- Email: [email protected]
The effect of unbound powdered materials on dog dental pulps
JOURNAL OF ENDODONTICS [ VOL 7, NO 10, OCTOBER1981
The effect of unbound powdered materials on dog dental pulps
P. Eleazer, DDS; O. Bolanos, DDS, I. Sinai, DDS; J. Martin, PhD; a n d S. Seltzer, D D S
T h e use of f i n e l y p o w d e r e d T e f l o n or c a l c i u m h y d r o x i d e as a p u l p d r e s s i n g c a u s e d a n i n f l a m m a t o r y r e s p o n s e , w h i c h i n c r e a s e d in s e v e r i t y a n d e x t e n t w i t h time. Clinical use of these m a t e r i a l s in p o w d e r e d f o r m as p u l p o t o m y d r e s s i n g s a p p e a r s to b e contraindicated.
Over the years, numerous materials have been recommended as pulp capping and pulpotomy agents. These materials include zinc oxide-eugenol'; calcium hydroxide2; polycarboxylate cements3; tricalcium phosphate4; cyanoacrylatesS; glucocorticoid preparations6; antibiotic pastesT; dentin shavingsS; collagen gels9,m and many others. Reports of the relative efficacy of these materials vary, but calcium hydroxide and zinc oxide-eugenol appear to have been more thoroughly investigated and used more in clinical situations than the others. Nonetheless, the search for a less toxic material for pulp capping and pulpotomy continues. Teflon has the potential of being a nonirritating pulp capping agent because it has been described as essentially inert when implanted into dental connective tissues. u'13 In a study by Granath and Hagman '4 on human premolars, pulpotomies were performed, and after irrigation with physiologic saline solution and ensuing hemostasis, discs of Teflon were placed on the dental pulps. On postoperative examination, the underlying pulps remained free of inflammation and were covered by reparative dentin. The purpose of this investigation was to compare the effects of finely
462
powdered Teflon and finely powdered calcium hydroxide on mechanically exposed pulps and pulpotomized dogs' teeth. MATERIALS AND METHODS The experimental animals were three mongrel dogs. They were anesthetized, using an intravenous mixture of .5 mg atropine, 1.0 mg Inovar (Vet), and 1.5 mg pentobarbitol. Incremental doses of .5 mg pentobarbitol were added as needed, to maintain a proper level of anesthesia. Deep cavities were prepared in four maxillary and four mandibular posterior
Fig 7--Mesiodistal section of maxillary left first premolar. Pulpotomy with calcium hydroxide. One week postpulpotomy. Dentin chips (DC) cover pulp with hemorrhagic infiltrate (tt) (orig mag X50).
teeth, using air-cooled, high-speed burs. A total of 48 teeth were opened and the pulps of the teeth were exposed to the depth of the pulp chamber floor. In most instances, a sterile spoon excavator was used to remove remnants of the coronal pulp tissue. Sterile physiologic saline solution was used to wash and debride the cavities; irrigation was continued until hemostasis occurred. Excess moisture was absorbed from the cavity with dry, sterile cotton pellets. Powdered Teflon (Fluo-Kem, Dupont) or calcium hydroxide (analytical reagent calcium hyroxide (max. 0.003% heavy metal impurity; dry heat sterilized to remove calcium carbonate, Mallinckrodt, Inc., St. Louis) was then gently tamped over the remaining pulp stump. The dressing and dentin were coated with varnish,
,
:~. T-a,~'4'~-~~""...
/ , , , ~ ,
9 :. . . .
'
,
~s ',
.,.
,~
,
\
=
2"~ii
",'S
Fig 2--Mesiodistal section of mesial root of maxillary left fourth premolar. Pulpotomy with Teflon orze week postoperatiz,ely. Illustrations, a, apical portion of root. P, pulp. D, dentin. 7, Teflon (ortg mag • b, higher magnification of a. 7, Teflon, AR, apical ramification. I, inflammatory exudate (orig mag • c, coronal pulp tissue. INF, inflammator'~, exudate (orig mag • d, higher magnification of c. Cells consist of lymphocytes and polymorphonuclear leukocytes (orig mag •
and the cavity was filled with dental amalgam. The occlusion was checked to ensure absence of premature contacts. The animals were killed to permit examination of pulp tissue with postoperative reactions of 1, 3, and 15 weeks. Under deep surgical anesthesia, the animals were killed with open-tipped, salinefilled, polyethylene cannulae that were inserted into the cervical portions of both external jugular veins and both common carotid arteries, with the open tips directed cephalad. The venous cannulas were opened, and heparinized physiologic saline solution was perfused through the arterial cannulas. When the perfusate began to clear, the solution was changed to heparinized normal formalin solution and perfusion was continued until the perfusate was dear. Thus, the tissues were fixed as the animal died. The jaws were resected, and blocks containing the experimental teeth Were prepared for light microscope examination. Six micron sections were stained with hemotoxylin and eosin.
