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 T2, 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