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Evaluation of the apical seal of root canal fillings with different methods
0099-2399/98/2410-0655503.00/0 JOURNALOF ENDOOONTICS Copyright © 1998 by The American Association of Endodontists
Printed in U.S.A.
VOL. 24, NO. 10, OCTOBER1998
Evaluation of the Apical Seal of Root Canal Fillings with Different Methods Kosmas G. Antonopoulos, DMD, Thomas Attin, DMD, and Elmar Hellwig, DMD
root that shows the highest degree of linear dye penetration is scrutinized. However, estimating leakage by evaluating four surfaces of each root has not been done. The objective of the present study was to compare the apical leakage obtained by passive dye penetration with the apical leakage obtained by dye penetration using negative pressure. Furthermore, a new dye penetration method using high pressure conditions was compared with these two methods.
The purpose of the study was to compare dye penetration methods conducted passively, under negative pressure, or under high pressure conditions. Ninety human maxillary incisors were instrumented and obturated with either the lateral condensation or single cone technique. India ink was used as a dye for passive and negative pressure (60 Torr) penetration methods. For dye penetration under high pressure conditions (200 MPa), a colored epoxy resin was used. Apical leakage was linearly measured evaluating both the root surface that showed the highest degree of penetration and all four surfaces of each root. The results revealed no significant difference between passive and negative pressure penetration methods. The amount of apical leakage obtained using dye penetration under high pressure conditions was significantly lower. Lateral condensation and single cone techniques yielded similar sealing abilities. It is concluded that there is no need to use negative pressure for evaluating the sealing ability of root canal fillings in vitro.
MATERIALS AND METHODS Ninety human maxillary incisors, which had been stored in 10% formalin after extraction, were used in this study. Access cavities were prepared, and the root canals were manually instrumented with the conventional preparation method up to #50, 1 nun short of the apex. K-type reamers and Hedstrom files were alternately used, and irrigation was with 3% hydrogen peroxide, followed by 1% sodium hypochlorite solutions. The patency of the apical foramen was proved during and after preparation of the root canal by passing the tip of a #10 reamer through the foramen. Forty-five teeth were obturated with the lateral condensation technique (LCT), and the remaining 45 with the single cone technique (SCT). Standardized gutta-percha points and AH Plus (DeTrey/Dentsply, Konstanz, Germany) sealer were used as filling materials for both groups. The access cavities were sealed with a zinc phosphate cement, and the teeth were stored in 100% humidity at 37°C for 7 days to ensure complete setting of the sealer. The 45 teeth obturated with the same technique were further distributed among three groups of 15 teeth each. Three different dye penetration methods (A to C) were used. Before exposure to India ink (Pelikan 4001, Hannover, Germany), the teeth used for dye penetration method A and B were coated with two layers of clear nail polish, except for the apical 1 to 2 mm. This coating was necessary to prevent dye penetration into the root canal by other routes than the apical foramen.
Ingle and Taintor (1) reported that up to 59% of endodontic failures may be attributed to apical leakage. Therefore, an effective endodontic obturation must provide a complete, three-dimensional filling of the root canal and of all accessory canals (2), preventing the communication of fluids between root canal and surrounding periapical tissues (3). The quality of root canal fillings can be objectively evaluated using in vivo studies. However, in vivo studies require long periods of time. Therefore, several methods have been introduced to evaluate the quality of root canal fillings in vitro. Usually, dye penetration tests conducted under normal atmospheric pressure are used (4-6). However, recent studies (7-9) reported that entrapped air inside the root canal system may inhibit the penetration of dyes. Thus, dye penetration tests performed under negative or high pressure conditions have been proposed (7-12). Linear measurements performed on teeth that are rendered transparent are often accomplished to determine the amount of leakage. With linear dye measurements, only the one surface of the
Method A
Method A consists of passive exposure to India ink dye under normal atmospheric pressure (LCT: n = 15, SCT: n = 15). The teeth were submerged in glass vials containing India ink and kept there for 7 days at 37°C. 655
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TABLE 1. Abbreviations used
Method B Method B consists of exposure to India ink dye under negative pressure (LCT: n = 15, SCT: n = 15). To establish a vacuum, a flask was connected with a vacuum pump (Whip-Mix Model D, Louisville, KT) using a pipette. The pipette was simultaneously used as a reservoir for the dye. By opening one valve of the pipette, the flask was connected with the vacuum pump and the air could be evacuated from the flask. By opening the other valve, the dye was released into the flask without allowing air to enter into the vacuum system. The teeth were placed on the bottom of the flask without contacting each other. A vacuum pressure of 60 Torr was applied for 10 min. Then, the dye was released into the flask until all teeth were completely submerged. The specimens remained in India ink under vacuum for I0 rain. Afterward, the vacuum was released, and the flask was stored for 7 days at 37°C.
