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Comparative tissue tolerance of a new endodontic sealer
dodonti Daniel Molloy, DLVD,~ Melvin Goldman, DDS,b Robert R. White, DMD,” and Sadru Kabani, DMD, MS,d Boston, Mass. TUFTS UNIVERSITY
SCHOOL OF DENTAL
MEDICINE
An experimental radiopaque resin root canal sealer was tested for tissue biocompatibility in rat connective tissue. The controls were four widely used sealers: Sealapex, Kerr’s sealer, AH-26, and Roth’s sealer. Polyethylene tubes were filled with the sealers and allowed to set for 24 hours in iOO% humidity. Each sealer was implanted in the connective tissue of Sprague-Dawley rats and removed after 3, 10, 20, 30, and 60 days, fixed, and histologically prepared for light microscope evaluation. At each time period there was practically no difference in the reaction of all the sealers. By 60 days, the total picture was one of well-tolerated biocompatibility. (ORALSURCORAL MEDORAL PATHOL1992;73:490-3)
he search for a biocompatible root canal sealer proceeds constantly, and there have been a number of new endodontic sealers introduced in the last several decades. Testing for biocompatibility is the first appropriate test, for without biocompatibility comparable to commonly used sealers, acceptance as a useful material would be doubtful. There have been many methods of testing reported over the years. Injection of the materials to be tested-along with several controls-directly into the subcutaneous tissue of a test animal has been advocated.lm4 Other investigators have used Teflon or polyethylene tubes filled with freshly mixed or set materials and have implanted these tubes subcutaneously or within bone. 5-11Recently, testing cytotoxicity on cell cultures of Hela cells and fibroblasts has been advocated.12-‘5 Each method has attributes and limitations. One thing seems apparent from the literature-absolute ranking of sealers really is not possible by any method. Test comparisons can be made, but they mean little. The one outstanding conclusion is, a sealer is clinaGraduate Student, Tufts University School of Dental bProfessor Emeritus in Endodontics, Tufts University Dental Medicine. CAssociate Professor of Endodontics, Tufts University Dental Medicine. dAssistant Professor of Oral Pathology, Tufts University Dental Medicine. 7/15/35007
Medicine. School of School of School of
ically acceptable when (1) it is not toxic, (2) it does not cause necrosis of tissue, and (3) after a brief initial period, it is readily accepted by the tissue with minimal inflammatory sequelae. The test material is an experimental resin root canal sealer to which precipitated silver has been added for radiopacity. It is easily mixed and has a very low viscocity so that it should flow readily into all the irregularities of the prepared canal space. Hopefully, this will help provide a superior seal of the filled root canal. The purpose of this study was to evaluate the inflammatory response of this resin sealer, to determine its biocompatibility when implanted into the soft tissues of rats, and to compare these responses with those elicited by several commonly used sealers. If the biocompatibility was acceptable, the sealer could then be tested for apical leakage, manipulation, and other factors to determine whether this would be suitable for use as a sealer in an endodontic filling technique. MATERIAL AND METHODS Ten mm lengths of polyethylene tubing (1 mm outside diameter, 0.7 mm inside diameter) were prepared and sterilized with ethylene oxide. Six root canal sealers were tested: (1) an experimental resin; (2) an experimental resin with silver added as a radiopacifier; (3) Sealapex (Kerr Manufacturing Co., Romulus, Mich.); (4) Kerr sealer (Kerr Manufacturing Co., Romulus, Mich.); (5) AH-26 (deTrey Co., Zurick, Switzerland); and (6) Roth’s sealer (Roth Drug Co.,
Volume 73 Number 4
Fig. 1. Sprague-Dawley rats with the six incisions for placement of the polyethylene tubes with sealer. Chicago, Ill.). These four control sealers, nos. 3,4, 5, and 6, were chosen because of their long history of successful use in endodontic treatment. They have been extensively tested by various means and have been judged to be relatively biocompatible, even though they may have demonstrated slight chronic inflammation.‘-” This has been judged to be clinically insignificant and the sealers are well tolerated. The side of the tube is its own control. The various sealers were mixed under sterile conditions, according to manufacturers’ directions, and then placed into the tubes. The outside surfaces of the tubes were wiped clean with sterile gauze and the materials were allowed to set in 100% humidity for 48 hours. Ten 200-gram Sprague-Dawley rats were used. After ether anesthesia, the implant sites were shaved and the skin was disinfected with povidone-iodine solution. Ten millimeter incisions were made, two at each shoulder, two at midabdomen and two at each hip, and a thumb forceps was used to tunnel a subcutaneous pocket. One tube was placed in each of the six locations, so that all six materials were in each animal. The wounds were closed with wound clips and the rats were fed rat chow and water ad libitum (Fig. 1). Two rats were killed at each of five time periods: 3 days, 10 days, 20 days, 30 days, and 60 days. The tubes were recovered in block sections, fixed in formalin, and prepared for histologic examination. They were sectioned at 6 microns and stained with hematoxylin and eosin stain. RESULTS All specimens underwent blind examination by three examiners; that is, the examiner did not know which sealer or which time period was being examined. Within all time periods, it was not possible to
Biocompatibility
of a new endodontic sealer
491
Fig. 2. Three day specimen of tissue around end of tube. Note the granulation tissue and inflammatory cells (Original magnification, X40).
