Clinical Relevance: A significant reduction in bond strength of restorative materials to dentin and enamel after home-use bleaching treatment has been reported. Antioxidizing agents may be a procedure to increase bond strength values. Although no reversal of bond strength values was found for sodium ascorbate, alpha-tocopherol formulated in solution resulted in a significant increase in bond strength of bleached enamel.

The purpose of this study was to assess the effect of home-use bleaching agents containing 10% carbamide peroxide and 7.5% hydrogen peroxide on enamel microhardness and surface micromorphology. Enamel slabs (n=10) received the bleaching agents for 1 h/day and remained in artificial saliva solution for 23 h/day, during a total period of 21 days. Control group was composed of enamel slabs that were not subjected to treatment with the agents and were maintained in artificial saliva solution. Microhardness tests were performed before treatment application, 21 days of treatment and 14 days after the end of treatment. Scanning electron microscopy analyses were performed after 14 days after the end of bleaching treatment by 3 calibrated observers who attributed scores. The Tukey's test (α=0.05) showed no significant differences in microhardness values among bleaching agents, at 21 days of treatment and a significant increase in microhardness for different agents after 14 days from the end of treatment. Fisher's exact test showed differences in micromorphology of enamel between control and experimental groups (p=0.0342). Bleaching agents containing 10% carbamide peroxide and 7.5% hydrogen peroxide may change surface micromorphology of enamel, although no changes in microhardness were observed.

Objectives: To evaluate the effect of different bonding strategies on the microtensile bond strength to deep and superficial permanent dentin.Methods: Forty-eight teeth were randomly flattened according to the dentin depth: superficial dentin (SD) and deep dentin (DD). Subsequently, three adhesive systems were applied (n=8): an etchand- rinse (Adper Single Bond 2 - SB), a “mild” two-step self-etching (Clearfil SE Bond - SE) and a one-step self-etching adhesive system (Futurabond – FB). Each specimen was restored with a composite resin and sectioned into 1.0-mm2 thick slabs. After 24 hours, resin-dentin sticks were submitted to tensile stress in a universal testing machine (0.5 mm/min). Data were submitted to two-way ANOVA and Tukey’s test at a level of 0.05%.Results: Superficial dentin showed the highest microtensile bond strength values, which differed statistically from those obtained in the deep dentin, irrespective of the adhesive system used. FB yielded the highest bond strength values, which were statistically similar to the bond strength values of SE, but statistically different from those obtained when the SB adhesive was used.Conclusions: Bond strength obtained in superficial dentin was significantly higher than in deep dentin, for all adhesive systems tested. Adhesion was affected by the different bonding strategies: the one-step, low pH, acetone-based self-etching adhesive promoted the higher bond strength values, which were statistically similar to those obtained with the two-step, water-based self-etching adhesive. (Eur J Dent 2010;4:110-117)