Abbreviation LCT-P LCT-NP
LC~HP SCT-P SCT-NP SCT-HP
x 4S
Method C SD
Method C consists of exposure to Rhodamine B dye mixed with epoxy resin (UHU Plus Endfest, Btihl, Germany), under high pressure conditions (LCT: n = 15, SCT: n = 15) according to the method described by Kutschker et al. (13). Before exposure to the dye, each tooth was submerged in a plastic tube containing freshly prepared self-curing acrylic, except for the apical 2 mm. The tubes were removed, and the teeth remained embedded in the acrylic. Coating with acrylic was necessary to permit dye penetration into the root canal only via the apical foramen. The teeth were placed in a container with a mix of freshly prepared epoxy resin and Rhodamine B as a dye. The container was put in an autoclave, and the pressure was increased up to 200 MPa. Thus, the colored epoxy resin could penetrate into voids and spaces of the root canal fillings. The epoxy resin was then cured for 24 h at 40°C and a solid epoxy block was produced. Finally, epoxy resin and acrylic were carefully removed from the teeth. All 90 teeth were rendered transparent according to the method described by Robertson et al. (14). The teeth were decalcified for 3 days in a 5% nitric acid solution and then rinsed in running tap water for 4 h. Afterward, the teeth were dehydrated by graded series (80%, 90%, and 100%) of ethyl alcohol, and finally were submerged and stored in glass vials containing 100% methyl salicylate to complete the clearing process. After 0.5 to 2 h, the teeth became transparent. The roots of the cleared teeth were photographed from four directions under a stereomicroscope at ×20 magnification, and colored slides were produced. To allow for photographing from four directions, the crowns of the teeth were fixed in silicone cubes that could be turned. Photographing was performed with the teeth kept in methyl salicylate to maintain transparency. Therefore, cube and tooth were placed in a receptacle containing 100% methyl salicylate during photographing. The amount of leakage was linearly measured on the projected slides and determined by using two methods (I and II).
Evaluation Method I This method consists of linear measurement (in mm) of leakage only at the surface of each root that revealed the highest degree of dye penetration.
Explanation Lateral condensation technique; passive dye penetration (n = 15) Lateral condensation technique; dye penetration using negative pressure (n = 15) Lateral condensation technique; dye penetration using high pressure (n = 15) Single cone technique; passive dye penetration (n = 15) Single cone technique; dye penetration using negative pressure (n = 15) Single cone technique; dye penetration using high pressure (n = 15) Mean value of the leakage evaluating the root surface that revealed the highest degree of dye penetration Mean value of the leakage evaluating four surfaces of each root Standard deviation
TABLE 2. Mean apical leakage Group LCT-P LCT-NP LCT-HP SCT-P SCT-NP SCT-HP
x 1S [+SD (mm)]
x4S [_+SD (mm)]
0.35 0.86 0.08 0.66 0.99 0.59
0.72 2.06 0.19 1.58 1.96 1.32
_+ 0.59 _+ 1.43 _+ 0.14 -+ 0.73 _+ 1.59 _+ 0.99
___1.08 _+ 3.65 +_ 0.39 _+ 1.91 _+ 2.92 _+ 2.33
Evaluation Method II This method consists of linear measurement (in mm) of leakage at all four surfaces of each root. For each root, the measurements of all four surfaces were added to obtain one value. Data were statistically analyzed with the Kruskal-Wallis test, modified by Heux, Schumacher, and Weckesser. Level of significance was set at p --< 0.05.
RESULTS Table 1 provides a survey of the various experimental groups and their abbreviations used throughout the text. Table 2 presents the mean apical leakage of the experimental groups. Figures 1 and 2 present the mean apical leakage obtained by using the two evaluation methods. The mean amount of apical leakage obtained by exposing the teeth to the dye using negative pressure was higher than the mean amount of apical leakage obtained by exposing the teeth to the dye passively. However, the difference between passive and negative pressure techniques was not statistically significant: p = 0.538 (evaluating the surface of each root that showed the highest degree of dye penetration) and p = 0.628 (evaluating four surfaces of each root). The mean amount of apical leakage obtained by exposing the teeth to the dye under high pressure conditions was lower than the mean amount of apical leakage obtained by exposing the teeth to the dye passively (p = 0.048, evaluating the surface of each root
Vol. 24, No. 10, October 1998
FIG 1. Mean apical leakage obtained by measuring the surface of each root that revealed the highest degree of dye penetration. P, dye penetration; NP, negative pressure; HP, high pressure.