distinguish differences in the sealers, with the exception of AH-26 at 10, 20, and 30 days. At 60 days, all sections appeared similar. At 3 days with all materials, there was still some acute inflammation with a few polymorphonuclear leucocytes, but mostly there were small amounts of granulation tissue and lymphocytes (Figs. 2 and 3). At 10 days, the sections were marked by a diminishing inflammation. There were some macrophages with birefringent material within the cells and a few giant cells surrounding small particles of the sealer (Fig. 4). The AH-26 group had some edema and inflammation with polymorphonuclear neutrophils and macrophages. At 20 days, the inflammation was diminishing-a condensed connective tissue pseudocapsule was forming and there were fewer giant cells. The AH-26 again demonstrated slight edema and inflammation. At 30 days, the inflammation was diminishing, the pseudocapsule was formed, and the numbers of giant cells had diminished and there were just scattered inflammatory cells (Fig. 5). The AH-26 still had some edema which was diminishing. At 60 days, everything was healing. The pseudocapsule was well established, with no inflammation. There were a few inflammatory cells at the open end of the tubes, and there were still a few giant cells and macrophages with insoluble particles within them (Fig. 6). The total picture was of very mild inflammation and healing. All the sealers appeared to be equally well tolerated. DISCUSSION Whenever a discussion of endodontic sealers or filling materials is held, invariably the numbers of
Fig. 3. Higher power of Fig. 2. Inflammatory cells, polymorphonuclear neutrophils, and lymphocytes are present (Original magnification, X200).
Fig. 5. Thirty day specimen. Note the beginning formation of a pseudocapsuleand diminishing number of inflammatory cells (Original magnification, X100).
Fig. 4. Ten day specimen. Diminishing infiammation. Note giant cell with engulfed particles (Original magnification, X 100).
ig. 6. Sixty days-the pseudocapsule is well established; very few inflammatory cells (Original magnification, X 100).
macrophages, lymphocytes, and giant cells are closely scrutinized. Attempts at quantifying these numbers have been made many times with very little success. Several authors9, l3 have pointed out that ranking materials is a very doubtful procedure at best. The interpretation of biocompatibility is often an exercise in semantics. At the Conference on Inflammation in 1976, sponsored by the American Association of Endodontists, a question was raised about small pieces of filling materials and sealer in the periapical tissues that seemed to be well tolerated. The answer by the lecturer, Dr. M. Spector, was that many things could be taken up by macrophages and could persist for 20 years or more. But if they are nontoxic to the macrophages, even if they are totally indigestible and nonsoluble, there is no reason any real damage should be donei Further on, in response to a comment that when one sets up standards for evaluation of dental materials, if one implants in an animal and ends up with mac-
rophages, that sort of reaction is considered a deplorable result.16 Dr. Spector’s colleague, Dr. H. Willoughby, responded that when one has a tattoo, there is an indigestible material that just sits nicely on the site. But it sits there inside cells and these cells do not start wandering. If the tattoo says “‘I love Janice,” it does not slowly move from the chest and become “I love Mary” on the hip.i6 That may seem a bit facetious, but it states the case clearly. Blackman et al. t7 describe test results of a glass ionomer cement with silver and state that the cements they tested were “not benign but are relatively biocompatible” because there were some macrophages and giant cells with engulfed particles. The control sealers are all widely accepted as being relatively biocompatible and have been in use for varying periods of time. The two experimental sealers elicited the same type of mild response as the controls. In addition, a report by the Council of Dental Materials, Instruments, and Equipment of the American
Volume 73 Number 4
Dental Association states that biocompatibility tests using tissue cultures and animals have shown that the components of composite resins, dentin bonding agents,and glass ionsomersdo not elicit damaging evidence to the safe use of these materials. ‘* As for the silver, Spangberg,‘* using a cell culture technique found that silver invariably had the weakesteffect and was the standard to which other materials were compared. B1ackma.net al. l7 found that a glass ionomer cement with silver was biocompatible. Kerr sealer, a long-acceptedmaterial and one of the controls, contains 25% silver. Further studies of this experimental sealer,such as usageand in vitro studies, are necessaryand underway. CONCLUSIONS
