Objective To analyze the possible damage to the remaining tooth and composite restorations when various mixing ratios of bases were used. Methods Testing elastic modulus and poission′s ratio of glass- ionomer Vitrebond and self- cured calcium hydroxide Dycal with mixing ratios of 1∶1, 3∶4, 4∶3. Micro- CT was used to scan the first mandibular molar, and the three- dimensional finite element model of the first permanent mandibular molar with class Ⅰ cavity was established. Analyzing the stress of tooth structure, composite and base cement under physical load when different mixing ratios of base cement were used. Results The elastic modulus of base cement in various mixing ratios was different, which had the statistic significance. The magnitude and location of stress in restored tooth made no differences when the mixing ratios of Vitrebond and Dycal were changed. The peak stress and spreading area in the model with Dycal was more than that with Vitrebond. Conclusion Changing the best mixing ratio of base cement can partially influence the mechanistic character, but make no differences on the magnitude and location of stress in restored tooth. During the treatment of deep caries, the base cement of the elastic modulus which is proximal to the dentin and restoration should be chosen to avoid the fracture of tooth or restoration.
