Interspecies comparison of alveolar bone biology: Tooth extraction socket healing in mini pigs and mice

Background in an effort to identify and validate which animal models are best suited for dental implant research, we used multiscale analyses to examine tooth extraction wound healing in a well-accepted model, the Yucatan mini pig and a more controversial model, the laboratory mouse. Methods first molar extractions were performed in adult, skeletally mature mini pigs and mice. Alveolar bone repair was evaluated at early, intermediate and late timepoints using quantitative micro-computed tomographic (mu CT) imaging, histology, molecular, and cellular assays. Vital dye labeling was employed to quantify mineral apposition rates (MAR) in both species. Results Despite a 3000-fold difference in weight, the relative proportions of the mini pig and murine maxillae and are equivalent. Quantitative mu CT demonstrated that within the posterior alveolar bone, the volume of mineralized bone was lower in mini pig than in the mice; during healing, however, the bone volume fraction was equivalent. The histologic appearance of healing sites was also comparable, and alkaline phosphatase (ALP) and tartrate resistant acid phosphatase (TRAP) staining showed a similar temporal and spatial distribution of bone remodeling. Vital dye labeling indicated equivalent MAR between the species. The absolute duration of the healing period differed: in mice, complete healing was accomplished in similar to 21 days. In mini pigs, the same process took four times longer. Conclusions Extraction socket healing is histologically equivalent between mini pigs and mice, supporting the hypothesis that the underlying mechanisms of alveolar bone healing are conserved among species.