Impact of Bioactive Glass-Based Toothpaste on Color Properties and Surface Microhardness of Bleached Enamel

Abstract

Objective The role of toothpaste used during aesthetic treatments is rarely investigated. The objective was to evaluate the effects of a bioactive glass-based toothpaste (BGT) used before or after the dental bleaching with 35% hydrogen peroxide (HP). Materials and Methods Bovine enamel blocks (4 × 4 mm; n = 12) were submitted to tooth bleaching and different treatments/storage, before or after HP, based on: (1) no toothpaste and immersion in artificial saliva (AS) after HP for 24 hours, 7 days, or 14 days (control); (2) daily BGT use and AS storage for 7 or 14 days (after HP); and (3) daily BGT use and AS storage for 7 or 14 days (prior to HP). Surface and in-depth color were determined using the CIE L*a*b∗ system (ΔL*, Δa*, Δb*, and ΔE) on enamel surface and underlying dentin. The surface microhardness (SMH) was evaluated using a Knoop microhardness tester. Statistical Analysis Data were submitted to analysis of variance (ANOVA) (color variables), repeated measures ANOVA (SMH), and Tukey's test (α = 0.05). Results The color changes on the enamel or underlying dentin were not statistically different among the groups (p > 0.05). Twenty-four hours after HP presented a decrease in SMH differing from baseline (p < 0.01). This decrease did not occur in the groups previously exposed to BGT (p > 0.05). BGT use after HP for 7 days differed from group with exclusive AS storage (p < 0.05). Conclusion In-office tooth bleaching can decrease the microhardness of enamel surface; however, the use of BGT promotes the protection or enables the mineral recovery of tooth without the influence the bleaching efficacy.