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Induced apical closure of permanent teeth in adult primates using a resorbable form of tricalcium phosphate ceramic
JOURNAL OF ENDODONTICS I VOL. 1, NO. 3, MARCH 1975
I n d u c e d a p i c a l c l o s u r e of p e r m a n e n t t e e t h in a d u l t p r i m a t e s u s i n g a r e s o r b a b l e f o r m of t r i c a l c i u m p h o s p h a t e c e r a m i c
Joseph F. Koeniqs, Cdr (DC) USN" Alfred L. Heller, DDS, MS; J. David Brilliant, DDS, MS" Rudy C. Melfi, DDS, PhD; and Thomas D. Driskell, BS, Columbus, Ohio
Conditions of a n open apex were simulated in four C y n a l m o l g u s m o n k e y s b y extirpatinq the vital pulps a n d b y preparinq the root c a n a l s throuqh the apex. The apical 3 m m of 20 teeth w a s treated with a tricalcium p h o s p h a t e resorbable ceramic. The periapical tissues of the treated teeth s h o w e d a minimal inflammatory response. The periodontal liqament tended to reqenerate. Formation of mineralized tissue within the root c a n a l occurred, but bridqinq w a s incomplete.
Various techniques 1"~ have been advocated for the management of pulpless permanent teeth with open apices. A favored method of treatment is induced apical closure using calcium hydroxide with camphorated monochlorophenol. A number of cases have been reported that indicate clinical success with this method of treatment.4,s, ~ l s However, even after two years, there are cases that have not responded to the treatment. 9,14 Torneck and others 15 have indicated that when apical closure takes place clinically, there is not complete bridging of the apex histologically. Periapical inflammation persists about the apices of many teeth because He-
102
crotic tissue exists in corners and crevices of the bridge. The presence of a clinically closed apex is not necessarily indicative of a normal periodontium. Narang and Wells 18 surgically implanted decalcified allogeneic bone matrix in the apices of teeth. The results show that an implanting material that is acceptable to the host will cause osteogenesis or cementogenesis in the apex of the tooth. This method of treatment is a departure from the techniques currently advocated. 4,1~ A major target area of biomedical research is a mechanism to restore lost bone. A resorbable ceramic* has been developed. 2~
The development of this resorbable ceramic is a significant departure from the traditional concept of permanent implants. In the resorbable ceramic apl~roach, a bone defect or void is filled with the specially prepared and processed form of calcium phosphate. As the ceramic resorbs, new tissues proliferate and calcify in the area filled with the ceramic. The results of studies using these special forms of calcium phosphate showed that the ceramic was replaced by bone. 22,2s'~r The purpose of the current study was to evaluate the effects of a tricalcium phosphate resorbable ceramic as an implanting material in the open apices of endodontically prepared teeth in adult monkeys. Fully formed teeth were selected to observe the physiological reaction to the material in the vital periodontal tissues at the apex and within the open apex of an endodontically prepared vital case. It was conjectured that the material might give better results than the resuits currently obtainable with preparations of calcium hydroxide.
JOURNAL OF ENDODONTICS I VOL. 1, NO. 3, MARCH 1975
MATERIALS AND METHODS Root canal preparation that extended through the apices was accomplished on 24 anterior teeth of 4 adult CynalmoIgus monkeys. The canals were prepared to the size of a no. 80 file to simulate an open apex. The apical 3 to 4 mm of 20 teeth was filled with calcium phosphate ceramic. The remaining four teeth served as controls and received no ceramic. All teeth were filled 3 m m short of the apex with gutta-percha using the lateral condensation technique. At intervals of 2-, 8-, 16-, and 24weeks, the animals were anesthetized and killed by perfusion with 10% Formalin through the left ventricle. Block sections were obtained; each block contained a tooth. After decalcification and preparation, serial longitudinal sections of 6 to 8 micrometers were obtained from each tooth. Every fifth section was stained with hematoxylin and eosin and examined under lhe light microscope.
RESULTS Histoloqic e v a l u a t i o n of four control teeth 9 Two-week postoperative control. Accumulations of chips of dentin and debris were seen in the root canal and in the area of the periradicular defect. The inflammatory response was severe; infiltrates of lymphocytes and neutrophils were observed.
