Activity and morphologic changes in the mandible after mandibular osteotomy.

INTRODUCTION: Orthognathic surgery accelerates orthodontic tooth movement, and tooth movement accelerates with demineralized bone and accelerated bone remodeling. The purpose of this study was to ascertain whether orthognathic surgery induces accelerated bone remodeling. The research design included a human model and an animal model.

METHODS: The levels of serum tartrate resistant acid phosphatase-5b (TRAP) and bone alkaline phosphatase (BALP) were measured in 15 patients after sagittal split ramus osteotomy. For the animal study, 18 rabbits were divided into 6 groups: a control group and 5 surgery groups. The rabbits in the surgery groups had osteotomies in the molar regions of the mandible. Changes in bone mass of the anterior mandibles were examined by microcomputed tomography, and changes in osteoblast and osteoclast numbers were analyzed by real-time polymerase chain reaction, hematoxylin and eosin staining, TRAP staining, and alkaline phosphatase staining.

RESULTS: In the 15 patients, TRAP-5b increased from 1 to 8 weeks postoperatively, and BALP increased significantly in 2 weeks postoperatively. In the rabbits, the levels of mRNA expression of TRAP were increased at 3 weeks, and matrix metalloproteinase 9 was increased at 4 and 8 weeks, whereas mRNA expression of BALP and bone morphogenetic protein 2 were increased at 4 weeks. Bone loss was detected from 1 week postoperatively and reached the maximum at 3 weeks; and bone mass and mechanical structure did not recoverer to preoperative levels until 8 weeks postoperatively.

CONCLUSIONS: These findings show active bone remodeling induced by osteotomy.