Evaluation of the Paper Point Technique for Locating the Root Canal Apical Exit
Jose Luis Marcos -Arenal
A thesis submitted to the faculty of the University of North Carolina at Chapel Hill in partial fulfillment of the
requirements for the degree of Master of Science in the School of Dentistry (Endodontics)
Chapel Hill
2007
Approved by:
Dr Martin Trope
Dr Eric M Rivera
Dr Daniel J Caplan ABSTRACT
Jose Luis Marcos -Arenal: Evaluation of the Paper Point Technique for Locating the Root Canal Apical Exit (under the direction of Drs Martin Trope, Eric M Rivera and Daniel J Caplan)
A new method for determining root canal working length ( WL ), the paper point technique (PPT) , has been claimed to be accurate and reproducible , but has not been formally evaluated.
Hypothesi s: WL determination is more accurate when the Electronic Apex Locator Technique (EALT) is supplemented with PPT compared to EALT alone .
The lengths of 84 root canals of unsalvageable human teeth were measured first using EAL T, then PPT.
Endodontic files were cemented to the position indicated by PPT . The teeth were extracted and microCT - scanned . In 71 canals that provided adequate readings for both EAL T and PPT , the RCAE to file tip distance was measured to 20 µm resolution .
Both techniq ues showed (1) moderate agreement and (2) excellent repeatab ilities . There was (3) a significantly greater accuracy in locating the RCAE when PPT was used compared to EALT alone (p ≤0.0 051 ).
Conclusion: It may be advisable to supplement the EALT measurement with PPT.
ii dedicated to the dentists of the Future
iii ACKNOWLEDGEMENTS
Dr T ro pe , Dr Rivera and Dr Caplan , you support ed me throughout this project and were patient with my innumerable questions .
Every one of the pati ent patient s who participated in the study .
And t he students and Admissions Desk staff (Sh irley †, Cynthia, Monty and Jean ) wh o referred them to us .
Wallace Ambrose taught me how to use the m icro -CT machine .
Hyuns oon , Lin and Dr G Koch from the UNC Biometric Co nsulting Lab oratory analyzed our data expecting no thing in return .
The UNC Department of Endod ontic provided funds and premises for this project.
Thank you. I will never forget it.
JLM A
iv TABLE OF CONTENTS
LIST OF TABLES ...... viii
LIST OF ILLUSTRATIONS ...... ix
LIST OF ABBREVIATIONS ...... x
CHAPTER 1: INTRODUCTION ...... 1
CHAPTER 2: REVIEW OF THE LITERATURE ...... 3
2.1 APICAL THIRD OF A ROOT ...... 3
2.1.1 Anatomy and Histology ...... 3
2.1.1.1 Of the tooth hard tissues ...... 3 2.1.1.2 Of the tooth soft tissues: the dental pulp ...... 6 2.1.1.3 Of the periodontal tissue surrounding the root canal exit...... 7 2.1.2 Physiology & Pathology ...... 7
2.2 WORKING LENGTH DE TERMINATION IN ENDODONTICS ...... 8
2.2.1 Definition ...... 8
2.2.2 The importance of a correct WL determination...... 8
2.2.2.1 Biological reasons ...... 8 2.2.2.2 Philosophical Reasons...... 9 2.2.3 The apical reference p oint in WL determination...... 9
2.2.4 Methods to determine WL: description, degree of accuracy and shortcomings ...... 11
2.2.4.1 Periodont al sensitivity/Patient response...... 11 2.2.4.2 Tactile Method...... 12 2.2.4.3 Radiographic ...... 12 2.2.4.4 Electronic ...... 16 2.2.4.5 Combined use of EAL and radiographs ...... 20 2.2.4.6 New method: the Paper Point Technique ...... 20 2.3 MICRO COMPUTED TOMOGRAPHY (CT) IN EXPERIMENTAL ENDODONTICS ...... 22
2.3.1 Introduction ...... 22
2.3.2 Resolution of micro -CT (for measurement of teeth length)...... 22
2.3.3 Limitations of micro -CT...... 23
v CHAPTER 3: MANUSCRIPT ...... 25
3.1 INTRODUCTION, LITERATURE REVIEW and RATIONALE for this PROJECT ...... 25
3.2 HYPOTHESIS ...... 27
3.3 PURPOSE and SPECIFIC AIMS ...... 27
3.4 MATERIALS and METHODS ...... 28
3.4.1 Overview of design...... 28
3.4.2 Subjects and Teeth ...... 28
3.4.2.1 Inclusion/exclusion criteria ...... 28 3.4.2.2 Collected data ...... 29 3.4.2.3 Sample size calculation: ...... 29 3.4.3 In vivo part of the study: ...... 30
3.4.3.1 Assessment of patients and teeth ...... 30 3.4.3.2 Anesthesia, operating field isolation and tooth decoronation ...... 30 3.4.3.3 Obtaining the EAL -length ...... 31 3.4.3.4 Obtaining the PPT -length ...... 32 3.4.3.5 Cementing an endodontic instrument to PPT -length ...... 35 3.4.3.6 Tooth extraction ...... 35 3.4.4 Ex vivo part of the study...... 35
3.4.4.1 Specimen preparation and storage ...... 35 3.4.4.2 Micro -CT image acquisition ...... 36 3.4.4.3 Volumetric reconstruction of the tooth apex ...... 38 3.4.4.4 Analysis of reconstructed apices: measuring the file -tip to RCAE distance ...... 38 3.4.4.5 Observations and Measurements ...... 39 3.4.5 Data Analysis ...... 40
3.4.5.1 Definition of Variables ...... 40 3.4.5.2 Analysis of the data ...... 40 3.4.5.3 Reliability of the Image Analysis...... 41 3.5 RESULTS ...... 42
3.5.1 Accuracy (n=71): ...... 43
3.5.2 Repeatability (n=9): ...... 46
3.5.3 Agreement (n=71): ...... 47
vi 3.6 DISCUSSION ...... 49
3.6.1 Regarding the Materials and Methods ...... 49
3.6.2 Regarding the Results ...... 53
3.6.3 Research questions for future projects ...... 61
3.6.4 The Pap er Point Technique in clinical context ...... 62
3.6.4.1 Implementing the PPT ...... 62 3.6.4.2 Excessively short PPT readings ...... 63 3.7 CONCLUSIONS ...... 64
APPENDIX A: RAW DATA of the STUDY ...... 65
REFERENCES ...... 66
vii LIST OF TABLES
Table 1 Inclusion Criteria 28
Table 2 Variables Data Collection 29
Table 3 Sample 42
Table 4 Continuous Accuracy of EALT and EALT/PPT 43
Table 5 Categorical Accuracy of EA LT and EALT/PPT (all intervals observed) 43
Table 6 Categorical Accuracy of EALT and EALT/ PPT ( RCAE as cut -off point ) 44
Table 7 Categorical Accuracy of EALT against EALT/ PPT 44
Table 8 Categorical Accuracy of EALT and PPT ( clinically -relevant ranges ) 45
Table 9 Repeated readings in 9 cases (raw data). 46
Table 10 Between -method disagreement within specific ranges 47
Table 11 Criteria for selecting the apical landmark 50
Table 12 Criteria for selecting a technique for an alyzing the specimens’ apices 53
Table 13 Potential error -source steps in EALT and PPT 60
Table 14 Two root canal therapy sequences incorporating the PPT 62
viii LIST OF ILLUSTRATIONS
Figu re 1. Root apex: (A) horizontal cross -section. (B) longitudinal section. P pulp, D dentin , C cementum , AF apical periodontal fibers , AB alveolar bone , E epithelium , GRAN granulomatous tissue . From Seltzer...... 4
Figure 2. Canals foramina rarely are at the root apex. From Gutierrez and Aguayo ...... 7
Figure 3. Endometric Probe. From Dummer and Lewis...... 16
Figure 4. Paper points showing the angle of the RCAE to the long axis of the canal. (A) From Rosenberg. (B) From W Watson Jr...... 20
Figure 5. Study teeth: isolated and de coronated...... 31
Figure 6: Kerr absorbent paper points ...... 33
Figure 7. Representation of a paper point right at (A) and past (B) the R CAE...... 34
Figure 8. TOP: Length of the longest paper point returning completely dry...... 34
Figure 9. Teeth labeled and stored in form alhaldehyde...... 36
Figure 10. Specimens were placed in plastic vials prior to micro -CT scanning process...... 37
Figure 11. A: SkyScan m icro -CT unit used in this project. B: Plastic vial containing specimen, positioned on rotating stand...... 37
Figure 12. Analysis of cross -sections: (A) the one to show the last evidence of the fi le tip, (B) the last one to show the root canal as a full oval...... 39
Figure 13. Parametric analysis of between -method agreement: paired mean reading lengths against paired difference of readings ...... 48
Figure 14. Repeatability analysis of the EALT and PPT (in 9 cases): mean against standard deviation. .... 55
ix LIST OF ABBREVIATIONS
3D three dimensional
2D two dimensional
AC Apical Constriction
AF Apical Foramen
CDJ Cemento Dentinal Ju nction
CT Computed Tomography
đ Mean paired error difference of the measurements
EAL Electronic Apex Locator
EALT Electronic Apex Locator Technique
EALT -accuracy distance from EALT -length to the RCAE
EALT -length length of the canal according to the EALT
IRB Institutiona l Review Board (also Ethical Review Board)
PPT Paper Point Technique
PPT -accuracy distance from PPT -length to the RCAE
PPT -length length of the canal according to the PPT
RA Radiographic Apex (of the root of a tooth)
RCAE Root Canal Apical Exi t
Sw within -subject standard deviation of each particular technique
Sd standard deviation of the between -method paired differences
UNC -CH University of North Carolina at Chapel Hill
WL Working Length
x GALILEO: My intention is not to prove that I was right
but to find out whether I was right.
In : Galileo, a play by Bertolt Brecht , 1952
xi
CHAPTER 1 : INTRODUCTION
Working length (WL) has been defined as “t he distance from a coronal reference point to the point at which canal preparation and o bturation should terminate ” 1.
Accurate determination of the endodontic WL is important . Why? In the short term, in order to avoid flare -ups 2,3,4,5,6,7. And in the long term to allow for successful treatment outcome because (1) being too short from the roo t canal apical exit ( RCAE ) prevents adequate microbial control 8a,9 which has been shown
repeatedly 2,10 ,11 ,12 to be the principal factor influencing the outcome and (2) being too long may cause a
periapical fore ign body reaction 13 ,14 ,15 ,16 ,17 ,18 ,19 ,20 ,21 ,22 ,23 ,24 ,25 ,26 and inability to optimally seal the root canal with
the filling material .
The accuracy and limitations of available techniques to determine WL has been widely reported in
the literature: periodontal sensitivity 27 , tactile 27 ,28 ,29 ,30 ,31 ,32 , radiographic 32 ,33 ,34 a,35 ,36 ,37 ,38 ,39 ,40 ,41 ,42 ,43 ,44 ,45 ,46 ,47 ,48 ,49 ,
50 ,51 ,52 ,53 and electronic 32 ,54 ,55 ,56 ,57 ,58 ,59 ,60 ,61 ,62 ,63 ,64 ,65 ,66 ,67 ,68 ,69 ,70 ,71 ,72 ,73 ,74 ,75 ,76 ,77 ,78 ,79 ,80 . Periodontal sensitivity and
tactile sensation have been generally abandoned due to their poor accuracy. In addition, it has been recommended that, since both radiographic and electronic methods are not absolutel y reliable, neither should be used as the only method f or WL determination 54 ,81 ,82 ,83 ,84 .
A new method, the “paper point technique” (PPT), has recently been introduced 85 ,86 . This technique uses conventional absorbent paper points , and it is based on the assumption that when the contents of the root canal system are removed, the canal should be dry, while the environment outside the root canal is
living and hydrated: periodontal ligament, granulation tissue, pus, blood, bone or som e other hydrated tissue
containing fluid. Rosenberg explains that if a paper point is placed into a dried canal short of the apical foramen, it should be retrieved dry 85 . If a paper point is placed into a dried canal and ta ken past the exit of the canal, it will be retrieved with f luid. The maximum length that a paper point can be placed into the canal and remain dry is then recorded as the length of the canal.
While Siqu eira has stated that using paper points for working le ngth determination is “imprecise, unreliable, empirical and fraught with limita tions” 84 , Rosenberg claims the PPT to be accurate and precise to
within 0.25 mm tolerances. However, the PPT has not been formally evaluated.
Testing the performance of WL techniques in unsalvageable teeth before they are extracted, and then analyzing their apexes ex vivo is the current approach. Micro -CT is currently a popular technique in experimental Endodontics, providing the advantages of it s multi -planar analysis, high resolution of images , sample non -destructiveness , and non -distortion 87 ,88 ,89 ,90 ,91 ,92 ,93 ,94 ,95 ,96 ,97 .
Since there i s no proof or evidence as to how often the tip of the longest paper point that remains
dry accurately locat es the RCAE , th e purpose of this proje ct was to compare the repeatability , error and
accuracy of locating the RCAE when the electronic technique is used alone or supplemented by the paper point technique .
