Micro-CT analysis of alveolar bone healing using a rat experimental model of critical-size defects

Objective: This study was designed to establish a rat model of a critical size alveolar bone defect. Materials and methods: Standardized buccal or mesiobuccal alveolar bone defects were made around the right first mandibular molar of 12-week-old rats, and the left was used as a control. Alveolar bone healing was examined quantitatively by three-dimensional micro-computed tomographic imaging. Bone matrix production of osteoblasts and osteocytes during repair of alveolar bone defects was examined with in situ hybridization for type I collagen. Results: Buccal defects were repaired significantly and the volume decreased by 88.3% in week 24, whereas mesiobuccal defects were repaired little. Osteoblasts and osteocytes expressed type I collagen in both defects in week 3 but showed little expression by week 6 and thereafter, leaving the mesiobuccal defects largely unrepaired. Conclusion: The mesiobuccal defect is a critical-size defect that is not ultimately repaired with bone. It may be an appropriate experimental model for investigating the effectiveness of bone regenerative agents in human alveolar bone loss.