目的 采用有限元方法对比分析不同厚度垫底材料对充填后牙体应力分布的影响。方法 选用正常形态下颌第1磨牙，基于Micro CT扫描建立Ⅰ类洞充填的三维有限元模型，选择Vitrebond和Dycal作为垫底材料，分别考虑4种不同的厚度（0.5、1.0、1.5和2.0 mm），施加250 N的咬合力，对各模型中牙体、充填体和垫底材料的最大/最小主应力进行比较。结果 Dycal垫底，厚度为2.0 mm，牙体的最大主应力峰值超过其抗拉强度，垫底材料的最大/最小主应力峰值分别超过其抗拉和抗压强度；垫底厚度为1.5 mm和2.0 mm，充填体的最大主应力峰值接近其抗拉强度的90%。Vitrebond垫底时，各材料的最大主应力峰值也都在1.5 mm或2.0 mm时达到极值。结论 从防止充填后牙体折裂的角度，建议临床上采用较薄的垫底层厚度，取0.5～1.0 mm。

Objective To study the effects of cement base with different thickness on the stress distributions of restored tooth by finite element method. Method A threedimensional finite element model of a restored first mandibular molar with class 1 cavity was developed based on Micro CT. The thicknesses of cement base with lightcured glass ionomer (Vitrebond) and selfcured calcium hydroxide (Dycal) were chosen as 0.5 mm, 1.0 mm, 1.5 mm and 2.0 mm, respectively. Occlusal load of 250N was applied to compare the peak maximum and minimum principal stresses of the tooth, restoration and cement base in each model. Results With Dycal of 2mm, the peak maximum principal stress of the tooth was higher than its tensile strengths, and the peak maximum/minimum principal stress of the cement base was both higher than its tensile and compressive strength. Moreover, the peak maximum principal stress of the restoration was about 90% closer to its tensile strength with Dycal of 1.5 mm and 2 mm. With Vitrebond, it also showed that the peak maximum principal stress of the tooth, restoration and cement base appeared in the models with cement base of 1.5 mm and 2.0 mm. Conclusions To prevent the failure in restored tooth, it is advised to use thinner cement base, and the thickness of cement base should be considered from 0.5 mm to 1.0 mm in clinic.

国家自然科学基金资助项目（10925208）