Chelating agents: Their effect on the permeability of root canal dentin J. G. Fraser, M.D.S.,” a.?ld A. J. La.ws, N.D.S., P.R.A.C.D.X.,** Va.mouver, B. C., Canada,, atld Duxediq New Zenlamd DEPARTMENT
OF RESTORATIVE DENTISTRY,
UNIVERSITY
0~ BRITISH
COLUBIBIA,
ANDDEPARTMENTOFPERIODO~TOLOGY,FACULTYOFDEII;TISTRY, OTAGOUNIVERSITY Chelating agents have been proposed for use in endodontics to increase the permeability of root canal dentin to antimicrobial medicaments placed in the canal. This study was undertaken to evaluate this propossl.
T
he chelating agent used in endodontics is ethylenediamine tetra-acetic acid (EDTA). It was first introduced into endodontics by iistby’ to soften root canal dentin. Some author&” have found that EDTA will increase the permeability of root canal dentin tubules to medicaments introduced into the root canal to reduce bacterial contamination. Marshall, Massler, and Dute’ studied the changes in root dentin permeabilit) after different endodontic procedures (mechanical reaming and the application of different medicaments) by isotope penetration. They found that EDTA produced a slight decrease in dentin permeability, as did reaming and filing with water irrigation. The alternate use of hydrogen peroxide and sodium hypochlorite solutions, however, produced a significant increase in dentin permcabilit! to the isotopes-more so than their individual use. In a similar experiment, using radioisotopes, Hampson and Atkinson 3 found that EDTA slightly increased the permeability of dentin. Stewart, Kapsimalas, and Kappaport described a preparation containing EDTA and urea peroxide in a. stable base of polyethylene glycol (Carbowax). This combination of EDTA and urea peroxide, they suggested, would aid a more rapid and complete enlargement of the root canal. In a dye-penetration study, they showed that this combination increased the permeabi1it.v of the * Assistant **Associate
534
Professor. Professor.
Volume 41 Number 4
Chelating
agents
535
dentinal tubules. The experimental and control roots in their study were not wholly comparable because a different irrigant was used in the experimental roots (sodium hypochlorite) as compared to the control roots (distilled water). According to Marshall and associates, sodium hypochlorite influenced the penetration of isotopes into the root canal dentin, especially in association with hydrogen peroxide, whereas the use of distilled water and mechanical reaming slightly decreased the penetration of the isotopes used. Similar effects might also have occurred in the dye penetration found by Stewart and associates. A comparison of the effects of acids, alkalis, and chelating agents upon dentin permeability was undertaken by Cohen, Stewart, and Laster.5 Solutions of 5 per cent sodium hypochlorite with a peroxide significantly increased dentin permeability in the middle and apical thirds of the roots. The preparation RCPrep,* when used alternately with 5 per cent sodium hypochlorite, altered dentin permeability in the middle and apical thirds of the root canal significantly more than any other solution they investigated, including EDTAC and the alternate use of urea peroxide and 5 per cent sodium hypochlorite. They stated that these findings substantiated those of Marshall and associates; however, the latter authors did not test any combination of EDTA and urea peroxide. Cohen and associates’ description of their method and table of results do not correlate. They stated that their findings were statistically evaluated but did not describe the tests used. The differences between RC-Prep and EDTA and RC-Prep and the alternate use of urea peroxide and 5 per cent sodium hypochlorite do not appear to be significant. The question as to whether EDTA, by itself or in combination with other materials, can alter dentin permeability from the root ca,nal surface appeared to be unanswered. The increased permeability after application of the EDTA preparation could be influenced by the solutions used to wash the material from the canal and the particular position studied within that canal. This study was undertaken to examine and compare the effect of three proprietary chelating agents on the permeability of root canal dentin. METHOD AND MATERIALS Three proprietary chelating agents were used : Decal,f Largal Ultra,$ and RC-Prep. Eighteen human upper anterior teeth, without carious lesions or restorations in the cervical third of the crown or in the root, were used. They had been stored in 10 per cent buffered neutral formalin solution from the time of extraction until use. The ages of the teeth were not known. The teeth were divided randomly into three groups of six, one group for each chelating agent. Because of possible variations in permeability between different teeth or between different roots of the same tooth, the control used was the opposite half of the same root. *A commercial preparation of the EDTA and urea peroxide combination Kapsimalas and Rappaport, manufactured by Medical Products Laboratories, Pa. tGlover Laboratories, Melbourne, Australia. tseptodent, Paris, France.
