Abstract: Objective To investigate the change rules of oxygen level and bone metabolism after mandibular ramus osteotomy and try to figure out the effects of jaw surgery on bone remodeling. Methods Thirty healthy seven-week-old male rats were randomly divided into 6 groups. A set of 5 rats were sacrificed at pre-operation and 1d, 3d, 5d, 7d, 14d respectively. Operation groups were treated by bilateral mandibular ramus osteotomy. The area of alveolar bone between the roots of the first molar was examined as region of interest. Hypoxyprobe-1 combined immunofluorescence staining was used to detect changes of oxygen environment at molecular level. Tartrate-resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP) staining were utilized to observe the changes in bone metabolism. Results Obvious hypoxia occurred at 1d and was maintained at 3d postoperatively. The degree of hypoxic condition began to decline at 5d, but there was still a statistical difference compared to the preoperative period. The hypoxia status was relieved and returned to preoperative levels at 7d. Alveolar bone metabolism was active after surgery. The alveolar bone resorption activity was significantly enhanced at 1d, peaked at 7d and decreased to preoperative levels at 14d. Alveolar bone osteogenesis activity was not obvious from 1d to 5d after surgery. However, early osteogenic differentiation was significantly active at 7d and 14d. Conclusion Hypoxic microenvironment of the alveolar bone at an early stage after osteotomy promotes bone resorption. Osteogenesis is enhanced when hypoxic condition is relieved.

Key words: osteotomy, Hypoxia, bone remodeling