Fig l - - L e f t : Eight-week postoperative control. Fibrous connective tissue (FCT) is within root canal (RC) associated with numerous vessels (II). There is active deposition el cementum (C) on canal wall. New bone ]ormation is evident at periapex (NB). Right: Eight-week postoperative ceramic results. Tricalcium phosphate ceramic (TCP) lines root canal (RC) walls; it exists in central portion o[ canal as islands (black) that are surrounded by [ibrous connective tissue (FCT). Thickened bank o/ ]ibrous connective tissue surrounds apex in semicircular arrangement. Hyalinizing material is evident in stroma o/ /ibrous tissue (H) (orig mag X63). liquefaction necrosis was immediately apical and subjacent to the root canal orifice with highly vascularized granulation tissue at the periphery.
9 Twenty-four-week postoperative control. The apical portion of the root
filled the root canal in the apical gion of the tooth specimen. In periodontal ligament immediately low the orifice of the canal, the flammatory response was mild.
9 Eight-week
postoperative
rethe bein-
results.
9 Sixteen-week postoperative control. The root canal space was devoid
Histoloqic e v a l u a t i o n of 20 teeth treated with tricalcium p h o s p h a t e ceramic
Ceramic particles filled the root canal to within a short distance of the apex (Fig 1, right). The ceramic particles in the apical portion of the canal and in the periradicular area were surrounded by compartments of fibrous connective tissue. Hyalinization was observed within these compartments. A thick band of fibrous tissue surrounded the apex in a semicircular arrangement. There was hyalinizing material within this stroma of fibrous tissue; it originated at the apex of the root and partially bridged the orifice of the root canal. There was a minimal inflammatory response.
9 Two-week
results.
9 Sixteen-week postoperative results.
of soft tissue elements. An area of
Ceramic particles almost completely
The root canal space was essentially
9 Eight-week postoperative control. Fibrovascular connective tissue filled the area of the periradicular defect (Fig 1, left). It was contiguous within the root canal as the tissues invaginated to fill it. Deposition of cementum was evident on the internal walls of the canal; it was thickest at the most apical portion of the canal. The inflammatory response was minimal.
canal and the periradicular area were filled with fibrovascular connective tissue (Fig 2). There was a mild to moderate inflammatory response within these tissues. There was cementogenesis on the internal walls of the root canal; the greatest thickness occurred apically. The continuity and orientation of fibers of the periodontal ligament at the apex were dissimilar to those observed in teeth that were not operated on.
postoperative
103
JOURNAL OF ENDODONTIC$ I VOL. 1, NO. 3, MARCH 1975
Fig 2 - - T w e n t y - f o u r - w e e k postoperative control. Fibrous connective tissue (FCT) is within root canal (RC) and periapex with accompanying vessels (V). There is a moderate inflammatory response (INF) within root canal and periapical tissues. Periodontal ligament regeneration (PDL) is not reestablished at apex of tooth (orig mag XIO0).
devoid of soft tissue elements. There was an area of liquefaction necrosis in the immediate area of the root canal orifice. Few ceramic particles were observed. Similar to the control tooth at this time period, all of the treated teeth in this monkey showed a severe inflammatory response. All treatments of these teeth were considered as failures. 9 T w e n t y - J o u r - w e e k postoperative results. The root canal was almost completely occluded by a mineralized tissue that contained entrapped nuclei (Fig 3, 4). Most of the tricalcium phosphate had been resorbed and replaced by the mineralized tissue. The mineralized tissue extended 3 to 5 mm into the root canal from the apical orifice. The mineralized tissue resembled cementum. The transition of tis104
sues from the dentinal wall to the occluding mineralized tissue was smooth and uninterrupted. The periradicular area was filled with regenerated hard and soft tissues that were in an advanced state of repair. The regeneration of the periodontal ligament, in form and in orientation, was similar to the periodontal ligament observed in teeth that were not operated on. There was little, if any, evidence of an inflammatory response associated with the periapical tissues. A portion of the root canal was not occluded by mineralized tissue; rather, a fibrovascular tissue ascended the root canal along one lateral wall. This tissue originated in the periodontal ligament and showed no evidence of an inflammatory infiltrate. The portion of the root canal occupied by fibrovascular tissue appeared to represent about a fifth of the total space available within the apical root canal.