RESULTS One animal died before conclusion of the study, and only 20 of the 32 remaining teeth were suitable for study after histologic processing. Coronal pulp, apical pulp, and periapical tissue were examined for the presence of inflammatory cells, necrosis, and tooth and bone resorption. The presence of extravasated red blood cells and the exogenously applied materials were also noted. One week. All of the one week specimens displayed acute inflammation. In all of the calcium hydroxide group, the coronal pulp tissue was necrotic. The intact radicular pulp tissues contained extensive hemorrhage (Fig 1) and were moderately infiltrated with polymorphonuclear
leukocytes. Some leukocytes were also seen in the apical periodontal ligament. In general, the one-week response to Teflon was milder than the response calcium hydroxide. Although necrosis was not evident the entire pulp was inflamed (Fig 2). Periapically, there was a milder inflammation than that observed in the calcium hydroxide treated teeth. Three weeks. After three weeks, the intensity of inflammatory reactions was approximately equal in the Teflon and calcium hydroxide capped teeth. Necrosis of the coronal pulp was seen under both materials. In both groups, the radicular pulps had also become necrotic and periapical granulomas had formed (Fig 3). Capping material was found in the apical pulp tissues in both gr6ups.
463
Fig 3--Afesiodistal section of apical portion of distal root of mandibular rtght first molar. "l'hree weeks postpulpotomy with calcium hydroxide. Apical pulp is necrotic (NP) and granuloma (G) surrounds root apex (orig mag XSO). Fifteen weeks. By fifteen weeks, pulpal necrosis with chronic periapieal inflammation and external tooth and bone resorption were seen under both materials (Fig 4, 5). Peripheral spread of both the powdered Teflon and the calcium hydroxide had increased to a point where the materials were found in both the necrotic pulp tissues and the inflamed periapical tissues.
DISCUSSION Finely powdered Teflon, rather than discs, was used in this study because it is more adaptable to irregularities in the cavity floor. However, although the material appeared to be well-adapted clinically, close adaptation was not evident in the microscope examination. The calcium hydroxide used was a
Fig d--Mesiodistal section of mesial root of mandibular right molar. Fifteen weeks postoperatively with calcium hydroxide. Pulp is necrotic (NP). Granuloma (G) surrounds root apex, which is resorbed (R) (orig mag X50).
finely powdered reagent grade. From the results of this study, the use of finely powdered materials in contact with the pulp would appear to be ill-advised because the calcium hydroxide caused more inflammation than anticipated and because many studies have shown that calcium hydroxide paste is well tolerated by the dental pulp. ~s-'' Inflammation and abscess formation, resulting from pulp capping with calcium hydroxide in powder form or as a paste made with distilled water, have been also reported by Pereira and others?' It is assumed that the results are in response to calcium hydroxide, only because the use of chemically pure calcium hydroxide should eliminate any untoward reaction to impurities or additives which may be present in mixed or less pure compounds. 2v24 The results of this experiment indicate that, for
more favorable results, the calcium hydroxide should not be used alone but should be bound to a base material. Apparently, the physical characteristics of a pulp-capping material also influence the pulp-tissue reaction. Teflon discs have been reported to be inert when placed on pulp tissue, TM whereas, granular Teflon produces irritation. Both Teflon and calcium hydroxide powders were seen within the pulp after a one-week observation period. Dispersion of other types of calcium hydroxide preparations in the pulp has also been reported by Stanley and Lundy (Dycal),24 PittFord (MPC), ~3and Pereira and others (dry powder or paste with distilled water). 2~ In time, the increased spread of the materials may result from venous and lymphatic drainage. 2s This spread of finely powdered material permits more tissue contact with the substance,
F~g 5--Mesiodistal section of distal root of maxillary right fourth premolar. Pulpotomy with l'eflon, 15 weeks postoperatively. Illustrations, a, coronal portion of pulp. Dentin bridge (B) over necrotic pulp (NP) (orig mag X50); b, apical portion of same tooth showing periapical granuloma (G) with root resorption (R) (orig mag X50).
