STUDY FOR EFFECTS OF MANDIBULAR DISTRACTION OSTEOGENESIS IN TMJ

下颌头显示软骨生长，并且该部位的生长被认为是下颌骨生长区域中数量最多的。通过CT和头部造影，该部位的软骨生长显示出不同的形态，其评价被认为是生长预测的关键。影响关节头生长的刺激因素包括咀嚼时产生的反作用力。近年来，在临床上，牵张成骨被用于治疗骨骼不协调。本研究以生长期大鼠为研究对象，观察下颌骨牵张成骨过程中髁突的生长情况，并根据咀嚼肌的运动速度和牙负荷计算出髁突关节头处的反力矢量。从动物实验结果来看，PTHrP在髁突软骨中有明显的变化。在临床评估的结果中，我们也使用压力感测片来确定牙列中的负载位置和负载。然后，我们确定了每个受试者的CT图像中的肌肉牵引方向和牙齿负载方向，从由每个负载的二维位置、其积分和咬合压力确定的向量计算力矩，并计算在关节头处产生的相反力。由咀嚼肌牵引向量和牙负荷计算的反力向量受牵引负荷的影响。特别是当咬合力改变时，反力的变化趋势更明显。我们正在分析向量的维数和增长量，我们希望这种方法能够预测分散的方向。

The mandibular head shows cartilaginous growth, and the growth at this site is considered to be the greatest quantitatively among the growth areas of the mandible. Cartilaginous growth at this site shows diverse morphology by CT and cephlography, and its evaluation is considered to be a key to growth prediction. Stimulatory factors that affect the growth of the joint head include the reaction force generated in mastication. Recently, in clinical orthodontics, distraction osteogenesis is performed for development of skeletal disharmony. However, details in the changes of mechanical condition at condyle is still unknown.In this study, we examined condylar growth with mandibular distraction osteogenesis with growing rats, also calculated the vector of the reaction force generated at the joint head from the vectors of masticatory muscle fraction and dental loads in each individual. From the resultant of animal experiment, the change on PTHrP was detected at condylar cartilage. In the result of clinical evaluation, we also determined the loading sites in the dentition and the loads using pressure-sensor sheets. We then determined the direction of muscle traction and direction of dental loading in the CT image of each subject, calculated the moments from vectors determined by the two dimensional position of each load, its integral, and occlusal pressure, and calculated the opposite force generated at the joint head. The vector of the reaction force calculated from the traction vectors of masticatoly muscles and dental loads was affected by distraction load. Particularly, the reaction force was inclined when the occlusal force was changed. We are analyzing the dimension of the vector and the quantity of growth, and we expect this method to make prediction of the direction of distraction possible.