Virtual Adjustment of the Occlusal surface for Complete Denture Tooth Arrangement Qi-Lei Fan, Xiao-Sheng Cheng, Ning Dai, Cheng Cheng, Renkai Huang School of Mechanic and Electronic Engineering University of Aeronautics &Astronautics Nanjing, China dai_ning@nuaa.edu.cn Yu-Chun Sun School of Stomatology Peking University Beijing, China Abstract—Complete denture CAD/CAM technology offers the prospects of drastically reducing the time to provide service to patients. The tooth arrangement and adjustment of the occlusal surface are key steps of complete denture CAD/CAM. This work presents an effective method of tooth arrangement and virtual adjustment of the occlusal surface for complete denture. After teeth features and oral features were extracted, auto tooth arrangement for complete denture based on feature-driven method was performed. Then, interference area Detection based on seed filling algorithm was taken. Finally, Laplacian local deformation was performed to minimize the over-interference on the occlusal surface. Some examples were tested in this work and the results demonstrated that the proposed method is effective and feasible. Keywords—complete denture; tooth arrangement; virtual occlusal adjustment; Local deformation; I. INTRODUCTION Full denture depletion is a common disease of the elderly. In China, with the aging of the population, there will be more edentulous patients in the future [1] . Complete denture, as the most effective way of treatment, is widely used. In the fabrication of complete denture, tooth arrangement and occlusal adjustment are essential steps as the quality of the artificial dentition determines the efficiency of mastication and recovery of facial shape. Nowadays in China, as all the complete dentures are fabricated by technicians via handwork, the precision of the complete dentures is still low and the treatment cycle costs a lot of time and money. With the increase of applications of CAD/CAM in oral medicine, the precision of prosthesis is efficiently enhanced and make it possible to shorten the treatment time down to single patient visit. After Francois Duret creatively brought CAD/CAM techniques into the design and fabricated of dental restorations, lots of commercial software for CAD/CAM of dental restorations appeared such as “Cerec3D” system from Siron and “KaVo mutiCAD” from Kavo [3-4] . Virtual adjustment of the occlusal surface, as a key step of computer-aided dental restoration design, is able to enhance the quality of prosthesis. Researches about virtual occlusal adjustment were taken since last century. Karol Myszkowski’s group [5] scanned patients’ jaw motion and performed articulation simulation. The adjustment of the occlusal surface for restorations was performed based on the simulation results. Xiang Zhang et al. [6] generated the distance map between the generic tooth and the opposite occlusal surface by using OpenGL selection mode. Deformation was performed to adjust the occlusal surface according to the distance map. Tomoaki Maruyama’s group developed a dental CAD system for designing functional occlusal tooth surfaces which harmonize with the patient’s stomatognathic function. In this work, a tooth arrangement method based on features is proposed to obtain the complete denture harmonize with the patient’s oral cavity. Interference detection of the dentition and local deformation method is performed to realize the virtual adjustment of occlusal surface. The following sections discuss the tooth arrangement method and the virtual occlusal surface adjustment method. II. TOOTH ARRANGEMENT METHOD Traditionally, the tooth arrangement for complete denture is done by handwork. Technicians arrange the artificial teeth according to the features on the patient’s edentulous jaw impression and the rules of stomatology. By imitating the technicians’ method of tooth arrangement, we proposed a digital tooth arrangement method to obtain the digital model of complete dentition. In the process of tooth arrangement, we define a liner transform matrix to describe the position of each artificial tooth. The final position of each tooth was affected by the oral features of the patient’s and the adjacent teeth. Spacing mapping between the oral features and the features on each tooth is established. The initial position of the tooth is calculated according to the features. To optimize the dentition, we adjust the position of each tooth concerning the contact between adjacent teeth. The matrix of every tooth can represent as the following equation: ( ) (1) In (1), ( ) is the liner transform matrix determined by the adjacent teeth and the paired tooth. is the liner transform matrix determined by the features on the impression and artificial teeth. The maxillary molars’ positions with respect to the occlusal plane are preliminarily defined. Thus, the maxillary