9
,. ill,>I
:i .. ~i . ~ ~ - 7
JOURNAL OF ENDODONTICS [ VOL 7, NO 10, OCTOBER 1981
and therefore, m a y effectively increase its toxicity. Both p o w d e r e d T e f l o n and calcium h y d r o x i d e have been s h o w n to cause cell vacuolization a n d d e g e n e r a tion in tissue c u l t u r e 26'27 a n d in electron microscope studies. 2~ H o w e v e r , w h e t h e r the g r e a t e r i n f l a m m a t o r y response was caused by d i s p e r s i o n of the materials or o t h e r factors is conjecture at the m o m e n t . Dr. Eleazer is in private practice in Albany, Georgia and is a clinical research associate at Emory University. Dr. Bolanos is assistant professor of endodontology at Temple University. Dr. Sinai is a professor and acting chairman of cndodontology at Temple University. Dr. Martin is assistant professor of physiology and biophysics at Temple University. Dr. Seltzer is professor emeritus and director of the Maxi[lo-Facial Pain Control Center at Temple University. Requests for reprints should be directed to Dr. Eleazer, 1503 Third Ave, Albany, Ga 21707.
References 1. Tronstad, L., and Mjor, I.A. Capping of the inflamed pulp. Oral Surg 34:477-485, 1972. 2. Nyborg, H. lIealing processes in the pulp on capping. A morphologic study. Experiments on surgical lesions of the pulp in dog and man. Acta Odontol Stand (Suppl 16) 13:9-130, 1955. 3. Safer, D.S., Avery, JK.; and Cox, C.F. Histopathologic evaluation of the effects of new polycarboxylatecements on monkey pulps. Oral 8urg 33:966-975, 1972. 4. Heller, A.I,., and others. Direct pulp capping of permanent teeth in primates using a resorbal)le form of tricaleium phosphate ceramic. J Endod 1(3):95-101, 1975. 5. Bhaskar, S.N., and others, tluman pulp Capping with isobutyl cyanoacrylate. J Dent Res 51:58-61, 1972.
6. Barker, B.C., and Lockett, B.C.: Reaction of dog pulp and periapical tissue to two glucocorticosteroid preparations. Oral Surg 33:249262, 1972. 7. McWalter, G.M.; El-Kafrawy, A.IL; and Mitchell, D.R. Pulp capping in monkeys with a calcium hydroxide compound, an antibiotic, and a polycarboxylate cement. Oral Surg 36:90-100, 1973. 8. Anneroth, G., and Bang, G. The effect of allogeneic demineralized dentin as a pulp capping agent in Java monkeys. Odontol Revy 23:315-328, 1972. 9. Carmichael, D.J.; Dick, H.M.; and Dodd, C.M. Histologic effects of antigenically altered collagen as a heterograft for mammalian pulp exposures. Arch Oral Biol 19(12):1121-1126, 1974. 10. Dick, H M . and Carmichael, D.J. Reconstituted antigenpoor collagen preparations as potential pulp-capping agents. J Endod 6(7):641-644, 1980. 11. Spfingberg, L. Comparison between tissue reactions to gutta-percha and polytetrafluorethylene implanted in the mandible of the rat. Svensk Tandlak T 61:705-715, 1968. 12. Shepard, H., and Witt, R. Reaction of bone to a Teflon implant. Israeli J Dent Med 22:13-15, 1973. 13. West, N.; Revere, J.; and England, M. A new approach to the use of silver cones: the effect of negatively charged Teflon: a preliminary study. J Endod 5(7):208-213, 1979. 14. Granath, L.E., and Itagman, G. Experimental pulpotomy in human bicuspids with reference to cutting procedure. Acta Ondontol Stand 29:155-163, 1971. 15. Attalla, M.N., and Noujaim, A.A. Role of calcium hydroxide in the formation of reparative dentin. Can Dent Assn J 35:267-269, 1969. 16. Sciaky, I., and Pisanti, S. Localization of calcium placed over amputated pulps in dogs' teeth. J Dent Res 39:1128-I 132, 1960. 17. Stark, M.N.; Myers, H.M.; and Gardner, R. The localization of radioactive calcium
