Experiment Research On Orthodontic Rapid Tooth Movement By Dentoalveolar Distraction Osteogenesis Technique

Traditional orthodontic tooth movement means slow movement in limited speed under pure orthodontic force and after a serial alveolar absorption and deposit. Under the biggest accepted tensile strength, the maximum of tooth physiological migration rate was 1-1.5mm/4-5weeks. This slow migration rate extremely extend the orthodontic course of treatment, especially in tooth extraction cases, the canine retrusion lasted always 6-8 months. Therefore how to increase the migration rate of orthodontic tooth and to shorten orthodontic therapy time is always an attentive topic by scholars. In spite of many methods such as electromagnetism stimulus, drug treatment, reduction of periodontal resistance and so on have been introduced, and they could really work, most of these methods were still not used in clinic, the effect of clinic application was still unknown.Distraction osteogenesis(DO) was a technique, by which a special extension apparatus was used between bone ends or bony suture to promote new bone formation, extend order widen bone. The utilization of DO to accelerate orthodontic tooth movement was the latest advancement in Orthodontics, it is also a new breakthrough in Orthodontic technique. In 2002, Turkish scholars used Dentoalveolar Distraction (DAD) to assist orthodontic tooth movement for the first time. The results showed: the migration rate of canine was extremely increased by this technique, at the same time no obvious complications and side effects were found out. The time of therapy was shortened. It could be called a revolution in Orthodontics history.But domestic and overseas correlated research and application have not been reported yet. It was very considerable to establish DO animal model and research the principle of this new technique and the influence to tooth migration rate and movement style. Through compare of DO and traditional orthodontic methods, new angle and thought could be afforded for tooth movement.1.Establishment of animal experimental model on orthodontic rapid tooth movement through dentoalveolar distraction osteogenesis Objective:To establish an animal model in dogs for rapid tooth movement by dentoalveolar distraction osteogenesis. Methods:Five native health hybrid dogs were used in the study. The second premolars on both sides were extracted, the dentoalveolar distraction surgical procedure was performed, and a custom-made intraoral, rigid, tooth-borne distraction device was placed onto the first and third premolars.5 days after operation, the distraction devices began to be activated at a rate of 0.25mm twice a day for 2 weeks, then to be fixed. The animals were sacrificed on the end of 0, 1,2,4,6 weeks respectively after the activation, then gross sample inspection, radiographic examination were performed. Results: All of the animals were alive successfully after the experiment. Definite ossification was seen in the area between the canine and the 1st premolar. The quality of bone mass increased with the maintain times. Conclusion: The rapid tooth movement was achieved impressively through dentoalveolar distraction osteogenesis, and it is feasible and repeatable of experimental model on this study.2. The rate and style of tooth movement through dentoalveolar distraction osteogenesis in dogsObjective: To observe the rate and style of tooth movement through dentoalveolar distraction osteogenesis in dogs. Methods: the 10 dogs'examinations and measurements of tooth movement and X rays were performed. Results: the distracted tooth moved by the mean distance of 4.002±0.266mm , and the contrast was 1.154±0.155mm (p<0.001);The inclination change of moved tooth was 5.52°±0.36°,and the contrast was 2.02°±0.30°(p<0.001); that of anchor tooth was 1.24°±0.36°,the contrast was 0.92°±0.33°(P>0.05);the vertical change of anchorage tooth was 0.45±0.22mm,the contrast was 0.31±0.17mm( P>0.05 ) .Conclusion: The rapid tooth movement was achieved impressively through dentoalveolar distraction osteogenesis, and tooth inclinations changed along with it.3. Histological study of periodontal ligament (PDL) remodeling through DADObjective: Biological characteristic of periodontal ligament changes, tissue construction variation of tooth extraction crypt and distraction area were observed by historical way. Methods: 10 dogs were operated and placed with self-made distraction device. After 2 weeks of distraction, every 2 dogs were sacrificed on the end of 0, 1,2,4,6 weeks of fixation. Specimen was observed histological. Results: in the initial stage of fixation, collagen fibers were observed in the middle of distraction gap. With the extension of fixation, osteogenesis and osteoclast were activated. At the end of fixation, bones were further rebuilt and mature, at the same time highly calcified. Conclusion: self-restore ability of body could be stimulated by distraction osteogenesis and tooth migration rate could also be increased.