下颌第一磨牙牙体缺损修复后静力与冲击动力的三维有限元分析

目的对下颌第一磨牙根管治疗术后远中!面牙体组织缺损复合树脂或银汞合金充填金属全冠修复模型进行静力与冲击动力的三维有限元法初步比较分析，为临床的修复设计提供理论依据。方法运用逆向工程技术法建立三维有限元模型，模拟上下颌第一磨牙牙尖交错!及尖对尖咬合状态，冲击动力选用半正弦脉冲型，冲击载荷较静载荷下的应力变化用冲击系数表示。结果在两种载荷下，复合树脂或银汞合金充填金属全冠修复的有限元模型的最大Mohr应力值均出现在金属冠上；而这两种修复方式中，牙本质的Mohr应力值差别不大，远小于牙本质拉伸极限强度；冲击系数接近于1。结论冲击载荷更符合口腔的实际情况，但适当的静载荷分析是可接受的。金属全冠修复是必要的；复合树脂或银汞合金充填金属全冠修复效果无明显差异。

Three-dimensional finite element initial analysis on the structure defect restoration of mandibular first molar under static and impact loads

Objective To make a mechanical analysis on three-dimensional finite element models of the mandibular first molar with the maximum distal occlusal(DO) structure defect after the root canal therapy and filling and crown restoration under static and impact loads and to provide a guideline for planning restoration for the clinic.Methods The research adopted reverse engineering technology to build the model of three-dimensional finite element.The form of the intercuspal occlusion and cusp to cusp occlusion during the circulation of posterior teeth occlusion movement were simulated.Half-sine pulse/impact was chosen for the impact dynamic.The impact ratio was indicated to the stress change between impact loads and static loads.Results Under the two kinds of loads,the maximum Mohr stress values of the metal crowns were shown in all models.The restoration effects between the two kinds of models were compared,the maximum Mohr stress value of the crown metal and dentin was not obviously difference.The maximum Mohr stress values of dentin were all obviously smaller than the stretch limit strength of dentin.The impact ratio closed to 1.Conclusion The impact loads accorded with the oral actual situation more than the static loads,but the suitable analysis of the static loads could be accepted.The restoration of metal crown is necessary.The effects between the amalgam filling and full crown restoration and composite resin filling and full crown restoration is not difference obviously.