Effects of pre- and post-simulated home bleaching with 10% carbamide peroxide on the shear bond strengths of different adhesives to enamel

AimThis in vitro study was undertaken to investigate the effects of pre- and post-simulated bleaching procedures with 10% carbamide peroxide on the shear bond strengths of different adhesives to enamel and to determine the failure modes of tested specimens.Materials and methodsThe specimens were randomly divided into three groups (n = 30) according to the sequence of bleaching and bonding procedures (control non-bleach, pre- and post-bleach groups). Each group was then subdivided into three subgroups (n = 10) according to the three types of adhesives: OptiBond Solo Plus (Kerr) and Single Bond Universal (3M-ESPE) used as etch-and-rinse and self-etch techniques. Resin composite cylinders were then placed with Filtek Z 250 (3M ESPE). The specimens were stored in distilled water at 37 °C for 24 hours prior to being thermocycled for 1000 cycles (at 5 and 55 °C). The samples in the pre- and post-bleach groups were also immersed daily in artificial saliva at 37 °C, and for two weeks after completion of the bleaching process. Shear bond strengths were measured with a cross-head speeds of 0.5 mm/min. Failure modes of debonded specimens were determined by stereomicroscopy (30×). The interface margins of resin composite to the different enamel conditions were observed by scanning electron microscopy (1000×) before shear bond strength testing.ResultsThere were no significant effects of different enamel conditions (control non-bleach, pre-bleach and post-bleach) on the shear bond strengths of OptiBond Solo Plus Adhesive Agent or etch-and-rinse Single Bond Universal Adhesive Agent. Pre- and post-simulated home bleaching of enamel with 10% carbamide peroxide had an adverse effect on the shear bond strengths of self-etch Single Bond Universal Adhesive Agent.ConclusionIn enamel, an etch-and-rinse approach with phosphoric acid remains the procedure of choice, since it guarantees the most durable bond to enamel. Therefore, selective phosphoric-acid-etching of enamel is highly recommended, followed by self-etching.