hydroxide Ca 4' overexposed pulps in rhesus monkey teeth: a preliminary study. J Oral Therap Pharmacol 1(3):290-297, 1964. 18. Schr~der, L'., and Granath, L.-E. Early reaction of intact human teeth to calcium hydroxide follow.ing experimental pulpotomy and its significance to the development of hard tissue barrier. Odontol Rev 22:379-396, 1971. 19. "l'ronstad, L. Reaction of the exposed pulp to Dycal treatment. Oral Surg 38:945-953, 1974. 20. Pereira, J.C., and others. Effect of calcium hydroxide in powder or in paste form on pulp-capping procedures: histopathologic and radiographic analysis in dog's pulp. Oral Surg 50:176-186, I980. 21. Sela, J.; Hirschfeld, Z.; and Ulmansky, M. Reaction of the rat molar pulp to direct capping with the separate components of Hydrex. Oral Surg 35:118-122, 1973. 22. Fisher, l".J. and McCabe, J.F. Calcium hydroxide base materials. Br Dent J '144:341344, 1978. 23~ PittFord, T.R. Pulpal response to MPC h)r capping exposures. Oral Surg 50:81-88, 1980. 24. Stanley, H.R. and Lundy, T. Dycal therapy fur pulp exposures. Oral Surg 34:818-827, 1972. 25. deDeus, Q.D., and Han, S.S. The fate of lP-cortisone applied on the exposed dental pulp. Oral Surg 24:404-418, 1967. 26. Homsy, C.A. Biocompatibihty in selection of materials for implantation. J Biomed Mater Res 4:341-356, 1970. 27. Kawahara, tI.; Yamagami, A.; and Nakamura, M., Jr. Biologic testing of dental materials by means of tissue culture, lnt Dent J 18:443-467, 1966. 28. Kukletova, M. and Svejda, T. Ultrastructure of blc,od vessels in damaged pulps. Bull (;roup Int Rech Sci Stomatol Odontol 13:445463, 197(I.
465
The effect of unbound powdered materials on dog dental pulps
P. Eleazer, DDS; O. Bolanos, DDS, I. Sinai, DDS; J. Martin, PhD; a n d S. Seltzer, D D S
T h e use of f i n e l y p o w d e r e d T e f l o n or c a l c i u m h y d r o x i d e as a p u l p d r e s s i n g c a u s e d a n i n f l a m m a t o r y r e s p o n s e , w h i c h i n c r e a s e d in s e v e r i t y a n d e x t e n t w i t h time. Clinical use of these m a t e r i a l s in p o w d e r e d f o r m as p u l p o t o m y d r e s s i n g s a p p e a r s to b e contraindicated.
Over the years, numerous materials have been recommended as pulp capping and pulpotomy agents. These materials include zinc oxide-eugenol'; calcium hydroxide2; polycarboxylate cements3; tricalcium phosphate4; cyanoacrylatesS; glucocorticoid preparations6; antibiotic pastesT; dentin shavingsS; collagen gels9,m and many others. Reports of the relative efficacy of these materials vary, but calcium hydroxide and zinc oxide-eugenol appear to have been more thoroughly investigated and used more in clinical situations than the others. Nonetheless, the search for a less toxic material for pulp capping and pulpotomy continues. Teflon has the potential of being a nonirritating pulp capping agent because it has been described as essentially inert when implanted into dental connective tissues. u'13 In a study by Granath and Hagman '4 on human premolars, pulpotomies were performed, and after irrigation with physiologic saline solution and ensuing hemostasis, discs of Teflon were placed on the dental pulps. On postoperative examination, the underlying pulps remained free of inflammation and were covered by reparative dentin. The purpose of this investigation was to compare the effects of finely
462
powdered Teflon and finely powdered calcium hydroxide on mechanically exposed pulps and pulpotomized dogs' teeth. MATERIALS AND METHODS The experimental animals were three mongrel dogs. They were anesthetized, using an intravenous mixture of .5 mg atropine, 1.0 mg Inovar (Vet), and 1.5 mg pentobarbitol. Incremental doses of .5 mg pentobarbitol were added as needed, to maintain a proper level of anesthesia. Deep cavities were prepared in four maxillary and four mandibular posterior
Fig 7--Mesiodistal section of maxillary left first premolar. Pulpotomy with calcium hydroxide. One week postpulpotomy. Dentin chips (DC) cover pulp with hemorrhagic infiltrate (tt) (orig mag X50).