1,5
1
0.5 0
FIG 2. Mean apical leakage obtained by measuring four surfaces of each root. P, dye penetration; NP, negative pressure; HP, high pressure. that showed the highest degree of dye penetration; p = 0.045, evaluating four surfaces of each root), or using negative pressure (p = 0.018, evaluating the surface of each root that showed the highest degree of dye penetration; p = 0.028, evaluating four surfaces of each root). The differences were statistically significant. The mean amount of apical leakage obtained using the LCT was lower than the mean amount of apical leakage obtained using the single cone method of obturation. However, the difference between the two obturation techniques was not statistically significant: p = 0.19 (evaluating the surface of each root that showed the highest degree of dye penetration) and p = 0.16 (evaluating four surfaces of each root). DISCUSSION The results of the present study revealed higher dye penetration in teeth exposed to the dye using negative pressure, compared with the teeth exposed to the dye passively. However, this difference was not statistically significant. These findings are in agreement with the conclusions of Dickson and Peters (15) and Masters et al. (16). Dickson and Peters (15) obturated root canals using lateral condensation of gutta-percha or a halothane dip technique. Within
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both obturation groups, they did not find a statistically significant difference between vacuumed (25 inches of Hg) and not vacuumed teeth, with respect to the dye penetration method. Masters et al. (16) observed that root canals filled with gutta-percha without sealer showed leakage of 95.5% of their entire lengths without vacuum and 100% with vacuum (25 Torr). This difference was not statistically significant. Goldman et al. (7), Sp~ngberg et al. (8), Oliver and Abbott (9), and Peters and Harrison (11) showed that the entrapped air in obturated root canals can cause artifacts when passive dye penetration tests are used, because this air does not allow the dye solutions to penetrate completely into the root canal system. However, these studies are partly open to question. Goldman et al. (7), who used 25 Torr pressure, Sp~ngberg et al. (8), and Oliver and Abbott (9) intentionally created voids containing air in root canal fillings using orthodontic wires. Thus, in vivo conditions were not simulated and the validity of their results for clinical practice is questionable. Furthermore, Sp~ngberg et al. (8) used 100 mTorr absolute pressure. At this pressure, water boils at room temperature. Thus, the teeth used in their study were first dehydrated using freeze-drying, and a glycerol-based methylene blue solution was used. It is conceivable that freeze-drying or the glycerol-based dye exerts an influence on the composition of the sealer and the dental hard tissue. Furthermore, Oliver and Abbott (9), who used 26 Torr pressure, did not use teeth but capillary glass tubes in their study. These specimens do not represent in vivo conditions, because their surfaces are dissimilar to root canal dentin. Finally, Peters and Harrison (11) compared the marginal apical leakage of root-end filling materials obturating resected roots. They observed statistically significant differences between dye penetration methods under vacuum (25 Torr) and nonvacuum conditions when Intermediate Restorative Material was used as a retrofill. However, no significant difference between the two dye penetration methods was observed when amalgam or orthograde gutta-percha with sealer were used as retrofills. The aforementioned references indicate that, even if entrapped air exists in root canal fillings, it does not inevitably exert an influence on dye penetration tests used in comparative studies. The results of this study revealed higher dye penetration in teeth exposed to the dye under normal atmospheric pressure or negative pressure than in teeth exposed to the dye under high pressure conditions. The difference was statistically significant. In a similar study, 0liver and Abbott (9) concluded that dye penetration methods using high pressure (centrifuging at 3000 rpm) showed significantly higher leakage when compared with the passive dye penetration method. In the present study, different dyes were used in dye penetration tests conducted passively or under negative pressure (India ink), and in dye penetration test conducted under high pressure conditions (mix of Rhodamine B and epoxy resin). One explanation for the difference between the latter and the first two dye penetration methods may be that India ink is more effective in penetrating the root canal system than Rhodamine B mixed with epoxy resin. Another possible explanation may be that India ink, being liquid, could penetrate further in the root canal during the clearing process in which various chemical agents are used. On the contrary, the mix of Rhodamine B and epoxy resin, being solid, could not penetrate further. The present study did not find a significant difference in the apical leakage between teeth obturated with the LCT and the SCT. This corresponds to Attin et al. (6), who also found no significant difference in the apical seal produced with those two methods of obturation. In their study using Sealapex (Kerr/Sybron, Romulus,
