In Vivo Comparative Investigation of Three Synthetic Graft Materials with Varying Compositions Processed Using Different Methods

Purpose: The aim of this study was to compare the osteoconductive potential and bone-healing pattern of biphasic calcium phosphates (BCPs) with varying compositions produced using different processing methods. Materials and Methods: Ten male New Zealand white rabbits were used. Four circular defects with a diameter of 8 mm were made in the rabbit calvarium. Each defect was assigned to one of the following BCP groups: control; BCP1, 70% hydroxyapatite (HA)/30% β-tricalcium phosphate (β-TCP); BCP2, 30% HA/70% β-TCP; and BCP3, 20% HA/80% β-TCP. The rabbits were killed either 2 (n = 5) or 8 weeks (n = 5) before surgery. Histologic and histomorphometric analyses were conducted. Results: The total amount of augmentation was significantly greater in the BCP groups than in the control group (P .05). The amount of new bone formation did not differ significantly among the groups at either 2 or 8 weeks. The resorption of BCPs was significantly greater in the BCP3 group than in the BCP1 and BCP2 groups at 2 weeks, but the difference became insignificant compared with the BCP2 group at 8 weeks. The patterns of new bone formation and material resorption varied markedly among the BCP groups. New bone lined the residual particles in the BCP1 group, but filopodia-shaped new bone was observed in the BCP2 group, and collagen fragments were scattered inside the residual particles in the BCP3 group. Multiple cracklike lines were observed on the particles in the BCP3 group. Conclusion: The specific HA-β-TCP ratios in the present study did not significantly influence new bone formation and space maintenance. The observed differences in healing patterns between the groups may be attributable to different physicochemical properties conferred upon the BCPs by the different processing methods used to produce them. Keywords: bone regeneration, bone substitutes, calcium phosphates