teeth, using air-cooled, high-speed burs. A total of 48 teeth were opened and the pulps of the teeth were exposed to the depth of the pulp chamber floor. In most instances, a sterile spoon excavator was used to remove remnants of the coronal pulp tissue. Sterile physiologic saline solution was used to wash and debride the cavities; irrigation was continued until hemostasis occurred. Excess moisture was absorbed from the cavity with dry, sterile cotton pellets. Powdered Teflon (Fluo-Kem, Dupont) or calcium hydroxide (analytical reagent calcium hyroxide (max. 0.003% heavy metal impurity; dry heat sterilized to remove calcium carbonate, Mallinckrodt, Inc., St. Louis) was then gently tamped over the remaining pulp stump. The dressing and dentin were coated with varnish,
,
:~. T-a,~'4'~-~~""...
/ , , , ~ ,
9 :. . . .
'
,
~s ',
.,.
,~
,
\
=
2"~ii
",'S
Fig 2--Mesiodistal section of mesial root of maxillary left fourth premolar. Pulpotomy with Teflon orze week postoperatiz,ely. Illustrations, a, apical portion of root. P, pulp. D, dentin. 7, Teflon (ortg mag • b, higher magnification of a. 7, Teflon, AR, apical ramification. I, inflammatory exudate (orig mag • c, coronal pulp tissue. INF, inflammator'~, exudate (orig mag • d, higher magnification of c. Cells consist of lymphocytes and polymorphonuclear leukocytes (orig mag •
and the cavity was filled with dental amalgam. The occlusion was checked to ensure absence of premature contacts. The animals were killed to permit examination of pulp tissue with postoperative reactions of 1, 3, and 15 weeks. Under deep surgical anesthesia, the animals were killed with open-tipped, salinefilled, polyethylene cannulae that were inserted into the cervical portions of both external jugular veins and both common carotid arteries, with the open tips directed cephalad. The venous cannulas were opened, and heparinized physiologic saline solution was perfused through the arterial cannulas. When the perfusate began to clear, the solution was changed to heparinized normal formalin solution and perfusion was continued until the perfusate was dear. Thus, the tissues were fixed as the animal died. The jaws were resected, and blocks containing the experimental teeth Were prepared for light microscope examination. Six micron sections were stained with hemotoxylin and eosin.
RESULTS One animal died before conclusion of the study, and only 20 of the 32 remaining teeth were suitable for study after histologic processing. Coronal pulp, apical pulp, and periapical tissue were examined for the presence of inflammatory cells, necrosis, and tooth and bone resorption. The presence of extravasated red blood cells and the exogenously applied materials were also noted. One week. All of the one week specimens displayed acute inflammation. In all of the calcium hydroxide group, the coronal pulp tissue was necrotic. The intact radicular pulp tissues contained extensive hemorrhage (Fig 1) and were moderately infiltrated with polymorphonuclear
leukocytes. Some leukocytes were also seen in the apical periodontal ligament. In general, the one-week response to Teflon was milder than the response calcium hydroxide. Although necrosis was not evident the entire pulp was inflamed (Fig 2). Periapically, there was a milder inflammation than that observed in the calcium hydroxide treated teeth. Three weeks. After three weeks, the intensity of inflammatory reactions was approximately equal in the Teflon and calcium hydroxide capped teeth. Necrosis of the coronal pulp was seen under both materials. In both groups, the radicular pulps had also become necrotic and periapical granulomas had formed (Fig 3). Capping material was found in the apical pulp tissues in both gr6ups.
463
Fig 3--Afesiodistal section of apical portion of distal root of mandibular rtght first molar. "l'hree weeks postpulpotomy with calcium hydroxide. Apical pulp is necrotic (NP) and granuloma (G) surrounds root apex (orig mag XSO). Fifteen weeks. By fifteen weeks, pulpal necrosis with chronic periapieal inflammation and external tooth and bone resorption were seen under both materials (Fig 4, 5). Peripheral spread of both the powdered Teflon and the calcium hydroxide had increased to a point where the materials were found in both the necrotic pulp tissues and the inflamed periapical tissues.
