University of Connecticut OpenCommons@UConn
SoDM Masters Theses School of Dental Medicine
June 2006 Retreatment of Resorcinol-Formalin Past Root Fillings : Studies on Dissolving Properties of Various Solutions. Stanislav Aleksandrovich Moline
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Recommended Citation Moline, Stanislav Aleksandrovich, "Retreatment of Resorcinol-Formalin Past Root Fillings : Studies on Dissolving Properties of Various Solutions." (2006). SoDM Masters Theses. 1. https://opencommons.uconn.edu/sodm_masters/1 Retreatment of Resorcinol-Formalin Paste Root Fillings: Studies on Dissolving Properties of Various Solutions
Stanislav Aleksandrovich Moline
D.M.D., Tufts University, 2002
A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Dental Science At the University of Connecticut 2006 APPROVAL PAGE
Master of Dental Science Thesis
Retreatment of Resorcinol-Formalin Paste Root Fillings" Studies on Dissolving Properties of Various Solutions
Presented by
Stanislav Aleksandrovich Moline, D.M.D.
Major Advisor Reza B. Kazemi D.M.D.
Associate Advisor Kamran Safavi D.M.D., M.Ed.
Associate Advisor Liisa Kuhn Ph.D.
University of Connecticut 2006 DEDICATION
To My Wife Tatyana Moline
iii TABLE OF CONTENTS Page
Title Page
Approval Page ii
Dedication iii
Table of Contents iv
Acknowledgement
List of Tables vi
List of Graphs viii
List of SEM Images ix
Introduction Purpose
Null Hypothesis
Materials and Methods
Results 19
Discussion 45
Conclusion 53
References 55
iv Acknowledgement
I would like to specially thank you Dr. Reza B. Kazemi for being not just an adviser, but also a true mentor. He was very supportive and patience in guiding me through this project.
I warn to also thank Dr. Safavi, Dr. Kuhn, Dr. Zhu, and Dr. Jiang for their advice in this research. I appreciate help of Dr. Walsh and Mr. Tsimikas with statistics.
I thank my fellow residents for their help and support.
I thank you very much my wife Tatyana for her patience, encouragement, and love. List of Tables Page Table 1 Weight of samples and their distribution between solutions
at the start of pilot study la 6
Table 2 Results of pilot study l a 7
Table 3 Weight of samples and their distribution between solutions
at the start of pilot study lb 8
Table 4 Results of pilot study 1 b 9
Table 5 Results of combined pilot studies la and 1 b 10
Table 6 Weight of samples and their distribution between solutions
at the start of pilot study 2 11
Table 7 Results of pilot study 2 12
Table 8 Weight of resorcin-formalin paste samples and their distribution
between solutions at the start of main study part 1 15
Table 9 Weight of dentin samples and their distribution
between solutions at the start of main study part 2 17
Table 10 Results of main study part 1 at 20 minutes 19
Table 11 Results of main study part 1 at 3 hours 20
Table 12 Results of main study part 1 at 6 hours 21
Table 13 Results of main study part 1 at 12 hours 22
Table 14 Results of main study part 1 at 24 hours 23
Table 15 Results of main study part 1 at 7 days 24
vi Page
Table 16 Resorcinol-formalin paste samples means weights in mg 29
Table 17- Resorcinol-formalin paste samples means weights in percent 31
Table 18 Results of main study part 2 at 20 minutes 35
Table 19 Results of main study part 2 at 3 hours 35
Table 20- Results of main study part 2 at 6 hours 35
Table 21 Results of main study part 2 at 12 hours 35
Table 22 Results of main study part 2 at 24 hours 35
Table 23 Results of main study part 2 at 7 days 35
Table 24 Dentin samples means weights in mg 37
Table 25- Dentin samples means weights in percent 38
vii List of Graphs
Page
Graph 1. Weights change of resorcinol-formalin paste samples 30
Graph 2. Weights change of resorcinol-formalin paste samples in percent 32
Graph 3. Weights change of dentin samples 37
Graph 4. Weights change of dentin samples in percent 38
viii List of SEM Images
Page
Image 1. SEM Analysis of 'Control' group at start 40
Image 2. SEM Analysis of 'Control' group at 7 days 40
Image 3. SEM Analysis of 'Control at 37 C' group at start 41
Image 4. SEM Analysis of 'Control at 37 C' group at 7 days 41
Image 5. SEM Analysis of'5.25% NaOCl' group at start 42
Image 6. SEM Analysis of '5.25% NaOCl' group at 7 days 42
Image 7. SEM Analysis of '2.625% NaOCl' group at start 43
Image 8. SEM Analysis of '2.625% NaOCl' group at 7 days 43
Image 9. SEM Analysis of '37% phosphoric acid' group at start 44
Image 10. SEM Analysis of '37% phosphoric acid' group at 7 days 44
ix
INTRODUCTION
Resorcinol-formalin root filling material has been used in many countries of Europe and
Asia, particularly in former USSR, Poland, Czech Republic, France, China, India (1), and probably other Asian countries. The main components of the paste are resorcinol and formaldehyde mixed with sodium hydroxide for hardening (1,2). The resin mixtures and placement techniques vary depending on the initial pulp vitality, canal anatomy, desired number of visits, etc. (1,2)
In general, using different methods and techniques of root canal treatment success is reported at 91% success (combined teeth with vital or non-vital pulp) (4), 62.1%-96.1% success (stratified by presence of lesion and bacteriae) (5), and 84%-98% (depending on initial conditions such as number of roots, vitality, presence of radiolucency, etc.) (6).