2 CHAPTER 2 : REVIEW OF THE LITERATURE
2.1 APICAL THIRD OF A ROOT
2.1.1 Anatomy and Histology
2.1.1.1 Of the tooth hard tissues
A horizontal cross section of the root apex shows how its structures are arranged (Figure 1A): the pulp is in the center, surrounded by dentin, which is covered by a layer o f cementum; the periodontal ligament encircles t he cementum , and bone surround s it all 98 .
In a longitudinal section of a typical root a pex we can see (Figure 1B): 1) the root canal , 2) the narrowest diameter, called apical constriction (AC) of the root canal , 3) and from that point apically a conic - shaped delta opens toward the root surface , ending at the apical foramen (AF) .
Kuttler 99 used a different approach to describe the tooth apex : the root canal of a tooth has two conical portions, (with opposing vertices); the long one walled by dentin, the short one by cementum.
According to him and to S tein and C orcor án100 , the distance from AF to AC ranges 0.5 to 1.5 mm .
Lateral canals and accessory foramina provide additiona l exits from the main canal into the periodontal tissues. The latter are particularly frequent in the apical portion of the root 101 ,102 , showing a large variation 103 ,104 . Essentially, they appear due to a 1) localized disintegration of the root sheath during the r oot development, or 2) lack of dentin formation around a blood vessel in the periradicular space 98 ,105 . Figure 1. Root apex: (A) horizontal cross -section . (B) longitudinal section . P pulp , D dentin , C cementum , AF apical periodontal fibers , AB alveolar bone , E epithelium , GRAN granulomatous tissue . From Seltzer 98 .
Morfis et al .106 observed more than one main A F in all teeth except in palatal and distal roots of
upper and lower molars respectively. In particular, the maxillary premolars appeared to have the largest number of accessory foramina. Brise ño-Marroquin et al . found 102 a t least two foramina in 87% of mesial and
71% of mesiobuccal roots of first mandibular and maxillary molars, respectively.
The following are four comments related to anatomical landmarks that are or may be used as apical references for determining WL in Endodontics:
(1) There is not an apical constriction in every tooth . The canal is often described to terminate at the apical constriction 48 , where the internal surface of the canal is supposed to meet the external surface
of the root. This exit of the canal can actually be considered an oval -shaped plane: the most apical cross -
section of the root canal.
4 However, some 44 ,107 ,108 ,109 ,110 ,111 authors question the presence of the apical constriction. Only les s
than half of the 270 teeth Dummer et al .108 analyzed had a single traditional AC, since in the rest of the
cases the canal was tapered or parallel or had several constrictions.
Simon 109 an d Coolidge 110 indicated that usually there is no constriction, especially in root resorption
or periradicular pathology cases.
Pommer et al .44 in 2002 s tate d that in necrotic cases (with inf lammatory root resorption) the
constriction may be altered or non -existent. And Hör et a l.111 in 2005 only found a constriction in 48% of 193 extracted teeth.
Consequently, not being present in every root canal, the AC is n ot an ideal apical limit for our endodontic procedures, since we need a landmark that is present in every tooth.
(2) T he cemento -dentinal junction (CDJ) rarely is at the AC . This is contrary to statements made by Kuttler 99 . T he CDJ usually is NOT at the AC and it is seen at different locations in subjects from
different countries 112 . In fact, the CDJ was found an average 1 mm from the AF 113 , meaning the cementum
often extends into the longer cone of the root cana l98 , since the average distance from AC to AF is 0.5 and
0.67 mm in young and older subjects respectively 114 .
Due to its unpredictable location within the root, the CDJ is not an ideal apical landmark for our endodontic procedures.
(3) The apical foramen rarely coi ncide s with the root apex . Brynolf 19 and M izutani et al .115
found this to be the case in upper anterior teeth . The di stance between the radiographic apex (RA) and the
AC may be 0.5 to 3mm 48 ,108 ,116 ,117 ,118 in approximately 50% of cases ; AC and RA coincide in 17 -
47% 119 ,120 ,121 ,122 ,123 (Fig 2).
5 Therefore, the root apex can not be our apical re ference landmark since from tooth to tooth the apex -to -foramen distance is variable ( the apical foramen is the concern in terms of microbial control and treatment outcome).
(4) Every roo t canal consistently has an apical exit /foramen . While w e found no stu dy showing this , it is obvious that in every root canal pulpal tissues communicate with the peri -radicular space via an
apical foramen of the canal. Since f oramen means opening , we termed it the Root Canal Apical Exit
(RCAE) .
For the purpose of our study, we defined the RCAE as the most /last apical cross -section of the
root canal still showing a full circle/oval canal section.
Regarding the RCAE, section 2.2.3 explain s why it must b e considered the apical reference landmark when determining WL . S ection 3.4. 4.5 shows the methodology we used to identify the RCAE in our study . And s ection 3.5 shows how well the EALT and the EAL/PPT locat e the RCAE.
2.1.1.2 Of the tooth soft tissues : the dental pulp
The apical dental pulp, c ompared to the corona l pulp, contains fewer ce lls and more fibers 98 . Th ese fibers of the apical pulp are identical to those of the periodontal ligament 98 .
This fibrous structure of the apical pulp tissue supports the blo od vessels and nerves entering the root canal. These blood vessels course through the bone trabeculae and through the periodontal ligament before entering the root 98 .
6 2.1.1.3 Of the periodontal tissue surrounding th e root canal exit .
Grove in 1921 s tated that the pulp extends only to the CDJ 105 . In 1928 he said that it extends only to the apical constriction 124 . Regardless of w hether th ese statements are compatible and still accepted or not , somewhere in this ap ex /periap ex region is where the pulpal tissue gradually turns into periapical tissue as it exits the root canal.
2.1.2 Physiology & Pathology
Both pulpal 125 and periapical 126 tissues are capable of developing an immune response to external agents. When the dental pulp cannot survive due to the persistence and/ or virulence of the attack, the immune response comes only from the periapical tissues. In this sit uation, the immune agents are n ot effective against noxious agents present in the cana l since the vessels and tissue they travel through are no longer present in the root canal.
Because of this, the immune system will typically resolve any infection or irritants outside the root canal 127 ,128 and what lies inside the canal requires treatment. A ll points apical to th e canal are considered in contact with the immune system, whereas all points with in the canal are considered relatively inaccessible to the immune system and therefore require endodontic therapy 124 .
Figure 2. Canals foramina rarely are at the root apex. From Gutierrez and Aguayo 118
7 2.2 WORKING LENGTH DETERMINATION IN ENDODONTICS
2.2.1 Definition
Working length has been defined as “ the di stance from a coronal reference point to the point at which canal preparation and obturation should terminate ”1.
2.2.2 The importance of a correct WL determination .
Accurate identification of the endpoint for trea tment is needed for proper and thorough instrumentation and obturation of the root canal system , which is relevant for (1) biological and (2) philosophical reasons .
2.2.2.1 Biological reasons
Ideally, the whole root canal should be disinfected, instrumented and fi lled so that there are neither overfilling nor residual empty, unfilled root canal areas 129 .
Microbi al Control Reasons .
In the short term , accurate WL determination contributes to controlling the incidence of inter - appointment flare -ups of microbial origin 3,4,5 which may result from working inadequately (1) long , causing apical extrusion of infected debris 2,3,6 and consequent periapical imbalance between aggression and defense , or ( 2) short , leading to incomplete chem o-me chanical canal preparation result ing in changes in the endodontic microbiota 7 and/or in the environmental conditions 5.
In the long term , c ontrolling the bacte rial population within the root canal is the key to successful therapy of teeth with apical periodontitis 10 ,11 ,11 ,12 ,130 . Since addressing the entire root canal with endodontic instruments and disinfectants aids in endodontic microbial control, then a ccurate WL determination contributes to successful endodontic thera py.
8 Non -Microbial -Related Reasons .
In the short term , accurate WL determination contributes to controlling the incidence of inter - appointment flare -ups of mechanical or chemical origin which may result from working inadequately long 2,3,4.
In the long term , instrumenting and filling the canal to the appropriate length reduce s the instances of foreign body reaction 13 ,14 ,15 ,16 ,17 ,18 ,19 ,20 ,21 ,22 ,23 ,24 ,25 ,26 .
2.2.2.2 Philosophical Reas ons .
Patients should be able to expect treatment that is customized to meet the requirements of their
unique anatomy. We do not place crowns that are designed on the basis of averages; we make a unique crown for each individually prepared tooth 85 . Why not follow the same approach in endodontic treatment?
Why would each root canal/tooth not be treated individually instead of according to averages?
Siqueira 84 s tate d that (1) instrumenting and fillin g to an arbitrary measurement short of the apex is not treating the root canal in its entirety, and (2) ideally, the entire infected root canal should be instrumented.
2.2.3 The apical reference point in WL determination.
Whether we should use clinical or non -cl inical standards to define the ideal apical end -point for endodontic treatment is an ongoing controversy 131 ,132 in the field of Endodontics. The clinical standard
essentially looks at how treatment outcome is influenced by filling the root canal to certain dis tances from the radiographic apex. Non -clinical landmarks are the apical constriction, apical foramen and cementum -
dentinal junction. Since none of these landmarks can be detected on radiographs (the means used to
determine the outcome of treatment), the c ontroversy will persist until we can determine the relevance of
using non -clinical landmarks as end -points for treatment in the outcome of endodontic treatment.
9 In th e meantime, researchers and practitioners are using two different units to measure the sam e thing : where to locat e the apical end of endodontic treatment. B oth may be referring to the same thing, but we will not find out until the equivalency of both standards (if any) is explained .
To add more to the controversy, (1) the traditionally recommen ded 121 ,133 anatomical point (the AC ),
may even be more conceptual than actual 114 , as justified earlier in this chapter , and (2) i t is difficult to locate
the AC and AF clinical ly as shown by several studies 17 ,18 ,19 ,134 .
Wu et al .134 consi der ed the r adiographic apex a more reliable point and recommend working 0 -
3mm from radiographic apex depending on pulpal diagnosis.
Schilder 135 recommended instrumenting and filling to or beyond the root radiographic terminus .
Schilder’s recommendation on th e use of the RA as apical reference was not based on outcome studies.
Shabahang et al .66 considered ±0.5 mm from the foramen as an acceptable range for clinical determination of the location of the apical foramen.
Weine 48 recommended working 1mm (short) from the radiographic apex if there is no bone or root resorption, and 1.5mm when there is bone or root resorption .
Clinical and biologic evidence recommends 21 ,136 the following: vital cases 2 -3mm from radiographic
apex (pulp stump protects periapical tissue from root filling material irritation); if pulp necrosis exists, 0-2mm gives best outcome (longer or shorter than that reduces success rate by 20%); in retreatment cases , 1 -2mm
short or RA give the best outcome .
Wu et al. 134 stated that the AF should be the apical WL reference for necrotic/infected and in retreatment cases.
10 Langeland 137 ,138 ,139 ,140 and Ricucci and Lange land 141 found the most favorable prognosis with
procedures going to AC and the worst when working beyond AC; these data was applicable to vital, necrotic and extra -radicular infections.
Therefore, since (1) the location of neither the apical constriction, no r the CDJ nor the root apex is a reliable landmark across teeth/canals , and (2) every root canal has an apical foramen /exit , our study used the RCAE as the apical reference for WL determination.
Therefore, r egardless of whether th is RCAE bisects cementum , dentin or both, whether there is an apical constriction or whether the canal exits right at the root apex, what is important is knowing its location 44 ,142 , so that root canal treatment procedures address the e ndodontic infection.
2.2.4 Methods to determine WL: description, degree of accuracy and shortcomings
Locating the apical endpoint for endodontic treatment clinically is difficult even for experienced
clinicians 143 mainly because , as we explained above , usually (1) there is no apical constriction (due to anatomic 107 ,108 ,111 or pathologic 44 ,107 ,109 ,110 reasons) and/or (2) the CDJ is not at the AC 98 ,112 ,113 ,114 and/or (3)
the distance from the AF to the root apex is not constant across teeth 18 ,48 ,108 ,115 ,116 ,117 ,118 ,119 ,120 ,121 ,122 ,123 . T his makes almost im possible to reliably determine the apical extent of root canal therapy 131 .
Techniques to determine WL are: perio dontal sensitivity, tactile, radiographic and electronic. A recent study performed in primary teeth shows no significant difference among all three techniques to determine endodontic WL 32 .
2.2.4.1 Periodontal sensit ivity /Patient response .
A file is advanced in a necrotic non -anaesthetized or completely prepared canal until the p atient
can feel it. The length of the file at that point is recorded. The abstract of Botusanov and Vladimirov ’s paper 27 says t his technique locates the “apex or 1.5 mm shorter than that” only 25.6% of the time.
11 Thei r result is not surprising, since (1) a necrotic pulp frequently contains vital inflamed tissue that extends several mm into the can al 144 , and (2) it has been observed that, in an unanesthetized patient, an instrument has passed several mm out of the apex without being detected 145 .