DISCUSSION Finely powdered Teflon, rather than discs, was used in this study because it is more adaptable to irregularities in the cavity floor. However, although the material appeared to be well-adapted clinically, close adaptation was not evident in the microscope examination. The calcium hydroxide used was a
Fig d--Mesiodistal section of mesial root of mandibular right molar. Fifteen weeks postoperatively with calcium hydroxide. Pulp is necrotic (NP). Granuloma (G) surrounds root apex, which is resorbed (R) (orig mag X50).
finely powdered reagent grade. From the results of this study, the use of finely powdered materials in contact with the pulp would appear to be ill-advised because the calcium hydroxide caused more inflammation than anticipated and because many studies have shown that calcium hydroxide paste is well tolerated by the dental pulp. ~s-'' Inflammation and abscess formation, resulting from pulp capping with calcium hydroxide in powder form or as a paste made with distilled water, have been also reported by Pereira and others?' It is assumed that the results are in response to calcium hydroxide, only because the use of chemically pure calcium hydroxide should eliminate any untoward reaction to impurities or additives which may be present in mixed or less pure compounds. 2v24 The results of this experiment indicate that, for
more favorable results, the calcium hydroxide should not be used alone but should be bound to a base material. Apparently, the physical characteristics of a pulp-capping material also influence the pulp-tissue reaction. Teflon discs have been reported to be inert when placed on pulp tissue, TM whereas, granular Teflon produces irritation. Both Teflon and calcium hydroxide powders were seen within the pulp after a one-week observation period. Dispersion of other types of calcium hydroxide preparations in the pulp has also been reported by Stanley and Lundy (Dycal),24 PittFord (MPC), ~3and Pereira and others (dry powder or paste with distilled water). 2~ In time, the increased spread of the materials may result from venous and lymphatic drainage. 2s This spread of finely powdered material permits more tissue contact with the substance,
F~g 5--Mesiodistal section of distal root of maxillary right fourth premolar. Pulpotomy with l'eflon, 15 weeks postoperatively. Illustrations, a, coronal portion of pulp. Dentin bridge (B) over necrotic pulp (NP) (orig mag X50); b, apical portion of same tooth showing periapical granuloma (G) with root resorption (R) (orig mag X50).
9
,. ill,>I
:i .. ~i . ~ ~ - 7
JOURNAL OF ENDODONTICS [ VOL 7, NO 10, OCTOBER 1981
and therefore, m a y effectively increase its toxicity. Both p o w d e r e d T e f l o n and calcium h y d r o x i d e have been s h o w n to cause cell vacuolization a n d d e g e n e r a tion in tissue c u l t u r e 26'27 a n d in electron microscope studies. 2~ H o w e v e r , w h e t h e r the g r e a t e r i n f l a m m a t o r y response was caused by d i s p e r s i o n of the materials or o t h e r factors is conjecture at the m o m e n t . Dr. Eleazer is in private practice in Albany, Georgia and is a clinical research associate at Emory University. Dr. Bolanos is assistant professor of endodontology at Temple University. Dr. Sinai is a professor and acting chairman of cndodontology at Temple University. Dr. Martin is assistant professor of physiology and biophysics at Temple University. Dr. Seltzer is professor emeritus and director of the Maxi[lo-Facial Pain Control Center at Temple University. Requests for reprints should be directed to Dr. Eleazer, 1503 Third Ave, Albany, Ga 21707.
References 1. Tronstad, L., and Mjor, I.A. Capping of the inflamed pulp. Oral Surg 34:477-485, 1972. 2. Nyborg, H. lIealing processes in the pulp on capping. A morphologic study. Experiments on surgical lesions of the pulp in dog and man. Acta Odontol Stand (Suppl 16) 13:9-130, 1955. 3. Safer, D.S., Avery, JK.; and Cox, C.F. Histopathologic evaluation of the effects of new polycarboxylatecements on monkey pulps. Oral 8urg 33:966-975, 1972. 4. Heller, A.I,., and others. Direct pulp capping of permanent teeth in primates using a resorbal)le form of tricaleium phosphate ceramic. J Endod 1(3):95-101, 1975. 5. Bhaskar, S.N., and others, tluman pulp Capping with isobutyl cyanoacrylate. J Dent Res 51:58-61, 1972.