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MI) as a sealer, root canal preparation, obturation, dye penetration, and leakage evaluation were similar with the present study. Furthermore, the results of the present study agree with those of Hantusch and Binus (17). They evaluated endodontically treated teeth in vivo. The examined teeth were obturated with LCT or the SCT, respectively, and chloropercha was used as a sealer. Their study demonstrated that the failure of endodontic therapy observed in 14.4% of the cases was equally shared between the two obtumoon techniques. No statistically significant difference between SCT and LCT was found. On the contrary, Beatty et al. (18) observed significantly more apical leakage in root canals obturated with the SCT, compared with root canals obturated with the LCT. However, Beatty et al. (18) prepared maxillary and mandibular canines up to #60. The root canals of these teeth are much wider in labiolingual direction than in mesiodistal direction. Thus, root canal preparation to a round cross-section, which is a prerequisite for the SCT (19), was rather difficult. Another possible explanation for the different findings of the present study and the study of Beatty et al. (18) may be due to the use of a different sealer. The sealer is essential for the quality of the root canal obturation, especially for the SCT, because the SCT requires more sealer, compared with the LCT. Thus, it could be conjectured that the choice of the sealer may be responsible for the different results of the present study, compared with the study of Beatty et al. (18). Evaluation of the root surface that revealed the highest degree of dye penetration and evaluation of all four surfaces of each root led to similar conclusions about the density of the root canal fillings. This observation was true for both obturation techniques and for all types of dye penetration. It was observed that teeth with apical leakage usually showed dye penetration at all of their surfaces. Only a few specimens with leakage showed dye penetration at only one surface. Furthermore, when leakage existed at only one surface, it was usually very low. Thus, the similar conclusions obtained using the two methods of leakage estimation were expected. The present study revealed an average apical leakage of 0.35 mm using the LCT and 0.66 mm using the SCT (dye penetration tests performed under normal atmospheric pressure). In this study, the new sealer material AH Plus, which is an improvement of AH26 (DeTrey/Dentsply, Zurich, Switzerland), was used. Other studies (4-6, 18, 20) using different sealers have found an average apical leakage of 0.25 to 5.3 mm using the LCT and 0.6 to 6.31 mm using the SCT. Thus, it is assumed that the apical seal obtained with AH Plus is satisfactory, beating in mind that comparisons between different studies are only partly admissible.
Dr. Antonopoulos is assistant professor, Dr. Attin is assistant professor, and Dr. Hellwig is professor and head, Department of Operative Dentistry and Periodontology, University of Freiburg, Clinic of Dentistry, Freiburg, Germany. Address requests for reprints to Dr. Thomas Attin, Department of Operative Dentistry and Periodontology, Clinic of Dentistry, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg i. Br., Germany.
References 1. Ingle JI, Taintor JF. Endodontics. 3rd ed. Philadelphia: Lea & Febiger, 1985:36. 2. Schilder H. Filling root canals in three dimensions. Dent Clin North Am 1967;11:723-44. 3. Coolidge ED, Kesel RG. Endodontology. 2nd ed. Philadelphia: Lea & Febiger, 1956:242. 4. Torabinejad M, Kahn H, Bankes D. Isopropyl cyanoacrylate as a root canal sealer. J Endodon 1984;10:304-7. 5. Smith MA, Steiman HR. An in vitro evaluation of microleakage of two new and two old root canal sealers. J Endodon 1994;20:18-21. 6. Attin T, Kielbassa AM, Lebke T, Schulte-M6nting J, Hellwig E. Wurzelkanalf011ungen mit Glasionomerzement-Sealern. Acta Med Dent Helv 1996;1: 7-12. 7. Goldman M, Simmonds S, Rush R. The usefulness of dye-penetration studies reexamined. Oral Surg 1989;67:327-32. 8. Sp&ngberg LSW, Acierno TG, Cha BY. Influence of entrapped air on the accuracy of leakage studies using dye penetration methods. J Endodon 1989;15:548-51. 