2.2.4.2 Tactile Method.
Essentially, the end point for instrumentation is determined by inserting a hand file in the canal to the point where it binds. The length from the tip of the instrument to a coronal reference point is measured.
In 1975 Seidberg et al .28 found the tactile technique more accurate in locating points s hort of the radiographic apex than a current versio n of an electronic apex locator at the time of their study.
Flaring the coronal portion of the root canal significantly increase s the accurate location of the AC when using the tactile technique 31 : ≈30% versus ≈80 % (non flared versus flared) 29 ,30 .
Botusanov and Vladimirov 27 found th e tactile technique effective 34% of the time to locate “the apex or 1.5 mm short of it”.
2.2.4.3 Radiographic
Traditionally, radiographs have been used to establish WL in Endodontics 33 . Through the years,
several techniques have been proposed to measure teeth length with the aid of radiographs.
Using radiographs to d etermin e WL involves two processes: (1) measuring lengths (of tooth and endodontic instrument) and (2) recognizing anatomical structures (root apex, a pical constriction ) in the radiographic image.
This is actually the reason why the radiographic method to determine WL i s poorly accurate and precise: a radiograph is a two -dimensional representation of a three -dimensional object, characterized by imperfec t clarity, size distortion , shape distortion 34 and unreliable interpretation 35 .
12 Clarity is a factor of sharpness and resolution . The degree of clarity of intr aora l radiographs is not enough to differentiate where apical constriction, CDJ or apical foramen are located 8b.
The lack of clarity to identify any one of these structures in the radiograph is why we use the root radiograp hic apex as apical reference: we calculate the length of the tooth to the root apex and then subtract an average length expecting the desired apical landmark to be present at this calculated length .
Unfortunately this entails two problems: (1) each individ ual treated tooth may not conform to the average distance from apex to constriction or from apex to foramen, and (2) the radiographic apex may not represent exactly the actual apex if the film and tooth are not parallel and/or if the tooth ’s long axis and x-ray beam are not perpendicular.
Image size distortion ( or proportional magnification) is the increase in size of the radiographic image compared to the actual object size.
This effect is counteracted by the mathematical formula recommended by B regman 36 and accepted
by Grossman 37 :
KLI × ALT CLT = ALI
where ALT and ALI are, respectively, the apparent lengths of the tooth and instrument in the radiograph , KLI is the known length of the act ual inst rument and CLT is the co rrect length of the tooth.
However, th is calculation is not applicable to every radiograph since images (particularly those of maxillary teeth) often have some shape distortion .
Image shape distortion is the result of non -pr oportional magnification (unequal magnification of different parts of the same object).
13 Interpretation. Goldman et al .35 showed less than 50% agreement (in ascertaining outcome of endodontic treatment) betwe en three o bserver s of radiographs , particularly when the images involved maxillary molars.
Regardless of all these limitations, radiographs have been and are still used to calculate WL during endodontic therapy procedures.
Bramante and Berbert 38 in 1974 compared the performance of Best’s ( 10 mm long pin fixed to
labial surface of tooth, then radiograph) , Sunada’s (electronic device) , Bregman’s, Ingle’s (distance from file tip to apex measured on x -ray) and Bramante’s (a vari ation of B regman’s and Ingle’s ) methods to d etermine
WL . They concluded that (1) Ingle’s method was the mo st precise and accurate, and (2) Sunada’s was the most accurate for palatal roots of maxillary molars and premolars.
Tamse et al .39 took 524 maxi llary bisecting -angle -technique radiographs, finding the zygomatic
arch interfere d with 42% of second and with 20% of first molars apices.
Olson et al 40 found that out of 305 canals (extracted te eth) in which they had placed a file to the apical foramen, the tip of the instrument appeared to be at the root surface (apical fo ramen) in 82 per cent of canals .
However, while radiographs were found appropriate to evaluate the length of root canal fil li ngs 40 ,42 ,43 , it has been concluded that they distort the length of the roots, p articularly in multirooted teeth 34 b.
The main disadvantage of using radiographs for RC length determination is that the canal constriction cannot be localized 44 .
When the file is 0-2 mm short of the radiographic apex, it is actually closer to the apica l foramen
than it appears on the radiograph , providing a basis for unintentional overinstrumentatio n45 .
14 When the file is beyond the canal exit, it is actually longer than it appears on the radiograph 46 ,47 .
And when the tip of the file is at the radiographic apex, it is long of the physiologic foramen
(according to the anatomic studies of Kuttler 146 , Green 11 6,117 and Dummer 108 ). If it is 1 mm short of the radiographic apex, the file is short of the foramen 147 .
Because of th ese inherent sh ortcomings of radiographic WL dete rmination , it has been suggested 48 ,49 ,50 that an acceptable WL may be obtained by working a certain distance short of the RA. The distance to be subtracted from the RA is based on studies measuring the average distance between the apical fora men and the RA 19 ,108 ,115 ,116 ,117 ,118 ,146 . From this, an average leng th discrepancy with a standard deviation is determined.
Because of all those limitations , it has been recommended not to base the determination of the working length on radiographic images alone 81 .
Rosenberg said that t he failure of this approximation technique is that the teeth being treated do not conform to an average, but are unique. A WL based on statistical research may fall within the standard deviation; however, the probability that an accurate canal length will be obtained using statistical averages and standard deviations is extremely low. The estimated length will always be long or short of the true exit of the canal. Thus, a t best, this technique should be regarded as a means of approximating rathe r than establishing an accurate working length 85 ,86 .
A variation of the radiographic approach that doe s not seem to be popular any more is the use of the Endo metric Probe (Maillefer SA, Switzerland) . Described in 1976 by Renggli 51 , t he Probe is an
endodontic instrument with a series of calibrated constrictions , allowing the possibility of improved canal length determination in b oth distorted and no t-distorted radiographic images ( Figu re 3). It was tested by
Dummer and Lewis 52 in 1987, concluding that using it was more reliable than using a K -file type instrument .
15 Figu re 3. Endometric Probe. From Dummer and Lewis 52 .
Rivera and Seraji 53 in 1994 found that 64 % of silver coated gutta -percha cones appeared to be within 0 and 1 mm fro m WL on the radiograph , while in reality only 36% were within that range.
2.2.4.4 Electronic
A greater degree of accuracy in length determination has been achieved using the electronic apex locator 55 ,56 ,57 . The idea of using electric current to measure the length of a root canal was described by
Custer 58 in 1918 . In 1942 Suzuki 59 was the first one to ap ply electric current to oral tissue . In 1962 Sunada 60
developed the fi rst EAL on the assumption that the resistance between the periodontal tissue and the oral mucosa is constant: 6.5 k Ω.
Two cords are connected to the EAL device: on the o pposite ends, one has a metal clip that will contact t he subject’s lip and the other one has a hook that will be attached to an endodontic instrument as it
advance s in the root canal. The EAL alerts t he operator with an audible and/or visual signal when it finds the tip of th is instrument is at the a dequate length.
Only when the very tip of the file protrudes through the foramen does the E AL indicate that the proper length has been reached 60 . This means that apical patency is necessary for the EAL to work. Rivera
and Seraji only found accurate E AL readings in patent canals 61 .
16 While the EFL is not infallible, and since it is not affected by the limitations of radiography (lack of
clarity 34 a, size and shape distortion 34 a and visual interpretation 35 ), there is no ch ance to misinterpret the information that the EAL presents.
Numerous studies have test ed several commercially available EAL brands , (1) comparing t hem to the radiographic technique , (2) analyzing if it has a beneficial influence in treatment outcome, (3 ) to find out how different variables influence its accuracy, and (4) to evaluate their accuracy for determining t he root canal’s true length.
(1) The EAL versus the radiographic technique
Pratten and McDonald 62 found the EAL more accurate than radiographs to determine the length of a to oth. Consequently, (a) it may be used even when radiographs cannot or should not be made 54 ,63 , and (b)
EAL s allo w the dentist to enlarge the apical portion of the canal more precisely than when the radiographic method is used 64 .
(2) The influence of using the EAL in treatment outcome
A clinical outcome retrospective s tudy by Murakami et al 65 concluded that the use of the Sono -
Explorer aided successful treatment of infected root canals .
(3) How different variables influence the EAL’s accuracy
Pulpal diagnosis:
EALs that analyz e several imped ance values have been found accurate to within 0.5 mm in 90% of
the cases, irrespective of pulpal diagnosis 44 ,66 ,67 ,69 ,70 ,71 . They are not affected by the preoperative pulpal status 44 ,67 ,72 .
17 Canal wetness /dryness:
Comparing four EAL brands, Fouad et al .73 in 199 3 found their accuracy was comparable in dry canals .
Apical foramen size and file size :
The accu racy of n one of the EAL tested by Fouad et al .73 seem ed to be affected by the size of the apical foramen .
Ebrahim et al .74 concluded that (1) the size of the file should be c lose to that of the instrumented canal when measuring its length in the presence of blood , and that (2) even when the file is much smaller than the canal diameter, the Root ZX was highly accurate if in the presence of NaOCl .
Canal contents:
Electrolytic so lutions. Kobayashi 75 found that they cause the EAL -length reading to be too short, or sometimes impossible to obtain. However, Haffner et al . recentl y said that newer electronic devices can make an accurate measurement 64 of the root canal length, even in the presence of a strong electrolyte in the root canal. Fouad et al .73 found that Ende x® was more accura te with conductive flu ids than three other brands .
NaOCl . The Root ZX showed high performance (even when the file was much smaller than the diameter of the canal) 74 in the presence of NaOCl .
Blood. As stated earlier, Ebrahim et a l.74 found that in the presence of blood in the canal, the file
used to measure th e canal’s length should be of similar size to the canal .
18 (4) How accurate EAL s are for determining the root canal’s true leng th.
To a clinically acceptable degree of validity, t he electronic method can determine the length of the
root canal to the end of the apical foramen 68 ,69 ,76 , and not to the radiographic apex which , a s Kobayashi 75
said in 1995, is its most important advantage .
Hör and Attin in 2004 and 2005 concluded that under ex vivo 148 and in vivo 77 conditions it is
possible to determine the region between the minor and major apical foram ima with the Justy II ® and the
Raypex4® EAL devices .
EALs analyzing several impedance values have been found accurate to within 0.5 mm in 90% of
the cases, irre spective of pulpal diagnosis 44 ,69 ,66 ,67 ,70 ,71 . And multi -frequency EALs are very accurate in locating the AC 56 ,77 ,78 .
Rivera and Seraji 53 only found 36% of silver -coated gutta percha cones where within 0 to 1 mm short of the actual WL when using an EAL to measure that length.
In a clinical study, Haffner et al .64 found the ROOT ZX and the Endy ® too long in 40% and 67% of
cases respectively.
Rosenberg 85 s tated that “it is important to note that, since what the EFL does is identify that the file
already reached t he periapical tissues [and not where the canal ends], it does not indicate where to terminate treatment of the root canal system ”.
Consequently, “the E AL presents a simil ar limitation posed by radiographs, namely, to what distance from the EFL reading shou ld the canal be instrumented? ”85 .
Clinicians adjust 79 the EAL reading according to the average length discrepancies (with a standard deviation) between the EFL reading and di rect observation 80 .
19 “Using averages and applying them to specific unique conditions m ost of the time results in that t he length will be either too short or too long. By applying these measurement techniques, we never can pr edict which canals will be treated long, short, or just right ”85 .
2.2.4.5 Combined use of EAL and radiographs
An endodontic instrument is taken to the length indicated by the EAL and then confirme d/adjusted after ta king a radiograph . This has been shown to be equal 54 to or more 82 ,83 , effective than us ing radiographs
alone.
Siquiera indicate d that EAL is not a substitute , but an adjunct to radiographs 84 .
2.2.4.6 New method: the P aper Point Technique
Recently, Rosenberg 85 ,86 proposed a new method to determine WL. He claims this method allows
(i) reliable and consistent locati on of the apical exit of every canal to tolerances of 0.25 mm, and (ii) to “see”
(Figure 4) the apical exit of the canal 85 ,86 .
(A) (B)
Figure 4. Paper points showing the angle of the RCAE to the long axis of the canal. (A) From Rosenberg 85 . (B) From W Watson Jr.
20 This technique uses paper points, and it is based on the assumption that when the contents of the root canal system are removed, the canal should be dry, while the environment outside the root cana l is living and hydrated: periodontal ligament, granulation tissue, pus, blood, bone or some other hydrated tissue containing fluid.
Rosenberg explains that “if a paper point is placed into a dried canal short of the apical foramen, it should be retrieved dry. If a paper point is placed into a dried canal and taken past the exit of the canal, it will be retrieved with fluid ”85 .
In short, the paper point technique as described by Rosenberg is as follows 85 ,86 : a paper point is placed in a dried, patent canal that has been instrumented 0.5 mm short of the E ALT length ; the paper point is advanced at 0.25 mm increments and the tip checked for moisture after each length increment . If the retrieved point is dry, it is advanced until it absorbs fluid. The point should not remain in the canal long enough for any capillary action to take place. The maximum length that a poin t can be placed into the canal and remain dry is then recorded as the length of the canal.
