Dental bleaching with ozone: effects on color and enamel microhardness

The aim of this in vitro study was to evaluate the effects of dental bleaching with ozone (O3) on color change and enamel microhardness. Enamel blocks (3 x 3 x 3mm) were randomly distributed for treatments (n=10). Color change (ΔE) and Knoop microhardness of the enamel blocks were evaluated before and after the following treatments: C - deionized water (control); HP - 37.5% hydrogen peroxide (Pola Office+/ SDI); PLA - placebo gel; O3 - ozone; and O2 - oxygen. Four 8-minute applications were used for HP and PLA, and one 19-minute application for O3 and O2.One-way ANOVA revealed that ΔE was not significantly influenced by the treatment (p = 0.112). For the treatments with HP, PLA, O3 andO2, ΔE was greater than 3.3. The paired t test showed significant decrease in microhardness after treatments (p < 0.001) but no significant difference between treatments (ANOVA; p = 0.313). Dental bleaching treatments with O3, HP, O2 and PLA induced enamel color changes that may be clinically discernible, although enamel microhardeness decreased.