No teeth showed complete bridging across the apex. At the conclusion of the treatment, periapical inflammation persisted around many teeth. This may be related to the residual debris within the main portion of the root canal and the necrotic tissue in the spaces and crevices of the bridge. The presence of a clinically closed apex was not indicative of a normal periodontium. The periapical zone of inflammation was not always radiographically apparent. Formation of an abscess within the periapical zone of inflammation occurred occasionally. The most important result was the persistence of inflammation in the periapical tissues in spite of what appears to be successful closure of the
DISCUSSION
The results of the study showed that a high purity, specially prepared and processed ceramic form of tricalcium phosphate induced bridging of the open apex by a mineralized tissue. A small channel was observed in the bridge; it was occupied by connective tissue and blood vessels. Regeneration of the periodontal ligament with normal orientation of fibers occurred. The bone structure about the root apices was in an advanced state of repair. A minimal inflammatory response was associated with the use of tricalcium phosphate ceramic. Perparations of calcium hydroxide are used routinely to induce apical closure. Their use is based on clinical investigations and on experiments in animals.4,s,l0,14,15,19-2~,~s-30 Since the current usage of preparations of calcium hydroxide is prevalent, it is important to mention a summary of research findings.
Fig 3 - - T w e n t y - / o u r - w e e k postoperative ceramic results. Root canal is nearly occluded by mineralized tissue (MT); mineralized tissue extends 3 to 5 m m into root canal. Periradicular area is filled with regenerated tissues, bone (B), and periodontal ligament (PDL). Periodontal ligament is regenerated to a state like that observed in teeth not operated on (orig mag X63).
JOURNAL OF ENDODONTICS I VOL. 1, NO. 3, MARCH 1975
apex. It is doubtful that elimination of debris within the spaces and crevices of the apical bridge can be accomplished. Inflammation in the periapical tissues appears to persist in the presence of debris. The results of apical closure using the tricalcium phosphate resorbable ceramic indicated that periapical repair and the formation of a mineralized tissue containing nuclei occurred within the root canal. There were no crevices or corners that contained trapped debris. There was a channel along one lateral wall of the canal that contained fibrovascular connective tissue. Perhaps this was necessary to support the vitality of the mineralized tissue that occluded the apical root canal. The inflammatory response was minimal.
Open apices that were created on fully formed, vital teeth of adult primates were closed with the use of a tricalcium phosphate resorbable ceramic. Apical closure has not been reported in fully formed adult teeth treated with calcium hydroxide. The tricalcium phosphate resorbable ceramic appeared to act as a matrix; it allowed invasion of mesenchymal tissue. There was subsequent differentiation, maturation, and deposition of hard tissue as the ceramic was resorbed. Currently, two investigations are being concluded with the use of tricalcium phosphate resorbable ceramic at Ohio State University. They are concerned with the treatment of nonvital, permanent human teeth with open apices, and with the treatment
of vital, fully formed permanent teeth in adult primates with created open apices and physiologically tapering apices. Calcium hydroxide preparations are being used as the control medication in both of the investigations. The results of these investigations will help to resolve two important questions: Will the tricalcium phosphate ceramic be effective in the treatment of nonvital, permanent teeth with open apices in humans? and, will the tricalcium phosphate ceramic induce a physiologic seal at the apices of fully formed adult primate teeth that are vital and are treated endodontically? The comparison between the teeth treated with tricalcium phosphate and the teeth treated with calcium hydroxide should show any difference in time factors that might be associated with the use of the two materials, and the relative effectiveness of the two materials to induce apical closure or to create a physiological seal at the apices of the treated teeth.
