Digital Dentition Modeling Based On Cbct And3D Scanning And Its Application

Three-dimensional digital dental model is the basis for other computer-aided dentalapplications. CBCTtechnologygainsitspopularityinrecentyearsamongdentaldiagnosismethods.3D scanning is able to obtain a more accurate description of the exact shape oftooth crown surface. The purpose of this study is to establish the3-D digital dentitionmodel from these two data sources.CBCT raw data is represented as DICOM files in computer system. In order toextract image data from the files and lower the impact of image defects like noise andfuzzy boundaries on subsequential operations, a parsing procedure based on the analysisoftheDICOMstandardisdesignedtoextracttheimagedatafromthesefiles,andafterthatthe image data goes through a preprocessing stage featuring image processing techniquesas thresholding, Gaussian filter and Laplacian enhancement in order to suppress the noiseand enhance the boundary of objects of interest.To identify the voxels belonging to teeth and build an accurate3-D model of them,usingtheresultsofthepretreatment,amedicalimagesegmentationand3-Dreconstructionalgorithm based on deformable triangular mesh model is proposed, simulating the defor-mation process of a bubble under constraint of internal pressure and external force field.The proposed method combines Affine Cell Image Decomposition(ACID) grid reparam-eterization technique to solve the problem of topological change during deforming witha deformable model inspired by the bubble, and is able to conduct the segmentation andreconstruction process simultaneously while working directly on CT volume data insteadofindividualimageslices. Experimentresultsshowthattheproposedmethodcanidentifythe structure of pulp cavity and distinguish between tooth and alveolar bone in the rootportion of teeth where the bone density are similar.To integrate the accuracy of3-D scan model and completeness of reconstructedmodel, after registering the two models using Iterative Closest Point(ICP) algorithm, atriangular mesh fusion method utilizing the topology adaptive feature of ACID grid isemployed.In order to make a qualitative evaluation of the methods proposed and make it easyto use reconstructed models and CT images simultaneously for diagnosis and treatment,this paper realizes a robust triangular mesh plane-cutting algorithm, with which the3-D mesh model is projected into CT image slices.To facilitate the verification of the algorithms as well as dental applications builtupon the reconstructed models, this paper developed a cross-platform3-D display andinteraction framework based on OpenGL and Qt libraries, providing a humane mode of3-D mouse interaction operation and an easy-to-extend programming interface. With thisframework, a3-D reconstruction system is built with the functionality of constructing3-D digital dental models from CBCT images and3-D scanning data. The system alsoprovides some simple tools for measuring distances and arch curves. A helper applicationfor Edgewise appliances design is also developed based on the reconstruction system.The experiment results with the implemented3-D reconstruction system on CBCTimage data of a female adult show that our algorithms can successfully achieve the recon-struction task of various types of teeth in the oral cavity.