不同基底料对银汞合金修复体的应力分布影响

目的：观察5种基底材料对银汞合金修复体的应力水平和变形影响．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，银汞合金修复体厚2mm，采用殆面中央集中加载，计算修复体底部应力水平和变形情况．结果：磷酸锌水门汀基底对银汞合金修复体应力水平和变形影响不明显；玻璃离子水门汀、氧化锌丁香油水门汀和氢氧化钙对银汞合金修复体应力分布和变形影响依次增大．结论：弹性模量越低，修复体内产生的应力越高，断裂的可能性越大，磷酸锌水门汀是目前临床上常用材料中最理想的基底材料。

Effects of cement bases on stresses and deflections in amalgam restorations

AIM: To evaluate the effects of 5 kinds of base materials on the stresses and deflections in amalgam restorations. METHODS: A computerized two dimensional mandibular first molar model was established. Various cement bases with a thickness of 0.5 mm and 2 mm of amalgam restorations were simulated in the cavity preparations and subjected to a 45 kg load. The stresses and deflections in the restorations were analyzed by the finite element method. RESULTS: No significant increase in the stresses and deflections induced in the amalgam restoration was found when 0.5 mm zinc phosphate cement was placed on the cavity floor, while slight increases occurred when zinc phosphate was replaced by 0.5 mm glass ionomer or reinforced zinc oxide eugenol cement and dramatic increases were found when 0.5 mm calcium hydroxide or common zinc oxide eugenol cement was used. CONCLUSION: Modulus of elasticity of cement base plays an important role in the fracture strength of the amalgam. The lower the modulus of elasticity, the higher the stresses and deflections induced in amalgam restorations. In view of mechanical property, zinc phosphate is one of the best cement used as base material for the present.