SUMMARY
| 4--Le/t: 24-week postoperative ceramic results. Mineralizing tissue within root Ral does not totally occlude it. Fibrous tissue (FCT) and vascular elements (BV) origi~le in periodontal ligament (PDL) and proceed coronally along one wall o/root canal bone; D, dentin (orig +rnag XIO0)). Right: Occluding mineralized tissue (MT) conins entrapped nuclei (NUC) and resembles cementum. Junction or transition (J) /rom Pntin (D) to occluding mineralized tissue is sharply demarcated but continuous (orig Ig X400).
Twenty-four fully formed, vital teeth of adult primates were endodontically prepared to simulate conditions of an open apex. The apical 3 mm of 20 of these teeth was treated with a tricalcium phosphate resorbable ceramic. Interpretation of six-month histologic materials showed that bridging of the open apices by a mineralized tissue occurred. A small channel containing fibrovascular connective tissue was evident on one lateral wall of the apical root canal. Histologically, the apical bridge was not complete. Regeneration of the periodontal ligament about the apices occurred. A minimal inflammatory response, consistent with healing, was associated with the use of the ceramic.
105
JOURNAL OF ENDODONTICS i VOL. 1, NO. 3, MARCH 1975
CONCLUSIONS
Tricalcium phosphate resorbable ceramic induces apical closure of fully formed, vital teeth of primates with created open apices. Regeneration of the periodontal ligament occurs around the apices of teeth treated with tricalciurn phosphate to induce closure. The inflammatory response associated with the use of tricalcium phosphate is minimal.
*Synthos: A high-purity, specially prepared and processed ceramic form of tricalcium phosphate. MITER, Inc., 633 High St, Worthington, Ohio 43085. Dr. Koenigs is an active duty endodontist (DC) USN; Dr. Heller is an endodontist in private practice; Dr. Brilliant is director of graduate endodontics, Ohio State University School of Dentistry; Dr. Melfi is chairman of biological studies, Ohio State University School of Dentistry; and Mr. Driskell is an adjunct professor, Ohio State University School of Dentistry. Requests for reprints Should be directed to Dr. Heller, 6586 Worthington-Galena Road, Worthington, Ohio 43085. References
1. Cooke, C., and Rowbotham, T.C. Root canal therapy in nonvitat teeth with open apices. Br Dent J 108:147 Feb 16, 1960. 2. Ostby, B.N. The role of the blood clot in endodontic therapy. Acta Odontol Scand 19:323 Dec 1961. 3. Ball, J.S. Apical root formation in a non-vital immature permanent incisor. Br Dent J 116:166 Feb 18, 1964. 4. Frank, A.L. Therapy for the divergent pulpless tooth by continued apical formation. JADA 72:87 Jan 1966.
106
5. Rule, D.C., and Winter, G.B. Root growth and apical repair subsequent to pulpal necrosis in children. Br Dent J 120:586 June 21, 1966. 6. Friend, L.A. Root treatment of teeth with open apices. Proc Roy Soc Med 59:1035 Oct 1966. 7. Bouchon, F. Apex formation following treatment of necrotizing immature permanent incisor. J Dent Child 33:378 Nov 1966. 8. Michanowicz, J.P., and Michanowicz, A.E. A conservative approach and procedure to fill an incompletely formed root using calcium hydroxide as an adjunct. J Dent Child 32:42 Jan 1967. 9. Day, R.M. Calcium hydroxide in root canal therapy. Dent Pract 17:384 July 1967. 10. Frank, A.L. Endodontic endosseous implants and treatment of the wide open apex. Dent Clin North Am 11:675 Nov 1967. 