Standardized Rat Model Testing Effects of Inflammation and Grafting on Extraction Healing

Background: Loss of alveolar ridge width and height after tooth extraction is well documented, but models to evaluate ridge preservation are neither standardized nor cost-effective. This rat model characterizes the pattern of bone turnover and inflammation after extraction and bone grafting with or without local simvastatin (SIM). Methods: Fifty retired-breeder rats underwent extraction of the maxillary right first molar and standard surgical defect creation under inhalation/local anesthesia. The left side of each animal served as unmanipulated control. Untreated groups (n = 8 to 9 per group) were compared (analysis of variance, t test) at days 0, 7, 14, and 28 for alveolar ridge height and width and for markers of inflammation and bone turnover by microcomputed tomography, histology, and enzyme-linked immunosorbent assay. Seventeen additional specimens had defects grafted with either bone mineralized matrix (BMM) or a BMM+ SIM conjugate. Results: Extraction-induced bone loss (BL) was noted on buccal, palatal, and interproximal height (P < 0.05) and ridge width (P < 0.01). Week 1 inflammation positively correlated with ridge height; thereafter, a more intense inflammatory reaction corresponded to reduction in alveolar bone height and density (r = 0.74; P < 0.05; Spearman). BMM+ SIM preserved the most interproximal bone height (P < 0.01), increased ridge width and bone density (P < 0.01), enhanced 7-day prostaglandin E2 (P < 0.01), and reduced 28-day inflammation density (P < 0.05). Conclusions: The standard defect used in the current study paralleled human postextraction alveolar BL. Defect grafting, especially BMM+ SIM, reduced inflammation and preserved bone.