| Three-dimensional digital models of teeth, dentition, occlusion, and jaw position, play an important role to the practitioners during orthodontic therapy. These models can visualize anatomical details of teeth, dentition and jaw bone in three-dimensional space, observe distance, area and volume, and record the change of jaw position in the course of orthodontic treatment. In the future, they will provide fast and accurate three-dimensional visualization and quantitative data, which have mang advantages, for example, with its intuitive, predictability, and Usability, and so on. Although clinicians extensively concern 3d digitizing model, the application of these models are restricted in clinical practice, because modeling methods and its registration have many problems at present.In this study, the 3D digital models of teeth, dentition, occlusion, and jaw position are reconstructed with the cloud points images and CT images, in order to establish the modeling method, which suit for clinical practice.1. The three-dimensional digital models of dental cast and Intercuspal occlusion1 case of normal women,26 years, Angle Class I, no missing teeth, no cavities, no gum disease, and cover the normal lamination, the upper and lower jaw no deformity, normal mouth opening and the open type, no temporomandibular joint disorders. The point cloud images have been gathered with three-dimensional laser scanning system for her upper and lower plaster models. In GeoMagic Studio 10.0 reverse engineering software, three-dimensional digital model of dental castes have been reconstructed, and these steps are as follows:Sets of locks, noise reduction, building area, splicing, fusion, polished. The model have so clear Anatomical landmark, such as:height of contour, line angle, dental cusp, ridge, groove, fossa. Intercuspal occlusion recording has been obtained withocclusal wax method. The digital models of intercuspal occlusions are rebuilt with the upper and lower dentition model in GeoMagic Studio 10.0. The correspondence relationship the upper and lower dentition clearly shows between the dental cusp and its fossa, over jet, over bite, and so on. The three-dimensional anatomical structure is very directly observed, and their biometric linear and volume measurements, such as the distance, the curve, the area, are obtained rapidly and accurately by using feature-dependent calculations independent of landmark placements.2. The three-dimensional digital model of Intercuspal positionTo the same for the object of study, the Frankfort horizontal plane is vertical, and the upper and lower dentitions are separated. A 64-slice spiral CT scan is used to acquire high resolution images data with thickness 0.625 mm. From the scanning data bone structures and soft tissues can be separated because their different grayscale pixel values. The CT-images of a patient are loaded into Mimics (Materialise, Leuven, Belgium) and are ordered in a way that correct sagittal, transverse and coronal views are reconstructed. On these reconstructed views, the region of interest is defined in a mask. A mask is defined as a part of the image where the gray values lie in a specified interval of Hounsfield units (HU). First of all, the maxillofacial jaw and mandibular bone model are reconstructed by means of Mimics 11.0 software (Materialise Corp. Belgium), which own Clear anatomic architectures and landmarks. The secondly, the three-dimensional digital model of intercuspal occlusion is registered with the maxillofacial jaw model, and then it is registered again the mandibular model. The three-dimensional digital model of Intercuspal position is set up by merging these models. It can visualize the position change btween the upper and lower dentition, jaws and temporomandibular joint in three-dimensional space, and it can be Measured and analyzed quantitatively. 3. The three-dimensional digital model of maxillofacial soft tissue and its clinical applicationsTo the same for the object of study, the two correcting appliances in maxillary arch are maked, whose thickness of the anterior labial are 5mm, and 2mm respectively. These appliances do not impede the activities of lips and tongue, and the opening and closing mouth are normal. They are used to simulate the models of Angle Class II cases and its treatment course. Object of study keepes sitting position, with horizontal Frankfort plane, head fixed, naturally closed eyelids and lips. The point cloud images of facial contour are gathered 3 times by three-dimensional laser scanning systems, which are treatment course of the primitive, the middle and the ending. The 3D digital patterns of maxillofacial soft tissue contour are established with GeoMagic10.0. The distance of Ls-EP, Li-EP, Si-EP and the angle of NLA in the digital maxillofacial model are carried using GeoMgic10.0 analysis tools. At the same time, using three-dimensional volume methods, the color change can be displayed directly maxillofacial soft tissue changes for the different treatment stages of the model.Conclusions(1) The three-dimensional digital models of dental cast and intercuspal occlusion can be reconstructed through 3D laser scanning system. These models play a role to record dental cast and occlusal relationships, furthermore their features also include measurement, analysis monitoring and evaluation of treatment results. In the future, they will be used for CAD/CAM.(2) The three-dimensional digital model of intercuspal position can be built by virtue of the jaw models and the digital intercuspal occlusion, which can visualize and quantitative measure anatomical details and landmarks(3) The digital model of maxillofacial soft tissue, through 3D laser scanning method, Can clearly show the anatomy landmark of maxillofacial contour, Accurately display the maxillofacial soft tissue changes in the course of orthodontic treatment. |
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