 4.2.4
In addition, the present study showed that there was a positive correlation between the
pain in the first day and the bacterial reduction between the irrigation groups, NaOCl
with air (p= 0.054) or Ozonated NaOCl (p= 0.015). This could be related to the
mechanisms of the lipopolysaccharide (LPS) induction of inflammation consequent to
the bacterial killing.
Most of the previous studies (Fox et al. 1970, O’Keefe 1976, Harrison et al. 1983)
investigating the association with periapical lesions on post-obturation pain have studied
the effect of their presence or absence. Ng et al. (2004) found that teeth with a periapical
lesion larger than 3 mm were associated significantly with less post-obturation pain than
those teeth with a smaller lesion. In contrast, Genet et al. (1987) found that teeth with a
periapical lesion larger than 5 mm were associated with a higher prevalence of pain than
those with no or a smaller lesion. The present study found there was no association
between the presence of a periapical lesion and the incidence of postoperative pain.
A 4-year review period is regarded as the gold standard treatment (Strindberg 1956).
However, the requirements for a pain study are different. Assessment of postoperative
pain is reliant upon an accurate pain history, which is more likely to be obtained over
shorter review intervals. A balance therefore had to be realized in allowing complete
periapical healing against a review period short enough not to compromise that memory
of pain history.
A 1-month review period (Marbach et al. 1982) was used in the present study to yield
accurate pain histories and proved to be a short interval. Thus, a 6 months recall period
was adopted in this study.
349
Discussion 4.2.4
It has been shown that apical periodontitis is often found in connection with root canal
treated teeth and that the quality of the root canal treatment is of importance for the
prognosis that such lesions to heal.
An interobserver difference always existed when more than one observer is involved
(Eckerbom et al. 1986). In order to minimize the risks, strict criteria were used for
positive recordings and the two observers were calibrated. Furthermore, after having
examined half of the material each, the material was re-examined by both examiners
together to reach full consensus in all cases (Molven et al. 2002). The use of periapical
radiographs instead of panoramic radiographs, increase the sensitivity of detecting apical
periodontitis in some regions (Molander et al. 1995), but it has to be considered that
even periapical radiographs will involve a risk for misinterpretations (Eckerbom &
Magnusson 1997).
In the current study the number of cases during the 6 month follow-up recall which had
a periapical radiolucency at the baseline for both treatment irrigation groups decreased
from 24 (30%) to 10 (12.5%) cases.
Factors that influence the outcome of endodontic treatment including: the particular
bacteria involved in the infection (Sundqvist 1976), correct diagnosis (Kerekes &
Tronstad 1979) and maintenance of long-term coronal seal (Kirkevang et al. 2001a). As
described earlier by many authors (Buckley & Spängberg 1995, Lupi-Pegurier et al.
2002, Loftus et al. 2005) a periapical radiolucency is found less frequently when the
quality of the endodontic treatment is good. Further research on the follow-up of these
cases is necessary for up to 4 years.
350
Discussion 4.2.4
Despite the percentage of post-obturation pain reported on the first and second day, no
post-operative pain persisted to the 7th and 30th day. This result should draw to the
attention of practitioners that early post-obturation symptoms should not always initiate
endodontic retreatment or extraction of the involved tooth.
Very promising results are shown with the reduction in periapical radiolucency
associated with the use of ozone and this warrants further clinical studies. Caution needs
to be exercised as the groups were skewed with most of the periapical radiolucency in
the ozone groups.
351
Conclusion 4.2.5
4.2.5 CONCLUSION
Under the conditions of this study, 25% of patients with pain associated with teeth treated at a single appointment with either NaOCl with air or ozonated NaOCl, experienced pain on the first day after treatment and less on the second day. The incidence of pain was not influenced by bubbling ozone into the irrigation solution compared to air.
The prevalence of some level of post-operative pain was not significantly influenced by tooth type (anterior or premolar) or tooth arch for both upper and lower jaw.