Saunders and Saunders in 2003 stated that
“A fine paper point placed into a dried canal and extended beyond the working length will absor b tissue fluid at the apex a nd, if withdrawn after just a few seconds in position, will allow measurement of the dry portion of the paper point and provide some indication of the working length. ”149
Since they suggested measuring the length of a WET paper point, t heir approach is diffe rent to
Rosenberg’s PPT, who measures the length of the longest DRY paper point.
Siquiera 84 has stated that u sing paper points for working length determination is imprecise, unreliable, empirical and fraught with limita tion s.
To date, the Paper Point Technique has not been formally evaluated .
21 2.3 MICRO COMPUTED TOMOGRAPHY (CT) IN EXPERIMENTAL ENDODONTICS
2.3.1 Introd uction
Traditional ly, methods to study the morphology of teeth either involved irreversible changes in the
specimen or only provided a 2D image of the tooth 87 . This changed with the introduction of computed tomography . Rhodes et al .90 explained that CT images are obtained from planar sections through objects.
These can be physical sections, optical sections (confocal micros copy) or CT reconstructions.
Micro -CT is x -ray imaging in 3D, by the same method used in hospital CT scans, but on a small scale with massively increased reso lution a. It really represents 3D microscopy, where very fine scale internal structure of objects is imaged non -destructively. No sample preparation, no staining, no thin slicing - a single scan will image your sample's complete internal 3D structure at hig h resolution, plus you get your intact sample back at the end! 89 .
How does micro -CT work? A micro -focus x -ray source illuminates the object and a planar x -ray detector collects magnified projection images. Based on hundreds of angular views acquired while the object rotates, a computer synthesizes a stack of virtual cross section slices through the object. You can then scroll through the cross sections, interpolating sections along different planes, to inspe ct the internal structure. Y ou can measure 3D morphometric parameters and create realistic visual models for virtual travel within the object 89 .
Micro -CT is a small -size form of conventional computed axial t omography that is nondestructive
and provides 3D images (specifically: volume view and multiplanar reconstructions 90 ). This makes micro -CT ideal for non -human studies in experimental Endodontics 91 ,92 ,93 ,94 ,95 . Tachiban a and Matsumoto 96
investigated the application of X -ray CT in Endodontics; they found that 3D reconstruction of teeth was feasible. This technique is versatile, allowing recreation of slices in any plane and data can be represented as 2D or 3D images.
2.3.2 Resolution of micro -CT (for measurement of teeth length ).
Earlier versions had low spatial resolution (such as in the one used in 1990 by Tachibana and
Matsumoto 96 : 0.6 mm ). Consequently, the CT images were not really fine enough for a detailed analysis.
Later, the resolution improved to within a 34 to 81 µm range 88 ,92
a R esolution or Least Count : smallest subdivision marked on a measuring instrument (author’s note).
22 Current micro -CT units employ cone -beam geometry (with an effective focal spot as small as
20 µm) and produced true 3D high spatial resolution reconstructions of the object (with cubic voxels and isotropic resolution )94 .
Spoor at al .97 shown that the maximum error range of their micro -CT unit when measuring thickness of actual human molar enamel slices was ±0. 1mm.
2.3.3 Limitation s of micro -CT.
Imaging at the resolut ion of micro -CT cannot be used as a clinical technique because (1) of the very high radiation dose that would be received by the patient 87 , and (2) t he exposure time ranges 20 min to
a few hours , depending o n what is being scanned , according to the review by Robinson et al 90 .
More -appropriate -for -use -on -dental -patients scanner units were developed afterwar ds 150 ,151 ,152 .
23 24 CHAPTER 3 : MANUSCRIPT
3.1 INTRODUCTION, LITERATURE REVIEW and RATIONALE for this PROJECT
Working length has been defined as “t he distance from a coronal reference point to the point at which canal preparation and obturation should terminate ”1.
Ac curate determination of the endodontic WL is important. In the short term, in order to avoid flare -
ups 2,3,4,5,6,7 and in the long term to allow for successful treatment outcome because (1) if t oo short , adequate micro bial control is prevented 8,9 which has been shown repeatedly 2,10 ,11 ,12 to be the principal factor influencing the outcome and (2) if too long , a periapical foreign body reaction 13 ,14 ,15 ,16 ,17 ,18 ,19 ,20 ,21 ,22,23 ,24 ,25 ,26
and /or inability to optimally fill the root canal REFS may be caused.
The accuracy and limitations of available techniques to determine WL has been widely reported in the literature: periodontal sensitivity 27 , tactile 27 ,28 ,29 ,30 ,31 ,32 , radiographic 32 ,33 ,34 a,35 ,36 ,37 ,38 ,39 ,40 ,41 ,42 ,43 ,44 ,45 ,46 ,47 ,48 ,49 ,
50 ,51 ,52 ,53 and electronic 32 ,54 ,55 ,56 ,57 ,58 ,59 ,60 ,61 ,62 ,63 ,64 ,65 ,66 ,67 ,68 ,69 ,70 ,71 ,72 ,73 ,74 ,75 ,76 ,77 ,78 ,79 ,80 . The former first two methods have been generally abandoned due to their poor accuracy. In addition, some have recommended that, since both radiographic and electronic methods are not absolutely reliabl e, neither should be used as the only method f or WL determination 54 ,81 ,82 ,83 ,84 .
A new method, the “paper point technique” (PPT), has been recently introduced 85 ,86 . This technique uses conventional absorbent paper points, and it is based on the assumption that when the contents of the root canal system are removed, the canal should be dry, while the environment outside the root canal is living and hydrated: periodontal li gament, granulation tissue, pus, blood, bone or some other hydrated tissue containing fluid. Rosenberg explains that “if a paper point is placed into a dried canal short of the apical foramen, it should be retrieved dry. If a paper point is placed into a d ried canal and taken past the exit of the canal, it will be retrieved with fluid. The maximum length that a point can be placed into the canal and remain dry is then recorded as the length of the canal.
While Sique ira said that using paper points for worki ng length determination is “imprecise, unreliable, empirical and fraught with limita tions” 84 , Rosenberg claims the PPT to be accurate and precise to within 0.25 mm tolerances. However, the PPT has not been formally evaluate d yet .
Testing the performance of WL techniques in unsalvageable teeth before they are extracted, and then analyzing their apexes ex vivo is the current approach. Micro -CT is currently a popular technique in experimental Endodontics, given the great advant ages of its multi -planar analysis, high resolution of images and sample non -destructiveness and non -distortion 87 ,88 ,89 ,90 ,91 ,92 ,93 ,94 ,95 ,96 ,97 .
Since (1) the location of neither the apical constriction, nor the CDJ nor the root apex is a reliable landmark across teeth/canals , and (2) every root canal has an apical foramen /exit, our study used the root canal apical exit (RCAE) as the apical reference fo r WL determination. For the purpose of our study, we defined the RCAE as the last apical cross -section of the root canal still showing a full circle/oval canal section.
Since there i s no proof or evidence as to how often the tip of the longest paper point that remains dry accurately locates the RCAE , the purpose of this project was to compare the repeatability, the accuracy of locating the RCAE when the electronic technique is used alone or supplemented by the paper point technique .
26 3.2 HYPOTHES IS
WL determi nation is more a ccurate when the EALT is supplemented with the PPT compared to using the
EALT alone.
3.3 PURPOSE and SPECIFIC AIM S
The purpose of the study was to test the hypothesis by addressing these specific aims:
Aim 1: to compare the accuracies of EALT and EALT/PPT in locating the RCAE.
Aim 2: to compar e the repeatabilit ies of the EALT and the EALT/ PPT .
Aim 3. to calculate the % of agreement of the EALT and EALT/ PPT within a clinically relevant range.
27 3.4 MATERIALS and METHODS
3.4.1 Overview of design.
The UNC -CH Biomedical IRB approved th e project #05 -2232 , a single in vivo/in vitro study on human subjects’ permanent teeth treatment -planned for extraction . One operator used the EALT and the
PPT to locate the RCAE of 93 root canals in 88 teeth from 24 patients o f the UNC School of Dentistry ; an endodontic instrument was cemented to the PPT reading and then the tooth extracted . The apices were micro -CT -scanned. In the resulting 3D images the distance from the cemented file tip to the root canal foramen was measure d. With t he data from the file -to -foramen measurements across teeth the performance of EALT and PPT were calculate d and compare d. All steps were performed at the U NC School of Dentistry .
3.4.2 Subjects and Teeth
3.4.2.1 Inclusion/exclusion criteria
Table 1 provides the inclusion criteria for subjects and teeth.
Table 1: Inclusion Criteria (all criteria had to be met) For Subjects: • need ing at least one tooth extracted • agreed that investigators would keep tooth • age ov er 21 (IRB requirement) • no known contraindications to d ental treatment • able to read/sign consent form For Teeth: • enough coronal structure left to hold rubber dam clamp • radiographic apical curvature within 0-10 degrees • absence of horizontal or vertical root fracture • not diagnosed as “Apical Periodontitis with Abscess” * • possible to attain apical patency ** * if diagnosis changed (with time or spontaneously after RC disinfection) , subject was enrolled in study **intra -operative criterion
28 3.4.2.2 Collected data
Table 2 shows the variables for which data was collected for each root canal included in the study .
Table 2: Variables Data C ollection PRE OP INTRA OP POST OP age of patient (years) pulpal diagnosis (healthy, inflamed, necrotic) apical resorption (yes/no ) root development (complete/incomplete) EALT reading* (mm) lesion attached (yes/no) tooth number (1 through 32) PPT reading* (mm) exit to apex distance (mm)
file tip to root canal exit name of root (single/buccal/lingual ) taper/tip size of last instrument (%/mm x10 -2) distance* (mm)
taper/tip size of cemented instrument name of canal** (single/bucc al/lingual) (%/mmx10 -2) apical resorption (present/ansent) peri -radicular diagnosis (present/absent)
*In bold font the only variables for which the recruited subjects showed enough vari ability to show any corre lation **in multi -canaled roots
3.4.2.3 Sample size calculation:
A pilot study w as conducted to gather preliminary data to use later in a definitively -powered study,
should one be indicated based on the preliminary results. We estimate d that given time issues w ith respect
to this being a Masters project, and given projections of the number of eligible study subjects (based on
previous projects within the Department of Endodontics), we could accrue as close to 100 root canals as
possible .
29 3.4.3 In vivo part of the stud y:
The ultimate purpose of the in vivo portion of this study was t o clinically obtain two sets of values: one containing root canal length according to the EALT; another containing the length of the same canals according to the PPT.
3.4.3.1 Assessment of patients and teeth
Patient s’ unsalvageable teeth were evaluated , including clinical and radiographic examinations. If the patient and the tooth met the inclusion criteria of the study, patient was informed about risks, benefits and options for the se teeth. Those wh o still wishe d to have the tooth extracted and to participate in the study were included as study subjects , and t he findings of the evaluation became the Pre -Operative Data of the study.
3.4.3.2 Anesthesia, operating field isolation and tooth decoronation
3.6 cm3 of 2% lidocaine and 1:100.00 epinephrine were administered to obtain local anesthesia.
Teeth w ere isolated from the rest of the oral cavity with a rubber dam in order to provide a safe and aseptic operating field. Teeth accessible surfaces and surrounding rubber dam were scrubbed with iodine solution.
Tee th w ere decoronated just coronal to the gingival margin with a cylindrical coarse diamond bur on a dental high -speed hand -piece , providing a flat horizonta l occlusal table to serve as reproducible reference point for measurements ( Figure 5). Remaining caries was removed and t he pulpal space accessed.
30 Figure 5. Study teeth: isolated and decoronated.
3.4.3.3 Obtaining the EAL -length
Working Length (WL) w as first det ermined for each canal with a Root -ZX E AL® (J Morita MFG.
Corp., Kyoto, Japan) and a 0.02 taper #10 or #8 LEXICON ™ K -File b (Tulsa Dental Specialties, Tulsa, OK) .
According to the manufacturer’s operation instruction manual 153 , the file was inserted until the meter read
0.5, then advanced slowly until the word APEX would flash, and finally withdrawn until meter re ad 0.5 again.
Then , the stopper was positioned at the coronal reference point and t he file was then removed from the tooth .
The length from the file tip to the stopper was measured with a n endodontic hand ruler c ( Union
Broach -Moyco , York, PA ) calibrated to a least count (resolution) of 0.5mm . The stopper was aligned with the edge of the ruler (by the 0mm reading) and u nder an Entrée Extra Global d micro scope (Global Surgical ™
Corp, St Louis, MO ) at 8.0 magnification the file tip position was compared against the ruler marks .
Measurements were made to the nearest ½ of the least count 154 (0.25 mm):
b http://store.t ulsadental.com/catalog
c http://www.miltex.com/prodInfo/dental/endodonticsB.aspx
d http://www.globalsurgical.com/den tal/dental.asp
31 When the very tip of the file was at the “full” or “half” mm mark, then, respectively, 0 (none) or 0.5
mm were added to the highest/ closest full mm the file was extended along; if the file tip was in between “full”
and “half”, or in between “half” and “full”, then, respectively, 0.25 or 0.75 mm were added. The leng th thus obtained was recorded as the “EAL length” e.