of Stewart, Philadelphia,
536
Fraser and Laws
EXPERIMENTAL (Labial1
Oral surg. April, 1976
CONTROL (Pal&d)
-
Fig. 1. The sectioned tooth showing areas read by planimeter. Fig. d. Reduced photograph illustrating horn the extent of dye penetration prior to planimeter reading. L, Labial experimental half; P, palntal control half.
was outlined
The teeth were split and backed with green wax, the experimental half was treated with the chelating agent for 15 minutes, and each half was washed with water, as described by Fraser. 0 Both halves were next immersed in 1 per cent phloxine dye for 40 minutes. It was considered possible that any excess dye remaining on each half after removal from the dye would continue to penetrate as the specimens were bench dried. To overcome this possible error, both sections were rinsed in a beaker of water for 5 seconds and any visible solution left on the surface was blown off with a chip blower. The sections bench dried for at least 30 minutes at a constant temperature (19 to 21° C.). A chip blower was used instead of compressed air because the latter was considered insufficiently powerful to alter the penetration of the dye. After drying, the backing wax was removed and the sections were attached together with sticky wax. The rejoined tooth was sectioned labiopalatally along the midline with an “NM” Slims disc under a jet of compressed air in an airrotor handpiece. A water spray was not used, as the dye is water soluble, but care was taken to ensure that minimal heat was produced. Each longitudinal section thus had a labial experimental half and a palatal control half (Fig. 1). These surfaces were smoothed lightly with a medium garnet sandpaper disk to remove small irregularities that remained from the sectioning. It was found difficult to section exactly through the root canal in the apical
Volume 41 Number 4
Chelating
agents
537
region. The section which showed the root canal more clearly was chosen for further study. The sections were photographed under standardized conditions and the image was enlarged 13 times. Only root dentin was examined for dye penetration. To ensure this, in each photograph a horizontal line was drawn from the labial and palatal amelocemental junctions to the root canal. The extent of dye penetration was outlined with contrasting ink and a fine nib. The cementodentinal junction and the root canal border were also outlined (Fig. 2). The apical root canal was lost in five of eighteen teeth, and at that point a horizontal line was drawn across the section. The areas of dye penetration were determined by using a planimeter in a standard surveying procedure. The method was as follows (Fig. 1) : The area of dye penetration in the root of the experimental half (area. a) was read twice and the average of the two readings calculated. The remaining root area of the experimental half (area b) was calculated by the same method. These two areas ((I and b) were then added together. The total area (a + b) was also read twice with the planimeter and the two readings were averaged. The two calculations for this area (a, + b by addition and a + b by measurement) were compared to ensure that there was little difference between them, otherwise the readings were repeated. The percentage of dye penetration was calculated using the readings of area a, and area (a + b) by addition. The three readings (a., b, and c1+ b by measuring) were used to assess the error or measurement. The same measurements and calculations were made for the control half (area c and d). The average error in measuring areas (I, b, c, and d in each tooth was found to be 4.63 sq. mm. (0.28 per cent). RESULTS
The percentages of dye penetration in the experimental and control halves and the differences between these percentages were calculated and are shown in Table I. In five of eighteen teeth, the sectioning did not pass through the apical portion of the root canal. These teeth are shown by an asterisk in Table I. In the remaining sections (thirteen of eighteen teeth), where a comparison could be made between the cervical, middle, and apical thirds, dye penetration was almost nonexistent in the apical region in comparison with the rest of the tooth. The column showing the intratooth differences shows that there was little apparent difference among the three agents, In an analysis of variance, no significant difference was found among the effects of the three agents (I? > 0.5). In every tooth there was a reduction in dye penetration in the experimental half when compared with the control half. The effect was common to all teeth. It was examined statistically by comparing the means of t,he intratooth differences with zero, using Student t tests. (A zero difference would have meant no reduction in dye penetration.) In each group there was a significant decrease in dye penetration in the experimental as compared to the control halves: RC-Prep (P < 0.001)) Largal Ultra (P < 0.001)) Decal (P < 0.01). The dye penetration in both the experimental and control halves in the group exposed to Largal Ultra is noticeably different from that in the other two groups.
