Research And Application On The Technologies For Extraction Dental Arch And NC Processing Of Molars Crown

CAD/CAM technology has been widely applied in the field of dental restoration and promotes the efficiency, precision, automation, and economy of prosthodontic technology. Dental restoration is the research object in this thesis. The extraction technology of dental arch feature curve is studied in this work. Based on the high speed cutting technology, computer graphics, CNC machining technology and the STL data model, the tool path generation algorithms of molar crown high-speed machining and the cutting performance of hard processing organic material was studied in this thesis.The main contributions of this work are as follows:1. The technology of data preprocessing of the triangle mesh surface is studied firstly. In this paper, an algorithm of quick search based on the balanced binary tree is proposed to increase the speed of rebuild topology. One algorithm that combines the advantage of Laplcian and Taubin operator is presented. While meeting the fairing accuracy requirement, this combinational algorithm enhances the efficiency of fairing. One method to simulate the ray tracing effect is brought out to evaluate the surface quality visually.2. One method of detection of the dental arch curve on the 3D mesh dental cast is presented, and it can detect the dental arch curve quickly, steadily and accurately. This method includes five steps. Firstly bite plane is located by simple human-computer interaction. Secondly the initial reference points are filtered. Thirdly the initial dental arch curve is fitted. Fourthly the final reference points are extracted. Lastly the final dental arch curve is fitted.3. Based on physical characteristics and working mechanism of the teeth, an algorithm of 5-axis machining tool path generation has been put forward and also been realized, which can help improving the local characteristics of the teeth forming accuracy and repair quality.4. Tool path optimization for complex molar surface by NC machining is studied. The vertex-based surface offset algorithm, a tool path optimization algorithm of high-speed molar crown machining and a tool path generation algorithm of high-speed 5-axis simultaneous milling in STL format is presented. These methods can improve the processing efficiency and achieved an even change of the tool-axis vector. On the basis of above research work, one automatically programming system of dental restoration is developed using VC++ and Hoops developing platform. The automatically programming algorithm of molar crown milling for the medical material Ti-6Al-4V and Zirconia is verified. The result shows that the manufacturing quality can satisfy the requirement of dental clinical restoration.