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Time-Dependent Effects of EDTA on Dentin Structures
JOURNAL OF ENDODONTICS Copyright © 2002 by The American Association of Endodontists
Printed in U.S.A. VOL. 28, NO. 1, JANUARY 2002
Time-Dependent Effects of EDTA on Dentin Structures Semra Çalt, DDS, PhD, and Ahmet Serper, DDS, PhD
The purpose of this study was to evaluate the effects of EDTA on smear layer removal and on the structure of dentin, after 1 and 10 min of application. Six extracted single-rooted teeth were instrumented to #60. Apical and coronal thirds of each root were removed, leaving a 5 mm middle third that was then cut longitudinally into two equal segments. Using 10 ml of 17% EDTA solution, halves belonging to the same root were irrigated for 1 and 10 min, respectively. All specimens were subjected to irrigation with 10 ml of 5% NaOCl. Then all the specimens were prepared for SEM evaluation. The results showed that 1 min EDTA irrigation is effective in removing the smear layer. However a 10-min application of EDTA caused excessive peritubular and intertubular dentinal erosion. Therefore we suggest that this procedure should not be prolonged >1 min during endodontic treatment.
MATERIALS AND METHODS Six extracted human permanent teeth with single canals were used in this study. The root canals were enlarged to the apical foramen with K-files to size 60. A standard flare was produced by the insertion of #2–#5 Gates- Glidden drills. Irrigation during cleaning and shaping was accomplished using a 5% NaOCl solution. After instrumentation apical and coronal thirds of each root were removed, leaving a 5 mm middle third that was then cut longitudinally into two equal segments. Using 10 ml of 17% EDTA solution (pH 7.4), halves belonging to the same root were irrigated for 1 and 10 min, respectively. All specimens were then subjected to irrigation with 10 ml of 5% NaOCl. After this procedure, the specimens were prepared for SEM (JEOL-SEM 6400) evaluation. Observations were made on halves obtained from the same root, and care was taken to compare the same relative surface regions of each half. RESULTS On specimens that were treated with 17% EDTA for 1 min, followed by 5% NaOCl, SEM examination showed that the smear layer was completely removed from the instrumented root surfaces, and dentinal tubules seemed to be open (Fig. 1). In 2 of 6
Disodium salt of EDTA is generally accepted as the most effective chelating agent with prominent lubricant properties and is widely used in endodontic therapy. It is used to enlarge root canals, remove the smear layer, and prepare the dentinal walls for better adhesion of filling materials (1–5). For effective removal of both the organic and inorganic components of the smear layer, irrigating root canals with 10 ml of 17% EDTA, followed by 10 ml of 5% NaOCl is recommended (6, 7). However there is no consensus on the duration of EDTA irrigation. EDTA has been reported to remove the smear layer in ⬍1 min if the fluid is able to reach the root canal wall surface (8), whereas another study suggested that the fluid should be kept in the root canal for at least 15 min to obtain the optimal result (9). Because EDTA solution has a strong demineralizing effect, it causes enlargement of the dentinal tubules, softening of the dentin, and denaturation of the collagen fibers (10). These effects may cause difficulty in adaptation of the root canal filling materials to the root canal wall. The purpose of this study was to evaluate the effects of EDTA on smear layer removal and on the structure of dentin after 1 and 10 min of applications.
FIG. 1. Effect of 17% EDTA for 1 min, followed by 5% NaOCl on the middle third of the root canal. The smear layer is completely removed and all of the tubule openings are clearly visible (⫻2500). 17
18
Çalt and Serper
FIG. 2. The same experimental procedure is applied as in Fig. 1. The smear layer is completely removed; all of the tubule openings are clearly visible, but slight erosive effects are observed on peritubular and intertubular dentin (⫻2500).
