The effect of bleaching agent on composite/enamel bonding.

This in vitro study evaluates the effect of an in-office light-activated hydrogen peroxide bleaching agent on the shear bond strength of composite resin to etched enamel. Specimens were divided into 4 groups. Group 1 specimens were not bleached and served as the control; Group 2 consisted of specimens bonded immediately after bleaching; Groups 3 and 4 of specimens bonded 1 and 2 weeks respectively after bleaching. The mean shear bond strengths (MPa) of Groups 2 (14.2 +/- 4.9), 3(19.2 +/- 3.2) and 4 (23.1 +/- 3.7) were lower than the value obtained in Group 1 (25.1 +/- 3.7). Groups 2 and 3 had significantly lower shear bond strengths than the unbleached Group 1 (25.1 +/- 3.7). It is suggested that bonding procedures be postponed for two weeks after any bleaching procedure had been done.