53% Fraser and Laws Table I. Percentage of teeth Agent
RC-Prep
Largal Ultra
Decal
of dye penetrations Tooth
1
in experimental
Experimental
)
Control
and control
halves
Difference
:
32.1 14.8
62.0 16.0
-29.9 -01.2
::
22.6 52.1
18.6 63.3
-56.0 -11.2
i* Mean
29.3 52.0 33.8
-23.4 -15.0 - 17.5 -22.7 -12.7 -24.3 -30.6 -20.1 -21.32 -11.8
i? Mean 1
32.5
67.0 52.7 56.6 35.8 35.9 33.0 51.1 54.0 52.3 43.7 44.3
:* 4
41.0 34.9 44.3
54.2 51.3 59.0
- 19.3 -10.3 - 14.7
68.7 60.4 56.3
-15.2 -33.3
1*
2 3 4
:, 27.1 53.5 Mean 38.9 *Apical portion of the root canal lost in sectioning.
-22.78
-17.43
DISCUSSION The results showed that all three agents caused a significant reduction of dye penetration into the root canal dentin. This differs from the results of the dye-penetration study of Stewart, Kapsimalas, and Rappaport4 They found that an EDTA-urea peroxide combination (the same as RC-Prep) markedly increased dye penetration as shown by the difference between their control and experimental roots. The difference between their control and experimental roots could be seen only in a small illustration of two longitudinal sections, one an experimental root and the other a control root. No table of results was given. Cohen, Stewart, and Lasters used a dye penetration study to show that by alternating RC-Prep with 5 per cent sodium hypochlorite the permeability of the dentinal tubules was significantly increased in the apical and middle thirds of the root. The technique of their experiment was the same as that of Stewart and associates, incorporating the same variables, except for their method of assessing the degree of dye penetration. For this they used a Dentin Permeability Index introduced by Marshall, Massler, and Dute.2 This is a potential source of variation as it involves a decision by the investigator as to whether or not a certa.in degree of dye penetration should be counted. By using a planimeter, this decision was eliminated in this study. Marshall and associates showed a slight decrease in isotope penetration after reaming canals in association with EDTA for 5 minutes, whereas Dampson and Atkinson showed a slight increase in isotope penetration after enlarging the canals and then placing EDTA in them for 5 minutes. In the controls of both
Volume 41 Number 4
Chelatiny
aye&~
539
studies the pulp tissue had been removed by barbed broaches, but the canals were not mechanically enlarged. Enlarging the canal in the experimental half would not only provide a greater root canal surface to react with EDTA but would also expose a dentin wall which must be different from one which has not been filed. This could conceivably alter surface tension or capillarity, both of which might have altered the isotope penetration. These authors obtained their results by comparing different groups of teeth. Simpson7 demonstrated that tooth-to-tooth variability within an experimental group could influence results. He considered that, unless the control was within the same tooth, comparison between different groups should be interpreted with caution. A definite variation in the degree of dye penetration was also noted between the groups of teeth in this present study, showing that definite tooth-to-tooth variations exist, but since the control or untreated portion was within the same tooth this factor should not have affected these results. Gutierriez and Garcia8 found that heavy crystalline deposits remained within canal irregularities following reaming and filing and use of EDTA. They suggest that these deposits were caused by precipitation of EDTA as a result of oversaturation in the canal. If precipitation occurred in the canal, it could occur in the pulpal openings of the dentinal tubules. This is a possible reason for the lowered dye penetration found in the experimental halves of this study. Possibly only partial occlusion by a Ca-EDTA sludge occurred, stopping the larger dye molecule used in this study to a greater extent than the smaller ions used in the isotope studies of Marshall and associates and Hampson and Atkinson. Electrolytic demineralization of dentin (in which calcium ions are withdrawn) causes a distortion of the organic framework of the dentin, so much so that this technique is not of value in preparing histologic demineralized sections of dentin. Possibly EDTA’s action causes a similar collapse, resulting in decreased dye penetration. a It is questionable how closely the results of an in vitro study showing variation in dentinal permeability can be applied to an in viva situation. As the experiment and control in this study were within the same root, it is considered that this finding of reduced dye penetration may be cautiously applied to an in vivo situation. SUMMARY
An in vitro assessment was made of the ability of three chelating agents used in endodontics to alter the dye penetration of dentinal tubules from the root canal surface. The experiment and control for this study were within the same root. It was found that all three agents significantly reduced the dye penetration into dentin, but that there was no difference among the agents in the degree of reduction of dye penetration. The authors would like to acknowledge the assistance of the Surveying Department of Otago University, New Zealand, with the planimeter readings and the assistance of Mr. D. H. McClymont (Preventive Dentistry Department) and Mr. G. S. Spears (Preventive Medicine
540
Fraser and Laws
Department), Otago the earlier study.
