Abstract: Objective To explore the impact of oxysterols coated bovine bone blocks (OBB) for regeneration of critical-sized defects in dog mandible at the early stage of bone healing. Methods Four beagle dogs were used in this study. After the mandibular third, fourth premolar, and first molar extraction, two standardized box-shaped defects (5 mm×10 mm×10 mm) were created on both sides of the mandible of each animal (n=4 animals, total 16 defects). Four weeks later, the defects were randomly augmented with OBB (n=8) or bovine bone blocks (n=8) in a split-mouth design. All animals were sacrificed 4 weeks after surgery. The specimens were decalcified for hematoxylin and eosin staining and immunohistochemical analysis of osteocalcin (OC). Results Histomorphometrical analysis (HE staining) revealed that the percentage of new bone was significantly higher in the OBB group (35.43±2.78)% in comparison with the BBB group (30.88±2.03）%, P<0.05. And the mean value of the number of vessels was (31.50±1.60) in the OBB group and (30.00±1.31) in the BBB group (P>0.05). The number of OC-stained cells was (63.50±7.50) in the OBB group and 55.50±5.15 in the BBB group. There is a significant difference in the numbers of OC-stained cells (P<0.05). Conclusion OBB can enhance the regeneration of critical-sized defects by stimulating the differentiation of osteoblastic cells at the early stage of bone healing.

Key words: Oxysterols, Osteoblasts, Bone defects