This studied determined the clinical effect of antibiotic use at the site of bone defect restoration in patients with osteoporosis, using tooth ash and plaster of Paris in ovariectomized rats. Forty-eight rats were assigned to four groups randomly and each group was further divided into 4 and 8 weeks after implantation. Histologic sections of the defects were obtained after surgery for histomorphometric analysis. Comparing each week, a significant difference was seen in bone formation by 4 weeks. Compared to controls, new bone formation increased significantly with tooth ash and saline, tooth ash and gentamicin, and tooth ash and gentamicin after ovariectomy. Tooth ash and saline resulted in the best bone formation. The degree of new bone formation was slightly lower when tooth ash and gentamicin were used compared to when tooth ash and saline were used. When tooth ash and gentamicin were compared according to ovariectomy, bone formation was significantly inhibited by ovariectomy at 4 weeks, while no significant difference was seen at 8 weeks.