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Histologic and histometric evaluation of rat alveolar wound healing around polyurethane resin implants
Int. Z Oral Maxillojhc. Sut\g. 1997; 26:14~152 Printed in Denmark. All rights reserved
Copyright 9 Munksgaard 1997
IntemadonalJoumdof
Oral& MaxillofacialSurgery ISSN 0901-5027
Histologic and histometric evaluation of rat alveolar wou nd healing around polyurethane resin implants
Teresa Ldcia Lamano Carvalho, Claudia Andrda Cavancanti de Albuquerque Aradjo, Juliana Mazzonetto Tebfilo, Luiz Guilherme Brentegani Department of Stomatology, Laboratory of Pathology, Dental School of Ribeir~to Preto, University of SAo Paulo, RibeirAo Preto, SP, Brazil
T. L. Lamano Carvalho, C. A. C. de Albuquerque Arafijo, J. M. Tedfilo, L. G. Brentegani: Histologic and histometric evaluation of rat alveolar wound healing around polyurethane resin implants. Int. J. Oral Maxillofac. Surg. 1997," 26." 149-152. 9 Munksgaard, 1997 Abstract. The biocompatibility of polyurethane resin implants derived from castor bean (Ricinus communis) was analyzed in the rat dental alveolus. Histometric evaluation of trial areas adjacent to the implants showed, by week 1, the polymer granules encircled by a conspicuous capsule and Surrounded by immature connective tissue. By weeks 2 and 3, the implants were surrounded by less prominent fibrous capsules, and most of the tested area was occupied by mature trabecular bone. By week 6, the fibrous capsule was thinner, and the tested area was almost totally covered with bone, which in several places was in close contact with the implants. The results suggest that the material is compatible, as it was progressively integrated into alveolar bone in the woundhealing process. Resumo. No presente trabalho testou-se a biocompatibilidade do polimero da mamona (Ricinus communis) implantado no interior do alv6olo dental de ratos. O exame histoldgico revelou grgnulos do polimero Iocalizados no tergo cervical, circundados por delgada cfipsula conjuntiva sem reagfio de corpo estranho. A anfilise histom6trica de/treas-teste adjacentes aos implantes mostrou quantitativamente o adelgagamento da c@sula conjuntiva e o aumento da neoformag~o 6ssea, paralela ~ diminuiqS,o de tecido conjuntivo, da 1a para a 6a semanas. Ao final da 6a semana as fireas-teste apresentavam-se quase totalmente preenchidas por tecido 6sseo maduro e, apesar da presenga de uma cfipsula bastante delgada, o trabeculado 6sseo estabelecia, em vfirios locais, intimo contato corn o material implantado. Os resultados sugerem que o material testado 6 biocompativel, sendo progressivamente osseointegrado no decorrer do reparo da ferida de extra,go dental.
Some polyurethane polymers have emerged as materials for biologic implants because of their mechanical properties, chemical stability, and biocompatible nature 3,12,tS,19,21,a3. A natural polyurethane resin made of fatty acids extracted from Ricinus communis (tropical castor bean) has recently been
tested as a matrix for bone and joint replacement 13,a5. Broader applications of this resin in orthopedics, plastic surgery, urology, and periodontics have been suggested. The present study aimed to test the biocompatibility of R. communis polyurethane resin for possible use as
Key words: biocompatibility; Ricinus communis; polyurethane resin; alveolar wound healing.
Accepted for publication 28 August 1996
implant surgery.
material
in
maxillofacial
Material and methods
Male Wistar rats (200 210 g body weight) were anesthetized with an intraperitoneal injection of 2,2,2,-tribromoethanol (ALDRICh,
150
Lamano Carvalho el al.
