下颌第一恒磨牙牙体缺损不同桩核材料全冠修复的应力分析

目的:对根管治疗后下颌第一恒磨牙较大远中(牙合)面牙体缺损铸造镍铬合金桩核全冠及金合金桩核全冠修复进行三维有限元应力分析,为临床修复材料的选择提供一定的理论依据.方法:通过三维激光扫描、三维造型设计建立了下颌第一恒磨牙髓室壁未破坏和髓室壁部分破坏的最大远中(牙合)面牙体缺损铸造镍铬合金桩核全冠或金合金桩核全冠修复的三维有限元模型.观察4种载荷下牙本质Mohr应力分布并比较牙本质最大Mohr值.结果:在最大、垂直、斜向载荷下,两种桩核全冠修复牙本质最大Mohr值均明显小于牙本质拉伸极限强度,镍铬合金桩核全冠修复的大于金合金桩核全冠修复,并且镍铬合金桩核全冠修复最大应力分布在最大载荷及水平载荷下更向根方分布.在水平载荷下牙本质最大Mohr值均有急剧增加,接近或超过牙本质拉伸极限强度.结论:金合金桩核全冠修复优于镍铬合金桩核全冠修复.

Stress analysis on structure defect with different post core materials and full crown restoration of the permanent mandibular first molar

Objective:To analyse the stress of 3-dimensional finite element models of cast NiCr alloy post core and crown and Au alloy post core and crown restoration for greater distal occlusal teeth defect of the mandibular first molars through root canal therapy.Methods:Three-dimensional finite element models of the maximum distal occlusal structure defect without involving pulp chamber wall and involving pulp chamber wall with cast NiCr alloy post core and crown and Au alloy post core and crown restoration were established by use of the advanced 3-dimensional laser scanning and 3-dimensional computer assisted design technique.The Mohr strength theory was applied for comparing the maximum Mohr stress value of dentin and stress concentration areas in four models under four different loads.Results:Within the maximum,vertical and inclined loads,the maximum Mohr stress values of dentin of the two kinds of post core and crown restorations were obviously smaller than the stretch limit strength of dentin.The maximum Mohr stress value of NiCr alloy post core and crown was obviously greater than that of Au alloy post core and crown and the stress concentration area of NiCr alloy post core and crown was prone to transfer to root parts under the maximum and horizontal loads.Under horizontal load,the maximum Mohr stress value of dentin increased markedly and close to or greater than the stretch limit of dentin.Conclusion:Au alloy post core and crown is superior to NiCr alloy post core and crown.