The success rate has been recorded based on the following various factors" presence of periapical lesion, pulp vitality, oral flora contamination, calcification, resorption, perforations, transportations, broken instruments, obturation material, etc. (2-6, 88, 91- 98).
Studies have shown mixed results of the treatment prognosis of cases obturated with the resorcinol-formalin root canal paste (1-3). Wu et al. (1) report 82.05% success rate.
However, in their study they refer to success as reduction of a lesion up to the complete resolution, but the results are not stratified based on the precondition of the teeth, including vitality or presence and size of periapical lesions. The findings of Gound et al. (3) reveal that on pre-retreatment evaluation; 22 teeth (24%) obturated with resorcinol- formalin presemed with clinical symptoms and 29 teeth (31%) had periapical radiolucency. Of total, 5% of the canals were completely filled and more then 50% had
'less then half of the canal(s) obturated'.
Retreatment of root-canal systems filled with resorcinol-formalin paste is also shown to be complicated (2-3). Gound et al. (3) find that only 59% of retreatment cases were optimal. However, their finding is not based on long-term observation. In addition, the presence of certain hardeners such as sodium hydroxide can make retreatment more complicated (2).
Formaldehyde toxicity is reported. Spfingberg L (12) reports that formaldehyde containing pastes 'in contact with vital tissue produced extensive damage in the form of necrosis'. Huang et al. (13) show cytotoxicity and 'persistent induction of c-jun and c-fos protooncogenes by formaldehyde-releasing root-canal sealers'. Negm et al. (14,15) assess a root canal filling material, which contains formaldehyde derivatives. When 'forced beyond the apex, in the majority of patients caused persistent pain and swelling. The periapical tissues were unable to absorb the excess material and had to be removed surgically'.
Negm at al. (14) point that 'this reaction increased with time and persisted throughout the period of the study with no signs of absorption of the material.' The reaction to formaldehyde is in contrast to silver amalgam, which causes inflammation until it sets (14). However, when formaldehyde is released temporarily as a by-product of setting reaction, the damage is also transient (16,17).
Due to need for retreatment of majority of root canals obturated with resorcin-formalin, and complexities to dissolve and remove the hardened resorcin-formalin, several solvents to dissolve resorcinol-formalin paste have been studied. Vranas et al. (8) examine four solutions: 0.9% sodium chloride, 5.25% sodium hypochlorite, chloroform, and Endosolv
R (R). The study shows that 'both sodium chloride and sodium hypochlorite exhibit a significant softening effect within 2 min; however, the paste used for the root canal obturation had no sodium hydroxide that is normally added for hardening of the paste (2).
Gambrel et al. (7) study six endodontic solutions on resorcinol paste containing sodium hydroxide" 0.9% sodium chloride, 5.25% sodium hypochlorite, chloroform, Endosolv R
(R), and two more solutions of: 3% hydrogen peroxide and 70% isopropyl alcohol. They find that 'Endosolv R (R), had significantly greater penetration within the mass of material than 5.25% sodium hypochlorite and chloroform. However, this finding was not significantly better than the control'. In both studies, solutions are applied up to 20 minutes, which may not be enough. Septodont, manufacturer of Endosolv R (R), recommends a two-visit approach in addition to a single-visit one (9). PURPOSE
With an estimated 2.6 million people from the above listed countries immigrated to the
United States in the past 24+ years (10, 11), it is a major challenge in endodontic re- treatments of patients with failed root canal treated teeth obturated with the resorcin-
formalin paste. The purpose of this study is to assess dissolving properties of various
solutions applied for a prolonged period in order to retreat failed cases obturated with the resorcinol-formalin root filling paste.