USA) at a dose of 25 mg/100 g body weight. The upper right incisors were extracted with a forceps after disconnection of the surrounding gingiva and luxation with an enamel hatchet with a cutting edge. Immediately after surgery, five calcified granules of the polymer were placed inside the alveolus, and the soft tissues were sutured with monophilic nylon 4.0. A single 0.2-ml intramuscular dose of antibiotic (Pentabidtico VeteriMrio, WYETH-WHITEHALL) was administered to each rat. The animals were killed by decapitation 1, 2, 3, and 6 weeks postoperatively (n=5-6 per group), their mandibles removed, and the heads immersed in 10% formalin for 48 h. After fixation, the maxilla was dissected and divided along the median saglttal plane. The right halves were cut tangenfially to the distal surface of the molars, decalcified, and processed for paraffin embedding. Longitudinal, semiserial 7-/~m-thick sections, cut at intervals of 70 #m, were stained with hematoxylin and eosin. Polymer granules Granules of the polymer (Poliosteo, BIO~'CECXMCA, Jati, SR~ Brazil) were prepared according to the manufacturer's instructions, by mixing together liquid polyol, liquid prepolymer, and calcium carbonate. After drying, the granules were sterilized in 70% alcohol and implanted into the alveolus. A light camera (ZEIss, JENA) was used to measure the mean granular volume in the same histologic sections examined for biocompatibility. Ten histologic sections of the granules per animal were used at a final magnification of • and the equatorial granular sections (those presenting the largest orthogonal diameters D1 and D2) were used for volume calculation by the following formula: V 1/67z D1 D2 (D1 D2) m. The mean granular volume was 0.54_+0.03 mm ~
Fig. 1 ~ t, Trial areas around castor bean polyurethane granules (G) implanted into rat dental alveolus, showing implants encircled by conspicuous capsule (arrows). Immature connective tissue (Fig. 1) or newly formed bone trabeculae (Fig. 2) surround implants by week 1; trabecular bone is observed at end of week 2 (Figs. 3 and 4). Magnifications: Figs. 1 3 (• Fig. 4 (• HE.
with n o foreign-body reaction, localized in the cervical third o f the alveolus. T h e healing process of the entire socket followed a n o r m a l p a t t e r n . T h e delicate b o n e trabeculae, w h i c h were i m m e r s e d in a b u n d a n t i m m a t u r e connective tissue by week 1, were progressively replaced by m a t u r e trabecular b o n e filling alm o s t the entire socket at the end of week 6.
By week 1, histologic a n d h i s t o m e t r i c evaluations of the trial areas a d j a c e n t to the implants showed the polymer g r a n ules encircled by a conspicuous capsule (35.0_+3.1 [tm), s u r r o u n d e d by i m m a ture connective tissue rich in fibroblasts a n d n e o f o r m e d capillaries (Fig. 1); newly f o r m e d bone trabeculae were observed in close contact with the capsule in several sites (Fig. 2). By week 2, the
Histometric determinations A light camera was used to estimate the volume fraction of alveolar components by a differential point-counting method, as previously described ~6. Microscopic images of the alveolus (magnification• were superimposed on sheets of paper with a grid containing 100 equidistant points. Two thousand points lying on connective tissue and bone trabeculae were counted per alveolus in trial areas (83• #m 2) contiguous to the implants. The fbrous capsule around the implants was also drawn (magnification• and mean thickness was estimated by direct measurement of five equidistant points per section (n=50 measurements per animal). Results Histologic e x a m i n a t i o n revealed unresorbed granules o f the polymer, surr o u n d e d by a thin connective capsule
Fig. 5-8. Trial areas around castor bean polyurethane granules (G) implanted into rat dental alveolus, showing implants encircled by thin connective capsule (arrows) and adjacent areas occupied by mature bone, at end of week 3 (Figs. 5 and 6). By week 6, mature bone was in close contact with implants at some sites (Figs. 7 and 8). Magnifications: Figs. 5 and 7 (• Figs. 6 and 8 (• HE.
