银汞合金充填术后牙体组织受力分析

Effects of dental cements on the stress distribution in amalgam-restored teeth

目的观察5种基底料对银汞合金修复后牙体组织的应力分布和变形影响。方法建立下颌第一磨牙二维有限元计算模型,基底厚度均为0.5mm,银汞合金厚2mm,采用合面中央集中加载,计算窝洞侧壁牙体组织上的应力分布和变形情况。结果高应力集中和较大水平变形主要发生在洞底线角局部,低弹性模量基底材料可以加剧这一趋势。普通型氧化锌丁香油水门汀和氢氧化钙组局部的最大压应力集中是磷酸锌水门汀组的3.3倍,是玻璃离子和加强型氧化锌丁香油水门汀组的2倍。变形较磷酸锌水门汀组增加了40%,较玻璃离子水门汀增加了25%。结论不同弹性模量的基底料对银汞合金充填后牙齿的强度有明显影响,弹性模量越低,局部牙体组织内产生的应力越高,断裂的可能性越大,从力学性能上看,磷酸锌水门汀是目前临床上常用基底料中最为理想的。

Object iv e To evaluate the effects of 5 kinds of base materials on the stress distributio n and deflection in amalgam-restored teeth. Methods A computerized two-dim ensional finite-element of the tooth model first molar was established. Various dental cements with a thickness of 0.5mm and amalgam restorations with thickness of 2 mm in the prepared cavity were simulated and subjected to micro hardness test (load=45 kg). The stresses and deflections along the cavity wall i nterface were analyzed by finite-element method. Results High stress and deflec tion occurred mainly at the line angle of the cavity, this could be magnified b y using cements with lower elasticity modulus. The maximum compressive stress at the line angle induced by common ZOE or Ca(HO) 2 was increased 3.3 times or 2 times and deflections increased by 40% and 25% respectively that by Zinc phosphate and glass ionomer. Conclusions Modulus ela sticity of cement plays an important role in affecting the fracture strength of the amalgam restored tooth. The lower the elasticity modulus, the higher the st resses and deflections induced in the dentine. From the point of mechanical pro perty, zinc phosphate is one of the best dental cements.