6. Barker, B.C., and Lockett, B.C.: Reaction of dog pulp and periapical tissue to two glucocorticosteroid preparations. Oral Surg 33:249262, 1972. 7. McWalter, G.M.; El-Kafrawy, A.IL; and Mitchell, D.R. Pulp capping in monkeys with a calcium hydroxide compound, an antibiotic, and a polycarboxylate cement. Oral Surg 36:90-100, 1973. 8. Anneroth, G., and Bang, G. The effect of allogeneic demineralized dentin as a pulp capping agent in Java monkeys. Odontol Revy 23:315-328, 1972. 9. Carmichael, D.J.; Dick, H.M.; and Dodd, C.M. Histologic effects of antigenically altered collagen as a heterograft for mammalian pulp exposures. Arch Oral Biol 19(12):1121-1126, 1974. 10. Dick, H M . and Carmichael, D.J. Reconstituted antigenpoor collagen preparations as potential pulp-capping agents. J Endod 6(7):641-644, 1980. 11. Spfingberg, L. Comparison between tissue reactions to gutta-percha and polytetrafluorethylene implanted in the mandible of the rat. Svensk Tandlak T 61:705-715, 1968. 12. Shepard, H., and Witt, R. Reaction of bone to a Teflon implant. Israeli J Dent Med 22:13-15, 1973. 13. West, N.; Revere, J.; and England, M. A new approach to the use of silver cones: the effect of negatively charged Teflon: a preliminary study. J Endod 5(7):208-213, 1979. 14. Granath, L.E., and Itagman, G. Experimental pulpotomy in human bicuspids with reference to cutting procedure. Acta Ondontol Stand 29:155-163, 1971. 15. Attalla, M.N., and Noujaim, A.A. Role of calcium hydroxide in the formation of reparative dentin. Can Dent Assn J 35:267-269, 1969. 16. Sciaky, I., and Pisanti, S. Localization of calcium placed over amputated pulps in dogs' teeth. J Dent Res 39:1128-I 132, 1960. 17. Stark, M.N.; Myers, H.M.; and Gardner, R. The localization of radioactive calcium
hydroxide Ca 4' overexposed pulps in rhesus monkey teeth: a preliminary study. J Oral Therap Pharmacol 1(3):290-297, 1964. 18. Schr~der, L'., and Granath, L.-E. Early reaction of intact human teeth to calcium hydroxide follow.ing experimental pulpotomy and its significance to the development of hard tissue barrier. Odontol Rev 22:379-396, 1971. 19. "l'ronstad, L. Reaction of the exposed pulp to Dycal treatment. Oral Surg 38:945-953, 1974. 20. Pereira, J.C., and others. Effect of calcium hydroxide in powder or in paste form on pulp-capping procedures: histopathologic and radiographic analysis in dog's pulp. Oral Surg 50:176-186, I980. 21. Sela, J.; Hirschfeld, Z.; and Ulmansky, M. Reaction of the rat molar pulp to direct capping with the separate components of Hydrex. Oral Surg 35:118-122, 1973. 22. Fisher, l".J. and McCabe, J.F. Calcium hydroxide base materials. Br Dent J '144:341344, 1978. 23~ PittFord, T.R. Pulpal response to MPC h)r capping exposures. Oral Surg 50:81-88, 1980. 24. Stanley, H.R. and Lundy, T. Dycal therapy fur pulp exposures. Oral Surg 34:818-827, 1972. 25. deDeus, Q.D., and Han, S.S. The fate of lP-cortisone applied on the exposed dental pulp. Oral Surg 24:404-418, 1967. 26. Homsy, C.A. Biocompatibihty in selection of materials for implantation. J Biomed Mater Res 4:341-356, 1970. 27. Kawahara, tI.; Yamagami, A.; and Nakamura, M., Jr. Biologic testing of dental materials by means of tissue culture, lnt Dent J 18:443-467, 1966. 28. Kukletova, M. and Svejda, T. Ultrastructure of blc,od vessels in damaged pulps. Bull (;roup Int Rech Sci Stomatol Odontol 13:445463, 197(I.
465