11. Steiner, J.C.; Dow, P.R.; and Cathey, G.M. Inducing root end closure of nonvital permanent teeth. J Dent Child 35:47 /an 1968. 12. Van Hassel, H.J., and Natkin, E. Induction of root end closure. J Dent Child 37:57 Jan-Feb t970. 13. Van Hassel, H.F., and Natkin, E. Induction of foraminal closure. J Can Dent Assoc 35:606 Nov 1969. 14. Steiner, J.C., and Van Hassel, H.G. Experimental root apexification in primates. Oral Surg 31:409 March 1971. 15. Torneck, C.D.; Smith, J.S.; and Grindall, P. Biological effects of endodontic procedures on developing incisor teeth. Oral Surg 35:541 April 1973. 16. Narang, R., and Wells, H. Experimental osteogenesis in periapical areas with decalcified allogeneic bone matrix. Oral Surg 35:136 Jan 1973. 17. Ostby, B.N. Nyere unders6kelser over rotbehandlings problemet. Odontol Tidskr 71:467, 1963. 18.'Kaiser, H J. Apical closure of nonvital teeth with open apices using calcium hydroxide. Presented before the Ameri-
can Association of Endodontists, Washington DC, April 1964. 19. Heithersay, G.S. Stimulation of root formation in incompletely developed pulpless teeth. Oral Surg 29:620 April 1970. 20. Feldman, G., and others. Endodontic treatment of vital and non-vital teeth with open apices. NY State Dent J 39:277 May 1973. 21. Duell, R.C. Conservative endodontic treatment of the open apex in three dimensions. Dent Clin North Am 17:125 Jan 1973. 22. Driskell, T.D., and others. Calcium phosphate ceramics: a potential alternative to bone grafting. J Dent Res (IADR Abstracts) 52:I23 Feb 1973. 23. Hulbert, S.F., and others. Materials of construction for bone gap bridges. Orthopedic surgery papers of the Duke University Medical Center and affiliated hospitals. /an 1969. 24. Bhaskar, S.N., and others. Biodegradable ceramic implants in bone. Electron and light microscopic analysi s. Oral Surg 32:336 Aug 1971. 25. Getter, L., and others. Three biodegradable calcium phosphate slurry implants in bone. J Oral Surg 30:263 April 1972. 26. Biggs, A., and others. Inducing osseous proliferation with biodegradable ceramic implants. J Dent Res (IADR Abstracts) 53:85 Feb 1974. 27. Mors, W., and others. Resorbable ceramic ,implants in surgically created cleft palates in dogs. J Dent Res (IADR Abstracts) 53:129 Feb 1974. 28. Law, D.B. Prevention and treatment of traumatized permanent anterior teeth. Dent Clin North Am 9:615 Nov 1961. 29. Ham, J.; Patterson, S.; and Mitchell, D. Induced apical closure of immature pulpless teeth in monkeys. Oral Surg 33:438 March 1972. 30. Dylewski, J. Apical closure of nonvital teeth. Oral Surg 32:82 July 1971.
I n d u c e d a p i c a l c l o s u r e of p e r m a n e n t t e e t h in a d u l t p r i m a t e s u s i n g a r e s o r b a b l e f o r m of t r i c a l c i u m p h o s p h a t e c e r a m i c
Joseph F. Koeniqs, Cdr (DC) USN" Alfred L. Heller, DDS, MS; J. David Brilliant, DDS, MS" Rudy C. Melfi, DDS, PhD; and Thomas D. Driskell, BS, Columbus, Ohio
Conditions of a n open apex were simulated in four C y n a l m o l g u s m o n k e y s b y extirpatinq the vital pulps a n d b y preparinq the root c a n a l s throuqh the apex. The apical 3 m m of 20 teeth w a s treated with a tricalcium p h o s p h a t e resorbable ceramic. The periapical tissues of the treated teeth s h o w e d a minimal inflammatory response. The periodontal liqament tended to reqenerate. Formation of mineralized tissue within the root c a n a l occurred, but bridqinq w a s incomplete.
