Effects of violet radiation and nonthermal atmospheric plasma on the mineral contents of enamel during in-office dental bleaching.

Abstract Aim This in vitro study assessed the effects of in-office bleaching with gels (35 % hydrogen peroxide [HP] or 37 % cabamide peroxide [CP]) and two activation sources (violet radiation [LED] or nonthermal atmospheric plasma [NTAP]) on the mineral content of bovine enamel. Material and Methods Dental blocks (n = 90) were assessed for initial microhardness before random distribution into nine groups: LED, LED + HP, LED + CP, NTAP, NTAP + HP, NTAP + CP, HP, CP and control (without treatment). Specimens were subjected to bleaching (2 clinical sessions, 7 days apart) using LED [20x/session, 1-min/each, 30 s apart] or NTAP [1x/session, 10 min]. μRaman determined contents of phosphate (PO43) and carbonate (CO32). Micro-energy dispersive X-ray fluorescence (μEDXRF) and spectrophotometry of enamel microbiopsy evaluated the calcium to phosphorous ratios (Ca/P). Two-way ANOVA and Tukey tests analyzed μRAMAN and μEDXRF results. Spectrophotometry results were analyzed using Kruskal-Wallis and Dunn tests. Pearson correlation tested μEDXRF and spectrophotometry results (α = 95 %). Results NTAP and NTAP + HP exhibited greater PO43− content than LED, LED + HP and control (p   0.05), spectrophotometry showed that Ca/P reduced for LED + HP (p   0.05). Conclusions Activation sources did not adversely impact enamel’s phosphate and carbonate concentrations after specimens’ exposure to bleaching gels (either HP or CP). Visible light radiation emitted by a LED source was shown to adversely impact specimens’ Ca/P ratios when treated with HP-containing bleaching gels.