Roughness and microhardness of composites after different bleaching techniques.

Background: The aim of this study was to evaluate the roughness and microhardness of SonicFill (TM) (Kerr), and compare it with Filtek (TM) Supreme XTE (3M ESPE) after 2 bleaching regimens. Methods: Sixty cylindrical specimens (10 x 2 mm) of each of the 2 composites were prepared and divided into 6 groups (n = 20): groups 1, 2: no treatment; groups 3, 4:10% carbamide peroxide (CP); and groups 5, 6: 35% hydrogen peroxide (HP) plus LED. After treatments, specimens were thermocycled (500 cycles, 5 degrees C/55 degrees C, dwell time 30 minutes). A mechanical roughness tester was employed to measure the surface roughness parameters and the Vickers test to measure microhardness. One-way ANOVA, Tukey and Bonferroni methods with a significance level of 5% were used for the statistical analysis. Results: For SonicFill (TM), there was no statistically significant difference in microhardness between the control group (no. 1) and the bleached groups (nos. 3, 5), but there was difference between CP and HP treatments; for Filtek (TM) Supreme XTE, there was no significant difference in microhardness among all groups. There was no significant difference in average roughness (R-a) and the root mean square of the roughness (R-q) among all groups. The mean roughness depth (R-z) parameter showed no statistically significant differences among all groups for SonicFill (TM), but in Filtek (TM) Supreme XTE, there was a significant increase between control and bleaching treatments; roughness skewness (R-sk) showed no statistically significant differences among all groups for SonicFill (TM) and Filtek (TM) Supreme XTE, except for nos. 2 and 4, where the R-sk increased with CP. Conclusions: The microhardness of Filtek (TM) Supreme XTE is less affected by bleaching than that of SonicFill (TM). Both bleaching treatments affect R-z in Filtek (TM) Supreme XTE in contrast to SonicFill (TM), but only the CP treatment affects the R-sk of Filtek (TM) Supreme XTE, with no significant effect of SonicFill (TM).