Various techniques 1"~ have been advocated for the management of pulpless permanent teeth with open apices. A favored method of treatment is induced apical closure using calcium hydroxide with camphorated monochlorophenol. A number of cases have been reported that indicate clinical success with this method of treatment.4,s, ~ l s However, even after two years, there are cases that have not responded to the treatment. 9,14 Torneck and others 15 have indicated that when apical closure takes place clinically, there is not complete bridging of the apex histologically. Periapical inflammation persists about the apices of many teeth because He-
102
crotic tissue exists in corners and crevices of the bridge. The presence of a clinically closed apex is not necessarily indicative of a normal periodontium. Narang and Wells 18 surgically implanted decalcified allogeneic bone matrix in the apices of teeth. The results show that an implanting material that is acceptable to the host will cause osteogenesis or cementogenesis in the apex of the tooth. This method of treatment is a departure from the techniques currently advocated. 4,1~ A major target area of biomedical research is a mechanism to restore lost bone. A resorbable ceramic* has been developed. 2~
The development of this resorbable ceramic is a significant departure from the traditional concept of permanent implants. In the resorbable ceramic apl~roach, a bone defect or void is filled with the specially prepared and processed form of calcium phosphate. As the ceramic resorbs, new tissues proliferate and calcify in the area filled with the ceramic. The results of studies using these special forms of calcium phosphate showed that the ceramic was replaced by bone. 22,2s'~r The purpose of the current study was to evaluate the effects of a tricalcium phosphate resorbable ceramic as an implanting material in the open apices of endodontically prepared teeth in adult monkeys. Fully formed teeth were selected to observe the physiological reaction to the material in the vital periodontal tissues at the apex and within the open apex of an endodontically prepared vital case. It was conjectured that the material might give better results than the resuits currently obtainable with preparations of calcium hydroxide.
JOURNAL OF ENDODONTICS I VOL. 1, NO. 3, MARCH 1975
MATERIALS AND METHODS Root canal preparation that extended through the apices was accomplished on 24 anterior teeth of 4 adult CynalmoIgus monkeys. The canals were prepared to the size of a no. 80 file to simulate an open apex. The apical 3 to 4 mm of 20 teeth was filled with calcium phosphate ceramic. The remaining four teeth served as controls and received no ceramic. All teeth were filled 3 m m short of the apex with gutta-percha using the lateral condensation technique. At intervals of 2-, 8-, 16-, and 24weeks, the animals were anesthetized and killed by perfusion with 10% Formalin through the left ventricle. Block sections were obtained; each block contained a tooth. After decalcification and preparation, serial longitudinal sections of 6 to 8 micrometers were obtained from each tooth. Every fifth section was stained with hematoxylin and eosin and examined under lhe light microscope.
RESULTS Histoloqic e v a l u a t i o n of four control teeth 9 Two-week postoperative control. Accumulations of chips of dentin and debris were seen in the root canal and in the area of the periradicular defect. The inflammatory response was severe; infiltrates of lymphocytes and neutrophils were observed.
Fig l - - L e f t : Eight-week postoperative control. Fibrous connective tissue (FCT) is within root canal (RC) associated with numerous vessels (II). There is active deposition el cementum (C) on canal wall. New bone ]ormation is evident at periapex (NB). Right: Eight-week postoperative ceramic results. Tricalcium phosphate ceramic (TCP) lines root canal (RC) walls; it exists in central portion o[ canal as islands (black) that are surrounded by [ibrous connective tissue (FCT). Thickened bank o/ ]ibrous connective tissue surrounds apex in semicircular arrangement. Hyalinizing material is evident in stroma o/ /ibrous tissue (H) (orig mag X63). liquefaction necrosis was immediately apical and subjacent to the root canal orifice with highly vascularized granulation tissue at the periphery.
9 Twenty-four-week postoperative control. The apical portion of the root
filled the root canal in the apical gion of the tooth specimen. In periodontal ligament immediately low the orifice of the canal, the flammatory response was mild.
9 Eight-week
postoperative
rethe bein-
results.
9 Sixteen-week postoperative control. The root canal space was devoid
Histoloqic e v a l u a t i o n of 20 teeth treated with tricalcium p h o s p h a t e ceramic
Ceramic particles filled the root canal to within a short distance of the apex (Fig 1, right). The ceramic particles in the apical portion of the canal and in the periradicular area were surrounded by compartments of fibrous connective tissue. Hyalinization was observed within these compartments. A thick band of fibrous tissue surrounded the apex in a semicircular arrangement. There was hyalinizing material within this stroma of fibrous tissue; it originated at the apex of the root and partially bridged the orifice of the root canal. There was a minimal inflammatory response.
9 Two-week
results.