NULL HYPOTHESIS
A solvent for hardener-containing resorcinol-formalin paste in clinical time frame is not identified. MATERIALS AND METHODS
Resodent (R) paste (VladMiVa, Belgorod, Russia) was used to make samples. The box with Resodent (R) contains a measuring spoon, instructions pamphlet, and three bottles: 1) treating liquid based on formaldehyde, 2) catalyst; liquid for hardening, and 3) powder based on resorcin and radiopaque filler (21). Resodent (R) was mixed as recommended by the manufacture: 1 drop of each liquid with 2 spoons of the powder (21). The formed dough was placed into Teflon tubules with a diameter of 1 mm and was left on bench for
24 hours to set as recommended by the manufacture. After the paste had been set, the tubules were cut into pieces of approximately 2mm each and the set-material was removed from them. Each piece was weighed by Acculab LA-60 (R) (Block Medical Inc.,
San Diego, CA), and weight was entered into Microsoft (R) Excel 2000 table. The samples were trimmed by sandpaper to bring their weights to closest weight calculated in the
Microsoft (R) Excel 2000 table (Microsoft Corp., Seattle, WA). Their set-weights were confirmed by Acculab LA-60 (R). Forty-one samples were chosen for pilot studies and a set of 160 samples was chosen for the main study. The samples were placed into individual 4-ml Wheaton (R) sample vials (Wheaton, Millville, NJ) with black screw caps in dark containers (22).
The pilot studies show that sodium hypochlorite dissolves the resorcinol-formalin paste in 24 hours regardless concentrations. It is more capable at full strength (5.25%), which effectively dissolves the samples at 6 hours. Other tested solutions showed mixed results and no conclusion can be drawn at this time.
13 Main study Part 1"
The samples of 7.2mg each were divided into 16 groups of 10 for immersion in 16 solutions of 1001al. The following 16 solutions were used (Table 8):
1. No solution as control
2. 5.25% sodium hypochlorite (NaOC1) 3. 2.625% sodium hypochlorite (NaOC1)
4. Dakin Solution (R) (w/0.5% NaOC1)
5. Solvadent (R)
6. Endosolv R (R)
7. 0.9% sodium chloride (Baxter Healthcare Corporation, Deerfield, IL)
8. Chloroform (Sultan Chemicals, Englewood, NJ)
9. 3% hydrogen peroxide (H202) (CVS, Woonsocket, RI)
10. 35% H202 as Superoxol (R) (Sultan Chemicals, Englewood, NJ) 11. Ethanol 200 proof (Pharmco, Brookfield, CT)
12. Cellosolve (Fluka Chemie, France)
13. 37% Phosphoric acid (3M ESPE, St. Paul, MN)
14. Eugenol (Fluka Chemie, Germany)
15. Butanone (Riedel-de Hahn, Germany)
16. 2% chlorhexidine gluconate (Vista Dental Products, Racine, WI)
14
Repeated-measures ANOVA (analysis of variances) tests at 99.67% confidence level
(a=0.0033) were used to assess change in weight, the dependent variable, overtime. Post- hoc tests were used to analyze differences between individual time periods. StatMost v
3.6 (Dataxiom Software Inc., Los Angeles, CA) and Microsoft (R) Excel 2000 were used
for statistics. Recommendations and advice were provided by Cemer for Biostatistics,
School of Medicine University of Connecticut Health Center (89, 90).
Main Study Part 2
Based on results of first part of the main study, three solutions were chosen for testing their impact on dentin:
5.25% sodium hypochlorite, 2.625% sodium hypochlorite, and 37% phosphoric acid.
Four single-rooted extracted human teeth, stored in 0.2% sodium azide solution, were used. After rinsing under running tap water for 30 minutes and decomamination in ionized water for one day, the teeth were decoronated l mm apical to CEJ using Buehler
(R) Isomet TM Low Speed Saw (Buehler, Lake Bluff, IL). The roots were further sectioned by Buehler (R) Isomet TM Low Speed Saw into dentin disks of 2 mm diameter. The detain disks were split by a mallet and a chisel into smaller pieces. Twenty-five of those dental pieces were trimmed by a diamond bur to form dentin samples with equal weight of
5.3mg as measured by Acculab LA-60 (R). The samples were placed into individual 4-ml
Wheaton (R) sample vials with black screw caps in dark containers.
16
Statistical Analysis
Repeated-measures ANOVA at 95% confidence level (a=0.05) were used to assess change in weight overtime. Post-hoc tests were used to analyze differences between four individual time periods. StatMost TM 3.6 and Microsoft (R) Excel 2000 were used for statistics. Recommendations and advice were provided by Center for Biostatistics, School of Medicine University of Connecticut Health Center. (89,90)
SEM Analysis
In addition to main study, SEM analysis of dentin samples of Main Study Part 2 was conducted. This was done in order to visualize possible effects of solutions on dentin.