FIG. 3. Effect of 17% EDTA for 10 min, followed by 5% NaOCl on the middle third of the root canal. This specimen is the counterpart of the same tooth examined in Fig. 1. Excessive erosion of the intertubular and peritubular dentin is seen leading to conjugation of tubular apertures and widening of tubular diameters (⫻2500).
specimens, we observed a slight erosive effect of EDTA in peritubular and intertubular areas (Fig. 2). To investigate the effects of prolonged application of EDTA, the specimens were irrigated with 17% EDTA for 10 min, followed by 5% NaOCl. In these specimens we observed that the smear layer was completely removed; however excessive erosion of the intertubular and peritubular dentin was seen. This excessive erosion led to conjugation of tubular apertures and widening of tubular diameters (Fig. 3). In two specimens we observed that this erosive effect was in excess on the root dentinal surfaces, leading to enlargement of dentinal tubular openings and deterioration of the dentinal surface (Fig. 4). Ten-minute application of EDTA caused peritubular and intertubular erosion. Having been subjected to more erosion than the inside of the dentinal tubules, the diameter of the openings are greater than the tubule itself. This gives rise to the “wormhole” appearance as shown in Fig. 5. This erosion is extensive in some regions to the extent that the intertubular dentin completely dis-
Journal of Endodontics
FIG. 4. Effect of 17% EDTA for 10 min, followed by 5% NaOCl on the middle third of the root canal. This specimen is the counterpart of the same tooth examined in Fig. 2. The erosive effect is in excess on the root dentinal surfaces, leading to enlargement of dentinal tubular openings and deterioration of the dentinal surface (⫻2500).
FIG. 5. Effect of same treatment of EDTA as in Fig. 4. Diameters of tubular openings are larger than the tubules. This appearance resembles that of a “wormhole” (⫻4000).
appears between tubules, combining individual tubule openings in close proximity. Most specimens showed that after the 10 min treatment. Tubule opening diameters are almost doubled (some up to 4 m), compared with their counterparts subjected to the 1-min treatment. DISCUSSION EDTA is widely used as a chelator in endodontic therapy. A chelator reacts with calcium ions in hydroxyapatite crystals, removing calcium ions from the dentin. EDTA is used at various concentrations and combinations in root canal treatment. The efficiency of such agents depends on many factors, such as the root canal length, penetration depth of the material, hardness of the dentin, duration of application, the pH, and the concentration of materials (2, 11). For effective removal of both organic and inorganic components of the smear layer, it is generally recommended to use EDTA followed by NaOCl (6, 7, 12). Baumgartner and Mader (12)
Vol. 28, No. 1, January 2002
reported that the combination of EDTA and NaOCl caused a progressive dissolution of dentin at the expense of peritubular and intertubular areas, and they suggested that this effect may have resulted from the alternating action of NaOCl, which dissolved the organic component of the dentin, and EDTA, which demineralized the inorganic component. The erosive effects of EDTA has also been reported in other studies (10, 13). Peritubular dentin is highly mineralized and therefore harder than intertubular dentin. The hardness of peritubular dentin may provide added structural support for the intertubular dentin. Lower collagen content makes peritubular dentin more quickly dissolvable in acid than is intertubular dentin (14). It is widely recommended that, under clinical conditions, EDTA and NaOCl should be applied in 10 ml volume each; however there is no accepted duration for applications. Yamada et al. (6) reported a few seconds of EDTA administration is sufficient. In contrast, Goldberg and Spielberg (9) reported that the optimum working time for EDTAC is ⵒ15 min. Meryon et al. (15) reported that the smear layer was completely removed with 10% EDTA for 1 min, resulting in increased tubular orifice size. Cergneux et al. (13) also reported similar findings when 15% EDTA was applied in root canals for 4 min. In this study we compared the smear layer removal capability and the structural effects of EDTA on root dentin with respect to duration of application. Our results showed that EDTA followed by NaOCl completely removed the smear layer in 1 min. When EDTA is applied for 10 min, excessive erosive effects were observed with dissolution of peritubular and intertubular dentin. According to our findings, to inhibit the erosion on dentin, EDTA solution must not be applied for longer than 1 min. Kennedy et al. (16) reported that once the smear layer was removed using REDTA, dentinal tubule openings could be created more easily in younger teeth, compared with physiologically older teeth, especially in the more sclerotic middle and apical thirds. We found that a 10-min application of EDTA specimens showed noticeable differences in the degree of dentinal erosion. These differences may be explained by the variability of the calcification rates of root dentin. Although chronological age of the teeth specimens used in our study were not documented, our findings still suggest that, to minimize erosive effects, precautions must be
Effects of EDTA on Dentin
19
taken when EDTA is used on young patients, and the application time should be short as possible. Drs. Çalt and Serper are affiliated with the Department of Endodontics, Hacettepe University, Faculty of Dentistry, Ankara, Turkey. Address requests for reprints to Dr. Semra Çalt, Department of Endodontics, Hacettepe University, Faculty of Dentistry, Sihhiye (06100), Ankara, Turkey.