Alveolar wound healing
Volume Vraction
Bon
Con
Cap
100
16
v
80
12
(1) > O O cc O
v
60
0)
8 r
9
40
0) cO
20
O_
9 4
cn
.L
0
O O
1
2
3
4
5
6
7
Time (weeks) Fig. 9. Volume fraction (%) of bone trabeculae (Bon), connective tissue (Con), and capsule (Cap) estimated 1 6 weeks after tooth extraction in trial areas around castor bean polyurethane granules implanted into rat dental alveolus (mean+SEM for 5 6 rats per group).
implants were surrounded by a less prominent fibrous capsule (23.4-+1.9 ~tm), and the trial areas were occupied by trabecular bone and connective tissue (Figs. 3 and 4). At the end of week 3, the capsule was thinner (15.5-+1.1 #m), and most of the test area was occupied by mature bone (Figs. 5 and 6). By week 6, the capsule thickness was reduced to 6.8-+0.7 #m, and the test area was almost totally covered with bone, which was in close contact with the implants at some sites (Figs. 7 and 8). Quantitative data confirmed the progressive bone formation parallel to a decrease of the volume fraction of connective tissue and fibrous capsule around implants (Fig. 9).
Discussion Experimental studies have been conducted to investigate the biocompatibility of various materials such as metals, ceramics and glass-ionomer cements implanted into the maxilla and mandible4,6,7,9,14,17,20,22,24. The biopolymers'~have also been tested mainly for application in orthopedic surgery and otorhinology 3'18'19'23,
the results demonstrating clear differences between materials in terms of foreign-body reaction around implants and growth of fibrous tissue and bone. The Department of AnalYtical Chemistry and Polymers Technology (University of S~,o Paulo, Sgo Carlos, Brazil) has developed a natural polyol derived from castor bean oil; a polyurethane was obtained by polymerization of the polyester polyol with diphenylmethanediisocyanate. KOJIMA et a1.15 have tested the castor bean polymer in the knee joint and medial condyle of rabbits and observed, by histologic examination up to 40 days after surgery, fibroblastic growth, progressively replaced by bone around and inside the pores of calcified cylinders implanted into the condyle, with absence of late inflammatory reaction and no signs of systemic toxic effects. Similar results were observed by IGN~CIO 13 in rabbit radii. Osseointegration is defined as a direct functional and structural connection between organized bone and the surface of implanted materials 5. A fibro-osseous integration occurs when a fibrous capsule encircles the material and is only acceptable during the initial
151
periods after implantation 25, as encapsulated implants are considered unstable I. In the present study, a commercially available castor bean polymer was tested for biocompatibility, rat alveolar wound healing being used as a model. Histologic examination of the entire socket revealed a normal healing pattern closely approximating known data 2,s,l~ Histometric evaluation around the implants showed progressive osteogenesis in conjunction with a decrease in the fibrous capsule thickness. Over the observed period, there was no foreign-body reaction or persistence of the inflammatory reaction; by week 6, a close contact between bone and implants was observed at some sites. The results suggest that the tested material is biologically compatible, as it was progressively integrated into alveolar bone in the healing process.
Acknowledgments. We thank Albertina A. Teixeira, Antonio de Campos, and Edna A. S. Moraes for technical assistance. The material for implant (PouOSTEO, Indtistria Comdrcio Produtos Ortopddicos Ltda, Av. Deputado Zien Nassif 880, 17204 140 Jail, SR Brazil, Fax (0146) 22-2576) was kindly donated by Dr Nilton Mazer.
