| Summary: | 博士 === 國立成功大學 === 醫學工程研究所碩博士班 === 92 === According to its design concept, a resin-bonded prosthesis, compared with the conventional fixed partial denture, is a weak and unstable structure. Therefore, a resin-bonded prosthesis induces a higher failure rate, especially in the posterior region. Recently, adhesion agents have been profoundly improved. However, the design guidelines of resin-bonded prosthesis have seldom been evaluated especially in the biomechanical aspect. The objective of this study was to investigate the biomechanical effects of the design parameters on posterior resin-bonded prostheses using finite element (FE) method. A solid model of a posterior mandibular resin-bonded prosthesis, which employed the second molar and second premolar as the abutment teeth, was constructed. After meshing, all nodes on the distal and proximal surface of alveolar bone were fixed as the boundary condition. Parallel experiment of five samples, which used fresh extracted teeth as abutments, were performed to validate the accuracy and reliability of the FE model before parametric analyze. Measured strains on specific locations were compared with numerical results. After validation, biological and mechanical factors were evaluated via the FE models. For biological factors, firstly, the effect of periodontal ligament was investigated. Secondly, seven independent occlusal loadings of 200N were applied respectively at various sites to identify the loading effect based on the stress level at the interface between the retainer and abutment teeth. For the mechanical factors, geometric design parameters of the resin-bonded prosthesis, were investigated according to the result of biological factors.
The percentage errors between the measured and simulated data were all within 15% (within one standard deviation), which supported the reliability of the established FE resin-bonded prosthesis model. The simulated results showed that periodontal ligament was an essential component in evaluation of resin-bonded prosthesis and should be included in the FE model to prevent from underestimating the interfacial stress on resin-bonded prosthesis. For the loading modes, lateral occlusal forces increased the retainer/abutment interfacial stresses more significantly than axial occlusal forces. The retainer/abutment interfacial stresses increased more obviously when occlusal force was applied on the premolar than on the molar. For the geometric design, the most important design parameter was retainer height. The secondary parameter was retainer thickness. Sufficient retainer height and thickness could effectively reduce the interfacial stresses. According to the assumptions of this study, the retainer height should cover as much as possible and the retainer thickness was suggested to be greater than 0.8mm for long-term survival of resin-bonded prosthesis. Occlusal rest seat was essential in framework design and grooves should be included in accompany with occlusion adjustment.
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