References 1. Ingle JI, Bakland LK, Peters DL, Buchanan LS, Mullaney TP. Endodontic Cavity Preparation. In: Ingle JI, Bakland LK, eds. Endodontics. 4th ed. Baltimore: Williams &Wilkins, 1994:180 – 4. 2. Sen BH, Wesselink PR, Türkün M. The smear layer: a phenomenon in root canal therapy. Int Endod J 1995;28:141– 8. 3. White RR, Goldman M, Lin PS. The influence of the smeared layer upon dentinal tubule penetration by plastic filling materials. J Endodon 1984;10: 558 – 62. 4. White RR, Goldman M, Lin PS. The influence of the smeared layer upon dentinal tubule penetration by endodontic filling materials. Part II. J Endodon 1987;13:369 –74. 5. Çalt S, Serper A. Dentinal tubule penetration of root canal sealers after root canal dressing with calcium hydroxide. J Endodon 1999;25:431–3. 6. Yamada RS, Armas A, Goldman M, Lin PS. A scanning electron microscopic comparison of a high volume final flush with several irrigating solutions. Part 3. J Endodon 1983;9:137– 42. 7. Goldman M, Goldman LB, Cavaleri R, Bogis J, Lin PS. The efficacy of several irrigating solutions for endodontics: a scanning electron microscopic study. Part 2. J Endodon 1982;8:487–92. 8. Spangberg LSW. Instruments, materials, and devices. In: Cohen S, Burns RC, eds. Pathways of the pulp .7th ed. St. Louis: Mosby, Inc., 1998:507. 9. Goldberg F, Spielberg C. The effect of EDTAC and the variation of its working time analyzed with scanning electron microscopy. Oral Surg 1982; 53:74 –7. 10. Garberoglio R, Becce C. Smear layer removal by root canal irrigants: a comparative scanning electron microscopic study. Oral Surg 1994;78:359 – 67. 11. Cury JA, Bragotto C, Valdrighi L. The demineralizing efficiency of EDTA solutions on dentin. Oral Surg 1981;52:446 – 8. 12. Baumgartner JC, Mader CL. A scanning electron microscopic evaluation of four root canal irrigation regimens. J Endodon 1987;13:147–57. 13. Cergneux M, Ciucchi B, Dietschi JM, Holz J. The influence of the smear layer on the sealing ability of canal obturation. Int Endod J 1987;20: 228 –32. 14. Trowbridge HO, Kim S. Pulp development, structure, and function. In: Cohen S, Burns RC, eds. Pathways of the pulp .7th ed. St. Louis: Mosby, Inc., 1998:391–3. 15. Meryon SD, Tobias RS, Jakeman KJ. Smear removal agents: a quantitative study in vivo and in vitro. J Prosthet Dent 1987;20:174 –9. 16. Kennedy WA, Walker WA, Gough RW. Smear layer removal effects on apical leakage. J Endodon 1986;12:21–7.
