Purpose: The purpose of this study is to investigate on the regenerative capacity by using different size of graft materials around bony defect around implant. Material and Methods: Dental implant fixtures(Bio-TIS, Korea) were placed into the tibia of 8 rabbits. After placement of implant, artificial defects were created for each group, and the size of bone graft materials were used according to each designated group. 4 weeks after surgery, 8 rabbits were sacrificed. The histologic and histomorphometrical study were done for comparison of the regenerative capacity using $80-90{mu}m$ and $200{sim}1000{mu}m$ size of grafting materials of OCS-$B^{(R)}$. Result: Matured bone formation was significantly increased more in Group E1($80-90{mu}m$) than in Group E2($200{sim}1000{mu}m$). Group E1($80-90{mu}m$) showed more significant augmentation in marginal length of graft material per unit area than Group E2($200{sim}1000{mu}m$). Group E1($80-90{mu}m$) showed more interspace in graft material than Group E2($200{sim}1000{mu}m$). Control group showed no new bone formation around and inside of implanted fixture. Conclusion: Small grafting material size has great influence on bone regeneration.