References T, SENNERBY L. Direct bone anchorage of oral implants: clinical and experimental considerations of the concept of osseointegration. Int J Prosthodont 1990: 3:30 41. 2. ASTRAND P, CARLSSON GE. Changes in the alveolar process after extractions in the white rat. A histologic and fluorescent microscopic study. Acta Odontol Scand 1969: 27: 113-27. 3. BAKKER D, BLITTERSWIJIKCA, HESSELING SC, KOERTENHK, KUIJPERW, GROTE JJ. Biocompatibility of a polyether urethane, polypropylene oxide and a polyester copolymer. A qualitative and quantitative study of three alloplastic tympanic membrane materials in the rat middle ear. J Biomed Mater Res 1990: 24: 489-515. 4. BAUCH G, GUGLIELMOTTIMB, CABRINI RL. A comparative study of hydroxyapatite and demineralized bone powder in rat alveolar wound healing. J Dent Res 1992: 71: 970. 5. BRXNEMARKPI, ZARBGA, ALBREKTSSON rE Tissue integrated prostheses. Osseintegration in clinical dentistry. Berlin: Quintessenz, 1985. 6. BRENTEGANI LG, BOMBONATO KE LAMANOCARVALHOTL. Histologic and histometric evaluation of the biocompatibility of a glass-ionomer cement in rat alveolar l. ALBREKTSSON
152
L a m a n o Carvalho et aL
wound healing. Biomaterials 1997 (in press). 7. CABRINI RL, RENOU S, GUGLIELMOTTI MB, KOKUBUG, ALMAGROJC. Osseointegration of Zry 4 particles in rat alveolar healing. J Dent Res 1992: 71: 970. 8. CARVALHO ACR OKAMOTO T. Interfer6ncias sist6micas sobre o processo de reparo em feridas de extragao dental. Rev Odontol UNESP 1985: 14:27 33. 9. GUGLIELMOTTI MB, ALONSO C, ITOIZ ME, CABRINIRL. Increased osteogenesis in alveolar wound healing elicited by demineralized bone powder. J Oral Maxillofac Surg 1990: 48: 487-90. I0. GUaLIELMOTTI MB, CABRINI RL. Alveolar wound healing and ridge remodeling after tooth extraction in the rat: a histologic, radiographic and histometric study. J Oral Maxillofac Surg 1985: 43: 359-64. 11. GUGLIELMOTTIMB, UBIOS AM, CABRINI RL. Alveolar wound healing after X-irradiation: a histologic, radiographic and histometric study. J Oral Maxillofac Surg 1986: 44: 972-6. 12. HENNING E, JOHN A, LEMM W, BUCHERT ES, WICK G,~GERLACH K. Biostability of polyurethanes. Z Exp Chir Transplant Kunstliche Organe 1989: 22:204 20. 13. IGN~.CIOH. UtilizaD~,o do cimento derivado do polimero da mamona no preenchimento de falha 6ssea. Estudo experi-
mental em coelhos. Master's Thesis, Faculty of Medicine of Ribeir'~o Preto, SE Brazil, 1995. 14. KAWAKAMIT, ANTHO M, HASEGAWAH, YAMAGISHIT, IYo M, EDA S. Experimental study on osteoconductive properties of a chitosan-bonded hydroxyapatite selfhardening paste. Biomaterials 1992: 13: 759-63. 15. KOJIMA KE, O'HARA GH, RossI JC, TELLES ML, SOARESTVC, SANDAM. Estudo experimental da biocompatibilidade do pollmero da mamona implantada intra-dsseo e intra-articular em coelhos. Ricinus Boletim Informativo no 2, ano I, dez., 1994. 16. LAMANOCARVALHOTL, BOMBONATOKF, BRENTEOANI LG. Histometric analysis of rat alveolar wound healing. Braz Dent J 1997 (in press). 17. MATSUIY, OHNO K, MICH1 KM, TACHIKAWA T. Histomorphometric examination of healing around hydroxyapatite implants in 6~ bone. J Oral Maxillofac Surg 1994: 52: 167-72. 18. NELSON JR STANFORD HG, CUTRIGHT DE. Evaluation and comparisons of biodegradable substances as osteogenic agents. Oral Surg 1977: 43: 836-43. 19. NIELSEN FF, KARRINGT, GOGOLEWSKIS. Biodegradable guide for bone regeneration. Acta Orthop Scand 1992: 63:66 9. 20. OGUCHI H, ISHIKAWA K, MIZOUE K,
SERO K, EGUCHIG. Long-term histological evaluation of hydroxyapatite ceramics in humans. Biomaterials 1995: 16:33 8. 2l. Oi'1 K. Towards an ideal polyurethane graft for hemodialysis. J Biometer Appl 1989: 4:141 57. 22. PARR GR, STEFLIKDE, SISK AL. Histomorphometric and histologic observations of bone healing around immediate implants in dogs. Int J Oral Maxillofac Impl 1993: 8: 534-40. 23. SCHMITT-FOURNIEJA, SERTL GO, SKONDIA V. The use of a biocompatible orthopaedic polymer in the treatment of loose total hip prostheses. J Int Med Res 1989: 17: 254-61. 24. SCHWEIGERJW Titanium implants in irradiated dog mandibles. J Prosthet Dent 1989: 62: 201. 25. W~Iss CM. Tissue integration of dental endosseous implants: description and comparative analysis of the fibro-osseous integration system. J Oral Implant 1986: 12:169 214.