352
Further investigation
FURTHER RESEARCH
The studies reported in this thesis have highlighted a number of areas that merit further study, in particular:
♠ A clinical study to assess the effect of ozone treatment as a new root canal irrigant without NaOCl.
♠ A clinical follow-up of the current patients to assess if ozone use was associated with significant improvement of the success rates.
♠ To assess the effectiveness of ozone in the treatment of medically compromised and disabled patients with RCT.
♠ To assess the efficacy of ozone in the treatment of open apices.
♠ More in-vitro studies to assess the effect of ozone treatment to remove the smear layer.
♠ More studies to evaluate the effect of ozonated NaOCl or ozone to kill microorganisms in in-vivo studies at different exposure times.
♠ A clinical study to assess the effect of ozone treatment in the retreatment root canal treatment cases.
♠ An in-vitro study to understand the molecular mechanisms of for example the ozonated NaOCl and ozonated sterilox.
♠ Long-term follow-up of these cases.
♠ Further work will be required to repeat and expand on these studies especially for testing groups which will not have the unfortunate allocations which occurred in the randomisation in this thesis.
353
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460
GENERAL CONCLUSION
Follow-up clinical studies have shown that root canal treatment can achieve healing rates of 84% (Smith et al. 1993) to more than 90% (Sjögren et al. 1990). Each of these studies reported data from endodontic specialists and university clinics. These studies may be misleading in estimating the realistic outcome of endodontic treatment in general practice that may approach 60-75% (Eriksen et al. 2002). This discrepancy in outcome may reflect a difference in the technical quality of the RCT performed.
Thus, new treatment approaches are required in an attempt to improve these success rates. Ozone was introduced as one of the treatment approaches to manage dental caries but has not been assessed for use as a new irrigant to remove the smear layer, to reduce microorganisms or for its effect on postoperative pain in root canal therapy or on healing of periapical radiolucency.
There was no statistically significant improvement in the quality of the second root canal filling when compared radiographically with the first clinical attempt of RCT. It could be suggested that the standard of teaching pre-clinically allowed the students to be competent to carry out RCT on a real patient. The fact that the quality did not improve with the second root canal filling supports competency training. It suggests that the students have reached a plateau in their learning. Further investigation is indicated to examine the factors contributing to failures in different postoperative periods.
461
Irrigation of ozonated NaOCl (Group 2) was the most effective at smear layer removal compared to all the other groups. Ozonated sterilox, ozonated water and NaOCl had favourable results to remove the smear layer.
The irrigation of root canals with gaseous ozone or sodium hypochlorite with air for 120 seconds kills all E. faecalis, when its concentration in suspension is 104/ml. Air had no significant effect. Sodium hypochlorite was less effective in reducing the number E. faecalis in the lower time of application of 10s, it takes more time to reduce the number of the microorganisms.
The application of ozone gas for a period of 10 to 120 seconds was capable of reducing the number of E. faecalis more than NaOCl and air and total eradication of E. faecalis occurred after ozone treatment with an exposure time of ≥ 40 seconds when the starting bacterial concentration was 5.9 x 104 for 40s and 5.8 x 106 for 60 or 120s respectively.
Ozone treatment has important potential clinical uses, particularly from the point of view of reducing the number of microorganisms.
Furthermore, this study found that both the irrigant groups had the ability to reduce the number of microorganisms. In addition, ozonated NaOCl had a strong significant additional antibacterial activity. The use of ozone led to significantly fewer microorganisms in the canal systems.
The use of ozone in root canal therapy was carried out in a convenient way and was able to get a seal around the treatment tooth in an easy way. This new approach is simple to use.
462
Twenty five percent of patients with pain associated with teeth treated at a single appointment with either NaOCl with air or ozonated NaOCl, experienced pain on the first day after treatment and less on the second day. The incidence of pain was not influenced by bubbling ozone into the irrigation solution compared to air.
The prevalence of some level of post-operative pain was not significantly influenced by tooth type (anterior or premolar) or tooth arch for both upper and lower jaw.
