Stress Analytic Study on Fractural Strength and Abutment Form of All Ceramic Crown

为了揭示全瓷冠的断裂强度与基台形式的关系，我们对全瓷冠进行了断裂试验和三维有限元分析。在断裂试验中，由于金属基牙在断裂试验中表现出非凡的强度，所以我们选择了拔除的人上颌门牙作为基牙。3D-FEA是我们之前介绍过的接触分析。在接触分析中，材料间的边界不固定，接触分析结果与全瓷冠实际断口吻合较好。对断裂强度与基台测量值进行了相关性分析。将相关分析结果与三维有限元分析结果进行比较。在相关分析中，断裂强度与边缘曲率高度呈强负相关，断裂强度与全瓷冠唇舌厚度呈强正相关。这些结果与三维有限元分析结果吻合较好。在三维有限元分析中，所有瓷冠边缘处都有拉应力集中，且边缘曲率越大，拉应力越高。全瓷冠唇舌厚度越厚，边缘拉应力越低。当边缘曲率较大时，位移向唇向倾斜产生拉伸力，冠厚时位移变小。这些似乎与基台的柔韧性密切相关。

In order to reveal the relation between fracture strength and abutment form of all ceramic crown, we performed fracture test and 3D-FEA of all ceramic crown. In fracture test we used extracted human maxillar incisors as abutment teeth because extraordinary strength were observed in fracture test using metal abutment. 3D-FEA was executed as contact analysis which was introduced by us previously. In contact analysis, the boundaries between materials were not fixed, and results of contact analysis showed good agree with actual fracture of all ceramic crown. Correlation analyses between fracture strength and measurements of abutment were performed. Results of correlation analyses were compared with results of 3D-FEA.In the correlation analyses, strong negative correlation was observed between fracture strength and height of marginal curvature, and strong positive correlation was observed between fracture strength and labial-lingual thickness of all ceramic crown. These results fitted in well with that of 3D-FEA.In 3D-FEA, concentration of tensile stress are observed at the margin of all ceramic crown, and the tensile stress became higher when marginal curvature became higher. When labial-lingual thickness of all ceramic crown became thick, the tensile stress at margin lowered.In case of high marginal curvature, stretching force were generated by tilting displacement toward labial direction, and in case of thick crowns, the displacement became smaller. These strongly seemed to be related to flexibility of abutment.