Address: Dra. Teresa L. Lamano Carvalho Faculdade de Odontologia de Ribeir~o P r e t o - USP Av. do Caf~ s/n 14040-904 Ribeir~o Preto SP Brazil
Copyright 9 Munksgaard 1997
IntemadonalJoumdof
Oral& MaxillofacialSurgery ISSN 0901-5027
Histologic and histometric evaluation of rat alveolar wou nd healing around polyurethane resin implants
Teresa Ldcia Lamano Carvalho, Claudia Andrda Cavancanti de Albuquerque Aradjo, Juliana Mazzonetto Tebfilo, Luiz Guilherme Brentegani Department of Stomatology, Laboratory of Pathology, Dental School of Ribeir~to Preto, University of SAo Paulo, RibeirAo Preto, SP, Brazil
T. L. Lamano Carvalho, C. A. C. de Albuquerque Arafijo, J. M. Tedfilo, L. G. Brentegani: Histologic and histometric evaluation of rat alveolar wound healing around polyurethane resin implants. Int. J. Oral Maxillofac. Surg. 1997," 26." 149-152. 9 Munksgaard, 1997 Abstract. The biocompatibility of polyurethane resin implants derived from castor bean (Ricinus communis) was analyzed in the rat dental alveolus. Histometric evaluation of trial areas adjacent to the implants showed, by week 1, the polymer granules encircled by a conspicuous capsule and Surrounded by immature connective tissue. By weeks 2 and 3, the implants were surrounded by less prominent fibrous capsules, and most of the tested area was occupied by mature trabecular bone. By week 6, the fibrous capsule was thinner, and the tested area was almost totally covered with bone, which in several places was in close contact with the implants. The results suggest that the material is compatible, as it was progressively integrated into alveolar bone in the woundhealing process. Resumo. No presente trabalho testou-se a biocompatibilidade do polimero da mamona (Ricinus communis) implantado no interior do alv6olo dental de ratos. O exame histoldgico revelou grgnulos do polimero Iocalizados no tergo cervical, circundados por delgada cfipsula conjuntiva sem reagfio de corpo estranho. A anfilise histom6trica de/treas-teste adjacentes aos implantes mostrou quantitativamente o adelgagamento da c@sula conjuntiva e o aumento da neoformag~o 6ssea, paralela ~ diminuiqS,o de tecido conjuntivo, da 1a para a 6a semanas. Ao final da 6a semana as fireas-teste apresentavam-se quase totalmente preenchidas por tecido 6sseo maduro e, apesar da presenga de uma cfipsula bastante delgada, o trabeculado 6sseo estabelecia, em vfirios locais, intimo contato corn o material implantado. Os resultados sugerem que o material testado 6 biocompativel, sendo progressivamente osseointegrado no decorrer do reparo da ferida de extra,go dental.