Printed in U.S.A. VOL. 28, NO. 1, JANUARY 2002
Time-Dependent Effects of EDTA on Dentin Structures Semra Çalt, DDS, PhD, and Ahmet Serper, DDS, PhD
The purpose of this study was to evaluate the effects of EDTA on smear layer removal and on the structure of dentin, after 1 and 10 min of application. Six extracted single-rooted teeth were instrumented to #60. Apical and coronal thirds of each root were removed, leaving a 5 mm middle third that was then cut longitudinally into two equal segments. Using 10 ml of 17% EDTA solution, halves belonging to the same root were irrigated for 1 and 10 min, respectively. All specimens were subjected to irrigation with 10 ml of 5% NaOCl. Then all the specimens were prepared for SEM evaluation. The results showed that 1 min EDTA irrigation is effective in removing the smear layer. However a 10-min application of EDTA caused excessive peritubular and intertubular dentinal erosion. Therefore we suggest that this procedure should not be prolonged >1 min during endodontic treatment.
MATERIALS AND METHODS Six extracted human permanent teeth with single canals were used in this study. The root canals were enlarged to the apical foramen with K-files to size 60. A standard flare was produced by the insertion of #2–#5 Gates- Glidden drills. Irrigation during cleaning and shaping was accomplished using a 5% NaOCl solution. After instrumentation apical and coronal thirds of each root were removed, leaving a 5 mm middle third that was then cut longitudinally into two equal segments. Using 10 ml of 17% EDTA solution (pH 7.4), halves belonging to the same root were irrigated for 1 and 10 min, respectively. All specimens were then subjected to irrigation with 10 ml of 5% NaOCl. After this procedure, the specimens were prepared for SEM (JEOL-SEM 6400) evaluation. Observations were made on halves obtained from the same root, and care was taken to compare the same relative surface regions of each half. RESULTS On specimens that were treated with 17% EDTA for 1 min, followed by 5% NaOCl, SEM examination showed that the smear layer was completely removed from the instrumented root surfaces, and dentinal tubules seemed to be open (Fig. 1). In 2 of 6
Disodium salt of EDTA is generally accepted as the most effective chelating agent with prominent lubricant properties and is widely used in endodontic therapy. It is used to enlarge root canals, remove the smear layer, and prepare the dentinal walls for better adhesion of filling materials (1–5). For effective removal of both the organic and inorganic components of the smear layer, irrigating root canals with 10 ml of 17% EDTA, followed by 10 ml of 5% NaOCl is recommended (6, 7). However there is no consensus on the duration of EDTA irrigation. EDTA has been reported to remove the smear layer in ⬍1 min if the fluid is able to reach the root canal wall surface (8), whereas another study suggested that the fluid should be kept in the root canal for at least 15 min to obtain the optimal result (9). Because EDTA solution has a strong demineralizing effect, it causes enlargement of the dentinal tubules, softening of the dentin, and denaturation of the collagen fibers (10). These effects may cause difficulty in adaptation of the root canal filling materials to the root canal wall. The purpose of this study was to evaluate the effects of EDTA on smear layer removal and on the structure of dentin after 1 and 10 min of applications.
FIG. 1. Effect of 17% EDTA for 1 min, followed by 5% NaOCl on the middle third of the root canal. The smear layer is completely removed and all of the tubule openings are clearly visible (⫻2500). 17
18
Çalt and Serper
FIG. 2. The same experimental procedure is applied as in Fig. 1. The smear layer is completely removed; all of the tubule openings are clearly visible, but slight erosive effects are observed on peritubular and intertubular dentin (⫻2500).
