Influence of Enamel Thickness on Bleaching Efficacy: An In-Depth Color Analysis.

This study evaluated the influence of different enamel thicknesses and bleaching agents on treatment efficacy in-depth by spectrophotometry color analysis. Eighty bovine dental fragments were previously stained in black tea solution and randomly assigned into eight groups (n=10), 1.75mm dentin thickness and different enamel thicknesses as follows: 0.5mm, 1.0mm planned, 1.0mm unplanned (aprismatic enamel), and absence of enamel. The 10% carbamide peroxide (CP) and 35% hydrogen peroxide (HP) bleaching gels were applied on the enamel surface following the manufacturer's recommendations. Color of underlying dentin was evaluated at four times: after staining with tea (baseline) and after each one of the three weeks of bleaching treatment, by CIE L*a*b* system using reflectance spectrophotometer (CM 700d, Konica Minolta). The ΔE, ΔL, Δa, and Δb values were recorded and subjected to repeated measures ANOVA and Tukey's test (α=0.05). The results showed an increase on lightness (L*), with decreased redness (a*) and yellowness (b*). At first and second week, bleaching with CP showed higher whitening effectiveness compared to bleaching with HP and the presence of aprismatic enamel significantly reduced ΔE for bleaching with CP. After three weeks of bleaching, few differences were observed between CP and HP groups, and outer enamel layer caused no influence on bleaching effectiveness. Overall, both at-home and in-office bleaching treatments were effective and the presence of aprismatic enamel did not interfere on the whitening efficacy.

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.

Microhardness evaluation of silorane and methacrylate composites submitted to erosion and abrasion processes.

Objective: The aim of this study was to evaluate the Knoop hardness number (KHN) of methacrylate (MC) and silorane (SC) composites after being submitted to erosion and abrasion processes. Material and methods: Forty samples were made with each composite: MC and SC. The samples were divided into eight groups (n = 10) according to the type of composite (G1-G4, MC; G5-G8, SC) and the beverages involved in the erosion process (G1 and G5 - Control (C), without erosion, with abrasion; G2 and G6 - Orange Juice (OJ), abrasion; G3 and G7 - Smirnoff Ice® (SI), abrasion; G4 and G8 - Gatorade® (GA), abrasion). The KHN test was performed 24 h after the last cycle of erosion/abrasion. Results: The MC groups showed smaller KHN values for the SI group (p < 0.05) when compared to the Control and OJ groups; however, for the SC groups, no differences were found (p > 0.05). Conclusion: Methacrylate composite when submitted to acidic beverages erosive challenge combined with abrasive process might alter its surface microhardness. However, the beverages used in the present study were not able to interfere in silorane composite surface microhardness.

Minimally invasive cosmetic dentistry: smile reconstruction using direct resin bonding.

Discrepancies in tooth size and shape can interfere with smile harmony. Composite resin can be used to improve the esthetics of the smile at a low cost while offering good clinical performance. This article presents an approach for restoring and correcting functional, anatomic, and esthetic discrepancies with minimal intervention, using composites and a direct adhesive technique. This conservative restorative procedure provided the patient with maximum personal esthetic satisfaction.