9 Sixteen-week postoperative results.
of soft tissue elements. An area of
Ceramic particles almost completely
The root canal space was essentially
9 Eight-week postoperative control. Fibrovascular connective tissue filled the area of the periradicular defect (Fig 1, left). It was contiguous within the root canal as the tissues invaginated to fill it. Deposition of cementum was evident on the internal walls of the canal; it was thickest at the most apical portion of the canal. The inflammatory response was minimal.
canal and the periradicular area were filled with fibrovascular connective tissue (Fig 2). There was a mild to moderate inflammatory response within these tissues. There was cementogenesis on the internal walls of the root canal; the greatest thickness occurred apically. The continuity and orientation of fibers of the periodontal ligament at the apex were dissimilar to those observed in teeth that were not operated on.
postoperative
103
JOURNAL OF ENDODONTIC$ I VOL. 1, NO. 3, MARCH 1975
Fig 2 - - T w e n t y - f o u r - w e e k postoperative control. Fibrous connective tissue (FCT) is within root canal (RC) and periapex with accompanying vessels (V). There is a moderate inflammatory response (INF) within root canal and periapical tissues. Periodontal ligament regeneration (PDL) is not reestablished at apex of tooth (orig mag XIO0).
devoid of soft tissue elements. There was an area of liquefaction necrosis in the immediate area of the root canal orifice. Few ceramic particles were observed. Similar to the control tooth at this time period, all of the treated teeth in this monkey showed a severe inflammatory response. All treatments of these teeth were considered as failures. 9 T w e n t y - J o u r - w e e k postoperative results. The root canal was almost completely occluded by a mineralized tissue that contained entrapped nuclei (Fig 3, 4). Most of the tricalcium phosphate had been resorbed and replaced by the mineralized tissue. The mineralized tissue extended 3 to 5 mm into the root canal from the apical orifice. The mineralized tissue resembled cementum. The transition of tis104
sues from the dentinal wall to the occluding mineralized tissue was smooth and uninterrupted. The periradicular area was filled with regenerated hard and soft tissues that were in an advanced state of repair. The regeneration of the periodontal ligament, in form and in orientation, was similar to the periodontal ligament observed in teeth that were not operated on. There was little, if any, evidence of an inflammatory response associated with the periapical tissues. A portion of the root canal was not occluded by mineralized tissue; rather, a fibrovascular tissue ascended the root canal along one lateral wall. This tissue originated in the periodontal ligament and showed no evidence of an inflammatory infiltrate. The portion of the root canal occupied by fibrovascular tissue appeared to represent about a fifth of the total space available within the apical root canal.
No teeth showed complete bridging across the apex. At the conclusion of the treatment, periapical inflammation persisted around many teeth. This may be related to the residual debris within the main portion of the root canal and the necrotic tissue in the spaces and crevices of the bridge. The presence of a clinically closed apex was not indicative of a normal periodontium. The periapical zone of inflammation was not always radiographically apparent. Formation of an abscess within the periapical zone of inflammation occurred occasionally. The most important result was the persistence of inflammation in the periapical tissues in spite of what appears to be successful closure of the
DISCUSSION
The results of the study showed that a high purity, specially prepared and processed ceramic form of tricalcium phosphate induced bridging of the open apex by a mineralized tissue. A small channel was observed in the bridge; it was occupied by connective tissue and blood vessels. Regeneration of the periodontal ligament with normal orientation of fibers occurred. The bone structure about the root apices was in an advanced state of repair. A minimal inflammatory response was associated with the use of tricalcium phosphate ceramic. Perparations of calcium hydroxide are used routinely to induce apical closure. Their use is based on clinical investigations and on experiments in animals.4,s,l0,14,15,19-2~,~s-30 Since the current usage of preparations of calcium hydroxide is prevalent, it is important to mention a summary of research findings.
Fig 3 - - T w e n t y - / o u r - w e e k postoperative ceramic results. Root canal is nearly occluded by mineralized tissue (MT); mineralized tissue extends 3 to 5 m m into root canal. Periradicular area is filled with regenerated tissues, bone (B), and periodontal ligament (PDL). Periodontal ligament is regenerated to a state like that observed in teeth not operated on (orig mag X63).