18
Statistical Analysis
Of the Main Study Parts 1 & 2
There was no statistical significant differences between different extended times
in weight of samples in control group.
ANOVA tests showed statistically significant difference between time periods for
5.25% sodium hypochlorite group (p<0.0001). Tukey's post-hoc test showed that
the mean weight (2.3mg) at 6 hours became statistically significant different from
the mean weight at start time (7.2mg). There was statistical difference in the mean
weights between 3 hours (6.5mg) and 6 hours (2.3mg), 6 hours (2.3mg) and 12
hours (0.0mg). There was no statistical difference in the mean weights between
any other extended times, as it remained constant.
ANOVA tests showed statistically significant difference between time periods for
2.625% sodium hypochlorite group (p<0.0001). Tukey's post-hoc test showed
that the mean weight (1.4mg) at 24 hours became statistically significant different
from the mean weight at start time (7.2mg). There was statistical difference in the
mean weights between 12 hours (5.9mg) and 24 hours (1.4mg). There was no
statistical significant difference in the mean weights between 24 hours (1.4mg)
and 7 days (1.0mg).
ANOVA tests showed statistically significant difference between time periods for
Dakin Solution (R) (0.5% sodium hypochlorite) group (p<0.0001). Tukey's post-
25 hoc test showed that at 12 hours the mean weight (6.7mg) became statistically
significant differem from the mean weight at start time (7.2mg). There was
statistical difference in the mean weights between 12 hours (6.7rag) and 24 hours
(5.5mg), 24 hours (5.5mg) and 7 days (4.6mg).
ANOVA tests showed statistically no significant difference between time periods
for Solvadem (R) group (p=O. 1899).
ANOVA tests showed statistically no significant difference between time periods for Endosolv R (R) group (p=0.0697).
ANOVA tests showed statistically significant difference between time periods for
0.9% sodium chloride group (p<0.0001). Tukey's post-hoc test showed that at 6 hours the mean weight (7.0mg) became statistically significant different from the mean weight at start time (7.2mg). There was no statistical difference in the mean weights between further times, as means remained constant at 7.0mg.
ANOVA tests showed statistically significant difference between time periods for chloroform group (p<0.0001). Tukey's post-hoc test showed that at 12 hours increased the mean weight (7.5mg) became statistically significant different from the mean weight at start time (7.2mg). There was no statistical difference in the mean weights between further times, as means remained within a range of 7.5-
26 ANOVA tests showed statistically significant difference between time periods for
3% hydrogen peroxide group (p<0.0001). Tukey's post-hoc test showed that at 20
minutes increased the mean weight (7.4mg) became statistically significant
different from the mean weight at start time (7.2mg). There was no statistically
significant difference in the mean weights between further times, as means remained within a range of 7.4-7.5mg.
ANOVA tests showed statistically no significant difference between time periods for Superoxol (R) group (p=0.0147). There was a trend of increase in weights of samples followed by their decrease. Tukey's post-hoc test showed that at 20 minutes mean increased weight (7.7mg) became statistically significant different from the mean weight at start time (7.2mg), and there was statistical difference in the mean weights between 24 hours (7.8mg) and 7 days (7.2mg).
ANOVA tests showed statistically significant difference between time periods for ethanol 200 proof group (p<0.0001). Tukey's post-hoc test showed that at 3 hours the mean weight (7.0mg) became statistically significant different from the mean weight at start time (7.2rag). There was no statistical difference in the mean weights between further times, as means remained constant at 7.0rag.
ANOVA tests showed statistically no significant difference between time periods for cellosolve group (p=0.4338).
27 ANOVA tests showed statistically significant difference between time periods for
37% phosphoric acid group (p<0.0001). Tukey's post-hoc test showed that at 20 minutes the mean weight (6. lmg) became statistically significant different from the mean weight at start time (7.2mg). There was statistical difference in the mean weights between 20minutes (6.1mg) and 3 hours (5.7mg), 3 hours (5.7mg) and 6 hours (5.4mg). There was no statistical difference in the mean weights between different extended times, as means remained constantly at 5.4mg.
ANOVA tests showed statistically no significant difference between time periods for eugenol group (p=0.0664).
ANOVA tests showed statistically significant difference between time periods for butanone group (p<0.0001). Tukey's post-hoc test showed that at 12 hours the mean weight (7. l mg) became statistically significant different from the mean weight at start time (7.2mg); there was no statistical difference in the mean weights between further times, as means remained constant at 7. l mg.
ANOVA tests showed statistically no significant difference between time periods for 2% chlorhexidine group (p=0.0213).
