不同Ⅳ类洞型设计树脂直接修复的三维有限元分析

Three dimensional finite element analysis of stress distribution in various class Ⅳ preparation designs with direct composite resin restoration

目的研究不同Ⅳ类洞型设计树脂直接修复后在正中和前伸2种载荷状态下树脂和牙体界面的应力分布状况。方法采用螺旋CT扫描建立上颌中切牙的三维实体模型并预备成Ⅳ类洞,洞缘分别设计成1mm和2mm斜面、沟槽、阶梯状沟槽4种固位形树脂修复的模型,对照组不做特殊固位形。分别在牙冠舌侧切1/3与中1/3交界处和牙冠切缘偏舌侧,加载与牙体长轴呈45°的力,大小100N,分析各组模型树脂和牙体界面的Von Mises值及应力分布状况。结果前伸时,树脂和牙体界面的应力值明显大于正中,而此时斜面设计界面的应力值比沟槽组稍小,但沟槽设计时应力分布比斜面组更均匀。结论从应力角度考虑,2种预备方法各具优势,但前伸时树脂和牙体界面的应力值明显大于正中,因此树脂直接修复切角缺损的患者应尽量避免前牙对刃啃咬硬物。

Objective To evaluate the interfacial stress distribution in different class Ⅳ preparation designs with composite resin restoration at centric occlusion and protrusive occlusion.Methods Three dimensional finite element model of maxillary central incisor with class Ⅳ preparation was established by spiral CT.It was designed into 1 mm and 2 mm bevels,chamfer,stair-step chamfer preparation and untreated model as control.All the models were restored with composite resin,and loaded under 100 N forming 45° with long axis.The interfacial Von Mises stress and distribution was recorded.Results The maximum Von Mises stress values of the interface at centric occlusion were obviously smaller than that of protrusive occlusion,at which the stess level of two bevels were smaller than two chamfers.Nevertheless,the distribution of stresses is more uniform in chamfers than that in bevels.Conclusion In view of stress and its distribution,the bevel and chamfer both have their superiorities.The maximum Von Mises stress values of the interface at protrusive occlusion were obviously higher than that of centric occlusion,thus class Ⅳ prepared teeth restored with composite resins should avoid biting hard food edge to edge.