JOURNAL OF ENDODONTICS I VOL. 1, NO. 3, MARCH 1975
apex. It is doubtful that elimination of debris within the spaces and crevices of the apical bridge can be accomplished. Inflammation in the periapical tissues appears to persist in the presence of debris. The results of apical closure using the tricalcium phosphate resorbable ceramic indicated that periapical repair and the formation of a mineralized tissue containing nuclei occurred within the root canal. There were no crevices or corners that contained trapped debris. There was a channel along one lateral wall of the canal that contained fibrovascular connective tissue. Perhaps this was necessary to support the vitality of the mineralized tissue that occluded the apical root canal. The inflammatory response was minimal.
Open apices that were created on fully formed, vital teeth of adult primates were closed with the use of a tricalcium phosphate resorbable ceramic. Apical closure has not been reported in fully formed adult teeth treated with calcium hydroxide. The tricalcium phosphate resorbable ceramic appeared to act as a matrix; it allowed invasion of mesenchymal tissue. There was subsequent differentiation, maturation, and deposition of hard tissue as the ceramic was resorbed. Currently, two investigations are being concluded with the use of tricalcium phosphate resorbable ceramic at Ohio State University. They are concerned with the treatment of nonvital, permanent human teeth with open apices, and with the treatment
of vital, fully formed permanent teeth in adult primates with created open apices and physiologically tapering apices. Calcium hydroxide preparations are being used as the control medication in both of the investigations. The results of these investigations will help to resolve two important questions: Will the tricalcium phosphate ceramic be effective in the treatment of nonvital, permanent teeth with open apices in humans? and, will the tricalcium phosphate ceramic induce a physiologic seal at the apices of fully formed adult primate teeth that are vital and are treated endodontically? The comparison between the teeth treated with tricalcium phosphate and the teeth treated with calcium hydroxide should show any difference in time factors that might be associated with the use of the two materials, and the relative effectiveness of the two materials to induce apical closure or to create a physiological seal at the apices of the treated teeth.
SUMMARY
| 4--Le/t: 24-week postoperative ceramic results. Mineralizing tissue within root Ral does not totally occlude it. Fibrous tissue (FCT) and vascular elements (BV) origi~le in periodontal ligament (PDL) and proceed coronally along one wall o/root canal bone; D, dentin (orig +rnag XIO0)). Right: Occluding mineralized tissue (MT) conins entrapped nuclei (NUC) and resembles cementum. Junction or transition (J) /rom Pntin (D) to occluding mineralized tissue is sharply demarcated but continuous (orig Ig X400).
Twenty-four fully formed, vital teeth of adult primates were endodontically prepared to simulate conditions of an open apex. The apical 3 mm of 20 of these teeth was treated with a tricalcium phosphate resorbable ceramic. Interpretation of six-month histologic materials showed that bridging of the open apices by a mineralized tissue occurred. A small channel containing fibrovascular connective tissue was evident on one lateral wall of the apical root canal. Histologically, the apical bridge was not complete. Regeneration of the periodontal ligament about the apices occurred. A minimal inflammatory response, consistent with healing, was associated with the use of the ceramic.
105
JOURNAL OF ENDODONTICS i VOL. 1, NO. 3, MARCH 1975
CONCLUSIONS
Tricalcium phosphate resorbable ceramic induces apical closure of fully formed, vital teeth of primates with created open apices. Regeneration of the periodontal ligament occurs around the apices of teeth treated with tricalciurn phosphate to induce closure. The inflammatory response associated with the use of tricalcium phosphate is minimal.
*Synthos: A high-purity, specially prepared and processed ceramic form of tricalcium phosphate. MITER, Inc., 633 High St, Worthington, Ohio 43085. Dr. Koenigs is an active duty endodontist (DC) USN; Dr. Heller is an endodontist in private practice; Dr. Brilliant is director of graduate endodontics, Ohio State University School of Dentistry; Dr. Melfi is chairman of biological studies, Ohio State University School of Dentistry; and Mr. Driskell is an adjunct professor, Ohio State University School of Dentistry. Requests for reprints Should be directed to Dr. Heller, 6586 Worthington-Galena Road, Worthington, Ohio 43085. References
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