Development of a system evaluating abutment teeth for CAD/CAM

Objectives: In dental treatment, dental CAD(Computer-aided Design)/CAM(Computer-aided Manufacturing) systems have been introduced, which assist dental technicians in fabricating dental prostheses. The fabrication process is as follows. First, the form of an abutment tooth is scanned by a 3d-scanner so that a 3d-model of the abutment tooth is created in a computer. Next, by using a CAD system, a dental technician designs a dental prosthesis which fits the abutment tooth. Then, the dental prosthesis is fabricated by using a CAM system and a machine tool. In the process using the CAD/CAM systems, the forms of abutment teeth sometimes bring about some problems. For example, a dental prosthesis may not be fabricated because of the sharp corners of an abutment tooth. The purpose of this study is the development of a system that can evaluate the appropriateness for abutment teeth. Methods: Visual C++ is used for developing the system. Taking the 3d-models of abutment teeth as input, the system identifies geometrical features (e.g., undercuts and sharp corners) automatically, which are used to examine: (1) whether the prostheses can be fabricated by using the machine tool; and (2) whether there are no undercuts on the abutment teeth. The abutment tooth models prepared by students in our dentist training school were evaluated by the system. The evaluation by the system was compared with that by a teacher, to show the effectiveness of the system. It is important to note that the system can use at chair sides as well as at dentist training schools because the system does not require the models of good abutment teeth prepared by teachers. Results: The comparison showed that the evaluation by the system was similar to that by the teacher. Conclusions: It is concluded that the system can be used for evaluating the abutment teeth.