Effects of black tea tooth staining previously to 35% hydrogen peroxide bleaching

Aim

To determine if the artificial staining with black tea (BT) influences the enamel microhardness before in-office bleaching and if BT staining is necessary to evaluate the efficacy of bleaching with 35% hydrogen peroxide

Methods

Enamel/dentin blocks were randomized into groups according to the staining protocol (n=5/group): (CO) control – maintained in artificial saliva solution (AS); (BT₄) immersed in black tea solution for 4 h; (BT₂₄) immersed in black tea solution for 24 h. After the staining protocols, all specimens were kept in AS for one week, followed by bleaching (three sessions of HP application for 40 min). Knoop surface microhardness (kgF/mm²) was determined at baseline (T₀), after staining (T₁), after 7 days of storage in AS (T₂), and after bleaching (T₃). The color (∆E₀₀) and coordinate changes (∆L, ∆a, ∆b) were measured using a digital spectrophotometer at T₀ and T₃. Data were submitted to one-way (∆E₀₀, ∆L, ∆a, ∆b) or two-way ANOVA repeated measures (kgF/mm²) and Tukey’s test (a=5%).

Results

The staining protocols (BT₄ and BT₂₄) promoted significantly lower microhardness (T₁ and T_2, p<0.05) than CO, whereas CO was the only group to maintain microhardness values over time. Bleaching promoted perceptible ∆E₀₀ without a significant difference among the groups regardless of the staining protocol (p=0.122). CO and BT₄ showed no differences in terms of ∆L and ∆a (p>0.05), but BT₄ displayed a higher ∆b than CO.

Conclusion

The artificial staining with BT negatively affected the enamel surface microhardness and was not essential to evaluate the efficacy of 35% hydrogen peroxide bleaching.

Bleaching agents; Hydrogen peroxide; Staining and labeling