Effects of Bleaching Agents Combined with Regular and Whitening Toothpastes on Surface Roughness and Mineral Content of Enamel.

OBJECTIVE: The purpose of this study was to evaluate surface roughness and changes in the composition of enamel submitted to different bleaching protocols and toothbrushing with regular and whitening toothpastes. BACKGROUND DATA: Bleaching treatment could promote morphological and chemical changes in enamel surface. METHODS: Enamel blocks were randomized into nine groups (n=10) according to the bleaching treatment (no bleaching, control group; 6% hydrogen peroxide, HP; or 10% carbamide peroxide, CP) and toothpaste used (placebo, PL; regular, R; or whitening dentifrice, W). Bleaching was performed according to manufacturers' instructions and all groups were submitted to 30,000 cycles of simulated toothbrushing with toothpaste (PL, R, or W). Mineral content evaluation and enamel roughness were evaluated initially (T1), after bleaching (T2), and after toothbrushing (T3), using an energy-dispersive micro X-ray fluorescence spectrometer and profilometry, respectively. Data were statistically analyzed with two way ANOVA, Tukey, and Dunnett tests (5%). RESULTS: Enamel surface roughness was influenced by bleaching and toothbrushing. Surface roughness increased for the groups that brushed with the placebo dentifrice (CP+PL, HP+PL, C+PL) and for the control group that brushed with whitening dentifrice (C+W). Enamel Ca/P ratio decreased after bleaching, but toothbrushing, regardless of the dentifrice used, did not reduce the enamel mineral content. CONCLUSIONS: The bleaching treatment resulted in a decrease of enamel mineral content, but the studied dentifrices did not contribute to surface mineral loss.

The effect of coffee solution on tooth color during home bleaching applications.

PURPOSE: To quantify the change in color of human and bovine teeth exposed to a coffee solution during a 16% carbamide peroxide (16% CP) home application bleaching treatment using photoreflectance analysis. METHODS: 40 enamel slabs (4 x 4 x 2 mm) were obtained from seven unerupted third human molars and seven bovine incisors, which were allocated into four groups: G1: human control group whitened and not exposed to a coffee solution; G2: bovine control group whitened and not exposed to a coffee solution; G3: human teeth whitened and exposed to a coffee solution; G4: bovine teeth whitened and exposed to a coffee solution. The home bleaching procedure was performed using 16% CP gel applied in a 1 mm-thick layer on the tooth surface over a period of 6 hours per day, for 28 days. Tooth color was evaluated using photoreflectance analysis throughout the bleaching procedure at intervals of 7, 14, 21 and 28 days, and posttreatment at 7, 15 and 30 days. Results were statistically analyzed using ANOVA and Tukey-Kramer tests. RESULTS: After 28 days of bleaching treatment, no significant difference was detected between photoreflectance analysis of specimens exposed to coffee solution and specimens not exposed to coffee solution (P < 0.05). However, when the teeth were exposed to a coffee solution during home bleaching treatment, the whitening effect was observed to be less stable (P < 0.05). Bovine and human enamel substrates behaved similarly in terms of staining and bleaching effects, although they presented inherent differences in color (P < 0.05).

Effects of 10% carbamide peroxide treatment and sodium fluoride therapies on human enamel surface microhardness.

This study sought to evaluate the microhardness of enamel submitted to 10% carbamide peroxide treatment and different methods of remineralization involving sodium fluoride (NaF). Non-erupted third molars were used and 75 enamel blocks with standardized dimensions (4.0 x 4.0 x 2.0 mm) were obtained. Enamel blocks were randomly divided into five groups (n = 15): one control (no bleaching and no fluoride treatment), one receiving a 10% carbamide peroxide treatment, one receiving 10% carbamide peroxide plus acidulated phosphate fluoride, one receiving 10% carbamide peroxide with 0.2% NaF, and one receiving 10% carbamide peroxide and 0.05% NaF. There were no differences among four of the groups (p > 0.05); the group receiving 10% carbamide peroxide only was different from all other groups (p < 0.05). Based on these results, NaF therapies are recommended during carbamide peroxide bleaching treatments.