463
SUBMISSION FOR PUBLICATION
Poster presentation:
Quality of the first root canal fillings performed by undergraduate dental students
Alawadi J, Hussey D, Lynch E. The annual meeting of the Irish Division of IADR
(January 28-29/2005).
Submitted for publication:
Two papers are submitted for publication to Oral Surgery Oral Medicine Oral
Pathology Oral Pathology Oral Radiology and Endodontics: the first entitled:
Quality of the first root canal treatment performed by undergraduate students.
Alawadi J, Lamey P-J, Hussey D and Lynch E.
And the second entitled Quality of the second root canal treatment performed by
undergraduate students.
Alawadi J, Lamey P-J, Hussey D, and Lynch E
Three papers have been submitted for publication to the International Endodontic
Journal: 1: Efficacy of some irrigants to remove the smear layer in root canals: an
SEM study.
Alawadi J, Lamey P-J, Cunningham JL, J.Figueiredo and Lynch E
464
The second entitled: Antimicrobial effect of ozone on microorganisms in root canals in-vivo.
Alawadi J, Lamey P-J, AlKhatib Z and Lynch E
And the third entitled: Influences of ozone treatment on post-operative pain after
RCT in-vivo.
Alawadi J, Lamey P-J, AlKhatib Z and Lynch E
465
APPENDICES
466
FLOW CHART OF THE STUDY 3.1 Smear layer removal capacity of disinfectant solutions: A SEM study
Aim: To determine the ability of ozone to remove dentinal debris and smear layer produced during canal preparation.
Material and methods
80 extracted premolar teeth externally cleaned
Radiographs of teeth with periapical film to exclude complicated root canal anatomy or previously root filled teeth
Crowns of teeth removed at the cement enamel junction using diamond fissure bur
Teeth divided into eight experiment groups with 10 roots each
Irrigation experiment as follows
Irrigation of the canal with a 27- gauge endodontic irrigating needle
Group 1: 1ml of 0.5% NaOCl + air for 10 seconds
Group 2: 1ml of 0.5% NaOCl + Ozone for 10 seconds
467
Group 3: 1 ml of distilled water + air for 10 seconds
Group 4: Ozone at exposure times 10 seconds in 1ml pH12 water Group 5: control group 1 ml of sterile physiological saline + air for 10s Group 6: 1 ml of saline + ozone at exposure times 10 seconds Group 7: 1 ml of sterilox + air for 10 seconds Group 8: 1 ml of sterilox + ozone at exposure times 10 seconds
Conventional techniques using step-back as follows
Canal length determined by size 15 K-file visually identifying at the apical foramen
Working length 1mm short of the canal length
Apical third shaped with size 20, 25, 30, 35 and 40 K-file using push-pull motion 45 K-file to 60, each size 1mm short of the preceding instrument
Irrigation after each instrument from page 2
Final irrigation with 1ml of distilled water to remove any precipitate that may form from the irrigation test
Canal dried with sterile paper points
Sectioned the root using a slow speed diamond saw blade (Buehler, Lake Bluff, Illinois, USA) or
468
a steel chisel for SEM
Specimens prepared for SEM, t mounted on stubs using an epoxy resin air-dried at 37℃ over 24
h
Then sputter coated in preparation for SEM using the Agar Auto Sputter Coater machine, coated with gold-palladium 30 nm thick to ensure the electric conductivity for SEM evaluation
The cervical, middle and apical third of the root canal evaluated
Takeda et al. 1998 index for smear layer measurement will be used
0 - No smear layer, open dentinal tubules, smear layer completely removed.
1- Thin smear layer covering the surface, outline of dentinal tubules and the location of
the tubule indicated by a crack.
2- Moderate smear layer, outlines of dentinal tubules observable, removed in some
areas.
3- Heavy smear layer with outlines of tubules obliterated.
