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

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).

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.

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).

The standard defect used in the current study paralleled human postextraction alveolar BL. Defect grafting, especially BMM+SIM, reduced inflammation and preserved bone.