OBJECTIVETo establish animal models for research of orthodontic tooth under rapid movement through distraction osteogenesis of the periodontal ligament, and to approach the rules of bone formation and the relationship between new bone formation and angiogenesis.

METHODS48 rats of which the right maxillary first molars were removed were randomly divided into experimental and orthodontic control group. The orthodontic model was established according to traditional method, and the stretch device was installed in the experimental group after reducing the second molar's mesial bone resistance. Four animals in each group were randomly selected to be killed at 6 time points (at day 0, 3, 5, 10, 20, and 30). After specimens were obtained, immunohistochemical staining was done. The expression of vascular endothelial growth factor (VEGF) and osteocalcin (OC) were investigated.

RESULTSIn the experimental group, VEGF was mainly expressed in vascular endothelial cells, fibroblasts, osteoblasts, osteoclasts, and bone cells. The positive expression of VEGF gradually increased, the peak appeared at day 10 on the tension side, and the other side was at day 5. OC-positive signals were seen in the extracellular matrix of periodontal ligament and osteoblastic cells, and its peak appeared at day 10 on both tension and pressure side. The expression of VEGF and OC were similar in orthodontic control group, but the level was lower.

CONCLUSIONVEGF and OC involve in the remodeling of periodontal tissues and play an important role during periodontal ligament distraction osteogenesis. Angiogenesis is earlier than bone formation, or both appear simultaneously.