The EALT -length was obtained once for each root canal except for the last nine cases, in which it was obtained thr ee times (so that the repeatability of the EALT could be tested) .
3.4.3.4 Obtain ing the PPT -length
Achieving canal apical patency
(1) a #15 k -file was taken to EAL-length (once smaller size files had reach ed that length );
(2) root canal enlargement and debris removal , by taking files S1 and S2 ProTaper ® and a series
20 GT ® file s ( both from Tulsa Dental Specialties, Tulsa, OK) that was appropr iate for the particular canal, all three to 0.5mm short of E ALT -length. Finally, a number 1 5 k -file wa s taken to E ALT-length, rotated 90 ˚ and removed .
Once the canal was accessed, t he chamber was filled with 2.5% Sodium Hypochlorite ( NaOCl ) at all times during the instrumentation phase . The irrigation sequence in between two rotary file s was as follows : new irrigant solution was passively applied in canal, a pre -bent #10 k -file used to EAL T-length to agitate debris and irrigant applied again (irrigant agitation irrigant) .
Whenever it was not possible to achieve patency by following the previously described steps , canals were r ecapitulated w ith small k -files , NaOCl and 17% Ethyl enediaminetetraacetic acid ( EDTA )f
(Pulpdent ® Corp, Watertown, MA ).
e This measuring method was employed every time a file or a paper point needed to be measured.
f http://www.pulpdent.com/endo/edta.html
32 Using Paper Points to locate the RCAE
Rosenberg ’s 85 ,86 description of the PPT procedures was followed. Kerr Absorbent Points ®g (Sybron
Dental Specialties Inc, Orange, CA) were the paper points used for this study (Figure 6).
Figure 6: Kerr absorbent paper points
First, the canal w as dried . Then, a paper point , of lesser tape r than the canal was prepared , w as
placed in the ca nal 2 mm short of the E ALT-length. I f this point wa s retrieved with moisture, a new one w as
used short of the previous one, until on e is found to come back dry out of the canal ( Figure 7). In every instance, dryness was verified visually, observing the paper point under the microscope.
This retrieved -dry point was advanced at 0.25mm len gth increments until it wa s just moist at the tip
(Figure 8). T he length it had been inserted in the canal the last time it came back dry wa s recorded .
Consequently, the length of the longest paper point that c ould be retrieved dry from the canal w as rec orded as the length of the canal according to the Paper Point Technique : th is was termed th e PPT -length . Paper points were kept at full length only for a second
g http://www.sybronendo.com/index/sybronendo -products -fill -absorbentpoints
33 The p rotocol for measuring the paper point ’s length ( Figure 8) was th e same as described for measuring files under Obtaining the EALT -length section: to ½ of the ruler’s least count (0.25 mm) .
The PPT -length was obtained once for each root canal except for the last nine cases, in which it was obtained thr ee times (so that t he repeatability of the PPT could be tested) .
A B Figure 7. Representation of a paper point right at (A) and past (B) the RCAE. Photos by Dr David B Rosenberg 85 . Reprinted with per mission of Dentistry Today.
Figure 8. TOP: Length of the longest paper point return ing completely dry. BOTTOM: First paper point returning moist had been i nserted 0.25 mm longer than the last o ne to
return dry .
34 3.4.3.5 Cementing an endo dontic instrument to PPT -length
At this point, a ProFile ®h .04 taper hand file (Tulsa Dental Specialties, Tulsa, OK) that could reach
the PPT -length and that wa s not loose at that length , was cemented to the PPT -length with Revolution ®i
Formula 2 ™ (Sybron Dental Specialties, Orange, CA ) flow able light -cure hybrid resin applied in the coronal space in the tooth around the ProFile ® instrument and light -cured for 40 seconds .
The portion of the file remain ing outside the tooth was carefully sectioned with as li ttle vibration as possible with a tapered diamond bur on a high -speed hand -piece. The rubber dam was then removed.
3.4.3.6 Tooth extraction
Study t eeth then were extracted as atraumatically as possible with conventional oral -surgery techniques and instruments . Mor e anesthetic was administered to those subjects who needed it before performing the extraction. Patients were given printed post -operative instructions. Extractions (as well as the rest of procedures) were performed at no cost for the subject.
3.4.4 Ex vivo part of the study .
The ultimate purpose of the ex vivo step was to obtain the set of values containing the actual lengths of the study root canals.
3.4.4.1 Specimen preparation and storage
Roots were placed in 5% NaOCl for 30 minutes to clean the root surface , then s tored individually in
4% Formalin (for the rest of the duration of the experiment ) and labeled . Each container was l abeled with the same number that particular canal had been assigned during the data collection ( Figure 9).
h http://store.tulsadental.com/catalog/
i http://www.kerrdental.com/index/kerrdental -products -composites -revolutionformula2
35 Before s torage in Formalin, the coronal diameter of the roots was reduced with a diamond bur so that each individual root could fit later in a plastic vial like th ose in Figure 10 .
Figure 9. Teeth labeled and s tored in formalhaldehyde.
3.4.4.2 Micro -CT image acquisition
One at a time, plastic vials (Figure 10 ) containing one root and filled up with water were positioned
in the SkyScan 1074 Portable X -Ray Microtomograph unit (Skyscan, Kontich , B elgium ), a stationary
compact micro -CT scanner with 22 µm pixel size spatial resolution . To make the visualization of the apexes
easier, s pecimens were stabilized in a position such that (1) the apical portion of the cemented file was as
vertical as possib le , and (2) the plane of the foramen was horizontal ( Figure 11 ).
36 Figure 10 . Specimens were placed in plastic vials p rior to micro -CT scanning process.
A B
Figure 11 . A: SkyScan micro -CT unit used in this project. B: Plastic vial containing specimen, positioned on rotating stand .
37 The scanner r an at 40 kV , 1000 µA and 40 W, for 480 to 5 40 m s. Acquiring 206 angular projections over half the perimeter of the specimen took about 14 min utes per sample scanned. Each projection created a .TIF image . T he images from a particular tooth were saved in a folder labeled with the tooth’s study number.
3.4.4.3 Vol umetric reconstruction of the tooth apex
The set of each tooth’s angular projections was entered in "N Recon" ( SkyScan's volumetric reconstruction software ) to create a set of cross section slices of the object. The program saves the reconstructed slices as .BMP imag es . Pre -reconstruction set -up include d beam -hardening correction, alignment optimization, ring artifact correction, reconstruction in a restricted volume of interest, external and internal calibration into Hounsfield units and interactive density window selection.
3.4.4.4 Analysis of reconstructed apices : measuring the file -tip to RCAE distance
Th e program SkyScan CT -Analy ser for 2D and 3D quantitative analysis of reconstr ucted volumes was used to measure the distance from the cemented file tip to the most apical cross section of the root
canal, the final objective of using this methodology.
The CT -Analyser screen shows two orthographic views of the same tooth apex: horizon tal cross - sectional view and vertical elevation view ( Figure 12 ). These two views provide 3D information about the apex since , together, both contain all three coordinate axes: the vertical view is outlin ed by axes X and Z, and th e horizontal view by axes Y and Z. For this reason, the sagittal view is not necessary in order to understand the volume of the apex .
CT -Analiser allowed visualization of cross -sections within the reconstructed volume . Distance
between section s was 0.02 mm (there were 50 sections for each 1 mm ) ( Figure 12 ).
38 Figure 12 . Analysis of cross -sections: (A) the one to show the last evidence of the file tip, ( B) the last one to show the root canal as a full oval.
(A) (B )
3.4.4.5 Observations and Measurements
One operator, traveling apically from section to section (distance between section s was 0.02 mm) ,
record ed the vertical (z) coordinate of two specific horizontal cross -sections:
1) the last one to show f ile tip presence ( Figure 12 A), and
2) the last one show ing a complete oval root canal cross -section (in this study the apical end of the root
canal : any cross -section apical to it does not show a complete oval section of the root canal) ( Figure 12 B).
The difference between these two vertical coordinates wa s the distance from the file tip to the
RCAE . Compar ing it to the EALT - and P PT-lengths, we tested the accuracy of each technique .
39 3.4.5 Data Anal ysis
The purpose of the Data Analysis was to calculate the accuracy , repeatability and agreement of the
EALT and the PPT, by comparing th e values in the ACTUAL -lengths set with the values in the EALT - lengths set first , and then with those values in t he PPT -lengths set .
3.4.5.1 Definition of Variables
Outcome variable s
Our outcomes were two continuous variables: EALT -accuracy (distance from EALT -length to the actual canal exit) and PPT - accuracy (distance from PPT -length to the actual canal exit) . Positive (+) outco me values represent that the technique gave a “long” reading (beyond the RCAE) , and Negative ( -) outcome values represent that the technique gave a reading “short” of the RCAE.
Poten tial ly confounding /involved variables
Values about variables shown in Tabl e 2 we re recorded, so that the accuracy, repeatability and
agreement of the EALT and the PPT could be calculated across different levels of these variables.
3.4.5.2 Analysis of the data
All d ata obtained was arranged into a spread -sheet t able (see Ap pendix A) . The objectives of the
data analysis were to calculat e 1 ) the measuring accuracy (continuous and categorical) , 2) the
repeatability and 3) the agreement of the EALT and the PPT.
The continuous accuracy of the EALT or the PPT w as expressed with both the median and the
mean (with standard deviation ) of the distance s from the RCAE obtained with each technique . The degree of significance of the contin uous a ccur acy difference between techniques was computed with a paired t-test .
40 The categorical a ccuracy of each tec hnique in specific error ranges was expressed in terms of the proportion of cases that fell in each specific range compared to the total of results obtained , respectively, with each technique . The significance of the categorical a ccur acy difference within error ranges for both technique s was calculated with the McNemar’s exact test 155 . Significance was set at p<0.05.
The repeatability was tested in nine root canals from each of which three readings were obtained with EALT and three with PPT. Repeatability of each technique was assessed by (1) the repeatability coefficient 156 , (2) the intraclass correlation and (3) a scatter -plot of the within -subject standard deviation against the mean.
The agreement of both techniques was analyzed with two approaches. The non p arametric 156
approach calculated (1) the between -method disagreement within specific lengt hs . The parametric approach included the (2) 95% limits of agreement and (4) Cohen’s 157 Kappa statistic .
3.4.5.3 Reliability of the Image Analy sis .
The intra -examiner reliability w as evaluated using the Kappa statistic. CT -Analyser images of 20 teeth not included in the study showing apical thirds of root canals with a file cemented to different lengths were displayed on the screen . The operator was asked to analyze them twice (10 days time elapse d in between analyses). The operator was asked to choose cross -sections in which, respectively, the file and the root canal were seen last .
The results the operator produce d the first time were compared t o the results he produce d the second time; this is the intra -operator reliability. This comparison w as be made using the Kappa statistic.
The Kappa value for an examiner must be 0.70 or greater for that examiner to be allowed to make formal measurements on study teeth. If the Kappa value falls below 0.70, the examiner will receive further training and be retested, or they will not be allowed to serve as an examiner for the study.
41 3.5 RESULTS
This study enrolled 24 subjects, age s 24 to 68 , from wh om 88 teeth ( 93 root canals) were obtained . B oth the EALT and the PPT could be evaluated in 71 root canals . The individual unit of measurement was the
“root canal” (i.e: 1 root canal = 1 case) (Table 3 ).
• the first 9 cases were considered “training in PPT cases” for the operator
• in 13 cases the EALT ( n= 2) , the PP T (n=8 ) or both (n= 3) could not be evaluated :
- in one case the cemented file did not stay in place after the tooth was extracted;
- EALT gave erratic readings in 4 cases.
- PPT gave no reading (no periapical moisture ) in 4 cases and could not be performed
because the canal could not be dried in 4 cases : excessive periapical moisture/bleeding
(n= 2) and incessant purulent drainage ( n= 2) .
Table 3 : Sample 9 PPT training 1 file was displaced during tooth extraction 13 4 (5%) EALT failed (erratic readings) (15%) 4 no moisture at all 8 (10%) PPT failed 4 excess of moisture
93 84 (100%) total experimental group 71 (85%) both EALT and EALT/PPT worked
42 3.5.1 Accuracy (n=71):
Cont inuous Accuracy
Table 4 shows the group conti nuous accuracies of the EALT and EALT/PPT.
Table 4 . Continuous Accuracy of EALT and EALT/PPT: distance from each technique’s reading to the RCAE (mm) Mean * SD minimum median Maximum 90% centered interval EALT 0.38 0.43 -0.6 0.37 1.91 -0.2 to 1.18 EALT /PPT -0.06 0.36 -0.88 -0.1 1.15 -0.66 to 0.55 *paired sample t test: statistical difference (p -value <0.0001) Minus sign indicates short of (or coronal to) root canal Apical Exit
Categorical Accura cy.
Table 5 show s all readings by both techniques arrang es in 0.25 mm wide accuracy intervals.
