Research And Application On Surface Measurement And Reconstruction Of Dental Restoration Based On Points Cloud

Along with the development and extended application of RE(reverse engineering ) technology in the field of bio-medical, CAD/CAM applied in Prosthodontics has seen significant development which makes Prosthodontics from traditional manual design into the digital &automatic era. Combined with the clinical application of oral medicine, this dissertation mainly does research on the measurement technology for 3D dental restoration objects and surface reconstruction technology from sampled point clouds, and Design&develop the professional medical system named dental CAD based on clinical experiments.The main contributions of this dissertation are as follows:(1)Propose an grating measurement method based on the combination coding technology of gray code and phase-shifting. the 3D measurement system with the proposed method is researched and developed independently,and also implement the correspondent system calibration. The 3D measurement system is integrated into Dental CAD, and can sample the surface points quickly and efficiently.(2)Modify an kernel estimation de-noising algorithm based on point clustering. A local likelihood measure capturing the probability that a 3D point is located on the sampled surface is associated with each point of the input data. The filtering procedure suppresses noise of different amplitudes and allows for an easy detection of outliers which are then automatically removed by simple thresholding.(3)Propose an novel KNN(K nearest neighbor)search algorithm based on measurement step, which can make the search region of KNN narrowed sharply and searching speed improved greatly, compared to The KNN algorithm based on space subdivision strategy. According to the k values of adjacent neighbors, Searching radius of current point is changed flexibly. The proposed algorithm implements the optimization KNN search of point clouds(4) Propose an normal direction adjustment algorithm based on distance between adjacent normals. The speed of path selection is given according to the normal distance threshold, and the deadlock problem which may appear during the normal spreading stage is solved by the third minimum distance method. The proposed normal direction algorithm is proved efficient and high qualitative.(5)The 3D dental restoration model is reconstructed through the improved MC isosurface extraction algorithm. Ambiguity triangles and holes are eliminated with hyperbola asymptotical discrimination approach. The optimization value of the cube'length of the MC algorithm is found through many experiments, which make the algorithm more efficient and improve fidelity and clearness of the reconstruction model greatly.(6)Design and develop the professional medical system named dental CAD based on clinical experiments. Restorations of veneer, procelain-fused metal crown, metal full crown and maxillofacial titanium mesh for specific patients reconstructed and designed under dental CAD system are achieved good results in clinical application...