Analysis of surface roughness of human enamel exposed to bleaching agent and submitted to brushing.

The aim of this study was to assess in vitro the surface roughness (Ra) of human enamel exposed or not exposed to the action of a bleaching agent containing 10% carbamide peroxide (CP) after brushing with different dentifrices. Ninety-six human enamel specimens were divided into 2 groups: GI--exposed to the action of 10% CP; GII--not exposed. These were subdivided into 4 brushing subgroups: (CEW) Close-Up Extra Whitening, (CUB) Colgate Ultra Branco, (CCP) Crest Cavity Protection and (DW) Deionized Water. The specimens from Group GI were exposed to 10% CP for 6 hours/14 days and those from Group GII were stored in artificial saliva for 14 days. Then they were submitted to 35.600 brushing cycles. Ra was measured before and after brushing. Ra difference was compared by two-way ANOVA. Ra was compared between subgroups using ANOVA and Tukey's test. Ra was compared between groups using T-test (alpha = 0.05). Final and initial Ra were compared by Paired t-test; using SPSS (15.0). Two-way ANOVA difference in the outcome revealed that the use of bleaching agent did not affect the difference in Ra (p = 0.45). Brushing significantly influenced the difference in Ra (p < 0.001), but the interaction between the two factors was not significant (p = 0.20). Among the brushing subgroups, a significant increase in Ra was observed for Subgroup CEW--GI: Rai 0.691 (0.112)a, Raf 0.993 (0.264)a; Raf-Rai: 0.303a (43. 7%)--G2: Rai 0.794 (0.167)a, Raf 1.006 (0.488)a; Raf-Rai: 0.212a (26.7%) with a statistical difference for Subgroup CUB--GI: Rai 0.639 (0.163)a, Raf 0.506 (0.113)b; Raf-Rai: -0.133b (-20.8%)--GII: Rai 0.647(0.166)a, Raf 0.472b (0.260); Raf-Rai: -0.134b (-0.27%). Regardless of whether or not the enamel had been exposed to 10% CP, Ra values varied according to the abrasives in the composition of the different dentifrices.