Research And Implementation Of Dental Surface Design System' Key Technique

With advances in measurement technology, discrete surface modeling and efficient processing technology of high hardness materials, both the software and hardware of the dental CAD/CAM system and equipment have achieved rapid development in the past 20-odd years. The dental CAD/CAM system and equipment are pushing forward a new era of dental restoration. Based on clinical science of stomatology, the research of this dissertation mainly focus on areas of the relevant basic theories, methodologies and key technologies of dental surface design and its extended applications in the dental CAD/CAM.The main innovative contributions of this dissertation are as follows:Firstly, to reconstruct the topology relation of the discrete surface model efficiently and completely, this dissertation has designed a new type of data structure used for the discrete surface model based on vertex'one ring neighborhoods. This dissertation has analyzed the performance and efficiency of the redundant points filtering algorithms used in the process of the topology reconstruction based on hash table and RB binary tree data structure comparatively, and has also designed the node structs stored in hash table and RB binary tree respectively. The experimental results show whichever filtering algorithm chosen: the time complexity of the surface reconstruction is less than O(NlogN), where N is the vertices total number of the discrete surface model.Secondly, this dissertation presents two kinds of surface offsetting method for the discrete surface model based on vertex normal vector and implicit surface respectively. In the process of surface offsetting based implicit surface method, the spatial data block sampling technique using octree data structure, vertices mapping technique based on Newton'iteration method and the original topology relation of the discrete model are used. Which offsetting method is more suitable when offsetting different discrete models is analyzed through lots of experiments.Thirdly, this dissertation presents a semiautomatic & Adaptive Algorithm for the preparation line extraction. The dentists only need to pick up some limited points in order near the real preparation line of the discrete model interactively, according to their clinical experiences. After that, the system can complete the preparation line extraction automatically.Fourthly, the trimming technique for discrete models is researched, and presents a newly trimming algorithm specifically for dental restorations. The presented trimming algorithm is composed of three steps including coarse trimming, fair trimming and boundary optimization, and has been applied in clinical trials proved efficiently and achieving satisfactory results.Fifthly, this paper presents a uniform processing method for triangular mesh's hole filling and stitching. The mesh patch obtained after hole filling or stitching using the presented method can fit across the boundary (boundaries) smoothly and continuously. the uniform processing method is proved efficiently and robust in many experiments of different kinds of boundary conditions including filling and stitching.Sixthly, the general model for dental restorations is given using UML according to the practical demands in clinical prosthodontics. Based on that, the dental restoration-oriented modeling software prototype system (DentalCAD system) is developed. Practicability and validity of the system are proved in clinical applications...