银汞合金充填术后基底料的应力分布

目的：观察银汞合金充填术后5种基底料的应力分布和变形情况。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He面中央集中加载，计算基底料中产生的应力和变形情况。结果：不同弹性模量的基底料中所产生的应力水平和变形不同。最大主应力中除磷酸锌水门汀表现为低的张应力外，其余基底料均表现为压应力。随着弹性模量的增加，基底料中所产生的最大压应力升高，变形减小。结论：本实验条件下，在承受咬合力时，目前临床上常用基底料一般不致断裂，临床上选用基底料时，应侧重于降低其对银汞合金修复体和牙体组织的不利影响。

Stress distributions in cement bases of amalgam restored teeth

AIM:To evaluate the deflections and stress distributions in 5 kinds of cement bases of amalgam restored teeth.METHODS:A computerized two-dimensional mandibular first molar model was established.Various cement bases with 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 base materials were analyzed by the finite element me- thod .RESULTS:Stresses and deflections induced in 5 tested cement bases varied. The maximum stresses in all tested bases were compressive stress except in Zinc phosphate cement. The higher the modulus of elasticity, the higher the maximum compressive stresses and the smaller the deflections induced in the cement bases.CONCLUSION:All tested cement bases would not fracture under the condition of this experiment. When a cement base needs to be used in a deep cavity, considerable attention should be given to its negative effect on the strengths of the amalgam restorations and dental materials.