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

为了揭示全瓷冠的抗折强度与基牙形态的关系，我们对全瓷冠进行了断裂试验和三维有限元分析。在折断实验中，由于金属基牙的折断试验中观察到了超常的强度，所以我们选择了拔除的人上颌切牙作为基牙。采用三维有限元方法进行接触分析，这是我们前面介绍的。在接触分析中，材料之间的边界并不固定，接触分析的结果与所有烤瓷冠的实际断裂情况吻合较好。对基牙断裂强度与基牙测量结果进行相关分析。将相关分析的结果与3D-FEA的结果进行比较。在相关分析中，所有烤瓷冠的断裂强度与边缘曲率高度呈显著负相关，而与唇舌厚度呈显著正相关。3D-FEA结果与三维有限元分析结果吻合较好。在3D-FEA中，所有烤瓷冠的边缘都存在张应力集中的现象，且边缘曲率越大，拉应力越大。当所有烤瓷冠的唇舌厚度变厚时，边缘的拉应力降低，当边缘曲率较大时，向唇侧倾斜位移产生拉力，而当冠较厚时，位移变小。这些似乎与基牙的灵活性有很大关系。

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.