9. Oliver CM, Abbott PV. Entrapped air and its effects on dye penetration of voids. Endod Dent Traumatol 1991;7:135-8. 10. Limkangwalmongkol S, Abbott PV, Sandier AB. Apical dye penetration with four root canal sealers and gutta-percha using longitudinal sectioning. J Endodon 1992;18:535-9. 11. Peters LB, Harrison JW. A comparison of leakage of filling materials in demineralized and non-demineralized resected root ends under vacuum and non-vacuum conditions. Int Endod J 1992;25:273-8. 12. Brown RC, Jackson CR, Skidmore AE. An evaluation of apical leakage of a glass ionomer root canal sealer. J Endodon 1994;20:288-91. 13. Kutschker P, Wilkie D, Uchtmann H. In vitro imaging of pore structures in sound and carious teeth [Abstract 89]. Caries Res 1994;28:206. 14. Robertson D, Leeb IJ, McKee M, Brewer E. A clearing technique for the study of root canal systems. J Endodon 1980;6:42 ;-4. 15. Dickson SS, Peters DD. Leakage evaluation with and without vacuum of two gutta-percha fill techniques. J Endodon 1993;19:398-403. 16. Masters J, Higa R, Torabinejad M. Effects of vacuuming on dye penetration patterns in root canals and glass tubes. J Endodon 1995;21:332-4. 17. Hantusch A, Binus W. M6glichkeiten der Wurzelkanalf(~llung mit Guttapercha. Stomatol DDR 1990;40:147-9. 18. Beatty RG, Baker PS, Haddix J, Hart F. The efficacy of four root canal obturation techniques in preventing apical dye penetration. J Am Dent Assoc 1989; 119:633-7. 19. H01smann M. Die Wurzelkanalfellung: Materialien und Techniken. Zahn~rztl Mitt 1991 ;81:872-7. 20. Zidan O, EIDeeb ME. The use of a dentinal bonding agent as a root canal sealer. J Endodon 1985;11:176-8.
Printed in U.S.A.
VOL. 24, NO. 10, OCTOBER1998
Evaluation of the Apical Seal of Root Canal Fillings with Different Methods Kosmas G. Antonopoulos, DMD, Thomas Attin, DMD, and Elmar Hellwig, DMD
root that shows the highest degree of linear dye penetration is scrutinized. However, estimating leakage by evaluating four surfaces of each root has not been done. The objective of the present study was to compare the apical leakage obtained by passive dye penetration with the apical leakage obtained by dye penetration using negative pressure. Furthermore, a new dye penetration method using high pressure conditions was compared with these two methods.
The purpose of the study was to compare dye penetration methods conducted passively, under negative pressure, or under high pressure conditions. Ninety human maxillary incisors were instrumented and obturated with either the lateral condensation or single cone technique. India ink was used as a dye for passive and negative pressure (60 Torr) penetration methods. For dye penetration under high pressure conditions (200 MPa), a colored epoxy resin was used. Apical leakage was linearly measured evaluating both the root surface that showed the highest degree of penetration and all four surfaces of each root. The results revealed no significant difference between passive and negative pressure penetration methods. The amount of apical leakage obtained using dye penetration under high pressure conditions was significantly lower. Lateral condensation and single cone techniques yielded similar sealing abilities. It is concluded that there is no need to use negative pressure for evaluating the sealing ability of root canal fillings in vitro.
MATERIALS AND METHODS Ninety human maxillary incisors, which had been stored in 10% formalin after extraction, were used in this study. Access cavities were prepared, and the root canals were manually instrumented with the conventional preparation method up to #50, 1 nun short of the apex. K-type reamers and Hedstrom files were alternately used, and irrigation was with 3% hydrogen peroxide, followed by 1% sodium hypochlorite solutions. The patency of the apical foramen was proved during and after preparation of the root canal by passing the tip of a #10 reamer through the foramen. Forty-five teeth were obturated with the lateral condensation technique (LCT), and the remaining 45 with the single cone technique (SCT). Standardized gutta-percha points and AH Plus (DeTrey/Dentsply, Konstanz, Germany) sealer were used as filling materials for both groups. The access cavities were sealed with a zinc phosphate cement, and the teeth were stored in 100% humidity at 37°C for 7 days to ensure complete setting of the sealer. The 45 teeth obturated with the same technique were further distributed among three groups of 15 teeth each. Three different dye penetration methods (A to C) were used. Before exposure to India ink (Pelikan 4001, Hannover, Germany), the teeth used for dye penetration method A and B were coated with two layers of clear nail polish, except for the apical 1 to 2 mm. This coating was necessary to prevent dye penetration into the root canal by other routes than the apical foramen.
