RESUMO
Objective:To compare the shear bond strength of dentin to composite resin in different post-treatment time period after tooth bleaching with the TREE dental whitening gel and observe the dentin/composite interface of each group. Methods:Eighteen intact premolars were randomly divided into 3 groups(n=6):A:The specimens were immersed into artificial saliva for 3 weeks then adhesion without bleaching; B:Adhesion immediately after bleaching for 3 weeks,during bleaching the specimens were immersed into artificial saliva; C:Before adhesion the specimens immersed in artificial saliva for further 2 weeks after bleaching for 3 weeks. Five specimens from each group were randomly submitted to shear bond strength test. The specimen remained in each group were sectioned to be observed by the scanning electron microscope.Results:(1)The shear bond strength of the group B (10.74?3.03) MPa was significantly lower than that of the group A (18.61?3.56) MPa or the group C (17.21?3.15) MPa (P0.05); (2)The resin tags present in the dentin/composite interface was scarce for the group B,and that were shorter than the group A; The resin tags of the group A and group C were similar in number,but that of the group C was shorter than that of the group A. Conclusion:The use of TREE whitening gel immediately before bonding significantly reduces bond strength,but immersion of bleached teeth in artificial saliva for 2 weeks before bonding results in a return to control bond strength.