University,
New Zealand,
for their
help with
the statistics
of this and
REFERENCES
1. iistby, B. N.: Chelation in Root Canal Therapy. Ethylenediamine Tetra-acetic Acid for Cleansing and Widening of R.oot Canals, Ondontol. Tidskr. 65: 3-11, 1957. Treatments on 2. Marshall, F. J., Massler, M., and Dute, H. L.: Effects of Endodontic Permeability of Root Dentin, ORAL SURG.13: 208-223, 1960. 3. Hampson, E. L., and Atkinson, A. M.: The Relation Between Drugs Used in Root Canal Theranv and the Permeabilitv of the Dentine. Br. Dent. J. 116: 546-550. 1964. 4. Stewa;:, G. G., Kapsimalas,” P., and Rappaport, H. : EDTA and Urea Peroxide for Root Canal Preparation, J. Am. Dent. Assoc. 78: 335338, 1969. 5. Cohen. S..‘Stemart. G. G.. and Laster. L. L.: The Effects of Acids. Alkalies. and Chelating ' Agents on Dentin Permeability, ORAL'SURG.29: 631-634, 1970. 6. Fraser. J. G.: Chelating Agents: Their Softening II Effect on Root Canal Dentin, ORAL
SURG.i7: 803~811,1974.-
-
7. Simpson, E. F.: Leakage of Phloxine Dye Around Class V Silver Amalgam Restorations, M.D.S. Thesis, University of Otago, 1967. 8. Gutierrez, J. H., and Garcia, J.: Microscopic and Macroscopic Investigation on Results of Mechanical Preparation of Root Canals, ORAL SURG.25: 108-116, 1968. Reprint requests to: J. G. Fraser, M.D.S. Department of Restorative Dentistry University of British Columbia Vancouver, B.C., Canada
OF RESTORATIVE DENTISTRY,
UNIVERSITY
0~ BRITISH
COLUBIBIA,
ANDDEPARTMENTOFPERIODO~TOLOGY,FACULTYOFDEII;TISTRY, OTAGOUNIVERSITY Chelating agents have been proposed for use in endodontics to increase the permeability of root canal dentin to antimicrobial medicaments placed in the canal. This study was undertaken to evaluate this propossl.
T
he chelating agent used in endodontics is ethylenediamine tetra-acetic acid (EDTA). It was first introduced into endodontics by iistby’ to soften root canal dentin. Some author&” have found that EDTA will increase the permeability of root canal dentin tubules to medicaments introduced into the root canal to reduce bacterial contamination. Marshall, Massler, and Dute’ studied the changes in root dentin permeabilit) after different endodontic procedures (mechanical reaming and the application of different medicaments) by isotope penetration. They found that EDTA produced a slight decrease in dentin permeability, as did reaming and filing with water irrigation. The alternate use of hydrogen peroxide and sodium hypochlorite solutions, however, produced a significant increase in dentin permcabilit! to the isotopes-more so than their individual use. In a similar experiment, using radioisotopes, Hampson and Atkinson 3 found that EDTA slightly increased the permeability of dentin. Stewart, Kapsimalas, and Kappaport described a preparation containing EDTA and urea peroxide in a. stable base of polyethylene glycol (Carbowax). This combination of EDTA and urea peroxide, they suggested, would aid a more rapid and complete enlargement of the root canal. In a dye-penetration study, they showed that this combination increased the permeabi1it.v of the * Assistant **Associate
534
Professor. Professor.