Ingle and Taintor (1) reported that up to 59% of endodontic failures may be attributed to apical leakage. Therefore, an effective endodontic obturation must provide a complete, three-dimensional filling of the root canal and of all accessory canals (2), preventing the communication of fluids between root canal and surrounding periapical tissues (3). The quality of root canal fillings can be objectively evaluated using in vivo studies. However, in vivo studies require long periods of time. Therefore, several methods have been introduced to evaluate the quality of root canal fillings in vitro. Usually, dye penetration tests conducted under normal atmospheric pressure are used (4-6). However, recent studies (7-9) reported that entrapped air inside the root canal system may inhibit the penetration of dyes. Thus, dye penetration tests performed under negative or high pressure conditions have been proposed (7-12). Linear measurements performed on teeth that are rendered transparent are often accomplished to determine the amount of leakage. With linear dye measurements, only the one surface of the
Method A
Method A consists of passive exposure to India ink dye under normal atmospheric pressure (LCT: n = 15, SCT: n = 15). The teeth were submerged in glass vials containing India ink and kept there for 7 days at 37°C. 655
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TABLE 1. Abbreviations used
Method B Method B consists of exposure to India ink dye under negative pressure (LCT: n = 15, SCT: n = 15). To establish a vacuum, a flask was connected with a vacuum pump (Whip-Mix Model D, Louisville, KT) using a pipette. The pipette was simultaneously used as a reservoir for the dye. By opening one valve of the pipette, the flask was connected with the vacuum pump and the air could be evacuated from the flask. By opening the other valve, the dye was released into the flask without allowing air to enter into the vacuum system. The teeth were placed on the bottom of the flask without contacting each other. A vacuum pressure of 60 Torr was applied for 10 min. Then, the dye was released into the flask until all teeth were completely submerged. The specimens remained in India ink under vacuum for I0 rain. Afterward, the vacuum was released, and the flask was stored for 7 days at 37°C.
Abbreviation LCT-P LCT-NP
LC~HP SCT-P SCT-NP SCT-HP
x 4S
Method C SD
Method C consists of exposure to Rhodamine B dye mixed with epoxy resin (UHU Plus Endfest, Btihl, Germany), under high pressure conditions (LCT: n = 15, SCT: n = 15) according to the method described by Kutschker et al. (13). Before exposure to the dye, each tooth was submerged in a plastic tube containing freshly prepared self-curing acrylic, except for the apical 2 mm. The tubes were removed, and the teeth remained embedded in the acrylic. Coating with acrylic was necessary to permit dye penetration into the root canal only via the apical foramen. The teeth were placed in a container with a mix of freshly prepared epoxy resin and Rhodamine B as a dye. The container was put in an autoclave, and the pressure was increased up to 200 MPa. Thus, the colored epoxy resin could penetrate into voids and spaces of the root canal fillings. The epoxy resin was then cured for 24 h at 40°C and a solid epoxy block was produced. Finally, epoxy resin and acrylic were carefully removed from the teeth. All 90 teeth were rendered transparent according to the method described by Robertson et al. (14). The teeth were decalcified for 3 days in a 5% nitric acid solution and then rinsed in running tap water for 4 h. Afterward, the teeth were dehydrated by graded series (80%, 90%, and 100%) of ethyl alcohol, and finally were submerged and stored in glass vials containing 100% methyl salicylate to complete the clearing process. After 0.5 to 2 h, the teeth became transparent. The roots of the cleared teeth were photographed from four directions under a stereomicroscope at ×20 magnification, and colored slides were produced. To allow for photographing from four directions, the crowns of the teeth were fixed in silicone cubes that could be turned. Photographing was performed with the teeth kept in methyl salicylate to maintain transparency. Therefore, cube and tooth were placed in a receptacle containing 100% methyl salicylate during photographing. The amount of leakage was linearly measured on the projected slides and determined by using two methods (I and II).
Evaluation Method I This method consists of linear measurement (in mm) of leakage only at the surface of each root that revealed the highest degree of dye penetration.
