Abstract: Objective To investigate the effect of various working time on the adhesive property of two commercial dual-cured resin cements. Methods 60 extracted human premolars were randomly assigned to two groups. Two commercial resin cements（EmbraceTM and ParaCore） were used to cement at three kinds of working time（1 min，3 min and 7 min).The whole process was conducted at 25 ℃. After 24 h, each tooth was embedded by PMMA. Then each tooth was sectioned into three blocks that were approximately 1mm thick from the coronal, cervical and apical parts of the tooth. All bond strength of specimens was tested by a universal testing machine. Contrast adhesive interface between original and tested specimens was observed by scanning electron microscope（SEM）. Results There was statistically significant difference in bond strength between ParaCore and EmbraceTM. The bond strength of ParaCore was higher than EmbraceTM at all kinds of working time. But as working time was 1 min, the cervical specimens of ParaCore showed higher failure rate than the same parts of EmbraceTM. Bond strength and failure rate decreased with the increase of the working time .Conclusion Although ParaCore can produce a higher adhesive property, clinical controlled time (CCT) is shorter, and it is more easily affected by the operational environment and it fails more easily. Although EmbraceTM bonding performance is weaker, its CCT is longer, and it is less susceptible to external environment influence. Whatever the bonding system is, the light curing time should be extended, to ensure sufficient time to work on and at the same time get better bonding strength and mechanical properties of the materials.

Key words: dual-cured resin cement, working time, bond strength