Volume 41 Number 4
Chelating
agents
535
dentinal tubules. The experimental and control roots in their study were not wholly comparable because a different irrigant was used in the experimental roots (sodium hypochlorite) as compared to the control roots (distilled water). According to Marshall and associates, sodium hypochlorite influenced the penetration of isotopes into the root canal dentin, especially in association with hydrogen peroxide, whereas the use of distilled water and mechanical reaming slightly decreased the penetration of the isotopes used. Similar effects might also have occurred in the dye penetration found by Stewart and associates. A comparison of the effects of acids, alkalis, and chelating agents upon dentin permeability was undertaken by Cohen, Stewart, and Laster.5 Solutions of 5 per cent sodium hypochlorite with a peroxide significantly increased dentin permeability in the middle and apical thirds of the roots. The preparation RCPrep,* when used alternately with 5 per cent sodium hypochlorite, altered dentin permeability in the middle and apical thirds of the root canal significantly more than any other solution they investigated, including EDTAC and the alternate use of urea peroxide and 5 per cent sodium hypochlorite. They stated that these findings substantiated those of Marshall and associates; however, the latter authors did not test any combination of EDTA and urea peroxide. Cohen and associates’ description of their method and table of results do not correlate. They stated that their findings were statistically evaluated but did not describe the tests used. The differences between RC-Prep and EDTA and RC-Prep and the alternate use of urea peroxide and 5 per cent sodium hypochlorite do not appear to be significant. The question as to whether EDTA, by itself or in combination with other materials, can alter dentin permeability from the root ca,nal surface appeared to be unanswered. The increased permeability after application of the EDTA preparation could be influenced by the solutions used to wash the material from the canal and the particular position studied within that canal. This study was undertaken to examine and compare the effect of three proprietary chelating agents on the permeability of root canal dentin. METHOD AND MATERIALS Three proprietary chelating agents were used : Decal,f Largal Ultra,$ and RC-Prep. Eighteen human upper anterior teeth, without carious lesions or restorations in the cervical third of the crown or in the root, were used. They had been stored in 10 per cent buffered neutral formalin solution from the time of extraction until use. The ages of the teeth were not known. The teeth were divided randomly into three groups of six, one group for each chelating agent. Because of possible variations in permeability between different teeth or between different roots of the same tooth, the control used was the opposite half of the same root. *A commercial preparation of the EDTA and urea peroxide combination Kapsimalas and Rappaport, manufactured by Medical Products Laboratories, Pa. tGlover Laboratories, Melbourne, Australia. tseptodent, Paris, France.
of Stewart, Philadelphia,
536
Fraser and Laws
EXPERIMENTAL (Labial1
Oral surg. April, 1976
CONTROL (Pal&d)
-
Fig. 1. The sectioned tooth showing areas read by planimeter. Fig. d. Reduced photograph illustrating horn the extent of dye penetration prior to planimeter reading. L, Labial experimental half; P, palntal control half.
was outlined
The teeth were split and backed with green wax, the experimental half was treated with the chelating agent for 15 minutes, and each half was washed with water, as described by Fraser. 0 Both halves were next immersed in 1 per cent phloxine dye for 40 minutes. It was considered possible that any excess dye remaining on each half after removal from the dye would continue to penetrate as the specimens were bench dried. To overcome this possible error, both sections were rinsed in a beaker of water for 5 seconds and any visible solution left on the surface was blown off with a chip blower. The sections bench dried for at least 30 minutes at a constant temperature (19 to 21° C.). A chip blower was used instead of compressed air because the latter was considered insufficiently powerful to alter the penetration of the dye. After drying, the backing wax was removed and the sections were attached together with sticky wax. The rejoined tooth was sectioned labiopalatally along the midline with an “NM” Slims disc under a jet of compressed air in an airrotor handpiece. A water spray was not used, as the dye is water soluble, but care was taken to ensure that minimal heat was produced. Each longitudinal section thus had a labial experimental half and a palatal control half (Fig. 1). These surfaces were smoothed lightly with a medium garnet sandpaper disk to remove small irregularities that remained from the sectioning. It was found difficult to section exactly through the root canal in the apical
Volume 41 Number 4
Chelating
agents
537
