Efficacy and Enamel Mineral Content of Bleaching Agents Containing Tif₄

Objectives: To evaluate color change, microhardness and surface morphology of enamel submitted to experimental bleaching agents containing 35% hydrogen peroxide (HP) combined with 4% titanium tetrafluoride (TiF₄) and different thickeners.
Methods: Experimental agents containing thickeners able to homogenize 4% TiF₄ were prepared and applied on bovine enamel standard specimens (n=8): HP (control); HP + natrosol + TiF₄ (HPnT); HP + natrosol + Chemygel® + TiF₄ (HPncT) and HP + Aristoflex® + TiF₄ (HPaT). Bleaching was performed in three 15-min applications in four sessions, with 72-h intervals and stored in artificial saliva (37^oC). Twenty-four hours after each session, color evaluation (CieLab), whiteness index (WI_D) and Knoop microhardness (KHN) were evaluated. At the end of bleaching, whiteness index differences (ΔWI_D) color changes (ΔE) and enamel morphology were investigated. Data were analyzed by two-way repeated measures ANOVA and Bonferroni post-hoc test (L*, a*, b*, WI_D, KHN), and one-way ANOVA and Tukey post-hoc test (ΔWI_D, ΔE) (α=5%).
Results: No differences in lightness (L*) were observed among groups (p>0.05), however HP promoted lower b* values (yellow appearance) than experimental agents (p = 0.038). HP presented the highest ΔE (p = 0.004) among groups, but similar ΔWI_D to HPncT, and similar WI_D to the other agents at each bleaching application (p>0.05). At the end of bleaching, HPncT exhibited higher microhardness values than HP (p = 0.003). No morphological changes were observed on HPncT-treated enamel.
Conclusions: 35% HP combined with 4% TiF₄, natrosol and Chemygel® promoted whitening effect and increased microhardness compared to HP, without compromising enamel morphology.