Histomorphometric Effects of 2% Risedronate Gel on Calvarial Bone Defects in Rabbits

STATEMENT OF THE PROBLEM: Alveolar bone resorption associated with periodontal disease is a common finding and generally irreversible. It impairs mastication and causes esthetic problems for patients. Bisphosphonates are the most commonly used antiresorptive agents for bone diseases. PURPOSE: Considering the risk of bisphosphonate-related osteonecrosis of the jaw, this study aimed to assess the effect of 2% risedronate gel on calvarial bone defects in rabbits. MATERIALS AND METHOD: In this animal study, critical-size defects of 8mm were created in the calvaria of 20 New Zealand white rabbits. In group 1 (n=10), 2% risedronate gel was applied into the right side defect while the left side defect remained empty and served as control. In group 2 (n=10), placebo gel was applied into the right side defect, while the left side defect remained empty and served as control. Five rabbits in each group were sacrificed at 1month and the remaining five at 2 month, post-operatively, and tissue samples were collected for histomorphometric analysis. Histomorphometric assessments included bone fill, degree of inflammation, number of osteoblasts, number of osteoclasts, and foreign body reaction at the site. Data were statistically analysed using SPSS version 25 via the Dunn test and Kruskal-Wallis test. RESULTS: No bone remodeling was noted in any group at 1 month. The risedronate group showed significantly higher bone fill than the other groups after 2 months (p= 0.016). At 2 months, the number of osteoblasts was significantly higher in the risedronate group (p< 0.05). The groups were not significantly different in terms of inflammation score at 1 (p= 0.31) or 2 (p=0.69) months. Foreign body reaction was not observed in any group at any time point. No osteoclast was detected in any group at any time point. CONCLUSION: Risedronate gel showed superior efficacy with regard to regeneration of rabbit calvarial bone defects compared to the placebo and control groups.