Effects of the Addition of Fluoride and Calcium to Low-Concentrated Carbamide Peroxide Agents on the Enamel Surface and Subsurface

Objective: The present study aimed to determine if the addition of fluoride (F) and calcium (Ca) to home-applied 10% carbamide peroxide (CP) bleaching agents reduces mineral loss on the enamel surface and subsurface. Background: Home-applied 10% carbamide peroxide effectively whitens teeth. However, bleaching possibly promotes adverse side effects such as tooth hypersensitivity and morphological and chemical alterations, such reductions in calcium and fluoride, that affect the enamel surface. Methods: Sixty human enamel slabs were selected based on evaluation of their surface microhardness (n = 10) and submitted to the application of either a placebo agent, Whiteness (TM), Opalescence (TM), Pola Night,(TM) or one of two experimental carbamide peroxide gels: the first with 0.2% fluoride added and the second with 0.2% calcium added. The gel was applied for 6 h/day for 14 days. Samples were submitted to FT-Raman spectroscopy to evaluate surface mineral content before and after treatment. Additionally, cross-sectional microhardness and polarized light microscopy were carried out, to determine enamel subsurface inorganic loss and lesion depth. Results: A significant decrease in mineral content was observed after carbamide peroxide treatment, which resulted in increased lesion depth (p < 0.05). Cross-sectional microhardness assessment and polarized light microscopy demonstrated that all groups (except the placebo) exhibited enamel subsurface mineral loss; however, the inorganic deficit could be effectively controlled by the addition of F and Ca to the experimental bleaching agents. Conclusions: The addition of F and Ca to home-applied bleaching agents may reduce enamel mineral loss.