Research And Application On The Modeling Key Technologies For Full Crown And Bridge

With the development of the computer and graphics technology, dental CAD/CAM repairtechnology which is efficient, accurate and intelligent is gradually replacing the traditional dentalrepair mode, and has led to a revolution in dental repair field. With the comprehensive application ofbiomedical engineering, computer aided design, mathematics, differential geometry and threedimension geometry modeling, several key technology about the digital design of the full crown andbridge are studied deeply in this dissertation. Main contents and achievements are as follows:1. New mesh blending algorithm based on the implicit surface and advancing front method ispresented for the smoothly splicing outer and inner mesh surface of full crown restoration. Thealgorithm first extracts two boundary curves and bridginges between them to convert mesh blendingproblem into mesh hole filling problem; then fills the holes with advancing front method. The fillingmesh surface would be optimized according to the space sphere rules to enhance the quality oftriangles. The implicit surface is generation as control surface making use of vertex normal vectors onthe boundary, and vertexes in the blending mesh are then projected on the implicit surface andreplaced by projected points, which ensures the smoothness of mesh transition.2. For the demand of individual design restoration, two local mesh deformation algorithms areproposed: local deformation driven by characteristic curves and local deformation based on surfaceminimum energy principle. According to the deformation diffusion principle, the reasonabledeformation density function is designed; Combining with deformation radius and approximateprojected points algorithm, curve-driven deformation method could build curve and local surfacemapping relations quickly and achieve deformation, which is applicable to adjust outline form ofrestoration. The other local deformation algorithm divides the selected mesh surface into differentareas, and deformation could be achieved when the control hand is translated,which is applicable toedit local characteristic of restoration.3. The digital design framework of full crown bridge based on skin subdivision is realized,including of connector mesh surface generation algorithm and mesh fusion algorithm, and brieflyintroducing pontic’s digital design. Traditional design method is to store connector model in systemdatabase and edits them in designing progress, and form full crown bridge through boolean operationat last, but the editing ability is poor and the efficiency is low. However, the skin subdivisionalgorithm could automatically generate connector surface rapidly between two projected curves and then be merged with fixed full crown through proposed cutting and stitching algorithms. Its editingability is strong and the section area could be calculated to detect the strength of connector further.4. According to the different property of tooth models and the characteristics of bite and contactrelationship in dental repair, the collision detection algorithm based on dynamic hybrid boundingboxes is presented, which could query model collision domains quickly. Next puncture depth ofmodels that happen to collide is calculated and the result will be displayed in the color map to guideoperation intuitively.