Two experimental resin root canal sealers,onewith and one without silver (for radiopacity), were tested by comparison of their biocompatibility with four commonly used sealers.All materials were placed in 10 mm sterilized polyethylenetubes and implanted in rats for periods of 3 to 60 days. All the implanted materials demonstrated mild initial inflammation, which subsided rapiidly. After 60 days, this study demonstratedall the materials to be comparable and well tolerated. Further studies to determine the usefulness of this resin a.sa root canal sealer are necessary and are underway. REFERENCES 1. Stewart G. A comparative study of three root canal sealing agents. ORAL SURG ORAL MED ORAL PATHOL 1958;11:102931. 2. Guttuso J. Histopathologic study of rat connective tissue responses to endodontic materials. ORAL SURC ORAL MED ORAL PATHOL 1963;115:713-26. 3. Morse DR, Martell B, Pike CC, Fantasia J, Esposito JV, Furst ML. A comparative tissue toxicity evaluation of gutta-percha root canal sealers. Part I: 6 hour findings. J Endod 1984; 10:246-9.
Biocompatibility of a new endodontic sealer 493 4. Yesilsoy C, Koren LZ, Morse DR, Kobayashi C. A comparative tissue toxicity evaluation of established and newer root canal sealers. ORAL SURG ORAL MED ORAL PA~HOL 1988; 65:459-69. 5. Browne RM, Friend LA. An investigation into the irritant properties of some root canal filling materials. Arch Oral Biol 1968;13:1355-69. 6. Friend LA, Browne RM. Tissue reactions to some root canal filling materials. Br Dent J 1968:125:291-4. 7. Frienh LA, Browne RM. Tissue ieactions to some root filling materials implanted in the bone of the rabbit. Arch Oral Biol 1969;14:629-38. 8. Safavi KE, Pascon EA, Langeland K. Evaluation of tissue reaction to endodontic materials. J Endod 1983;9:421-9. 9. O&son B, Sliwkowski A, Langeland K. Subcutaneous implantation for the biological evaluation of endodontic materials. J Endod 1981;7:355-69. 10. Orstavik D, Mjor IA. Histopathology and X-ray microanalysis of the subcutaneous tissue response to endodontic sealers. J Endod 1988;14:13-23. 11. Wennberg A. Biologic evaluation of root canal sealers using in vitro and in vivo methods. J Endod 1980;6:784-7. 12. Spangberg L. Biologic effects of root canal filling materials 4. Effect in vitro of solubilized root canal filling materials on Hela cells. Odontol Rev 1989;20:289-99. 13. Kettering JD, Torabinejad M. Cytotoxicity of root canal sealers: a study using Hela cells and fibroblasts. Int Endod J 1984;17:60-6. 14. Safavi KE, Spangberg L, Costa NS, Sapounas G. An in vitro method for longitudinal evaluation of toxicity of endodontic sealers. J Endod 1989;15:484-6. 15. Briseno BM, Willershausen B. Root canal sealer toxicity on human gingival fibroblasts 1. Zinc oxide based sealers. J Endod 1990;8:383-6. 16. Blechman H. Inflammation: a defense mechanism? J Endod 1977;3:369-93. 17. Blackman R, Gross M, Seltzer S. An evaluation of a glass ionomer silver cement in rat connective tissue. J Endod 1989; 15:16-9. 18. Council of Dental Materials. Instruments and equipment biocompatibility and postoperative sensitivity. J Am Dent Assoc 1988;116:767-8. Reprint requests. Melvin Goldman, DDS Department of Endodontics Tufts University School of Dental Medicine One Kneeland St. Boston, MA 02111
SCHOOL OF DENTAL
MEDICINE
An experimental radiopaque resin root canal sealer was tested for tissue biocompatibility in rat connective tissue. The controls were four widely used sealers: Sealapex, Kerr’s sealer, AH-26, and Roth’s sealer. Polyethylene tubes were filled with the sealers and allowed to set for 24 hours in iOO% humidity. Each sealer was implanted in the connective tissue of Sprague-Dawley rats and removed after 3, 10, 20, 30, and 60 days, fixed, and histologically prepared for light microscope evaluation. At each time period there was practically no difference in the reaction of all the sealers. By 60 days, the total picture was one of well-tolerated biocompatibility. (ORALSURCORAL MEDORAL PATHOL1992;73:490-3)