Table 5. Categorical Accuracy of EALT and EALT /PPT (all intervals observed) distance from RCAE EALT EALT /PPT (mm) n=71 % n=71 % -1≤distance< -0.5 1 1.4 5 7 -0.5 ≤distance< -0.25 2 2.8 15 21 -0.25 ≤distance<0.0 9 12. 7 25 35 0.0 ≤distance<0.25 12 17 14 19.7 0.25 ≤distance<0.5 24 34 8 11.2 0.5 ≤distance<0.75 14 19.7 2 2.8 0.75 ≤distance<1 3 4.2 1 1.4 1≤distance<2 6 8.4 1 1.4 Minus sign indicates short of (or coronal to) root canal Apical Exit
43 Table 6 shows that cate gorizing the results as shorter than/equal to/longer than the actual root canal, 85% of the EALT readings were longer and 62% of the EALT/ PPT of the readings were shorter than
the actual respective canals.
Table 6. Categorical Accuracy of EALT and EALT /PPT (RCAE as cut -off point ) EALT EALT /PPT reading n (%) n (%) short er 10 (14) 44 ( 62 ) than actual canal at the RCAE 1 (1) 2 (3) long er 60 ( 85 ) 25 (35) than actual canal 71 (100) 71 (100)
Table 7 shows the accurac y of EALT against EALT/PPT in 0.25 -mm -wide intervals .
Table 7. Categorical Accuracy of EALT against EALT /PPT EAL accuracy SHORT LONG
[-1 ≤error<-0.5] [-0.5 ≤error<-0.25] [-0.25 ≤error<0.0] [0.0 ≤error<0.25] [0.25 ≤error<0.5] [0.5 ≤error<0.75] [0.75 ≤error<1] [1 ≤error<2]
[-1 ≤error<-0.5] 7.04
T 22 1 5 R
O [-0.5 ≤error<-0.25] 24243 15 21.13 H
S [-0.25 ≤error<0.0] 13710 31 25 35.21 y
c [0.0 ≤error<0.25] 174 214 19.72 a r
u [0.25 ≤error<0.5] 3212811.27 c G c N a [0.5 ≤error<0.75] 11 22.82 O T L P [0.75 ≤error<1] 1.41
P 11
[1 ≤error<2] 111.41 12912 24 14 3671 100.00 71 1.41 2.82 12.68 16.90 33.80 19.72 4.23 8.45 100.00 71
44 Table 8 shows the accuracy of each technique in specific accuracy ranges with clinical relevance. In each particular accuracy range, the EALT/ PPT has a si gnificantly greater number of readings than the
EALT.
Tab le 8. Categorical Accuracy of EALT and EALT /PPT : arranged in clinically -re levant ranges accuracy range s EALT EALT /PPT p-value * (mm) cases (%) cases (%) (-0.25 :0) 10 (1 4) 27 ( 38 ) 0.0 023 (-0.5 :0) 12 ( 17) 42 (5 9) <0.0001 (-0.25 :+0.25) 21 ( 30 ) 39 (5 5) 0.0051 (-0.5 :+0.25) 23 ( 32) 54 (7 6) <0.0001 (-0.5 :+0.5) 47 (66) 62 (87) 0.0026 *McNemar’s 155 exact test was used to compute p-value .
45 3.5.2 Repeatability (n=9) :
Repeatabil ity coefficient. According to Bland and Altman 156 two readings by the same technique
will be within 2.77 Sw mm for 95% of canals (where Sw is the within -subject standard deviation of each
2 2 particular technique ). This value is the repeatab ili ty coefficient . Since Sw = Sw (where Sw is the within - subject variance for one particular technique) , one -way analysis of variance was performed for each technique regarding those ni ne cases in which rep eated measures were obtained.
2 Since for EALT Sw was 0.006944 , the repeatability coefficient of this technique was 0.231 mm for
2 95% of the canals . And , since for EALT/ PPT Sw was 0.004629, the repeatability coefficie nt of this technique was 0. 18 9 mm for 95% of the canals . The EALT/ PPT repeatability coefficient is 18% smaller than that of the EALT. This means that for 95% of the canals the difference between two readings by the PPT is expected to be 18% smaller than t hat between two readings by the EALT.
Table 9 . Repeated readings by EALT and EALT /PPT s in 9 cases (raw data).
case # EALT EALT/PPT 63 17 17 17 16.75 16.5 16.75 64 15.25 15 15 14.75 14.75 14.5 65 17 17 17 16.5 16.5 16.5 66 14.75 14.75 14.75 14.5 14.5 14.5 67 18.75 19 18.75 18.25 18.25 18.25 68 17.25 17.25 17.25 16.5 16.5 16.5 69 18.5 18.75 18.5 18.5 18.5 18.5 70 15.25 15.25 15.25 14.5 14.5 14.5 71 15.5 15.5 15.5 15.25 15.25 15.25
Intra -class Correlation coefficient .
Both techniques showed very good repeatability: t he intra -class correlation for PPT wa s 0.998
(0.9941, 0.99 95) and for EALT was 0.997 (0.9910, 0.9993) , with a 95% confidence interval for both .
46 3.5.3 Agreement (n=71):
A) Non parametric analysis : Between -method di sagreement within specific lengths .
Table 10 shows that i n 1 0 cases ( 14 %) the di sagreement between EALT and PPT was nonexistent .
In 32 cases ( 45%) the di sagreement was ≤0.25 mm. In 52 cases ( 73%) the di sagreement was ≤0.5 mm. In
62 (87%) it was ≤0.75 mm and in 69 (97%) it was ≤1 mm.
Table 10. Be tween -method di sagreement within specific length s lengths disagreement mm N (%) 0 10 ( 14 ) ≤0.25 32 ( 45) ≤0.5 52 ( 73) ≤0.75 62 (87) ≤1 69 (97) ≤1.5 71(100)
According to Table 7, whenever the disagreement was >0 mm, it was always in the same direction: the EAL tended to give longer readings than PPT (except in one case, in which the PPT reading was longer than that of the EA LT) .
B) Parametric analysis :
Values measured by both techniques in each canal .
The mean reading difference , đ, of the measurements (EALT -PPT) was 0.447 mm , the Standard
156 Deviation , Sd, of the differences being 0.351 mm. According to Bland and Altman , if these differences are normally distribu ted, we would expect 95% of them to lie in the interval ( đ±1.96 Sd) mm . Therefore, nearly
all pairs of measurements by the two methods were closer together than the extreme values, ( -0.24 ,
+1.135) , called 95% limits of agreement .
47 Figure 13 shows (1) the lack of agreement (otherwise dots would be closer to x -axis than they are ),
(2) outlying observation s and (3) that the difference between methods is no t affecte d by the tooth length.
Difference against mean for tooth length measurements
2 )
m 1.5 m ( ) T 1 P P - T
L 0.5 Series1 A E (
e 0 c 0510 15 20 25 n e r e
f -0.5 f i D
-1 Mean of EALT-length and PPT-length (mm)
Figure 13 . Param etric analysis of between -method agreement : paired mean reading lengths against paired difference of readings .
Kappa statistic.
The Kappa [ (ASE): 0.0283 (0.0457) , 95% confidence interval: ( -0.0612, 0.1178)] shows a poor agreement between PPT and EAL when looking at categorize d accuracy ranges as in Table 7 .
48 3.6 DISCUSSION
This project tested the hypothesis that supplementing the EALT with the PPT is more accurate for
WL determination than the EALT alone. The hypothesis was tested by compar ing the repeatability and the accuracy in locating the RCAE of both techniques in vivo in a series of root canals . The teeth were extracted and 3D micro -CT images obtained and analyz ed . Our results show that , while the repeatability of both techniques was no t significantly different (both were extremely high ly repeatable), their accuracies w ere significantly different (the EALT supplemented with the PPT appears to be more accurate an approach than using the EALT alone).
3.6.1 Regarding the Materials and M ethod s
Testing the PPT was justified since it had never been before and yet it had been claimed 85 ,86 to be more accurate and reliable than currently accepted techniques for WL determination .
Our in vivo -ex v ivo approach overcame the limitations of an only -in-vivo study, which would have
prevent ed precise assessment of RCAE and file tip location s. An only -ex -vivo study would not have be en
adequate either , because the PPT needs presence of body fluids .
We chose the RCAE as the apical landmark (Table 11 ) in relation to which test the accuracy of the
EAL T and EALT/ PPT because of (1) the location of neither the apical constriction, n or the CDJ 98 ,112 ,113 ,114
nor the root apex is reliable acros s teeth/canals , (2) every root canal has an apical foramen /exit , and (3) the apex of the tooth has no relevance to the physiolog y and patho -physiolog y of periapical disease (al though it is under standable outcome studies used it as reference , since the se ma inly look at the success/failure rate of surviving teeth) .
49 Table 11 . Criteria for selecting the apical landmark. Relevant to Physiology/ Present in every Anatomic/ Histologi c landmark Pathophysiology of tooth? periapical disease actual a pex YES No YES apical foramen YES YES YES CDJ * YES No YES apical constriction YES YES No *Cemento Dentinal Junction
Only teeth with roots showing radiographic apical curvatures with ≤10 degrees were selected for the study, so that the most apical portion of the canal could be oriented perpendicular to the rotational axis of the micro -CT SkyScan scanner as much as possible . Because of this our results may only be pertinent to teeth wit h this same degree of curvature.
Apical patency was an enrollment criterion because both EALT and PPT require the exit of the canal be open for each of them to work .
Repeatedly tested and found one of the most accurate apex locators 74 , the RootZX ® was an appropriate devi ce for our study , and i s quite popular j among those practicing Endodontics.
Both the EAL and PPT lengths were not recorded at the same poi nt in the canal instrumentation
because (1) obtaining the EAL reading before initiating the canal instrumentation reproduces the way that a
large num ber of practitioners perform this technique , and (2) the first step in the PPT sequence is obtaining
the EAL -length 86 .
Since the EAL and PPT rea dings were not obtained at the same point, both methods may actually
have been exposed to measure two different lengths , as shown by Schroeder et a l. 158 , who found canals to
be slightly ( but statistically significantly ) shorter after (1) straight line access and (2) canal flar ing .
j This is a personal impression of this Thesis’ author.
50 In our study all teeth were decoronated 1 mm above the free gingiva level prior to obtaining EALT and PPT readings. Therefore, obtaining coronal straight line access could not have contribute d to both techniques being exposed to mea sure different lengths.
However, we tested the EALT prior to flaring the canal . And the PPT right afterward. This may have exposed both techniques to measure somewhat different lengths, according to Sch roeder et al 158 .
Nevertheless, the y consid ered the combined effect of straight line access and canal flaring in the canal length change to be unimportant . W e could assume that flaring the canal alone is even le ss influential in how much the length changes from before to after being flared . This is even more so in our particular case , since we di d not include in the study roots with a radiographic curvature >10 ˚.
Absorbent paper points are conventionally used during root cana l treatment to dry the canal . This same type of paper points were used to locate the apical end of the root canal according t o the PPT 85 ,86 , which assumes that once the canal has been dried, paper points (1) taken exactly to the canal terminus will always come back completely dry ou t of the tooth ( Figure 7A) AND (2) taken to an additional 0.25 to 0.5mm longer l ength will always get wet ( Figure 7B).
Pumarola -Su ñé et al .159 in 1998 studied the 5 -second fluid absorbency of several absorb ent point
brands. Ker r points were among the highest -absorbing ones. This finding is relevant to our study because high -absorbency points could be expected to give short canal -length readings since they would tend to catch moisture quicker than lower -absor bency points. However, our results show that 1 -second readings with Kerr’s points are ONLY an average 0.06 mm (± 0.36 mm) short of the RCAE.
In 1983 Nishikawa et al .160 performed an ex vivo trial to compare plastic (Type II) and paper endodontic points. They found plastic points to be completely moisturiz ed after 14 seconds, and paper points after 28 seconds. However, paper points could absorb 3.5 times more fluid than the plastic points.
What is the performance of a Plastic Point Technique for locati ng the R CAE remains unknown, since this
study did not address that question.
51 Every patient in this study received 2% lidocaine with 1:100.000 epinephrine, administered via a periapical infiltrative injection for the tooth in question. Additionally, for lower teeth , an inferior alveolar or mental nerve block was perfo rmed . The arteries present at each injection site supply all the hard and soft tissues in th at particular area 161 . It is known that epinephrine causes vasoconstriction in the oral tissues 162 .
When obtaining the PPT -length , blood seemed to be the fluid impregnating the paper point tip most of the time. We could expect the PPT to perform differently than in this study if no vasoconstriction ( absence of epinephrine ) or more intense vasoconstriction (when 1:50.0 00 epinephrine ) is used . However, th e effect of the epinephrine in the performance of the PPT was not addressed by our study .
We used a Moyco/Union Broach ® ruler to measure the endodontic instruments and paper points because (1) its resolution is 0.5 mm an d (2) it is c ommonly j used by those practicing Endodontics.
Intra -operative measurements were made at x8.0 magnification i n order t o be able to m ake them to the nearest half of the Moyco’s ® rule r’s resolutio n: 0.25 mm .