Some polyurethane polymers have emerged as materials for biologic implants because of their mechanical properties, chemical stability, and biocompatible nature 3,12,tS,19,21,a3. A natural polyurethane resin made of fatty acids extracted from Ricinus communis (tropical castor bean) has recently been
tested as a matrix for bone and joint replacement 13,a5. Broader applications of this resin in orthopedics, plastic surgery, urology, and periodontics have been suggested. The present study aimed to test the biocompatibility of R. communis polyurethane resin for possible use as
Key words: biocompatibility; Ricinus communis; polyurethane resin; alveolar wound healing.
Accepted for publication 28 August 1996
implant surgery.
material
in
maxillofacial
Material and methods
Male Wistar rats (200 210 g body weight) were anesthetized with an intraperitoneal injection of 2,2,2,-tribromoethanol (ALDRICh,
150
Lamano Carvalho el al.
USA) at a dose of 25 mg/100 g body weight. The upper right incisors were extracted with a forceps after disconnection of the surrounding gingiva and luxation with an enamel hatchet with a cutting edge. Immediately after surgery, five calcified granules of the polymer were placed inside the alveolus, and the soft tissues were sutured with monophilic nylon 4.0. A single 0.2-ml intramuscular dose of antibiotic (Pentabidtico VeteriMrio, WYETH-WHITEHALL) was administered to each rat. The animals were killed by decapitation 1, 2, 3, and 6 weeks postoperatively (n=5-6 per group), their mandibles removed, and the heads immersed in 10% formalin for 48 h. After fixation, the maxilla was dissected and divided along the median saglttal plane. The right halves were cut tangenfially to the distal surface of the molars, decalcified, and processed for paraffin embedding. Longitudinal, semiserial 7-/~m-thick sections, cut at intervals of 70 #m, were stained with hematoxylin and eosin. Polymer granules Granules of the polymer (Poliosteo, BIO~'CECXMCA, Jati, SR~ Brazil) were prepared according to the manufacturer's instructions, by mixing together liquid polyol, liquid prepolymer, and calcium carbonate. After drying, the granules were sterilized in 70% alcohol and implanted into the alveolus. A light camera (ZEIss, JENA) was used to measure the mean granular volume in the same histologic sections examined for biocompatibility. Ten histologic sections of the granules per animal were used at a final magnification of • and the equatorial granular sections (those presenting the largest orthogonal diameters D1 and D2) were used for volume calculation by the following formula: V 1/67z D1 D2 (D1 D2) m. The mean granular volume was 0.54_+0.03 mm ~
Fig. 1 ~ t, Trial areas around castor bean polyurethane granules (G) implanted into rat dental alveolus, showing implants encircled by conspicuous capsule (arrows). Immature connective tissue (Fig. 1) or newly formed bone trabeculae (Fig. 2) surround implants by week 1; trabecular bone is observed at end of week 2 (Figs. 3 and 4). Magnifications: Figs. 1 3 (• Fig. 4 (• HE.
with n o foreign-body reaction, localized in the cervical third o f the alveolus. T h e healing process of the entire socket followed a n o r m a l p a t t e r n . T h e delicate b o n e trabeculae, w h i c h were i m m e r s e d in a b u n d a n t i m m a t u r e connective tissue by week 1, were progressively replaced by m a t u r e trabecular b o n e filling alm o s t the entire socket at the end of week 6.
