Objective: This study used the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) method to evaluate the percentage of antioxidant activity (%AA) of green tea (GT) and sodium ascorbate (SA) gel in three concentrations (10%, 20% and 30%), and the influence of these concentrations on the microshear bond strength (μ-SBT) values of bleached enamel, using 10% carbamide peroxide (CP). Materials and methods: Eighty intact third molars were selected to perform the μ-SBT test, and were randomly divided into eight experimental groups: G1: positive control – no treatment; G2: negative control – bleached with CP; G3: PC +10% GT; G4: PC +20% GT; G5: PC +30% GT; G6: PC +10% SA; G7: PC +20% SA and G8: PC +30% SA. After applying the treatments, adhesive procedures were performed using Single Bond 2 and Filtek Z350XT. After 24 h, the samples were tested in a universal testing machine until fracture. The %AA was assessed in triplicate by DDPH method using a UV–VIS spectrophotometer. Results: In the μ-SBT, ANOVA revealed no significant difference between the antioxidants evaluated (p = .625), but did reveal significant effects of the concentrations studied (p = .007). A negative correlation was observed between μ-SBT and solution concentrations. The values of %AA were from 90.58 to 96.75. Conclusions: The reverse results occurred in μ-SBT values, only when the antioxidants were used in a 10% concentration and, %AA did not influence μ-SBT.

This study evaluated the effect of tooth whitening on resin composites (RC) on roughness, microhardness and flexural strength. There were three RC: one Bulk Fill type resin (Filtek Bulk Fill) and two conventional, Filtek Z350 (Z350) and Z250 (Z250). Twenty-four bar-shaped specimens were made for each RC. First, the initial roughness and microhardness were evaluated; thus, the RC were subdivided into 3 other groups, according to treatments: control group (C), this did not receive bleaching treatment; home bleaching with 10% carbamide peroxide (10%CP) (Opalescence PF),  8h/14 days; home-office bleaching with 40% hydrogen peroxide (40%HP) (Opalescence Boost PF) 3 ´ 15 minutes for 3 days at 48 hour intervals. After treatments, roughness and microhardness were again evaluated and then the samples submitted to the three-point flexural test. Data were tabulated, normality assessed, then submitted to ANOVA followed Tukey’s test (p <0.05). The results showed that the bleaching change the roughness of RC, but 10%CP had a significant increase. The gel concentration does not influence microhardness and flexural strength. After bleaching, Z350 has a lower elastic modulus. Based in the results obtained, could be concluded that the different bleachings did not promote significant changes on the RC studied.

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