Effects of Granule Size on the Osteoconductivity of Bovine and Synthetic Hydroxyapatite: A Histologic and Histometric Study in Dogs
Two bovine hydroxyapatites (BHAs), one with granule size of 150 to 200 μm and one with granule size of 300 to 329 μm, and 2 synthetic hydroxyapatites (SHAs), with granule size of 150 and 300 μm, respectively, were compared for effectiveness in repairing circumferential bone defects in dogs. The hydroxyapatites (HAs) were characterized through powder x-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Three trephined bone defects (5.0 mm wide × 4 mm long) were created in the humeruses of 8 dogs. In a random manner, the defects on each side were treated with either BHA with small granules (BHA[s]), BHA with large granules (BHA[l]), SHA with small granules (SHA[s]), SHA with large granules (SHA[l]), or left to heal unaided (bilateral control). Four dogs were sacrificed after 6 and 12 postoperative weeks, respectively. Ground sections of each defect were submitted to histologic and histomorphometric analysis (percentage of area occupied by bone, bone marrow, and biomaterial). As a rule, the HA granules exhibited direct bone contact, regardless of the origin and the size of the granules. Control sites were related and had an increased amount of connective tissue infiltration. At 12 weeks, BHA(s) exhibited improved bone formation compared with SHA(s) and SHA(l). The SHA(s) delivered reduced amounts of bone compared with the remaining groups (control included). The area of bone measured in BHA(s) sites was significantly higher at 12 weeks than 6 weeks. The XRD revealed the tested HA samples to be highly crystalline, while BHA appeared with rougher surface at SEM analysis. The BHA(s) performed better than the SHA(s) and SHA(l), as assessed by the amount of bone measured in both implantation sites at 12 weeks. The BHA's material characteristic itself rather than granules size accounted for the distinctive biological behavior. The increased roughness of the BHAs' surface, as assessed through SEM, seemed to benefit the osteoconduction process.Abstract




Scanning electron microscopy (SEM) of BHA(s) and BHA(l) and SHA(s) and SHA(l) granules. (a) Image of surface of the BHA(s) granules. (b) Higher magnification of a granule in A. (c) Image of surface of the BHA(l) granules. (d) Higher magnification of a granule in C. (e) Image of surface of the SHA(s) granules. (f) Higher magnification of a granule in E. (g) Image of surface of the SHA(l) granules. (h) Higher magnification of a granule in G.
Contributor Notes
Alexandre L. Carvalho, Paulo E. P. Faria, Marcio F. M Grisi, Sergio L. S. Souza, Mario Taba, Jr, Daniela B. Palioto, Arthur B. Novaes, Jr, and Luiz A. Salata are with the Department of Oral and Maxillofacial Surgery and Periodontics, Faculty of Dentistry of Ribeirão Preto, The University of São Paulo at Ribeirão Preto, SP, Brazil. Address correspondence to Dr Luiz Antônio Salata, Department of Oral and Maxillofacial Surgery and Periodontics, Faculty of Dentistry of Ribeirão Preto, The University of São Paulo at Ribeirão Preto, SP, Brazil. Avenida do Café, s/n, 14040–904, Ribeirão Preto, SP, Brazil (e-mail: lasalata@forp.usp.br).
Alexandre F. Fraga is with the Department of Materials Engineering, Faculty of Chemistry, The Federal University of São Carlos, São Carlos, SP, Brazil.
L. Sevgi Ozyegin is with the Department of Dental Technology, Vocational School of Health Related Professions, and Faik N. Oktar is with the Department of Industrial Engineering, Faculty of Engineering, Marmara University, Istanbul, Turkey.