A study on a computerized support system for orthodontic treatment

正畸治疗必须根据正畸医生的经验和技能，对病人进行几年的治疗。我们已经研究了一种用于正畸治疗的计算机支持系统的可行性，并展示了优化治疗程序的巨大潜力。(1)一个治疗的计算机计划系统已经开发出来，它允许正畸医生在计算机图形显示上构建一个设置模型。该系统是基于我们以前开发的设备获得的牙科铸件轮廓数据的三维运动。使用该系统，正畸医生可以在治疗前定量预测每颗牙齿的3D运动。(2)我们还开发了一种系统，可以根据治疗过程中牙齿的三维运动和正畸力来调整正畸矫治器。用有限元法计算了各作用力的大小和方向，包括反旋转和山墙弯曲引起的动量。(3)我们估计了患者牙槽骨的吸收率。通过对牙齿、牙周膜和牙槽骨的有限元模型计算应力分布，并结合三维牙齿运动和应力分布，得出了该速率。吸收量与应力有良好的相关性，约为4mum /g/mm^2/day。(4)为了评估咬合接触，该系统还用于测量上、下牙之间的距离分布。治疗期间咬合接触面积增加。这一结果验证了该系统作为治疗评价手段的有效性。

Orthodontic treatment must be conducted over a period of a few years on a patient, depending on experience and skill of an orthodontist. We have studied feasibility of a computerized support system for orthodontic treatment and demonstrated enormous potentialities to optimize a treatment procedure.(1) A computerized planning system for the treatment has been developed, which allows an orthodontist to construct a setup model on a computer graphic display. This system is based on the 3D movements of dental cast profile data obtained by our apparatus previously developed. Using this system an orthodontist can predict quantitatively the 3D movement of each tooth prior to the treatment. (2) We have also developed a system to readjust an orthodontic appliance on the basis of 3D tooth movements during the treatment and orthodontic forces. The magnitude and direction of the forces, including the momentum caused by anti-rotation and gable bends, are obtained by a finite element method (FEM). (3) We estimated a resorption rate of alveolar bone on patients. The rate was obtained from both the 3D tooth movement and the stress distribution calculated with a FEM model of a tooth, periodontal membrane and alveolar bone. The resorption was correlated well with the stress and was found to be about 4 mum/g/mm^2/day. (4) To evaluate the occlusal contact the system was also applied to the measurement of distance distribution between upper and lower teeth. The occlusal contact area increased during the treatment. This result verifies the usefulness of the system as a mean of treatment evaluation.