Color stability of enamel treated with different antioxidant agents following at-home bleaching with 10% hydrogen peroxide

Abstract

Objective: This study evaluated the color stability of enamel submitted to 10% hydrogen peroxide (HP) followed by antioxidants agents, and the pH and antioxidant activity (AA%) of these agents.

Methodology: Bovine enamel-dentin blocks were randomly distributed into groups (n=10/group): GNC (negative control: no treatment); GPC (positive control: bleaching only); TOC_10% (HP+10% α-tocopherol); GT_10% (HP+10% green tea extract); GS_5% (HP+5% grape seed extract); SA_10% (HP+10% sodium ascorbate); QUI_10% (HP+10% quinoa extract); and QC_1% (HP+1% quercetin). Color (ΔE00) and whiteness index (ΔWID) changes were analyzed using a digital spectrophotometer. The pH and AA% were determined using a pH meter and the DPPH method, respectively. Data were analyzed by ANOVA/Tukey's and Dunnett's tests (α=0.05).

Results: At 14 days post-bleaching, GNC promoted the lowest ΔWID and ΔE00 (p<0.05), and no differences were found between GPC and the remaining groups submitted to the antioxidant agents (p>0.05). QC_1% and QUI_10% exhibited acidic pH levels (3.64 and 4.75, respectively), whereas TOC_10% and GS_5% exhibited alkaline pH (7.07 and 7.64, respectively). No differences in AA% were found between the agents (p>0.05), ranging from 92.6 to 97.6%.

Conclusion: The antioxidant agents did not interfere in bleached enamel color stability, showing satisfactory antioxidant activity. However, QUI and QC gels displayed acidic pH. Clinical significance: The antioxidants evaluated showed high AA% and no impact on post-bleaching color stability, suggesting that their capacity to recover bond strength demonstrated elsewhere would not compromise the esthetic efficacy of tooth bleaching. However, those with acidic pH should be used with caution due to potential enamel damage.

Figure 1. Protocol for the Application of Bleaching and Antioxidant gels on the groups

Figure 2. Mean and standard deviation of the color variation (ΔE00) according to the respective treatments and time intervals: (A) immediately after bleaching (T1 – T0), (B) after antioxidant application (T2 – T0), and (C) after 14 days from the procedures (T3 – T0). Different letters indicate statistical differences between groups (p<0.05).

Figure 3. