Efeito do uso e do momento de aplicação de dentifrícios dessensibilizantes na cor, refletividade, rugosidade e nanodureza do esmalte clareado

Abstract

This in vitro study aimed to investigate the effect of desensitizing toothpastes applied before or after dental bleaching on the enamel surface shade, reflection intensity (SRI), roughness (Ra, RMS) and nanohardness (NH). Inter-rater agreement for SRI measurements and SRI association with enamel shade and roughness were also evaluated. Enamel and dentin blocks (36 mm²) were obtained from 42 bovine incisors. The specimens were randomly divided into seven groups (n = 6) according to the desensitizing toothpastes and the moment of application (G1: control, bleached and stored in artificial saliva; G2: Sensodyne Repair & Protect + dental bleaching; G3: dental bleaching + Sensodyne Repair & Protect; G4: Colgate Sensitive Pro-Relief + dental bleaching; G5: dental bleaching + Colgate Sensitive Pro-Relief; G6: Elmex Sensitive + dental bleaching; G7: dental bleaching + Elmex Sensitive. Three bleaching sessions using 35% hydrogen peroxide were realized with seven day intervals (T1, T2, T3). After each day of treatment, the specimens were stored in artificial saliva. Dental shade was measured using spectrophotometer (VITA Easyshade) and CIE L*a*b* system before treatment beginning (T0) and 7 days after finishing treatment (T4). SRI was measured by two raters (R1, R2) using optical reflectometer at T0, T1, T2, T3 and T4. Enamel surface roughness (Ra, RMS) and NH (GPa) were evaluated with an atomic force microscope and nanoindenter (Asylum Research) at T4. Multiple comparisons among groups were assessed by Kruskal-Wallis and Dunn-Bonferroni post hoc tests. Inter-rater agreement was evaluated by Intraclass Correlation Coefficient (ICC). Multiple comparisons for SRI according to moments of evaluation for each group were assessed by Friedman and Dunn-Bonferroni post hoc tests. Correlation between variables was accessed by Pearson correlation test. For Ra (p = 0.007), RMS (p = 0.018), shade (p = 0.016) and SRI (p = 0.009) significant differences between groups were found. For NH (p = 0.920) no significant difference among groups was found. After Dunn-Bonferroni adjustment, significant differences between G1 and G5 for Ra (p = 0.033) and SRI (p = 0.004) at T4 were found. There was an excellent inter-rater agreement (ICC = 0.873, Confidence Interval 95% = 0.828/0.905). Considering times of SRI evaluation, no significant difference between T0 and T4 was found for all groups. SRI presented a moderate negative correlation with Ra (r = -0.602) and RMS (r = -0.501). It was concluded that Colgate Sensitive Pro-Relief applied after dental bleaching showed higher roughness and lower SRI than control group. For the other groups, the desensitizing toothpaste applied before or after dental bleaching did not interfere in NH, roughness, shade and SRI of enamel. Optipen 2 reflectometer provided excellent inter-rater agreement. SRI did not change after bleaching and desensitizing toothpaste application with storage in artificial saliva and has inverse correlation with enamel roughness.