Objective Based on a periosteal distraction to periosteum of cleft palate edge, to observe the structural features of newly formed bone in each phase, study its forming process and rule, and make a preliminary study on the mechanism of repairing cleft palate. Methods Firstly, develop model of cleft palate in 8 healthy hybrid juvenile dogs. Then place Nitinol periosteal distraction device under the periosteum of cleft palate edge and fix it and distract the periosteum with a force of（2.45±0.20）N. The opposite edge belongs to control group. Every 2 dogs were killed after 20, 30, 40, 60 days respectively. Results New bone eventually generated under the periosteum after the periosteal distraction at the edge of cleft. Histological observation indicates the increase of osteoblasts in the new bone and the changes of the directions of the collagenous fiber and bone trabecula. A large amount of collagenous fibers arrayed toward the direction of distraction, under the influence of proliferation of osteoblasts, was calcified and become new bone, which gradually became more mature. Conclusion Newly formed bone is completed along the distracting direction in the periosteum. New bone generates in the distraction zone 20 days after the implantation of periosteal distraction device. With the time of placement extending, bone grows, which is most vigorous on the 40th day and becomes relatively mature in terms of calcification on the 60th day focusing on transformation and modeling.
