| Summary: | 碩士 === 國立成功大學 === 口腔醫學研究所 === 96 === Anchorage plays an important role in the planning of tooth movement for orthodontic treatment. Unwanted tooth movement known as loss of anchorage can be a determinate effect on the treatment outcome. The bone plate can provide an absolute anchorage, and allow treatment to proceed more effectively with more predictable results. With bone plate as the orthodontic anchorage, some biomechanical factors could influence its success rate such as: type of bone plate, thickness of cortical bone, screw length, screw implanted depth, orthodontic force magnitude, force direction, screw number, and bone quality. Unfortunately, there were limited studies focused on these biomechanical factors. The purpose of this study is to analyze the biomechanical factors which influence the bone plate success rate by using finite element simulation. In this study, we collect the data form twelve patients who had bone plate as orthodontic anchorage to intrude teeth and move posterior teeth or full arch teeth distally at the NCKUH since 2004. Then, we set up the model and variation according to these data. The biomechanical influences of success factors on bone plate were quantified by using the three-dimensional finite element method (FEM). In the FEM analysis, we found that stress in all structure was concentrated around the screw. Different type of bone plate, different direction and magnitude of force, screw number and plate bending influenced the stress distribution. The screw length and thickness of cortical bone effect were not significant to influence the peak value of the stress. In comparing between miniscrew and bone plate, the bone plate system was better than miniscrew system, but if the patient had thick cortex with short screw exposure length there were no significant different between the two systems. The setting of miniscrew system used in maxillary with 1.75mm cortical bone and 6mm screw exposure length was closed to average situation and the stress in this setting was larger than bone plate system. According to this study, the force direction and the plate type influence the stress value and the cortical bone thickness and screw exposure length determinate what system should we chose
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