FIG. 3. Effect of 17% EDTA for 10 min, followed by 5% NaOCl on the middle third of the root canal. This specimen is the counterpart of the same tooth examined in Fig. 1. Excessive erosion of the intertubular and peritubular dentin is seen leading to conjugation of tubular apertures and widening of tubular diameters (⫻2500).
specimens, we observed a slight erosive effect of EDTA in peritubular and intertubular areas (Fig. 2). To investigate the effects of prolonged application of EDTA, the specimens were irrigated with 17% EDTA for 10 min, followed by 5% NaOCl. In these specimens we observed that the smear layer was completely removed; however excessive erosion of the intertubular and peritubular dentin was seen. This excessive erosion led to conjugation of tubular apertures and widening of tubular diameters (Fig. 3). In two specimens we observed that this erosive effect was in excess on the root dentinal surfaces, leading to enlargement of dentinal tubular openings and deterioration of the dentinal surface (Fig. 4). Ten-minute application of EDTA caused peritubular and intertubular erosion. Having been subjected to more erosion than the inside of the dentinal tubules, the diameter of the openings are greater than the tubule itself. This gives rise to the “wormhole” appearance as shown in Fig. 5. This erosion is extensive in some regions to the extent that the intertubular dentin completely dis-
Journal of Endodontics
FIG. 4. Effect of 17% EDTA for 10 min, followed by 5% NaOCl on the middle third of the root canal. This specimen is the counterpart of the same tooth examined in Fig. 2. The erosive effect is in excess on the root dentinal surfaces, leading to enlargement of dentinal tubular openings and deterioration of the dentinal surface (⫻2500).
FIG. 5. Effect of same treatment of EDTA as in Fig. 4. Diameters of tubular openings are larger than the tubules. This appearance resembles that of a “wormhole” (⫻4000).
appears between tubules, combining individual tubule openings in close proximity. Most specimens showed that after the 10 min treatment. Tubule opening diameters are almost doubled (some up to 4 m), compared with their counterparts subjected to the 1-min treatment. DISCUSSION EDTA is widely used as a chelator in endodontic therapy. A chelator reacts with calcium ions in hydroxyapatite crystals, removing calcium ions from the dentin. EDTA is used at various concentrations and combinations in root canal treatment. The efficiency of such agents depends on many factors, such as the root canal length, penetration depth of the material, hardness of the dentin, duration of application, the pH, and the concentration of materials (2, 11). For effective removal of both organic and inorganic components of the smear layer, it is generally recommended to use EDTA followed by NaOCl (6, 7, 12). Baumgartner and Mader (12)
Vol. 28, No. 1, January 2002
reported that the combination of EDTA and NaOCl caused a progressive dissolution of dentin at the expense of peritubular and intertubular areas, and they suggested that this effect may have resulted from the alternating action of NaOCl, which dissolved the organic component of the dentin, and EDTA, which demineralized the inorganic component. The erosive effects of EDTA has also been reported in other studies (10, 13). Peritubular dentin is highly mineralized and therefore harder than intertubular dentin. The hardness of peritubular dentin may provide added structural support for the intertubular dentin. Lower collagen content makes peritubular dentin more quickly dissolvable in acid than is intertubular dentin (14). It is widely recommended that, under clinical conditions, EDTA and NaOCl should be applied in 10 ml volume each; however there is no accepted duration for applications. Yamada et al. (6) reported a few seconds of EDTA administration is sufficient. In contrast, Goldberg and Spielberg (9) reported that the optimum working time for EDTAC is ⵒ15 min. Meryon et al. (15) reported that the smear layer was completely removed with 10% EDTA for 1 min, resulting in increased tubular orifice size. Cergneux et al. (13) also reported similar findings when 15% EDTA was applied in root canals for 4 min. In this study we compared the smear layer removal capability and the structural effects of EDTA on root dentin with respect to duration of application. Our results showed that EDTA followed by NaOCl completely removed the smear layer in 1 min. When EDTA is applied for 10 min, excessive erosive effects were observed with dissolution of peritubular and intertubular dentin. According to our findings, to inhibit the erosion on dentin, EDTA solution must not be applied for longer than 1 min. Kennedy et al. (16) reported that once the smear layer was removed using REDTA, dentinal tubule openings could be created more easily in younger teeth, compared with physiologically older teeth, especially in the more sclerotic middle and apical thirds. We found that a 10-min application of EDTA specimens showed noticeable differences in the degree of dentinal erosion. These differences may be explained by the variability of the calcification rates of root dentin. Although chronological age of the teeth specimens used in our study were not documented, our findings still suggest that, to minimize erosive effects, precautions must be
Effects of EDTA on Dentin
19
taken when EDTA is used on young patients, and the application time should be short as possible. Drs. Çalt and Serper are affiliated with the Department of Endodontics, Hacettepe University, Faculty of Dentistry, Ankara, Turkey. Address requests for reprints to Dr. Semra Çalt, Department of Endodontics, Hacettepe University, Faculty of Dentistry, Sihhiye (06100), Ankara, Turkey.