Explanation Lateral condensation technique; passive dye penetration (n = 15) Lateral condensation technique; dye penetration using negative pressure (n = 15) Lateral condensation technique; dye penetration using high pressure (n = 15) Single cone technique; passive dye penetration (n = 15) Single cone technique; dye penetration using negative pressure (n = 15) Single cone technique; dye penetration using high pressure (n = 15) Mean value of the leakage evaluating the root surface that revealed the highest degree of dye penetration Mean value of the leakage evaluating four surfaces of each root Standard deviation
TABLE 2. Mean apical leakage Group LCT-P LCT-NP LCT-HP SCT-P SCT-NP SCT-HP
x 1S [+SD (mm)]
x4S [_+SD (mm)]
0.35 0.86 0.08 0.66 0.99 0.59
0.72 2.06 0.19 1.58 1.96 1.32
_+ 0.59 _+ 1.43 _+ 0.14 -+ 0.73 _+ 1.59 _+ 0.99
___1.08 _+ 3.65 +_ 0.39 _+ 1.91 _+ 2.92 _+ 2.33
Evaluation Method II This method consists of linear measurement (in mm) of leakage at all four surfaces of each root. For each root, the measurements of all four surfaces were added to obtain one value. Data were statistically analyzed with the Kruskal-Wallis test, modified by Heux, Schumacher, and Weckesser. Level of significance was set at p --< 0.05.
RESULTS Table 1 provides a survey of the various experimental groups and their abbreviations used throughout the text. Table 2 presents the mean apical leakage of the experimental groups. Figures 1 and 2 present the mean apical leakage obtained by using the two evaluation methods. The mean amount of apical leakage obtained by exposing the teeth to the dye using negative pressure was higher than the mean amount of apical leakage obtained by exposing the teeth to the dye passively. However, the difference between passive and negative pressure techniques was not statistically significant: p = 0.538 (evaluating the surface of each root that showed the highest degree of dye penetration) and p = 0.628 (evaluating four surfaces of each root). The mean amount of apical leakage obtained by exposing the teeth to the dye under high pressure conditions was lower than the mean amount of apical leakage obtained by exposing the teeth to the dye passively (p = 0.048, evaluating the surface of each root
Vol. 24, No. 10, October 1998
FIG 1. Mean apical leakage obtained by measuring the surface of each root that revealed the highest degree of dye penetration. P, dye penetration; NP, negative pressure; HP, high pressure.
1,5
1
0.5 0
FIG 2. Mean apical leakage obtained by measuring four surfaces of each root. P, dye penetration; NP, negative pressure; HP, high pressure. that showed the highest degree of dye penetration; p = 0.045, evaluating four surfaces of each root), or using negative pressure (p = 0.018, evaluating the surface of each root that showed the highest degree of dye penetration; p = 0.028, evaluating four surfaces of each root). The differences were statistically significant. The mean amount of apical leakage obtained using the LCT was lower than the mean amount of apical leakage obtained using the single cone method of obturation. However, the difference between the two obturation techniques was not statistically significant: p = 0.19 (evaluating the surface of each root that showed the highest degree of dye penetration) and p = 0.16 (evaluating four surfaces of each root). DISCUSSION The results of the present study revealed higher dye penetration in teeth exposed to the dye using negative pressure, compared with the teeth exposed to the dye passively. However, this difference was not statistically significant. These findings are in agreement with the conclusions of Dickson and Peters (15) and Masters et al. (16). Dickson and Peters (15) obturated root canals using lateral condensation of gutta-percha or a halothane dip technique. Within
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both obturation groups, they did not find a statistically significant difference between vacuumed (25 inches of Hg) and not vacuumed teeth, with respect to the dye penetration method. Masters et al. (16) observed that root canals filled with gutta-percha without sealer showed leakage of 95.5% of their entire lengths without vacuum and 100% with vacuum (25 Torr). This difference was not statistically significant. Goldman et al. (7), Sp~ngberg et al. (8), Oliver and Abbott (9), and Peters and Harrison (11) showed that the entrapped air in obturated root canals can cause artifacts when passive dye penetration tests are used, because this air does not allow the dye solutions to penetrate completely into the root canal system. However, these studies are partly open to question. Goldman et al. (7), who used 25 Torr pressure, Sp~ngberg et al. (8), and Oliver and Abbott (9) intentionally created voids containing air in root canal fillings using orthodontic wires. Thus, in vivo conditions were not simulated and the validity of their results for clinical practice is questionable. Furthermore, Sp~ngberg et al. (8) used 100 mTorr absolute pressure. At this pressure, water boils at room temperature. Thus, the teeth used in their study were first dehydrated using freeze-drying, and a glycerol-based methylene blue solution was used. It is conceivable that freeze-drying or the glycerol-based dye exerts an influence on the composition of the sealer and the dental hard tissue. Furthermore, Oliver and Abbott (9), who used 26 Torr pressure, did not use teeth but capillary glass tubes in their study. These specimens do not represent in vivo conditions, because their surfaces are dissimilar to root canal dentin. Finally, Peters