Effect of in-office bleaching gels with calcium or fluoride on color, roughness, and enamel microhardness.

BACKGROUND: Commercial bleaching gels with remineralizing agents were developed to reduce the adverse effects of dental bleaching. The present study evaluated the effects on teeth of in-office bleaching gels containing 35-40% hydrogen peroxide (HP) with Calcium (Ca) or Fluoride (F). MATERIAL AND METHODS: Bovine enamel/dentin blocks (4x4x2.5 mm) were randomly divided into the following groups (n=12): no treatment (control); 35% HP (Whiteness HP, FGM); 35% HP with Ca (Whiteness HP Blue, FGM); 40% HP with F (Opalescence Boost, Ultradent). The specimens were analyzed for color (ΔL*, Δa*, Δb*, and ΔE), roughness (Ra), and Knoop microhardness (KHN). The color and KHN data were submitted to ANOVA and Tukey's test, while Ra values were analyzed using mixed models for repeated measures and Tukey-Kramer's test (α=0.05). RESULTS: The bleached groups did not exhibit statistical differences among them for color. For roughness, 35% HP provided a slight increase of Ra, which was statistically different from the control. For microhardness, 35% HP and 40% HP with F presented KHN values that were statistically lower from the control, while the 35% HP with Ca did not statistically differ from the control. CONCLUSIONS: The presence of Ca or F in bleaching gels did not interfere with bleaching efficacy. However, only the enamel exposed to the bleaching gel containing Ca obtained microhardness values similar to unbleached enamel. Key words:Hydrogen peroxide, tooth bleaching, tooth bleaching agents, laboratory research.