Statistical analyses
Results
469
ETHICAL APPROVAL FOR THE IN-VIVO STUDY STUDIES 4.1 & 4.2
470
471
472
July 04th , 2005 Dr Jameela Alawadi PHD Student at Queen’s University Belfast Northern Ireland Endodontic Department
Subject: “Clinical Study to Evaluate postoperative pain after the ozone treatment”
This is in reference to your kind reply dated June 28, 2005. The Committee would like to thank you for the clarifications that you have supplemented to your proposal, and is pleased to inform you that your submitted project entitled: “Clinical Study to Evaluate Rotary Versus Conventional Root Canal Preparation With Different Irrigants” has been approved.
Please note that it is the Research Ethics Committee’s policy that the investigator should promptly report to the Committee of the following: 1) Any deviations from, or a changes of, the protocol (to be justified) 2) Any changes affecting the conduct of the trial 3) All adverse drug reactions (ADRs) that are both serious and unexpected 4) Any new information that may affect adversely the safety of the subjects or the conduct of the trial 5) Any expected delays in the completion of the study
It is also important that the committee be informed of the progress of the study and of any relevant developments that might take place during the course of it. Thus, the committee expects that a regular follow up report to be submitted every 6 months.
The Research Ethics Committee has been organized and operates according to the Good Clinical Practice (GCP) Guideline.
Wishing you all the best
Dr Khalil I. Qayed Chairman, Research Ethics Committee
Sent by email not signed.
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INFORMATION LETTER TO PATIENTS AND THEIR PARENTS/GUARDIANS.
EVALUATION OF THE SAFETY AND EFFICACY OF THE USE OF OZONE FOR THE ROOT
CANAL TREATMENT.
Study purpose:
Your are asked to participate in a research study being conducted by Prof.E Lynch
Prof. J P Lamey, Dr. Zuhair Al-Khatib and Miss. Jameela ALawadi of Queen’s
University Belfast, Division of Restorative Dentistry and Endodontics and the
Endodontic Department at Rashid Hospital, Dubai
The objective of this feasibility clinical study is to investigate the safety and efficacy of an investigational ozone treatment regime as a new irrigation method in endodontic treatment. The ozone will be administrated through use of the HealOzoneTM ozone delivery device. Your are being invited to participate in a clinical study.
A maximum of 100 patients will be needed at this study. The duration of study will be
12 months from the date of initial dental treatment. Information will be collected just before treatment, at follow-up assessments after 24 hours, 48 hours, 7 days , 30 days and
6 months.
This form is to inform you about the nature and risks of the clinical study in which your has been invited to participate. You should carefully read this informed Consent (I C) form before you decide to grant approval or not for your participation. You will be given a copy of this IC form if you decide to participate in this study.
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Background:
Ozone was first suggested as a disinfectant for drinking water in the 19th Century in view of its powerful ability to kill bugs. The modern development of ozone’s application to medicine began in the 1950s in Europe and gradually spread throughout the continent and then to Australia, Cuba, Brazil and Columbia. In World War 1, ozone was used medically to treat wounds and other infections. It is used in water purification and sewage treatment.
Benefits of participation:
No benefits from the study will be guaranteed. This study will provide important knowledge regarding the value of the ozone delivery device and the ozone treatment regimen for treating the root canal.
Possible risks/discomforts:
Ozone is known as a harmful gas but it is one of nature’s most powerful oxidants. When applied in large amounts and for a short time, it is proven that ozone is a useful gas.
While the level of ozone to be used in the study is high, up to 2,100 ± 10 parts per million (ppm), the gas will be applied for a very brief period of only 10 seconds.
Precautions, which should limit potential ozone exposure, include:
The tight fitting design of the delivery device made by the cup and tooth should
contain the ozone treatment.
Ozone is well known to be toxic to living tissue. The dentist performing the
treatment will be trained to prevent any large amounts of ozone escaping.
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The device operates by suction only; the pathway for ozone being under negative
pressure, meaning ozone should not leak out. In the event of leak, only air should
leak in- no ozone should leak out.
If an incomplete seal occurs or if a leak arises, a flow sensor will shut down the
ozone generator.
After 10 seconds delivery of ozone, the suction will remain on for an additional
10 seconds to purge away any remaining ozone.
