计算机辅助牙齿隐形正畸系统

Computer Aided Invisible Orthodontic Treatment System

针对牙齿隐形正畸术依赖于预先排齐错位牙齿的需求,提出了包括牙齿形状建模以及虚拟矫治2个部分的完整的计算机辅助牙齿隐形正畸系统.该系统的输入是由光学扫描获得的牙颌数字模型,输出用于快速成型加工的中间母模模型,主要包括牙齿分割、牙齿修复、牙齿运动设计、牙龈变形、矫治方案制定以及虚拟咬合等环节.基于牙颌模型的几何特征,采用两步牙齿模型分割方法:首先确定分割区域,进而利用控制曲线裁切获得光滑边界;对于相邻牙齿之间的缺失区域,利用控制曲线网指定曲面位置约束,并利用微分坐标方法重建;采用移动最小二乘插值解决牙龈变形中由于求解大规模线性系统而导致的消耗内存过多问题.该系统是生产隐形矫治器的关键步骤,同时也为医生诊断病情提供了可视化虚拟环境.近50例临床试验结果表明,该系统能够有效地进行牙齿矫治,并正在进行产业化.

The invisible orthodontic surgery depends on pre-alignment of the misplaced teeth. Based on this requirement, a computer aided invisible orthodontic treatment system consisting of tooth shape modeling and virtual treatment planning is proposed. The input of the system is a digital dental model obtained by optical scanning and the output is the intermediate models ready for rapid prototyping manufacturing. The system consists of the following main steps： tooth segmentation, tooth restoration, tooth movement design, gum deformation, orthopedic scheme determination and virtual occlusion. The tooth model is segmented from the dental model using a two-step procedure. The segmenting region is firstly searched by exploiting the geometry features, and then the boundary is trimmed out by projecting the control curves. By specifying positional constraints using a network of control curves, the missing region between adjacent teeth is repaired based on differential coordinates. For gum deformation, the moving least-square interpolation scheme is employed to solve the problem on excessive consumption of memory space when solving the large-scale linear system. This system is the key step to manufacture invisible aligners. It also provides a visual environment for diagnosing the illness. Clinical trials on 50 cases show that our invisible orthodontic treatment system provides an efficient orthodontic treatment method.