region. The section which showed the root canal more clearly was chosen for further study. The sections were photographed under standardized conditions and the image was enlarged 13 times. Only root dentin was examined for dye penetration. To ensure this, in each photograph a horizontal line was drawn from the labial and palatal amelocemental junctions to the root canal. The extent of dye penetration was outlined with contrasting ink and a fine nib. The cementodentinal junction and the root canal border were also outlined (Fig. 2). The apical root canal was lost in five of eighteen teeth, and at that point a horizontal line was drawn across the section. The areas of dye penetration were determined by using a planimeter in a standard surveying procedure. The method was as follows (Fig. 1) : The area of dye penetration in the root of the experimental half (area. a) was read twice and the average of the two readings calculated. The remaining root area of the experimental half (area b) was calculated by the same method. These two areas ((I and b) were then added together. The total area (a + b) was also read twice with the planimeter and the two readings were averaged. The two calculations for this area (a, + b by addition and a + b by measurement) were compared to ensure that there was little difference between them, otherwise the readings were repeated. The percentage of dye penetration was calculated using the readings of area a, and area (a + b) by addition. The three readings (a., b, and c1+ b by measuring) were used to assess the error or measurement. The same measurements and calculations were made for the control half (area c and d). The average error in measuring areas (I, b, c, and d in each tooth was found to be 4.63 sq. mm. (0.28 per cent). RESULTS
The percentages of dye penetration in the experimental and control halves and the differences between these percentages were calculated and are shown in Table I. In five of eighteen teeth, the sectioning did not pass through the apical portion of the root canal. These teeth are shown by an asterisk in Table I. In the remaining sections (thirteen of eighteen teeth), where a comparison could be made between the cervical, middle, and apical thirds, dye penetration was almost nonexistent in the apical region in comparison with the rest of the tooth. The column showing the intratooth differences shows that there was little apparent difference among the three agents, In an analysis of variance, no significant difference was found among the effects of the three agents (I? > 0.5). In every tooth there was a reduction in dye penetration in the experimental half when compared with the control half. The effect was common to all teeth. It was examined statistically by comparing the means of t,he intratooth differences with zero, using Student t tests. (A zero difference would have meant no reduction in dye penetration.) In each group there was a significant decrease in dye penetration in the experimental as compared to the control halves: RC-Prep (P < 0.001)) Largal Ultra (P < 0.001)) Decal (P < 0.01). The dye penetration in both the experimental and control halves in the group exposed to Largal Ultra is noticeably different from that in the other two groups.
53% Fraser and Laws Table I. Percentage of teeth Agent
RC-Prep
Largal Ultra
Decal
of dye penetrations Tooth
1
in experimental
Experimental
)
Control
and control
halves
Difference
:
32.1 14.8
62.0 16.0
-29.9 -01.2
::
22.6 52.1
18.6 63.3
-56.0 -11.2
i* Mean
29.3 52.0 33.8
-23.4 -15.0 - 17.5 -22.7 -12.7 -24.3 -30.6 -20.1 -21.32 -11.8
i? Mean 1
32.5
67.0 52.7 56.6 35.8 35.9 33.0 51.1 54.0 52.3 43.7 44.3
:* 4
41.0 34.9 44.3
54.2 51.3 59.0
- 19.3 -10.3 - 14.7
68.7 60.4 56.3
-15.2 -33.3
1*
2 3 4
:, 27.1 53.5 Mean 38.9 *Apical portion of the root canal lost in sectioning.
-22.78
-17.43
DISCUSSION The results showed that all three agents caused a significant reduction of dye penetration into the root canal dentin. This differs from the results of the dye-penetration study of Stewart, Kapsimalas, and Rappaport4 They found that an EDTA-urea peroxide combination (the same as RC-Prep) markedly increased dye penetration as shown by the difference between their control and experimental roots. The difference between their control and experimental roots could be seen only in a small illustration of two longitudinal sections, one an experimental root and the other a control root. No table of results was given. Cohen, Stewart, and Lasters used a dye penetration study to show that by alternating RC-Prep with 5 per cent sodium hypochlorite the permeability of the dentinal tubules was significantly increased in the apical and middle thirds of the root. The technique of their experiment was the same as that of Stewart and associates, incorporating the same variables, except for their method of assessing the degree of dye penetration. For this they used a Dentin Permeability Index introduced by Marshall, Massler, and Dute.2 This is a potential source of variation as it involves a decision by the investigator as to whether or not a certa.in degree of dye penetration should be counted. By using a planimeter, this decision was eliminated in this study. Marshall and associates showed a slight decrease in isotope penetration after reaming canals in association with EDTA for 5 minutes, whereas Dampson and Atkinson showed a slight increase in isotope penetration after enlarging the canals and then placing EDTA in them for 5 minutes. In the controls of both
