Effect of bleaching on shear bond strength to dentin of etch-and-rinse and self-etching primer adhesives

This study evaluated in vitro the influence of enamel bleaching on bond strength to dentin. One hundred and twenty bovine incisors were divided into 12 groups (n = 10), according to adhesive system: Adper Single Bond 2 (ASB2), Prime & Bond 2.1 (PB), Adhese (AD) and Clearfil SE Bond (SE). The experimental groups were exposed to 10% carbamide peroxide for 4 hours a day over a period of 10 days. After the bleaching, they remained stored in artificial saliva for a further 24 hours or 7 days. The control groups were stored in artificial saliva for 24 hs. Resin composite (Z250) cylinders were made, and the specimens were stored in distilled water (37 degrees C/24 h), until the shear strength test was performed. The results were statistically analyzed using ANOVA 3-way and Turkey's test (a < 0.05). The highest mean value of experimental groups was obtained for ASB2 (7 d) and the lowest for PB (24 h). Significant differences were observed for bleaching and adhesive system, but not for storage time. Moreover, the interaction between the factors under study was shown to be significant. Statistical differences were observed between the tested adhesives for the different bleaching situations and storage times. It may be concluded that dental enamel bleaching and storage time in artificial saliva interfered with the bond strength to subjacent dentin provided by the Prime & Bond 2.1 and Clearfil SE Bond.