Although clinicians do not routinely measure endodontic instruments or paper points to such resolution, the lowest reasonably -attained possible resolution for the study measurements is justified since the lower the ir resolution, the better the y show the actual accuracy of each technique.
In 1972 Pineda and Kuttler 121 said the anatomy of root canals could be investigated using nine different methods. M icro -CT, was not available for this purpose until the 1990s. Micro -CT tech nology gives
the highest resolution; it does not require tooth distortion and provides multiplanar visualization of the apex
(Table 12 ). Grinding 163 ,164 the apexes is a destructive approach allow ing only for single -plane analysis (the
one the apex i s shaved along) with not ideal image resolution . Clearing a tooth is a nondestructive method,
but the clearing process makes it shrink 165 about 3.2% , deeming it not useful for our study.
52 Table 12 . Criteria for selecting a technique * for analyzing the specim ens’ apices multi -planar Technique nondestructive non -distorting resolution visualization macroscopic direct observation yes yes no low?? microscopic direct observation yes yes no hundreds µm Macroscopic observation of sections no yes no low microscop ic observation of sections no yes no hundreds µm transverse sections and no yes no hundreds µm micrometric measurements intraoral radiographs yes no no low? Canal filling and decalcification yes no no low to high** canal filling and clearing yes no no low to high** grinding and radiographs no no no Low micro -CT *** yes yes yes 20 µm *first 9 techniques, as listed by Pineda and Kuttler 121 ; **depending on whether it is a macroscopic or microscopic observa tion; ***to our knowledge, this is the first study using micro -CT to analyze the accuracy of a technique to determine endodontic working length.
3.6.2 Regarding the Results
Even though (1) we obtained a variable number of teeth from each patient and (2) some tee th provided more than one canal for the study, for statistical purposes, all observations were considered independent.
It took the operator performing the EALT/ PPT in 9 cases before this technique’s readings became
adequate. For this reason, these initial 9 cases were considered “training” in the PPT and were not included
in the dataset used for the statistical analysis (Table 3) .
While the EALT did not work adequately 5% (4/84 cases) of the time (erratic readings) , the PPT did
not work 1 0% (8/84) of the ti me ( half due to total lack of moisture, the other half due to excessive moisture ).
The performance of both techniques was evaluated using the results obtained from those 71 cases in which both the EALT and the PPT worked (Table 3) .
53 ACCURACY:
Continuous Acc uracy: Since the group EALT -continuous accuracy is (1) smaller than (as shown by their means and medians) and (2) significantly different from t hat of the EALT/ PPT (as shown by the
paired t -test ), we can infer that the EALT is significantly less accurate t han the EALT/ PPT (Table 4) .
The relevance of the sign of the group EALT/ PPT -accuracy being negative and that of the EALT -
accuracy positi ve, has not been addressed by this study.
Categori cal Accuracy : In accordance with the Continuous Accuracy results, Tab le 6 shows that the EALT gave readings longer than the actual RCAE location 85% of the time, while 62% of the time the
EALT/ PPT gave reading s short of the RCAE.
Table 8 shows that in each clinically acceptable range, the proportion of PPT readings is signif icantly higher , than those of the EAL T (p -values << 0.05) . This means that , no matter how restricted the eva luated range is, the PPT always had a significantly greater number of readings in it than the EALT.
54 REPEATABILITY :
Regarding the 9 root canals in wh ich repeated measures were obtained (Table 9) , Figure 14 show s that in 6 out of 9 cases for the EALT and in 7 out of the 9 for the PPT, the re was no variability (SD=0 mm) in the readings obtained from each root canal.
The intra -cl ass corre lation coefficient s of both techniques show that (1) both are highly repeatable and (2) that the repeatability difference is not significant.
The repeatability coefficient of the EALT was 0.231 mm and that of the PPT was 0.189 mm ( 18 % smaller ). Th is means that for 95% of the canals the difference between two readings by the PPT is expected to be 18% smaller than that between two readings by the EAL T. W e do not find this difference clinically significant, since , after all, the repeatability coeffici ent of each technique is smaller than 0.25 mm, resolution clinicians do not usually work to and are not likely to go beyond in the future.
The repeatability coefficient , compared to the intra -class coefficient , presents these two advantages: (1) facilitate s the comparison with the limits of agreement and (2) helps in the interpretation of the individual measurements, since it is in the same units 156 .
Figure 14 . Repeatability analysis of the EALT and PPT (in 9 cases): mean against standard deviation.
55 AGREEMENT :
When the true values (gold standard) remain unknown, evaluating the agreement between techniques is almost the only way to determine whether a new measuring technique should be implemented
or not (depending on whether it agrees sufficiently or not with the standard technique) 156 . For this reason, this part of the analysis was not very relevant in ou r study, since we were able to test each technique (EALT and EALT/ PPT) against the gold standard ( true canal length ).
From Table 10 , we infer that the disagreement between the techniques was >0.5 mm 27 % of the time, and > 0.25 mm 55% of the time.
The limits of agreement of this study show that 95% of all pairs of me asurements by the two methods will be closer than the extremes of the interval (-0.24, +1.135) . Such a large range reflects the
great variation of the differences and maybe a small sample size 156 .
If differences within the 95% limits of agreement are not clinic ally important, we can use EALT and
EALT/ PPT interchangeably 156 . However, the limits of agreement in our study give a fairly clinically unacceptable range: 1.38 mm. T his makes for a mod erate agreement between both techniques when clinically -relevant differences are considered.
Therefore, the analysis of the degree of clinically -relevant agreement showed that both techniques do not agree enough to be interchangeable . But this does not rev eal which technique gives more accurate readings. However, since the accuracy of supplementing EALT with EALT/ PPT was significantly different from (and greater than ) the accuracy of the EALT alone, we could theorize that their agreement is not ideal due to EALT alone not performing as well as when supplemented with the EALT/ PPT.
56 It is not easy to compare our results against those of previous studies, for two main reasons: (1)
previous studies evaluating the EAL T do not use the RCAE as the apical landmark, and (2) the PPT has not
been formally evaluated previously.
Hör and Attin found that under ex vivo 148 and in vivo 77 conditions it is possible to determine the region between the minor and major apical foramima with the Justy II ® and the Raypex4® EAL devices .
Haff ner et al 64 found the Root ZX ha s an average +0.3 ( ±0.6 ) mm error in locating the apical constriction. Our study showed a +0.39 (± 0.43 ) mm error in locating the RCAE . The reasons for this difference may be (1) they dried the canals before the EAL measurement; (2) they measured the lengths to a 0.5 mm resolution , while ours was 0.25 mm.
Welk et al .163 and Tselnik et al .164 shown that , respectively, 75% (n=32) and 89% (n=36) of the
readings obtained with the RootZX were long of the apical reference. Our study found the RootZX to be
85% (n=71) of the time longer than the apical reference (Table 6).
In our study, t he EALT/ PPT show ed significantly greater accuracy than the EALT, therefore it may be advisable to supplement current WL determination techniques with the PPT.
Do any of the clinical varia bles affect the accuracy of EALT or EALT/ PPT ? Only 15% of the teeth were diagnosed as necrotic pulp; t he rest were classified as healthy pulp . Only 11% were diagnosed as
Chronic Apical Periodontitis ; t he rest were classified as healthy pulp . Given th ese lo w-variability results within the pool of patients/teeth enrolled in our study , the actual influence of such variables (pulpal and periapical diagnoses) could not be shown .
57 Clinically -acceptable accuracy interval limits : Our accuracy analysis focused on spe cific ranges
[( -0.25:0), ( -0.25:+0.25)…]. The decision of which ranges to analyze was difficult, b ecause th e anatomical landmark both techniques were tested against was the apical exit of the canal , wh ereas treatment outcome studies assess th e role of t he root filling length in relation to the radiographic apex ( which is 0.5 to 3 mm away from the canal exit 50% of the time 19 ,108 ,115 ,116 ,117 ,118 ,146 ).
For th is reason , in addition to the above mentioned ranges, we include Table s 5 and 7 with EALT and EALT/ PPT accurac ies categoriz ed in 0.25mm -wide intervals . Th e reader has the opportunity to choose a clinically acceptable/unacceptable cut -point different from the one[s] chosen in our analysis in Table 8 .
Influence of individual steps in the overall accuracy of each technique : Total error (or analytical error ) is the difference between the result of an individual measurement an d the true value. Under this definition , accuracy is related to total error. In our study, for each measuring technique and for each root canal , the total erro r of each measurement is the difference between the measured and the true length s.
Multiple variables/steps contribute to the magnitude of th e total error of a given measurement 166 .
Some steps involved in the EALT and the EALT/ PPT are listed in Table 13 . We did not measure the error
magnitude of each step . T his could be the subject of another graduate thesis.
However, since most variables involved in the EALT are also involved in the EALT/ PPT , we can at least say that the error associated with t hese common st eps do es not play a role in the accuracy differe nce between EALT and EALT/ PPT . Example: “m easuring a file with the ruler” should have close -to -none impact when comparing the total error of EALT and EALT/ PPT , since that step is utilized in both techniques .
Therefore, we theorize that o ut of all the variables , the way the reading is obtained (with apex locator or paper points ) is the major factor in the accuracy dif ference s between EALT and EALT/ PPT.
Below is a simple mathematical model to explain it :
58 Let k │T.E. EALT │= E CommonSteps + E EAL and
│T.E. PPT │= E CommonSteps + E PP ,
then:
│T.E. EALT │-│T.E. PPT │= E PP - EEAL
This shows that the difference in the total error (difference of accuracies) between both techniques would equal the difference between the actual EALT and PPT reading errors . This means that when compar ing the accuracies of EALT and PPT ( one aim of this study) , it is not necessary to measure the error associated with their common steps since the se do not influence the total error difference.
Other variables are: 1) pulpal status, 2) number of repetitions, 3) attentiveness of the observer, 4) measuring of the paper point, 5) measuring of the file to be cemented, 6) micro -structural damage of the root tip during extraction, 7) soundness of the scanning process, 8) consistency of the image digital acquisition, 9) adequacy of computer measurements of the canal exit -to -file distance.
k │T.E. │: Total Error of either technique; E CommonSteps : error of steps that are common to both techniques; E EAL : error of the EAL, a
step in EALT; E PP : error of reading the paper points, a step in PPT.
59 Table 13 . Potential error -source steps in EALT and PPT # times executed in Steps /Variables EALT PPT Only involve d in EALT: 1 - intrinsics of the EAL machine (its accuracy and precision) - proficiency of operator at using the EAL 1 Only involved in the PP T: - intrinsics of how Paper Points work: ( size , taper, paper capillarity , humidity/dryness of canal and periapex …) 1 - measuring paper point length ( from tip to where cotton pliers gra b it ) ( invol ves "operator" and "hand -ruler" ) ( measurement is length of canal according to PPT ) 1 - operator ’s expertise at measuring w/ P aper Points 1
Involved in b oth techniques : - making sure rubber stopper touch es coronal reference point 2 1 - measuring file length from tip to rubber stopper (measurement is length of canal according to EALT) 2 1 - cementing a larger file to the PPT length: (its distance to RCAE sh ow ac curacy of EAL and PPT) 1 1 - extraction of the tooth 1 1 - micro -CT scanning of the tooth * ( resolution of image acquisition process? ) 1 1 - measuring distance from file tip to RCAE * (measuring quality of image analysis software? ) 1 1
* procedures not involved in clinical but research procedures
Analysis of actual and/ or absolute values . Absolute values do not reflect in which direction the
measurement moves away from zero (at the RCAE) : into the positive (long measurement ) or negativ e
va lues (short measurement ). In Endodontics, we aim for zero , but two symmetrically -deviat ed -from -zero
measurements (same number into the positive and negative) do not have the same clinical significance .
Given the same “absolute continuous accuracy ” of a giv en WL measurement , does (+) have a
different influence in the t reatment outcome compared to ( -)? Is (+2 ) better or worse OR THE SAME as ( -2)
in relation to t reatment outcome? Does a 2 mm length beyond the RCAE influence the outcome of treatment
any differ ently from 2 mm short of the RCAE?
60 When it comes to choose between absolute and actual values for the analysis of our results , our options were :
If the influence of any two same -value different -sign measurements in the clinical outcome is the same, then we should us e the absolute values because the sign does not matter .
If the influence of any two same -value different -sign measurements in the clinical outcome is different, then we should us e the actual values because the sign matters then.
If we do not know if the influence of any two same -value different -sign measurements in the clinical outcome is the same, then we should us e the actual values because the sign may matter.
For our study, hav ing foun d no clear evidence to support whether the sign of a readin g matters or not, we opted to use the actual values, in case the sign matters.
3.6.3 Research questions for future projects
1) What is the contribution to the total error of individual steps of EALT and PPT? Could those partial error sources be isolated (random) and eliminated or compensated (systematic)?
2) Would lower -absorbency points (maybe even plastic instead of paper points ) give readings closer to the RCAE than Ker r’s?
3) Would reagent color -changing points make the act of reading the PPT -length more accu rate and repeatable ?