By week 1, histologic a n d h i s t o m e t r i c evaluations of the trial areas a d j a c e n t to the implants showed the polymer g r a n ules encircled by a conspicuous capsule (35.0_+3.1 [tm), s u r r o u n d e d by i m m a ture connective tissue rich in fibroblasts a n d n e o f o r m e d capillaries (Fig. 1); newly f o r m e d bone trabeculae were observed in close contact with the capsule in several sites (Fig. 2). By week 2, the
Histometric determinations A light camera was used to estimate the volume fraction of alveolar components by a differential point-counting method, as previously described ~6. Microscopic images of the alveolus (magnification• were superimposed on sheets of paper with a grid containing 100 equidistant points. Two thousand points lying on connective tissue and bone trabeculae were counted per alveolus in trial areas (83• #m 2) contiguous to the implants. The fbrous capsule around the implants was also drawn (magnification• and mean thickness was estimated by direct measurement of five equidistant points per section (n=50 measurements per animal). Results Histologic e x a m i n a t i o n revealed unresorbed granules o f the polymer, surr o u n d e d by a thin connective capsule
Fig. 5-8. Trial areas around castor bean polyurethane granules (G) implanted into rat dental alveolus, showing implants encircled by thin connective capsule (arrows) and adjacent areas occupied by mature bone, at end of week 3 (Figs. 5 and 6). By week 6, mature bone was in close contact with implants at some sites (Figs. 7 and 8). Magnifications: Figs. 5 and 7 (• Figs. 6 and 8 (• HE.
Alveolar wound healing
Volume Vraction
Bon
Con
Cap
100
16
v
80
12
(1) > O O cc O
v
60
0)
8 r
9
40
0) cO
20
O_
9 4
cn
.L
0
O O
1
2
3
4
5
6
7
Time (weeks) Fig. 9. Volume fraction (%) of bone trabeculae (Bon), connective tissue (Con), and capsule (Cap) estimated 1 6 weeks after tooth extraction in trial areas around castor bean polyurethane granules implanted into rat dental alveolus (mean+SEM for 5 6 rats per group).
implants were surrounded by a less prominent fibrous capsule (23.4-+1.9 ~tm), and the trial areas were occupied by trabecular bone and connective tissue (Figs. 3 and 4). At the end of week 3, the capsule was thinner (15.5-+1.1 #m), and most of the test area was occupied by mature bone (Figs. 5 and 6). By week 6, the capsule thickness was reduced to 6.8-+0.7 #m, and the test area was almost totally covered with bone, which was in close contact with the implants at some sites (Figs. 7 and 8). Quantitative data confirmed the progressive bone formation parallel to a decrease of the volume fraction of connective tissue and fibrous capsule around implants (Fig. 9).
Discussion Experimental studies have been conducted to investigate the biocompatibility of various materials such as metals, ceramics and glass-ionomer cements implanted into the maxilla and mandible4,6,7,9,14,17,20,22,24. The biopolymers'~have also been tested mainly for application in orthopedic surgery and otorhinology 3'18'19'23,
the results demonstrating clear differences between materials in terms of foreign-body reaction around implants and growth of fibrous tissue and bone. The Department of AnalYtical Chemistry and Polymers Technology (University of S~,o Paulo, Sgo Carlos, Brazil) has developed a natural polyol derived from castor bean oil; a polyurethane was obtained by polymerization of the polyester polyol with diphenylmethanediisocyanate. KOJIMA et a1.15 have tested the castor bean polymer in the knee joint and medial condyle of rabbits and observed, by histologic examination up to 40 days after surgery, fibroblastic growth, progressively replaced by bone around and inside the pores of calcified cylinders implanted into the condyle, with absence of late inflammatory reaction and no signs of systemic toxic effects. Similar results were observed by IGN~CIO 13 in rabbit radii. Osseointegration is defined as a direct functional and structural connection between organized bone and the surface of implanted materials 5. A fibro-osseous integration occurs when a fibrous capsule encircles the material and is only acceptable during the initial
151
periods after implantation 25, as encapsulated implants are considered unstable I. In the present study, a commercially available castor bean polymer was tested for biocompatibility, rat alveolar wound healing being used as a model. Histologic examination of the entire socket revealed a normal healing pattern closely approximating known data 2,s,l~ Histometric evaluation around the implants showed progressive osteogenesis in conjunction with a decrease in the fibrous capsule thickness. Over the observed period, there was no foreign-body reaction or persistence of the inflammatory reaction; by week 6, a close contact between bone and implants was observed at some sites. The results suggest that the tested material is biologically compatible, as it was progressively integrated into alveolar bone in the healing process.