28
All samples of resorcinol-formalin paste immersed in sodium hypochlorite were the only ones, which not only decreased in weight, but also disintegrated completely or partially, over period of time. Action of sodium hypochlorite was time and concentration dependent. Full strength sodium hypochlorite (5.25%) showed the trend of effect by 3 rd hour and had completely dissolved the samples by 12th hour. By 12th hour, half-strength sodium hypochlorite (2.625%) showed the trend of effect and completely dissolved 70% of samples by 24th hour. Dakin Solution (R), containing 0.5% sodium hypochlorite, showed the trend of effect by 12th hour, and by 7th day all samples lost an average of
36% of weight. There were, however, no samples completely dissolved at any time.
Chloroform showed no activity until 12th hour. At this measuring point, the weights of samples were found increased by average of 5% from the original. It was also noticeable that chloroform was evaporated at this measuring point. There was no significant weight change thereafter.
Hydrogen peroxide solutions caused a 3-7% increase in samples' weight by 20th minute with the mean weight of 7.4mg for 3% hydrogen peroxide and 7.7mg for Superoxol (R)
(35% hydrogen peroxide). By 24th hour, some samples in Superoxol (R) group reached the weight of 8.0mg. However, the average weight was not much different from the weight at 20 minutes: 7.5mg for 3% hydrogen peroxide and 7.8mg for Superoxol (R) (35% hydrogen peroxide). At the 7-day measuring point, there was no change for samples immersed in 3% hydrogen peroxide. However, Superoxol (R) group presented with two samples reached their weight to 8.0 mg, while most of other samples had their weight
33 decreased. By 7th day, two samples of Superoxol (R) group had their weights reduced to
3.8mg and 6.0mg respectively and showed signs of disintegration.
37% phosphoric acid caused significant weight loss of samples of resorcinol-formalin paste, with average loss exceeding 15% at 20 minutes. The reduction of weight continued ever since, but at a slower pace. At 6 hours the average weight was down more than 25% from original weight. However, there was no significant weight change after 6t hour.
Solvadem (R), Endosolv R (R), 0.9% sodium chloride, ethanol 200 proof, cellosolve, eugenol, butanone, 2% chlorhexidine, and control generally showed no significant effects on weight loss of samples over the period of times of the experiments.
34
There were no statistically significant differences between weights of samples over extended time periods in both control groups and both sodium hypochlorite groups of 5.25% and 2.625% concentrations.
ANOVA tests showed statistically significant difference between time periods for
37% phosphoric acid group (p<0.0001). Tukey's post-hoc test showed that at 20 minutes the mean weight (4.4mg) became statistically significant different from the mean weight at start time (5.3mg). There were statistically significant differences in the mean weights between 20 minutes (4.4mg) and 3 hours
(3.7mg); 3 hours (3.7rag) and 6 hours (3.2mg); 3 hours (3.7mg) and 7 days
(2.3mg).
36
DENTIN TESTING RESULTS
In tests of dentin, 37% phosphoric acid caused significant weight loss of detain samples, with average loss of 16% at 20 minutes. The weight reduction continued and by 7th day the average weight loss was 57% from the original weight. One dentin sample had a weight reduction down to 0.5mg (>90% loss).
Sodium hypochlorite and controls showed no significant effects on weight of dentin at any time.
SEM RESULTS (Pictures 1-1 O)
Analysis of samples in the group 'Control' shows presence of smear layer with no visible change in dentin structure. In the group 'Comrol at 37C ', there is visible smear layer and there are no detain structure changes. In the group '5.25% NaOCl', there is visible smear layer and there are no dentin structure changes. In the group '2.625% NaOCl', there are also no dentin structure changes. As for the group '37% Phosphoric acid', this is the only group with visible changes to dentin: with open dentinal tubules.
39 SEM Analysis (testing on dentin) 'Control'
Start Picture 1
SEM Analysis (testing on dentin) 'Control'
7 days There is presence of smear layer and there is no visible change in dentin structure Picture 2
4O SEM Analysis (testing on dentin) 'Control at 3 7 C'
Start Picture 3
SEM Analysis (testing on dentin) Gro 'Control at 37 C'
7 days There is presence of smear layer and there is no visible change in dentin structure Picture 4
41 SEM Analysis (testing on dentin) Gro '5.25% NaOCI'
Start Picture 5
SEM Analysis (testing on dentin) Gro ' 5.25% NaOCI'
7 days There is presence of smear layer and there is no visible change in dentin structure Picture 6
42 SEM Analysis (testing on dentin) '2.625% NaOCI'
Start Picture 7
SEM Analysis (testing on dentin) Gro- '2.625% NaOCI'
7 days There are no detain structure changes. Picture 8
43 SEM Analysis (testing on dentin) '37% Phosphoric Acid'
Starl Picture 9
SEM Analysis (testing on dentin) Gro '37% Phosphoric Acid'
7 days There are visible changes to dentin:open tubules. Picture 10
44 DISCUSSION
Recently published studies (7,8) have been performed in order to find a solvent for resorcinol-formalin paste. Although one study (7) showed that 'sodium chloride and sodium hypochlorite exhibit a significant softening effect on this root canal paste within 2 min,' this was not confirmed in subsequent study (8). It might be due to absence of sodium hydroxide, the hardening agent (2), in the first study. The combined results of both studies are thus inconclusive, which may also be attributed to very short application times of solvents on the resorcinol-formalin paste. I n both studies, solutions were applied up to 20 minutes. Septodont, manufacturer of Endosolv R (R), recommends a two-visit approach in addition to a single-visit one (9). VladMiVa, manufacturer of Solvadent (R), also recommends multi-visit approach (75).