61 3.6.4 The Paper Point Technique in clinical context
3.6.4.1 Implementing the PPT
According to the results of this study , the accuracy of the combined use of EALT and PPT is better than that of the EALT alone . Therefore, it seems reasonable to supple ment the EALT by implement ing the
PPT in to the routine root canal therapy procedural sequence.
The PPT will not replace the EALT, s ince, as detailed in our Materials & Methods section, the electronic canal -length determination is a part of the PPT sequence , and we have, therefore, compared the use of EAL or EAL/PPT .
Rather (in accordance with Rosenberg 85 ,86 ), the PPT may be used to refine the endodontic WL so
that the final apical 1/3 instrumentation and the c anal f illing phases may be performed with a higher degree
of length control.
Table 14 shows two examples of how the PPT may be incorporated into the root -canal -therapy sequence.
Table 14. T wo r oot canal the rapy sequence s incorporating the PPT.
access to pulpal chamber
early WL measurement with EALT * coronal 2/3 instrumentation coronal 2/3 instrumentation * early WL measurement with EALT early apical 1/3 instrumentation final WL measurement with PPT fin al apical 1/3 instrumentation root canal filling *sequence followed in this study (up to the “final WL measurement with PPT” step ).
62 3.6.4.2 Excessively short PPT readings
For obvious reasons, t he PPT gives largely inaccurate s hort readings when continual periap ical bl ood or purulence drain s into the canal. In these cases, paper points will not come back completely dry unless they are inserted several mm short of the RCAE, or may even return always moist , no matter how short they are placed in the canal .
Therefor e, poor performance in the presence of continuous moisture is a n obvious limitation of the
PPT . However, when ever the canal cannot be dried completely it should not be root -filled either , as proven by the fact that filling the canal in the presence of mois ture increases the potential for leakage, which reduces the chances of successful treatment outcome .
In these situations , the completion of the case (and the PPT measurement) should be put off until a later visit, when the canal can be dried completely, so that (1) the PPT -length is obtained under more reliable conditions, and (2) the canal will remain dry dur ing the obturation phase.
63 3.7 CONCLUSIONS
1. The operator in this study needed a training perio d of about 10 cases before becom ing proficient wi th
the P PT .
2. After th e training period , the proportions of no or inadequate readings were 5% with EALT and 10%
with PPT .
3. In the 71 canals where both methods could be evaluated, the EALT and EALT/PPT had a moderate
agree ment , since (1) only 14% of the time both tech niques gave the same readings, (2) only 45% of
the time the difference between readings was ≤0.25 mm , and (3) the range within the l imits of
agreement is too large to consider the techniques interchangeable from a clinical -relevance
perspective.
4. In the 9 c anals where repeated measures were taken, the repeatabilit ies of the EALT and the
EALT/ PPT were both were excellent and not significantly different .
5. In the 71 canals where both methods could be evaluated, supplementing the EALT with the PPT
showed signific antly higher accuracy than the EALT alone ( p value <0.0001 for continuous and
≤0.0051 for categorical accurac ies ).
6. Although the clinical significance of this degree of accuracy has not been established, it may be
advisable to supplement current WL determination techniques with the PPT , since the results of the
study support our hypo thesis .
64 APPENDI X A : RAW DATA of the STUDY
pre operative data intra operative data post operative data case# pt age tooth # root canal name periapDx pulpalDx EAL1 EAL2 EAL3 PPT1 PPT2 PPT3 EALok PPTok FileZ ExitZ PPTerror EALerror MeanPairedError MeanPairedReading EAL-PPT 12 7 44 20 sing single HP HP 20.5 20.25 1 1 8.877 8.774 0.103 0.353 0.052 20.375 0.25 14 9 43 21 sing single HP HP 15.5 15.25 1 1 6.991 7.442 -0.451 -0.201 -0.226 15.375 0.25 15 10 63 6 sing single HP HP 18.5 18 1 1 6.171 6.068 0.103 0.603 0.052 18.25 0.5 16 10 63 7 sing single APA HP 15.5 14.5 1 1 5.638 6.519 -0.881 0.119 -0.441 15 1 17 11 55 22 sing single HP HP 16 15.5 1 1 10.127 10.189 -0.062 0.438 -0.031 15.75 0.5 18 11 55 29 sing single CAP NP 14.75 13.75 1 1 7.606 8.098 -0.492 0.508 -0.246 14.25 1 19 11 55 28 sing BUCC CAP NP 13 12.5 1 1 4.674 4.756 -0.082 0.418 -0.041 12.75 0.5 20 11 55 27 sing single HP HP 15 14.5 118.631 8.446 0.185 0.685 0.093 14.75 0.5 21 12 63 8 sing single CAP NP 15 14.5 117.749 6.806 0.943 1.443 0.472 14.75 0.5 22 12 63 9 sing single HP HP 13.25 13.25 114.674 4.777 -0.103 -0.103 -0.051 13.25 0 23 12 63 10 sing single HP HP 16 15 116.56 6.847 -0.287 0.713 -0.144 15.5 1 24 13 52 9 sing single 11.5 11 115.597 5.74 -0.143 0.357 -0.071 11.25 0.5 25 14 42 10 sing single HP j 11.5 11.5 115.392 5.515 -0.123 -0.123 -0.061 11.5 0 27 14 42 8 sing single CAP NP 12 12 115.269 5.638 -0.369 -0.369 -0.185 12 0 28 14 42 12 BUCC single HP HP 18 18 118.18 8.262 -0.082 -0.082 -0.041 18 0 30 15 53 24 sing single HP HP 14.5 13.5 118.2 8.426 -0.226 0.774 -0.113 14 1 32 15 53 20 sing single HP HP 16.5 16 117.503 8.2 -0.697 -0.197 -0.349 16.25 0.5 34 15 53 22 sing single HP HP 20 19.25 1110.189 9.912 0.277 1.027 0.139 19.625 0.75 35 14 42 14 DB single HP HP 12.25 12.25 116.765 7.114 -0.349 -0.349 -0.175 12.25 0 36 14 42 14 PALAT single HP HP 16.5 16.25 113.67 4.059 -0.389 -0.139 -0.195 16.375 0.25 37 14 42 23 sing single HP HP 16.5 16 117.114 7.36 -0.246 0.254 -0.123 16.25 0.5 38 14 42 22 sing single HP 21.75 21.75 1110.168 9.758 0.41 0.41 0.205 21.75 0 39 14 42 21 sing single HP HP 20 19.75 117.688 8.077 -0.389 -0.139 -0.195 19.875 0.25 42 14 42 23 sing single HP HP 15 14.5 117.606 7.545 0.061 0.561 0.031 14.75 0.5 43 14 42 24 sing single HP HP 16 15.75 117.237 6.683 0.554 0.804 0.277 15.875 0.25 44 14 42 26 sing single HP HP 16 15.75 1 1 8.282 8.098 0.184 0.434 0.092 15.875 0.25 45 14 42 27 sing single HP HP 21 21 1 1 6.376 6.376 0 0 0.000 21 0 46 14 42 28 sing single HP HP 20.5 20.5 1 1 9.533 9.123 0.41 0.41 0.205 20.5 0 47 15 53 25 sing single HP HP 16 15.75 1 1 6.355 6.294 0.061 0.311 0.031 15.875 0.25 48 15 53 28 sing single HP HP 19 18 1 1 7.134 7.134 0 1 0.000 18.5 1 49 16 53 4 sing PALAT HP HP 17.25 16 1 1 8.938 9.492 -0.554 0.696 -0.277 16.625 1.25 50 16 53 5 PALAT single HP HP 16 15.25 1 1 6.847 7.155 -0.308 0.442 -0.154 15.625 0.75 51 17 39 15 PALAT single CAP PT 17 16.5 1 1 5.494 5.679 -0.185 0.315 -0.093 16.75 0.5 52 18 48 22 sing single HP HP 16.5 15.5 1 1 6.273 6.581 -0.308 0.692 -0.154 16 1 53 18 48 23 sing single HP HP 15.75 15.5 1 1 8.241 7.093 1.148 1.398 0.574 15.625 0.25 57 18 48 27 sing single HP HP 18.5 18.5 1 1 8.18 7.739 0.441 0.441 0.221 18.5 0 59 19 56 9 sing single HP HP 17 16.25 1 1 5.597 5.781 -0.184 0.566 -0.092 16.625 0.75 60 19 56 8 sing single HP HP 16 15.5 1 1 6.437 6.13 0.307 0.807 0.154 15.75 0.5 61 19 56 7 sing single HP HP 15.25 14.5 114.879 5.146 -0.267 0.483 -0.134 14.875 0.75 62 20 24 13 sing single APST NP 17.5 16.75 113.588 3.916 -0.328 0.422 -0.164 17.125 0.75 63 20 24 12 sing BUCC HP HP 18.25 18 118.323 8.549 -0.226 0.024 -0.113 18.125 0.25 64 20 24 11 sing single CAP NP 20.5 20 117.79 7.708 0.082 0.582 0.041 20.25 0.5 65 20 24 10 sing single HP HP 20.5 20.25 117.38 7.524 -0.144 0.106 -0.072 20.375 0.25 67 20 24 8 sing single HP NP 18.75 18.25 114.715 4.879 -0.164 0.336 -0.082 18.5 0.5 68 20 24 7 sing single HP HP 20 19.25 115.084 5.315 -0.231 0.519 -0.116 19.625 0.75 69 20 24 5 PALAT single HP HP 17 16.75 114.9 4.469 0.431 0.681 0.216 16.875 0.25 70 20 24 4 sing single HP HP 15.5 15.25 117.524 7.708 -0.184 0.066 -0.092 15.375 0.25 71 21 68 29 sing single HP HP 15.5 15.25 119.287 9.205 0.082 0.332 0.041 15.375 0.25 72 21 68 4 BUCC single HP HP 14 13.75 115.289 5.248 0.041 0.291 0.020 13.875 0.25 73 21 68 5 BUCC single HP HP 14.75 14.5 115.228 5.187 0.041 0.291 0.020 14.625 0.25 74 21 68 5 PALAT single HP HP 14.25 14 115.945 5.822 0.123 0.373 0.062 14.125 0.25 75 21 68 6 sing single HP HP 19.5 18.5 119.758 9.574 0.184 1.184 0.092 19 1 76 21 68 10 sing single HP HP 11.75 11 113.834 4.182 -0.348 0.402 -0.174 11.375 0.75 77 21 68 11 sing single HP HP 19 17.5 118.795 8.385 0.41 1.91 0.205 18.25 1.5 78 21 68 12 PALAT single HP HP 15.5 15.25 118.733 9.02 -0.287 -0.037 -0.144 15.375 0.25 80 22 42 5 BUCC single HP HP 16 15.5 116.909 6.929 -0.02 0.48 -0.010 15.75 0.5 81 22 42 5 PALAT single HP HP 15.75 15.5 1 1 6.581 6.622 -0.041 0.209 -0.020 15.625 0.25 82 23 50 10 sing single HP NP 15 15.5 1 1 4.715 4.818 -0.103 -0.603 -0.051 15.25 -0.5 83 23 50 7 sing single HP HP 18 17.25 1 1 7.483 7.503 -0.02 0.73 -0.010 17.625 0.75 84 22 42 6 sing single HP HP 21 20.5 1 1 3.998 4.059 -0.061 0.439 -0.031 20.75 0.5 85 22 42 7 sing single HP HP 15.5 15 1 1 9.779 9.943 -0.164 0.336 -0.082 15.25 0.5 86 22 42 8 sing single HP HP 15.5 15.25 1 1 8.959 9.02 -0.061 0.189 -0.031 15.375 0.25 87 24 67 11 sing single CAP NP 17 17 17 16.75 16.5 16.75 1 1 9.451 9.041 0.41 0.66 0.205 16.875 0.25 88 24 67 10 sing single CAP NP 15.25 15 15 14.75 14.75 14.5 1 1 6.437 6.765 -0.328 0.172 -0.164 15 0.5 89 24 67 9 sing single HP NP 17 17 17 16.5 16.5 16.5 1 1 6.95 7.155 -0.205 0.295 -0.103 16.75 0.5 90 24 67 8 sing single HP HP 14.75 14.75 14.75 14.5 14.5 14.5 1 1 5.105 5.187 -0.082 0.168 -0.041 14.625 0.25 91 23 50 28 sing single HP HP 18.75 19 18.75 18.25 18.25 18.25 1 1 8.61 8.877 -0.267 0.233 -0.134 18.5 0.5 92 23 50 27 sing single HP HP 17.25 17.25 17.25 16.5 16.5 16.5 1 1 4.756 5.617 -0.861 -0.111 -0.431 16.875 0.75 93 23 50 22 sing single HP HP 18.5 18.75 18.5 18.5 18.5 18.5 1 1 7.626 6.991 0.635 0.635 0.318 18.5 0 94 22 42 9 sing single HP HP 15.25 15.25 15.25 14.5 14.5 14.5 1 1 4.9 5.556 -0.656 0.094 -0.328 14.875 0.75 95 22 42 10 sing single HP HP 15.5 15.5 15.5 15.25 15.25 15.25 115.597 5.72 -0.123 0.127 -0.061 15.375 0.25
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