Effects of dental bleaching protocols with violet radiation on the color and chemical composition of stained bovine enamel.

ABSTRACT Objectives To evaluate the bleaching efficacy of a violet radiation (VR) combined or not with bleaching gels on the color and mineral content of stained teeth. Material and Methods Enamel/dentin blocks were obtained and stained (n = 50) with coffee, red wine, tobacco smoke, or were left non-stained. The stained or not-stained blocks (n = 10) were distributed into five bleaching groups (n = 10): VR, CP (37% carbamide peroxide), VR/CP, HP (35% hydrogen peroxide), and VR/HP. Color (ΔE00, ΔL, Δa, and Δb) and whiteness index (ΔWID) changes were evaluated after staining and after bleaching using a spectrophotometer. Calcium (Ca), phosphorous (P), and Ca/P contents (in wt%) were measured after bleaching using energy-dispersive X-ray spectroscopy (EDS). Data was statistically analyzed (α = 0.05) using two-way ANOVA and Tukey tests (ΔE00, ΔWID, ΔL, Δb, wt%) or Kruskal-Wallis and Dunn tests (Δa). Results VR alone caused higher colorimetric changes on coffee, tobacco and red wine-stained groups compared to non-stained enamel (p   0.05). No differences were observed for the wt% of Ca, P and Ca/P between the groups. Conclusions The violet radiation was more effective in bleaching stained rather than non-stained teeth. VR combined with 37% carbamide peroxide was as effective as the HP agent. Besides, no adverse effects could be observed in the enamel mineral content, regardless of the bleaching protocol tested, according to the EDS semi-quantitative analysis.