In this study, the time periods were chosen based on the following:
20 minutes because it was final testing time in studies of Vranas et al. (7) and
Gambrel et al. (8);
3 hours, 6 hours, and 12 hours because in the pilot studies, these time periods
were found to show significant changes;
24 hours and 7 days because in the pilot studies, these time periods were found to
show significant changes, 'next day or some day later' is recommended by
solvents' manufactures (9,25), and they are clinically relevant.
45 In many studies, samples were tested against solutions while inside of the molds (7,22-
24). In this study, it was decided to remove samples out of Teflon covering in order to increase contact surface area to facilitate dissolving action.
The solutions for the study on resorcinol-formalin paste were selected for the following reasons"
'No solution' to be a negative control
5.25% sodium hypochlorite was used in studies of Vranas et al. (7) and Gambrel
et al. (8), where it shows some effect. Sodium hypochlorite showed to be effective
in the pilot studies as well;
2.625% sodium hypochlorite and Dakin Solution (R) (with 0.5% NaOC1) were
chosen to compare effect of lower concentrations of sodium hypochlorite on the
paste. These concentrations of sodium hypochlorite showed to be effective in the
pilot study 2;
Solvadent (R) and Endosolv R (R) are commercially available solvents for
resorcinol-formalin paste; Endosolv R (R) was also used in studies of Vranas et al.
(7) and Gambrel et al. (8);
0.9% sodium chloride and chloroform were used in studies of Vranas et al. (7)
and Gambrel et al. (8) as well;
3% hydrogen peroxide and Superoxol (R) (with 35% H202) were chosen to
compare effect of different concentration of hydrogen peroxide on the paste; 3%
hydrogen peroxide was also used in studies of Vranas et al. (7) and Gambrel et al. (8);
46 Ethanol 200-proof is a common solvem;
Cellosolve (R) is a solvent for oils, resins, waxes, and other compounds;
37% phosphoric acid is etching agem commonly used in demistry;
Eugenol is used as part of Intermediate Restorative Material (IRM);
Butanone is a solvem for lacquers, adhesives, rubber and rubber cement, paints, etc.(39)
2% chlorhexidine gluconate is an antiseptic that has demal application.
This study showed that sodium hypochlorite was most capable of dissolving resorcinol- formalin paste. Chlorine was discovered by Karl Wilhelm Scheele (1742-1786) of
Sweden. During experiment with black oxide of manganese, Scheele incidentally during the course of series of experimems discovered chlorine. (42, 43) In speaking on experiment: 'When marine (hydrochloric) acid stood over manganese in the cold it acquired a dark reddish-brown color. As manganese does not give any colorless solution without uniting with phlogiston [hydrogen], it follows that marine acid can dissolve it without this principle. But such a solution has a blue or red color. The color is here more brown than red, the reason being that the very finest portions of the manganese, which do not sink so easily, swim in the red solution; for without these fine particles the solution is red, and red mixed with black is brown. The manganese has here attached itself so loosely to acidum salis that the water can precipitate it, and this precipitate behaves like ordinary manganese. When, now, the mixture of manganese and spiritus salis was set to digest, there arose an effervescence and smell of aqua regis' (43).