Acknowledgments. We thank Albertina A. Teixeira, Antonio de Campos, and Edna A. S. Moraes for technical assistance. The material for implant (PouOSTEO, Indtistria Comdrcio Produtos Ortopddicos Ltda, Av. Deputado Zien Nassif 880, 17204 140 Jail, SR Brazil, Fax (0146) 22-2576) was kindly donated by Dr Nilton Mazer.
References T, SENNERBY L. Direct bone anchorage of oral implants: clinical and experimental considerations of the concept of osseointegration. Int J Prosthodont 1990: 3:30 41. 2. ASTRAND P, CARLSSON GE. Changes in the alveolar process after extractions in the white rat. A histologic and fluorescent microscopic study. Acta Odontol Scand 1969: 27: 113-27. 3. BAKKER D, BLITTERSWIJIKCA, HESSELING SC, KOERTENHK, KUIJPERW, GROTE JJ. Biocompatibility of a polyether urethane, polypropylene oxide and a polyester copolymer. A qualitative and quantitative study of three alloplastic tympanic membrane materials in the rat middle ear. J Biomed Mater Res 1990: 24: 489-515. 4. BAUCH G, GUGLIELMOTTIMB, CABRINI RL. A comparative study of hydroxyapatite and demineralized bone powder in rat alveolar wound healing. J Dent Res 1992: 71: 970. 5. BRXNEMARKPI, ZARBGA, ALBREKTSSON rE Tissue integrated prostheses. Osseintegration in clinical dentistry. Berlin: Quintessenz, 1985. 6. BRENTEGANI LG, BOMBONATO KE LAMANOCARVALHOTL. Histologic and histometric evaluation of the biocompatibility of a glass-ionomer cement in rat alveolar l. ALBREKTSSON
152
L a m a n o Carvalho et aL
wound healing. Biomaterials 1997 (in press). 7. CABRINI RL, RENOU S, GUGLIELMOTTI MB, KOKUBUG, ALMAGROJC. Osseointegration of Zry 4 particles in rat alveolar healing. J Dent Res 1992: 71: 970. 8. CARVALHO ACR OKAMOTO T. Interfer6ncias sist6micas sobre o processo de reparo em feridas de extragao dental. Rev Odontol UNESP 1985: 14:27 33. 9. GUGLIELMOTTI MB, ALONSO C, ITOIZ ME, CABRINIRL. Increased osteogenesis in alveolar wound healing elicited by demineralized bone powder. J Oral Maxillofac Surg 1990: 48: 487-90. I0. GUaLIELMOTTI MB, CABRINI RL. Alveolar wound healing and ridge remodeling after tooth extraction in the rat: a histologic, radiographic and histometric study. J Oral Maxillofac Surg 1985: 43: 359-64. 11. GUGLIELMOTTIMB, UBIOS AM, CABRINI RL. Alveolar wound healing after X-irradiation: a histologic, radiographic and histometric study. J Oral Maxillofac Surg 1986: 44: 972-6. 12. HENNING E, JOHN A, LEMM W, BUCHERT ES, WICK G,~GERLACH K. Biostability of polyurethanes. Z Exp Chir Transplant Kunstliche Organe 1989: 22:204 20. 13. IGN~.CIOH. UtilizaD~,o do cimento derivado do polimero da mamona no preenchimento de falha 6ssea. Estudo experi-
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Address: Dra. Teresa L. Lamano Carvalho Faculdade de Odontologia de Ribeir~o P r e t o - USP Av. do Caf~ s/n 14040-904 Ribeir~o Preto SP Brazil