Effect of Raloxifene on Bone Formation Around Implants in the Osteoporotic Rat Maxilla: Histomorphometric and Microcomputed Tomographic Analysis

Purpose: Raloxifene, an antiresorptive drug, prevents bone loss and promotes bone formation by secondary anabolic action. The purpose of this study was to investigate the effectiveness of raloxifene on the osseointegration of implants in the rat model of the osteoporotic maxilla. Materials and Methods: Thirty Sprague-Dawley female rats aged 10 weeks were randomly assigned to the following groups: (1) raloxifene (RAL) group (n = 10), (2) ovariectomized (OVX) group (n = 10), and (3) control group (sham-operated, n = 10). Both ovaries were removed to induce osteoporosis, and the maxillary right molar was extracted. After 4 weeks, an implant was placed on the same edentulous area. Raloxifene 1 mg/kg/day was administered to the experimental animals in the RAL group, while those in the ovariectomized group and sham-operated group were given the same amount. All experimental animals were sacrificed at 4 weeks after implants were placed. Histomorphometric measurements of the bone area ratio (BA, %) and bone-to-implant contact ratio (BIC, %) around the implant were performed. Three-dimensional (3D) microcomputed tomographic (micro-CT) analysis of peri-implant bone microarchitecture was also performed and statistically analyzed. Results: In the histomorphometric analysis, the BA ratio of the implant in the RAL group was higher than that in the OVX group (53.3% ± 7.2% vs 38.2% ± 11.7%, P = .024). BIC around the implant in the RAL group did not show a statistical difference compared with that in the OVX group (42.7% ± 15.0% vs 34.5% ± 16.2%, P > .05). In microstructural analysis, the RAL group showed a significant increase of trabecular thickness compared with the OVX group (0.09 ± 0.02 mm vs 0.06 ± 0.01 mm, P = .013). However, raloxifene did not show convincing differences between the groups in other micro-CT parameters (P > .05). Conclusion: The results show that raloxifene administration demonstrated enhanced new peri-implant bone formation in the osteoporotic rat maxilla. Further research is needed to reveal the effect of raloxifene on the clinical outcome of patients with poor bone quality who undergo dental implant treatment. Keywords: histomorphometric analysis, implant, osteoporosis, raloxifene, 3D micro-CT