The "effervescence" Scheele refers to was chlorine. He very soon noted the decolorizing or bleaching effects of this product, finding that it decolorized flowers, vegetables, and
47 many other substances (42). Although Scheele first pointed out the bleaching quality of his newly discovered gas, it was Claude-Louis Berthollet (1748-1822) of France, who, acting upon Scheele's discovery was led to suspect that this property might be turned to account in destroying the color of cloth. In 1785 he presented a paper before the
Academy of Sciences of Paris, in which he showed that bleaching by chlorine was entirely satisfactory, the color but not the substance of the cloth being affected. He found that the chlorine gas was soluble in water and could thus be made practically available for bleaching purposes (42). In 1789, potassium hypochlorite ('Eau de Javelle' for the name of chemical factory and French town Javel, which is now part of Paris) was prepared by passing chlorine gas through a water solution of potash (potassium carbonate); it was used to bleach cotton (44). In 1799, Charles Tennant (1768-1838) of Scotland developed, patented, and manufactured at Tennant. Knox & Co bleaching power Ca(C10)2 (chloride of lime) formed by action of chlorine on slaked lime (45,46). In 1820, Antoine Germaine
Labarraque (1777-1850) of France replaced potash liquor by the cheaper caustic soda liquor and obtained sodium hypochlorite solutions, which were called "Eau de
Labarraque" and used for disinfection (47, 48). Sodium hypochlorite has been used in medicine since Henry Drysdale Dakin (1880-1952) of England discovering the effect of buffered 0.5% sodium hypochlorite on infected tissues (27) and its interaction with blood serum (49). It is the amount of available chlorine, not the osmolarity, pH, or buffer capacity, which is responsible for the tissue-dissolving properties of sodium hypochlorite with chlorination and oxidation as main reactions (34,58,86,87). Grossman found sodium hypochlorite 'the most effective pulp tissue solvent', which 'dissolved pulp tissue in less than two hours, occasionally effecting complete solution in less then twenty minutes'
48 (62). Sodium hypochlorite is potem antibacterial agent (51,74). In this study, the action
of sodium hypochlorite was time and concentration dependent with 5.25% concentration
to be the most effective, which is inline with The (28), Hand et al. (29), Johnson et al.
(30), Baumgartner et al. (50), Nakamura et al. (52), Abou-Rass et al. (53), Shih et al,
(59), Trepagnier et al. (60), Harrison et al. (61), and Koskinen et al. (73). Higher
temperature increases dissolving action of sodium hypochlorite (52-54). Direct surface
contact is needed for sodium hypochlorite to act; narrow spaces reduce its effectiveness
(32,55-57). This study lasted one week and all solutions were either poured out of new
bottles or freshly prepared. Tissue dissolving activity of freshly prepared solutions of
5.25% sodium hypochlorite, 2.625% sodium hypochlorite, and 0.5% buffered with
NaHCO3 do not change during first week (30,33). At 0.5% concentration sodium hypochlorite still possesses antibacterial property (51), but does not dissolve vital tissue
(27). Austin et al. (72) note that fall in chlorine concemration of Dakin's hypochlorite
solution is more rapid in contact with necrotic than in contact with normal tissue. This is beneficial in wound cleansing, but may result in incomplete pulpal tissue removal (50).
McComb (57) points out that 1% and 2.5% sodium hypochlorite produce cleaner canals compare to water, but less then EDTA; however, there is no differemiation of effect between vital and non-vital teeth. Harrison JW (78) highly recommends usage of full strength 5.25% sodium hypochlorite for its superior antibacterial and tissue-dissolving properties compare to other solutions including diluted sodium hypochlorite. However,
5% sodium hypochlorite is highly toxic and irritating to tissue, while toxicity of 0.5% sodium hypochlorite is reduced (31). Pashley et al. (79) find 5% sodium hypochlorite 'a very caustic, nonspecific agent whose action is not limited to necrotic tissue'; they found
49 it to be cytotoxic to all but heavily keratinized epithelial cells because of 'very strong oxidizing effect'. Sodium hypochlorite is found cytotoxic to PDL cells at the concentrations of 0.025% or greater (80) and 5%-5.25% sodium hypochlorite is toxic to fibroblasts and lymphoblasts at dilution of 1:10000 or higher (81,82). Extruded solution of 3%-5.25% sodium hypochlorite behind the apex of a root canal causes immediate pain, and erythema or discoloration, edema, hematoma, possible anesthesia, paraesthesia, hypoesthesia, and infection can occur, which usually subside over two weeks to two months following palliative and antimicrobial treatments (63-68, 76-77). Mucosal scarring, tissue necrosis, occasional surgical intervention, and long-term paraesthesia are also reported (63-68, 76-77). Additionally, trismus and airway obstruction are possible when erroneously used for mandibular block anesthesia (69). Allergic reactions to sodium hypochlorite are reported (70-71). Beside symptoms reported with extruded sodium hypochlorite including difficulty breathing, hypotension, positive allergy skin test, and history of skin rash or sensitivity to householdcleaning agents (70-71).
Nevertheless, Harrison et al. (83) finds no difference in interappointment pain between
5.25% sodium hypochlorite and saline. Lamers et al. (84) report no statistically significant difference in inflammatory reaction, cementum and bone resorption between
1% sodium hypochlorite and controls. The et al. (85) discover no significant difference in the inflammatory response between sodium hypochlorite in the concentration range 2 to 8 percent and physiological saline solution. The findings of the present study suggested no significant changes in weight of dentin samples from application of sodium hypochlorite.