and Harrison (11) compared the marginal apical leakage of root-end filling materials obturating resected roots. They observed statistically significant differences between dye penetration methods under vacuum (25 Torr) and nonvacuum conditions when Intermediate Restorative Material was used as a retrofill. However, no significant difference between the two dye penetration methods was observed when amalgam or orthograde gutta-percha with sealer were used as retrofills. The aforementioned references indicate that, even if entrapped air exists in root canal fillings, it does not inevitably exert an influence on dye penetration tests used in comparative studies. The results of this study revealed higher dye penetration in teeth exposed to the dye under normal atmospheric pressure or negative pressure than in teeth exposed to the dye under high pressure conditions. The difference was statistically significant. In a similar study, 0liver and Abbott (9) concluded that dye penetration methods using high pressure (centrifuging at 3000 rpm) showed significantly higher leakage when compared with the passive dye penetration method. In the present study, different dyes were used in dye penetration tests conducted passively or under negative pressure (India ink), and in dye penetration test conducted under high pressure conditions (mix of Rhodamine B and epoxy resin). One explanation for the difference between the latter and the first two dye penetration methods may be that India ink is more effective in penetrating the root canal system than Rhodamine B mixed with epoxy resin. Another possible explanation may be that India ink, being liquid, could penetrate further in the root canal during the clearing process in which various chemical agents are used. On the contrary, the mix of Rhodamine B and epoxy resin, being solid, could not penetrate further. The present study did not find a significant difference in the apical leakage between teeth obturated with the LCT and the SCT. This corresponds to Attin et al. (6), who also found no significant difference in the apical seal produced with those two methods of obturation. In their study using Sealapex (Kerr/Sybron, Romulus,
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Antonopoulos et al,
MI) as a sealer, root canal preparation, obturation, dye penetration, and leakage evaluation were similar with the present study. Furthermore, the results of the present study agree with those of Hantusch and Binus (17). They evaluated endodontically treated teeth in vivo. The examined teeth were obturated with LCT or the SCT, respectively, and chloropercha was used as a sealer. Their study demonstrated that the failure of endodontic therapy observed in 14.4% of the cases was equally shared between the two obtumoon techniques. No statistically significant difference between SCT and LCT was found. On the contrary, Beatty et al. (18) observed significantly more apical leakage in root canals obturated with the SCT, compared with root canals obturated with the LCT. However, Beatty et al. (18) prepared maxillary and mandibular canines up to #60. The root canals of these teeth are much wider in labiolingual direction than in mesiodistal direction. Thus, root canal preparation to a round cross-section, which is a prerequisite for the SCT (19), was rather difficult. Another possible explanation for the different findings of the present study and the study of Beatty et al. (18) may be due to the use of a different sealer. The sealer is essential for the quality of the root canal obturation, especially for the SCT, because the SCT requires more sealer, compared with the LCT. Thus, it could be conjectured that the choice of the sealer may be responsible for the different results of the present study, compared with the study of Beatty et al. (18). Evaluation of the root surface that revealed the highest degree of dye penetration and evaluation of all four surfaces of each root led to similar conclusions about the density of the root canal fillings. This observation was true for both obturation techniques and for all types of dye penetration. It was observed that teeth with apical leakage usually showed dye penetration at all of their surfaces. Only a few specimens with leakage showed dye penetration at only one surface. Furthermore, when leakage existed at only one surface, it was usually very low. Thus, the similar conclusions obtained using the two methods of leakage estimation were expected. The present study revealed an average apical leakage of 0.35 mm using the LCT and 0.66 mm using the SCT (dye penetration tests performed under normal atmospheric pressure). In this study, the new sealer material AH Plus, which is an improvement of AH26 (DeTrey/Dentsply, Zurich, Switzerland), was used. Other studies (4-6, 18, 20) using different sealers have found an average apical leakage of 0.25 to 5.3 mm using the LCT and 0.6 to 6.31 mm using the SCT. Thus, it is assumed that the apical seal obtained with AH Plus is satisfactory, beating in mind that comparisons between different studies are only partly admissible.
Dr. Antonopoulos is assistant professor, Dr. Attin is assistant professor, and Dr. Hellwig is professor and head, Department of Operative Dentistry and Periodontology, University of Freiburg, Clinic of Dentistry, Freiburg, Germany. Address requests for reprints to Dr. Thomas Attin, Department of Operative Dentistry and Periodontology, Clinic of Dentistry, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg i. Br., Germany.
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