Ozone is stable for only a very brief time. It decomposes to form oxygen and
hence disappears very quickly.
In principle, the potential toxicity of ozone should not prevent its use as a therapeutic agent. At the correct dose, ozone can be useful as a therapeutic agent.
While the potential risks of ozone exposure have been considered and are felt to be minimized in the design of the delivery device, this study does involve an investigational device and may have risks, which are currently unforeseen. While the probability of ozone exposure is low, 100% capture of ozone delivered is not assured and certain risks do exist. Your exposure will be for only 10 seconds.
You will be informed of any new findings that may affect your willingness to continue to participate
Participation/alternatives:
You/your participation in this study are strictly voluntary and it is your right to refuse participation or to withdraw from the study without penalty or loss of benefits to which you/your is entitled. You/your are not obligated to participate in this study.
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Study procedure:
The study will involve 2 different treatment groups (ozone and air) with follow-up assessments being conducted over the course of 1 year. All treatment groups will need to come for follow-up monthly for 1, 2, 7, 30 days and 6 months. Each follow up appointment will take approximately 30-60 minutes. You will be asked to complete a separate medical consent form and a separate medical form to confirm current medical status during your first visit.
It is very important for study purposes that you return for all evaluation visits. If you agree to participate in this study, you are expected to return for all follow-up visits and remain in contact with the medical centre/clinical to monitor your progress.
Responsibility/compensation:
You will not be provided with any financial compensation for voluntarily participating in this study. You or your insurance company will be responsible for any routine treatment cost.
In the unlikely event, physical injury occurs as a result of participating in this study, the necessary facilities, emergency treatment and professional medical services will be available to research patients, just as they are to general community. If you injured you should immediately contact Miss Jameela Alawadi 0506703949. Further information can be obtained from the hospital/clinic Division of Endodontic.
In the event of physical injury, your dentist will inform your doctor regarding your injury and participation in this study.
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Ethical committee approval:
You understand that approval for this study and approval to initiate patient enrolment has been obtained from Ethical Committee at Rashid Hospital. If you have any questions regarding patient right as a research subject you can call the Ethical Committee representative at telephone number 04 337111
Termination of study:
This study may be terminated by the study investigators, Prof Edward Lynch and Prof
P-J Lamey
Record/report:
You understand that the data collected from your participation will be used solely to evaluate the HealOzoneTM Ozone delivery device. You will not be identified in any publication or photograph without your expressed written permission. By participating in this study, you will allow officials from regulatory agencies to have access to and inspect you/your child’s dental/medical records to verify the accuracy or validity of the data. You will also allow them to photocopy information from your dental/medical records for study purposes. Your participation in this study will remain confidential.
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CONSENT FORM FOR THE IN-VIVO STUDY (4.1& 4.2) Study to evaluate the safety and efficacy of the use of ozone for root canal therapy
Statement of consent:
Your signature on this form indicates that you have understood to your satisfactions the information regarding participation in the research project and agree to have your participate as a subject. In no way does this waive your legal rights nor release the investigators, sponsors, or involved institutions from their legal and professional responsibilities. You understand that your participation is voluntary and that he/she is entitled to receive either ozone treatment or only air. You should feel free to ask for clarifications or new information throughout your research. For any further question your rights as a research subject, please contact Miss. Jameela Alawadi 0506703949.
If you or your children have any questions concerning your rights as a possible participant in this research, please contact the Ethical Committee representative at telephone number 04 337111 or 072229666.
Participant’s Name (please print):…………………...... Participant’s Signature:………………………………………………… Date Parent/Guardian’s Name (please print):……………………………….... ………... Date Parent/Guardian’s Signature:……………………………………………
Investigator/Delegate’s Name (please print):…………………………… ………... Date
Investigator/Delegate’s Signature:…………………………………………
A copy of this form has been given to you to keep for your record and reference.