References 1. Ingle JI, Bakland LK, Peters DL, Buchanan LS, Mullaney TP. Endodontic Cavity Preparation. In: Ingle JI, Bakland LK, eds. Endodontics. 4th ed. Baltimore: Williams &Wilkins, 1994:180 – 4. 2. Sen BH, Wesselink PR, Türkün M. The smear layer: a phenomenon in root canal therapy. Int Endod J 1995;28:141– 8. 3. White RR, Goldman M, Lin PS. The influence of the smeared layer upon dentinal tubule penetration by plastic filling materials. J Endodon 1984;10: 558 – 62. 4. White RR, Goldman M, Lin PS. The influence of the smeared layer upon dentinal tubule penetration by endodontic filling materials. Part II. J Endodon 1987;13:369 –74. 5. Çalt S, Serper A. Dentinal tubule penetration of root canal sealers after root canal dressing with calcium hydroxide. J Endodon 1999;25:431–3. 6. Yamada RS, Armas A, Goldman M, Lin PS. A scanning electron microscopic comparison of a high volume final flush with several irrigating solutions. Part 3. J Endodon 1983;9:137– 42. 7. Goldman M, Goldman LB, Cavaleri R, Bogis J, Lin PS. The efficacy of several irrigating solutions for endodontics: a scanning electron microscopic study. Part 2. J Endodon 1982;8:487–92. 8. Spangberg LSW. Instruments, materials, and devices. In: Cohen S, Burns RC, eds. Pathways of the pulp .7th ed. St. Louis: Mosby, Inc., 1998:507. 9. Goldberg F, Spielberg C. The effect of EDTAC and the variation of its working time analyzed with scanning electron microscopy. Oral Surg 1982; 53:74 –7. 10. Garberoglio R, Becce C. Smear layer removal by root canal irrigants: a comparative scanning electron microscopic study. Oral Surg 1994;78:359 – 67. 11. Cury JA, Bragotto C, Valdrighi L. The demineralizing efficiency of EDTA solutions on dentin. Oral Surg 1981;52:446 – 8. 12. Baumgartner JC, Mader CL. A scanning electron microscopic evaluation of four root canal irrigation regimens. J Endodon 1987;13:147–57. 13. Cergneux M, Ciucchi B, Dietschi JM, Holz J. The influence of the smear layer on the sealing ability of canal obturation. Int Endod J 1987;20: 228 –32. 14. Trowbridge HO, Kim S. Pulp development, structure, and function. In: Cohen S, Burns RC, eds. Pathways of the pulp .7th ed. St. Louis: Mosby, Inc., 1998:391–3. 15. Meryon SD, Tobias RS, Jakeman KJ. Smear removal agents: a quantitative study in vivo and in vitro. J Prosthet Dent 1987;20:174 –9. 16. Kennedy WA, Walker WA, Gough RW. Smear layer removal effects on apical leakage. J Endodon 1986;12:21–7.