Research And Implementation For Parametric And Multiple-constrained Tooth Preparation Model Design

The promotion and application of digital technology make it possible to prepare toothautomatically. Digital tooth prepare can not only improve the accuracy of operation, but also increasethe efficiency and excellent rate of tooth prepare significantly. It is the inevitable trend of dentalrestoration. For the characteristics of discrete mesh, we come up with the parametic modelingmethod of preparation. The main contents and achievements are as follows:(1) a geodesic distance based tooth long axis extraction method is proposed. First we selectsource near the center of occlusal surface and calculate geodesic distance, and then stratify the modelaccording to the distance value, finally center of each layer is fitted to generate the long axis whichmeet our requirements. The method is simple and robust and have higher precision and stability.(2) a history based and multi-constrained preparation parametic design method is proposed.Firstly, by analysising relationship of dimension constraints, we proposed parametric operations ofpreparation model generation, and then model tectonic history is rerun timely to realize preparation’sdynamic modification. The method is proved work well in preparation’s parametric design.(3) a digital evaluate method of preparation is proposed. Firstly, by measuring the size ofparameters in each predetermined section, the parameter index is obtained by statistical analyses, andthen we computed model distance and displayed the cloud map by color interpolation. The methodassessed preparation quality well and achieved good effect in our experiments.On the basis of the above algorithm, we completed software development of the parameticpreparation design system with VC++2008and OpenGL. The wizard-operation process is very simpleand easy to use. The system was conformed excellently suitable and stable in the clinical trials.