he search for a biocompatible root canal sealer proceeds constantly, and there have been a number of new endodontic sealers introduced in the last several decades. Testing for biocompatibility is the first appropriate test, for without biocompatibility comparable to commonly used sealers, acceptance as a useful material would be doubtful. There have been many methods of testing reported over the years. Injection of the materials to be tested-along with several controls-directly into the subcutaneous tissue of a test animal has been advocated.lm4 Other investigators have used Teflon or polyethylene tubes filled with freshly mixed or set materials and have implanted these tubes subcutaneously or within bone. 5-11Recently, testing cytotoxicity on cell cultures of Hela cells and fibroblasts has been advocated.12-‘5 Each method has attributes and limitations. One thing seems apparent from the literature-absolute ranking of sealers really is not possible by any method. Test comparisons can be made, but they mean little. The one outstanding conclusion is, a sealer is clinaGraduate Student, Tufts University School of Dental bProfessor Emeritus in Endodontics, Tufts University Dental Medicine. CAssociate Professor of Endodontics, Tufts University Dental Medicine. dAssistant Professor of Oral Pathology, Tufts University Dental Medicine. 7/15/35007
Medicine. School of School of School of
ically acceptable when (1) it is not toxic, (2) it does not cause necrosis of tissue, and (3) after a brief initial period, it is readily accepted by the tissue with minimal inflammatory sequelae. The test material is an experimental resin root canal sealer to which precipitated silver has been added for radiopacity. It is easily mixed and has a very low viscocity so that it should flow readily into all the irregularities of the prepared canal space. Hopefully, this will help provide a superior seal of the filled root canal. The purpose of this study was to evaluate the inflammatory response of this resin sealer, to determine its biocompatibility when implanted into the soft tissues of rats, and to compare these responses with those elicited by several commonly used sealers. If the biocompatibility was acceptable, the sealer could then be tested for apical leakage, manipulation, and other factors to determine whether this would be suitable for use as a sealer in an endodontic filling technique. MATERIAL AND METHODS Ten mm lengths of polyethylene tubing (1 mm outside diameter, 0.7 mm inside diameter) were prepared and sterilized with ethylene oxide. Six root canal sealers were tested: (1) an experimental resin; (2) an experimental resin with silver added as a radiopacifier; (3) Sealapex (Kerr Manufacturing Co., Romulus, Mich.); (4) Kerr sealer (Kerr Manufacturing Co., Romulus, Mich.); (5) AH-26 (deTrey Co., Zurick, Switzerland); and (6) Roth’s sealer (Roth Drug Co.,
Volume 73 Number 4
Fig. 1. Sprague-Dawley rats with the six incisions for placement of the polyethylene tubes with sealer. Chicago, Ill.). These four control sealers, nos. 3,4, 5, and 6, were chosen because of their long history of successful use in endodontic treatment. They have been extensively tested by various means and have been judged to be relatively biocompatible, even though they may have demonstrated slight chronic inflammation.‘-” This has been judged to be clinically insignificant and the sealers are well tolerated. The side of the tube is its own control. The various sealers were mixed under sterile conditions, according to manufacturers’ directions, and then placed into the tubes. The outside surfaces of the tubes were wiped clean with sterile gauze and the materials were allowed to set in 100% humidity for 48 hours. Ten 200-gram Sprague-Dawley rats were used. After ether anesthesia, the implant sites were shaved and the skin was disinfected with povidone-iodine solution. Ten millimeter incisions were made, two at each shoulder, two at midabdomen and two at each hip, and a thumb forceps was used to tunnel a subcutaneous pocket. One tube was placed in each of the six locations, so that all six materials were in each animal. The wounds were closed with wound clips and the rats were fed rat chow and water ad libitum (Fig. 1). Two rats were killed at each of five time periods: 3 days, 10 days, 20 days, 30 days, and 60 days. The tubes were recovered in block sections, fixed in formalin, and prepared for histologic examination. They were sectioned at 6 microns and stained with hematoxylin and eosin stain. RESULTS All specimens underwent blind examination by three examiners; that is, the examiner did not know which sealer or which time period was being examined. Within all time periods, it was not possible to
Biocompatibility
of a new endodontic sealer
491
Fig. 2. Three day specimen of tissue around end of tube. Note the granulation tissue and inflammatory cells (Original magnification, X40).
