APPLICATION OF COMPUTER ASSISTED SIMULATION TECHNIQUE TO ORTHODONTICS

为了研究颌面复合体的形态与肌肉功能之间的关系，进一步理解咀嚼的意义和正畸治疗的生物学基础，我们开发了新的分析系统。所述系统包括两个不同的部件：1）根据从每个受试者获得的计算机断层扫描（CT）数据开发3D重建和自动FEM的系统，所述计算机断层扫描（CT）数据包括咬合压力测量;以及2）利用CT数据和来自EMG活动的TMJ处的力矩计算，利用三维重建的下颌骨开发下颌骨运动的系统。研究了4名正常志愿者。基线或原始测量值从三个来源获得：CT扫描、全咬合压力检测纸上的咬合压力和数字记录的下颌运动。有限元分析是在32位计算机上自动生成元素的结果。自动化的FEM显示了在每个人确定的握紧过程中产生的应力分布。对CT图像和运动检测器的坐标进行变换和组合，以生成重建下颌骨的运动图像。结果表明，正常人的高切应力区呈双侧对称分布。下颌骨畸形的年轻受试者表现出两侧的应力分布不平衡。这种不平衡在下颌畸形的老年受试者中并不明显。下颌畸形患者的两个髁状突头在缓慢最大张开和闭合过程中的运动速度与正常人相比没有差异。这些计算机辅助程序可用于获得临床上有用的信息，应力分布在下颌骨和运动的髁状突在个别科目。

In order to investigate the relationship among morphology and muscle function in maxillofacial complex, and further understanding of the meaning of mastication and biological basis of Orthodontic treatment, we have developed new analyzingsystems. The systems include two different components : 1) a system that develops 3D reconstruction and an automated FEM from computed tomography (CT) data obtained from each subject that includes bite pressure measurements ; and 2) a system that develops mandibular motion with a three-dimensionally reconstructed mandible using the CT data and moment calculation at TMJ from EMG activity. Four normal volunteer subjects were studied. Baseline or original measurements were obtained from three sources : CT scanning, biting pressure on full-occlusion pressure-detecting paper, and digitally-recorded jaw movements. The FE analysis resulted from automated generation of elements performed on a 32-bit computer. The automated FEM indicated stress distributions generated during clenching that were determined for each individual. Coordinates in the CT images and from the motion detector were transformed and combined to generate a moving picture of the reconstructed mandible. The results showed that the normal subjects had a bilaterally symmetrical distribution of regions with high shear stress. The younger subjects with mandibular deformities demonstrated a bilateral imbalance in distribution of stresses. This imbalance was not evident in older subjects with jaw deformities. The velocity of movement of the two condylar heads during slow maximum opening and closing was not different in the subjects with jaw deformities as compared to the normal subjects. These computer-assisted programs can be used to derive clinically useful information about stress distributions in the mandible and movement of the condyles in individual subjects.