Volume 41 Number 4
Chelatiny
aye&~
539
studies the pulp tissue had been removed by barbed broaches, but the canals were not mechanically enlarged. Enlarging the canal in the experimental half would not only provide a greater root canal surface to react with EDTA but would also expose a dentin wall which must be different from one which has not been filed. This could conceivably alter surface tension or capillarity, both of which might have altered the isotope penetration. These authors obtained their results by comparing different groups of teeth. Simpson7 demonstrated that tooth-to-tooth variability within an experimental group could influence results. He considered that, unless the control was within the same tooth, comparison between different groups should be interpreted with caution. A definite variation in the degree of dye penetration was also noted between the groups of teeth in this present study, showing that definite tooth-to-tooth variations exist, but since the control or untreated portion was within the same tooth this factor should not have affected these results. Gutierriez and Garcia8 found that heavy crystalline deposits remained within canal irregularities following reaming and filing and use of EDTA. They suggest that these deposits were caused by precipitation of EDTA as a result of oversaturation in the canal. If precipitation occurred in the canal, it could occur in the pulpal openings of the dentinal tubules. This is a possible reason for the lowered dye penetration found in the experimental halves of this study. Possibly only partial occlusion by a Ca-EDTA sludge occurred, stopping the larger dye molecule used in this study to a greater extent than the smaller ions used in the isotope studies of Marshall and associates and Hampson and Atkinson. Electrolytic demineralization of dentin (in which calcium ions are withdrawn) causes a distortion of the organic framework of the dentin, so much so that this technique is not of value in preparing histologic demineralized sections of dentin. Possibly EDTA’s action causes a similar collapse, resulting in decreased dye penetration. a It is questionable how closely the results of an in vitro study showing variation in dentinal permeability can be applied to an in viva situation. As the experiment and control in this study were within the same root, it is considered that this finding of reduced dye penetration may be cautiously applied to an in vivo situation. SUMMARY
An in vitro assessment was made of the ability of three chelating agents used in endodontics to alter the dye penetration of dentinal tubules from the root canal surface. The experiment and control for this study were within the same root. It was found that all three agents significantly reduced the dye penetration into dentin, but that there was no difference among the agents in the degree of reduction of dye penetration. The authors would like to acknowledge the assistance of the Surveying Department of Otago University, New Zealand, with the planimeter readings and the assistance of Mr. D. H. McClymont (Preventive Dentistry Department) and Mr. G. S. Spears (Preventive Medicine
540
Fraser and Laws
Department), Otago the earlier study.
University,
New Zealand,
for their
help with
the statistics
of this and
REFERENCES
1. iistby, B. N.: Chelation in Root Canal Therapy. Ethylenediamine Tetra-acetic Acid for Cleansing and Widening of R.oot Canals, Ondontol. Tidskr. 65: 3-11, 1957. Treatments on 2. Marshall, F. J., Massler, M., and Dute, H. L.: Effects of Endodontic Permeability of Root Dentin, ORAL SURG.13: 208-223, 1960. 3. Hampson, E. L., and Atkinson, A. M.: The Relation Between Drugs Used in Root Canal Theranv and the Permeabilitv of the Dentine. Br. Dent. J. 116: 546-550. 1964. 4. Stewa;:, G. G., Kapsimalas,” P., and Rappaport, H. : EDTA and Urea Peroxide for Root Canal Preparation, J. Am. Dent. Assoc. 78: 335338, 1969. 5. Cohen. S..‘Stemart. G. G.. and Laster. L. L.: The Effects of Acids. Alkalies. and Chelating ' Agents on Dentin Permeability, ORAL'SURG.29: 631-634, 1970. 6. Fraser. J. G.: Chelating Agents: Their Softening II Effect on Root Canal Dentin, ORAL
SURG.i7: 803~811,1974.-
-
7. Simpson, E. F.: Leakage of Phloxine Dye Around Class V Silver Amalgam Restorations, M.D.S. Thesis, University of Otago, 1967. 8. Gutierrez, J. H., and Garcia, J.: Microscopic and Macroscopic Investigation on Results of Mechanical Preparation of Root Canals, ORAL SURG.25: 108-116, 1968. Reprint requests to: J. G. Fraser, M.D.S. Department of Restorative Dentistry University of British Columbia Vancouver, B.C., Canada