distinguish differences in the sealers, with the exception of AH-26 at 10, 20, and 30 days. At 60 days, all sections appeared similar. At 3 days with all materials, there was still some acute inflammation with a few polymorphonuclear leucocytes, but mostly there were small amounts of granulation tissue and lymphocytes (Figs. 2 and 3). At 10 days, the sections were marked by a diminishing inflammation. There were some macrophages with birefringent material within the cells and a few giant cells surrounding small particles of the sealer (Fig. 4). The AH-26 group had some edema and inflammation with polymorphonuclear neutrophils and macrophages. At 20 days, the inflammation was diminishing-a condensed connective tissue pseudocapsule was forming and there were fewer giant cells. The AH-26 again demonstrated slight edema and inflammation. At 30 days, the inflammation was diminishing, the pseudocapsule was formed, and the numbers of giant cells had diminished and there were just scattered inflammatory cells (Fig. 5). The AH-26 still had some edema which was diminishing. At 60 days, everything was healing. The pseudocapsule was well established, with no inflammation. There were a few inflammatory cells at the open end of the tubes, and there were still a few giant cells and macrophages with insoluble particles within them (Fig. 6). The total picture was of very mild inflammation and healing. All the sealers appeared to be equally well tolerated. DISCUSSION Whenever a discussion of endodontic sealers or filling materials is held, invariably the numbers of
Fig. 3. Higher power of Fig. 2. Inflammatory cells, polymorphonuclear neutrophils, and lymphocytes are present (Original magnification, X200).
Fig. 5. Thirty day specimen. Note the beginning formation of a pseudocapsuleand diminishing number of inflammatory cells (Original magnification, X100).
Fig. 4. Ten day specimen. Diminishing infiammation. Note giant cell with engulfed particles (Original magnification, X 100).
ig. 6. Sixty days-the pseudocapsule is well established; very few inflammatory cells (Original magnification, X 100).
macrophages, lymphocytes, and giant cells are closely scrutinized. Attempts at quantifying these numbers have been made many times with very little success. Several authors9, l3 have pointed out that ranking materials is a very doubtful procedure at best. The interpretation of biocompatibility is often an exercise in semantics. At the Conference on Inflammation in 1976, sponsored by the American Association of Endodontists, a question was raised about small pieces of filling materials and sealer in the periapical tissues that seemed to be well tolerated. The answer by the lecturer, Dr. M. Spector, was that many things could be taken up by macrophages and could persist for 20 years or more. But if they are nontoxic to the macrophages, even if they are totally indigestible and nonsoluble, there is no reason any real damage should be donei Further on, in response to a comment that when one sets up standards for evaluation of dental materials, if one implants in an animal and ends up with mac-
rophages, that sort of reaction is considered a deplorable result.16 Dr. Spector’s colleague, Dr. H. Willoughby, responded that when one has a tattoo, there is an indigestible material that just sits nicely on the site. But it sits there inside cells and these cells do not start wandering. If the tattoo says “‘I love Janice,” it does not slowly move from the chest and become “I love Mary” on the hip.i6 That may seem a bit facetious, but it states the case clearly. Blackman et al. t7 describe test results of a glass ionomer cement with silver and state that the cements they tested were “not benign but are relatively biocompatible” because there were some macrophages and giant cells with engulfed particles. The control sealers are all widely accepted as being relatively biocompatible and have been in use for varying periods of time. The two experimental sealers elicited the same type of mild response as the controls. In addition, a report by the Council of Dental Materials, Instruments, and Equipment of the American