It is in contrast to Barbosa et al. (26), which reported 14% of weight loss of dry dentin in
24 hours. It is probably due to the fact that in Barbosa's study samples were dried for 12
5O hours before weighing, while in this study they were weighed almost immediately after taking out of sodium hypochlorite and drying with Kimwipes (R) EX-L for 5 seconds.
Therefore, it is possible that the samples retained some moisture. Nevertheless, Sim et al.
(25) show that the application of 5.25% NaOC1 for two hours reduced the elastic modulus and flexural strength of dentin, while White et al. (37) find that after five weeks of the application of sodium hypochlorite the fracture resistance of dentin decreased 59%.
Dogan et al. (35) show that 2.5% sodium hypochlorite alters the Ca/P ratio significantly when compared with the control group. Unexplained findings of Ari et al. (36) reveal that
2.5% sodium hypochlorite causes Ca and P levels of dentin to decrease after 15 minutes of treatment, but find that the application of 5.25% sodium hypochlorite after the same amount of time has no significant effect on Ca/P level when compared with the control group.
In the present study, 37% phosphoric acid caused decreasing weights of samples of resorcinol-formalin paste through the first 6 hours of application. In contrast, it had been dissolving dentin throughout the week. In an SEM study of the dentin samples exposed to phosphoric acid (38) the high magnifications revealed three distinct zones within the demineralized dentin layer: an upper porous zone of residual smear layer or denatured collagen, an intermediate area with randomly oriented collagen fibers, and a lower zone with a submicron hiatus, few collagen fibers, and scattered hydroxyapatite inclusions.'
Etched dentin surface appears smooth 'with wide, open funnel shaped dentinal tubules';
'the diameter of tubules being 3 to 5 gm compared with 1 to 2 gm normally, 'peritubular dentin nearest the surface was totally removed and intertubular surface covered by a film
51 consisting probably of organic substance including collagen'. (40, 41) SEM analysis in this study showed that 37% phosphoric acid caused opening of dentinal tubules in dentin.
Chloroform was unique in sense of the only solution evaporated despite tightened caps over vials within 12 hours. All dentin samples submersed in chloroform showed some increasing in weight.
Other solutions including Solvadent (R) and Endosolv R (R) showed no significant effect on resorcinol-formalin paste at any time. Gambrel et al. (7) notice that 'Endosolv R had significantly greater penetration than 5.25% sodium hypochlorite (p 0.0033) and chloroform (p=0.0018). However, it was not significantly better than the control (p
=0.0812). Early, Vranas et al. (8) showed that, at 2 min, sodium hypochlorite and sodium chloride had significantly greater penetration than the other groups, including Endosolv
R. Although both studies (7, 8) are conducted at the same institution, but they differ in methodology, including exposure of the resorcinol-formalin pastes to different solutions, presence and sources of the components (hand-made mixtures versus commercially available product), making it difficult to compare the results. In the present study, a commercially available product was used. Therefore, it is possible that difference in results is also attributed to difference in resorcin-formalin pastes.
The present study idemified sodium hypochlorite as the solvem of choice for resorcinol- formalin pastes. Future studies should concentrate on in-teeth evaluation of dissolving
52 ability of sodium hypochlorite on differem resorcinol-formalin pastes as well as re- evaluation of Superoxol (R) with larger sample size and longer time periods.
CONCLUSION
Sodium hypochlorite is most capable in dissolving resorcinol-formalin paste. Its action is concentration and time dependem. 5.25% sodium hypochlorite dissolved 100% of the samples in 12 hours, while 2.625% sodium hypochlorite dissolved 70% of samples in 24 hours. There was no weight change among dentin samples treated with sodium hypochlorite of different concentrations in the present study.
37% phosphoric acid decreased the weights of samples of resorcinol-formalin paste by
25% within 6 hours of application with no further change. However, it was able to dissolve the dentin samples throughout the week with an average of 68% weight loss of the dentin samples.
Chloroform did not dissolve the resorcinol-formalin paste; in contrary it caused the samples' weights to increase.
Hydrogen peroxide also increased samples' weights. Although, on the 7th day, Superoxol
(R) group presented with two samples, which had their weights reduced and showed signs of disintegration, but the results are inconclusive.
53 The Solvadent (R), Endosolv R (R), 0.9% sodium chloride, ethanol 200 proof, cellosolve, eugenol, butanone, 2% chlorhexidine, and control groups showed no significant effect on the resorcinol-formalin paste at any time.
Future studies should concentrate on in-teeth evaluation of dissolving ability of sodium hypochlorite on different resorcinol-formalin pastes as well as re-evaluation of Superoxol
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64