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FLOW CHART OF THE CLINICAL STUDY (4.1)
ANTIMICROBIAL ASPECTS, POSTOPERATIVE PAIN INCIDENCE AND PRACTICALITIES
OF IRRIGATION WITH AND WITHOUT OZONE: A CLINICAL STUDY
Aim: to investigate root canal treatment performed using NaOCl with air or ozone as the irrigants. Material and methods Ethics approval by Ethics committee at UAE Ministry of Health. In-vivo study in UAE
Collect patients from waiting list in Endodontic Department
Consent form and a separate medical form to confirm their current health status during their visits
Patient with a diagnosis of diabetes or any immunocompromising disease, no previous root canal treatment excluded from the study
100 patients included in this study Age between 17-50 years Single teeth indicated for root canal treatment
Preoperative radiographs
Randomly divided into two equal groups One group with ozone and the other with air
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In all groups, root canal prepared using K3 nickel titanium rotary instrumentation Group A (control group): Irrigating the root canals with 0.5% sodium hypochlorite and then air for 10 seconds Group B (study group): Irrigating the root canals with 0.5% sodium hypochlorite and then ozone for 10 seconds
Endodontic procedure
Procedure to obtain microbial sample from the RC (Moller 1966) Isolation the tooth with rubber dam clean by polishing with pumice with brush, tooth clamp and the rubber dam, cleansed with 30 percent hydrogen peroxide rinsing , swabbed with 5 percent tincture of iodine, after the tincture dried the tooth surface swabbed with sterile 5 percent sodium thiosulfate solution to inactivate the tincture of iodine. To check the decontamination steps have been effective, a control sample is required to ensure reliable sterility of the operative field prior to entry into the canal
K3 instrument used according to the manufacturer
Canal length estimated using electronic apex locator and x ray
The root canal of all groups prepared using the crown-down technique
Irrigation of root canal in group A will be done using a disposable syringe and 30-gauge irrigating needle
1 ml of 0.5 % of sodium hypochlorite will be introduced into the canal after each file and soaked up by means of a vacuum ejector in group A
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In all treatment in group a total of 10ml of the irrigating solution will be used. Air delivered for 10 seconds To avoid an influence of the sodium hypochlorite solution of the results of the microbiologic evaluation, the canal filled with saline solution after instrumentation was completed and then dried and refilled with 5 percent sodium thiosulfate solution to inactivate remnants of sodium hypochlorite (Möller 1966) The canal filled with saline solution and a specimen for microbiological examination
The root canal irrigated with 1 ml of 0.5 % sodium hypochlorite and then ozone delivered from the HealOzone at an exposure time of 10seconds in group B
Samples taken for culturing
Canal dried with sterile paper points
All the root canals in both groups filled with gutta-percha and sealer
Canal orifices sealed with 3 mm of Cavit ™ and the patients returned to the referring dentists
Patient enrolled for recall days and scheduled for visits after approximately 1, 2, 7, 30 days and after 6 months postoperatively, each appointment took approximately 30-60 minutes
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During these recall appointments, clinical symptoms (e.g. pain on percussion) will be assessed and radiographs assessment at 6 months
Evaluated the radiographs according to criteria score used in study 2.1 1: Normal periapical area without clear evidence of periapical widening 2 : Periapical widening extending less than 2mm vertically beyond the end of the apex 3: Periapical radiolucency, extending 2mm or more vertically beyond the apex 8: Film unreadable due to technical problem
To evaluate the influence of factors affecting the pain data will be recorded for each case: Pre-operative data for example age and gender, tooth type, location (upper or lower jaw) and tooth side (right or left) Pre-operative clinical signs and symptoms associated with toothache: History of pain (within previous 24 h)
Statistical analysis
Results
Conclusion
The study will prove or disprove the capability of Ozone treatment as a new irrigant in root canal treatment for removal the smear layer, to reduce the number of microorganisms in root canal systems, reduce postoperative pain and reduce periapical radiolucency.
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Diagram showing the protocol for the study of assessment of use of ozone as an antimicrobial agent
Ease of use assessment Microbiological analysis
Radiographic assessment In – vivo study
Clinical signs
Clinical symptoms
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