Volume 73 Number 4
Dental Association states that biocompatibility tests using tissue cultures and animals have shown that the components of composite resins, dentin bonding agents,and glass ionsomersdo not elicit damaging evidence to the safe use of these materials. ‘* As for the silver, Spangberg,‘* using a cell culture technique found that silver invariably had the weakesteffect and was the standard to which other materials were compared. B1ackma.net al. l7 found that a glass ionomer cement with silver was biocompatible. Kerr sealer, a long-acceptedmaterial and one of the controls, contains 25% silver. Further studies of this experimental sealer,such as usageand in vitro studies, are necessaryand underway. CONCLUSIONS
Two experimental resin root canal sealers,onewith and one without silver (for radiopacity), were tested by comparison of their biocompatibility with four commonly used sealers.All materials were placed in 10 mm sterilized polyethylenetubes and implanted in rats for periods of 3 to 60 days. All the implanted materials demonstrated mild initial inflammation, which subsided rapiidly. After 60 days, this study demonstratedall the materials to be comparable and well tolerated. Further studies to determine the usefulness of this resin a.sa root canal sealer are necessary and are underway. REFERENCES 1. Stewart G. A comparative study of three root canal sealing agents. ORAL SURG ORAL MED ORAL PATHOL 1958;11:102931. 2. Guttuso J. Histopathologic study of rat connective tissue responses to endodontic materials. ORAL SURC ORAL MED ORAL PATHOL 1963;115:713-26. 3. Morse DR, Martell B, Pike CC, Fantasia J, Esposito JV, Furst ML. A comparative tissue toxicity evaluation of gutta-percha root canal sealers. Part I: 6 hour findings. J Endod 1984; 10:246-9.
Biocompatibility of a new endodontic sealer 493 4. Yesilsoy C, Koren LZ, Morse DR, Kobayashi C. A comparative tissue toxicity evaluation of established and newer root canal sealers. ORAL SURG ORAL MED ORAL PA~HOL 1988; 65:459-69. 5. Browne RM, Friend LA. An investigation into the irritant properties of some root canal filling materials. Arch Oral Biol 1968;13:1355-69. 6. Friend LA, Browne RM. Tissue reactions to some root canal filling materials. Br Dent J 1968:125:291-4. 7. Frienh LA, Browne RM. Tissue ieactions to some root filling materials implanted in the bone of the rabbit. Arch Oral Biol 1969;14:629-38. 8. Safavi KE, Pascon EA, Langeland K. Evaluation of tissue reaction to endodontic materials. J Endod 1983;9:421-9. 9. O&son B, Sliwkowski A, Langeland K. Subcutaneous implantation for the biological evaluation of endodontic materials. J Endod 1981;7:355-69. 10. Orstavik D, Mjor IA. Histopathology and X-ray microanalysis of the subcutaneous tissue response to endodontic sealers. J Endod 1988;14:13-23. 11. Wennberg A. Biologic evaluation of root canal sealers using in vitro and in vivo methods. J Endod 1980;6:784-7. 12. Spangberg L. Biologic effects of root canal filling materials 4. Effect in vitro of solubilized root canal filling materials on Hela cells. Odontol Rev 1989;20:289-99. 13. Kettering JD, Torabinejad M. Cytotoxicity of root canal sealers: a study using Hela cells and fibroblasts. Int Endod J 1984;17:60-6. 14. Safavi KE, Spangberg L, Costa NS, Sapounas G. An in vitro method for longitudinal evaluation of toxicity of endodontic sealers. J Endod 1989;15:484-6. 15. Briseno BM, Willershausen B. Root canal sealer toxicity on human gingival fibroblasts 1. Zinc oxide based sealers. J Endod 1990;8:383-6. 16. Blechman H. Inflammation: a defense mechanism? J Endod 1977;3:369-93. 17. Blackman R, Gross M, Seltzer S. An evaluation of a glass ionomer silver cement in rat connective tissue. J Endod 1989; 15:16-9. 18. Council of Dental Materials. Instruments and equipment biocompatibility and postoperative sensitivity. J Am Dent Assoc 1988;116:767-8. Reprint requests. Melvin Goldman, DDS Department of Endodontics Tufts University School of Dental Medicine One Kneeland St. Boston, MA 02111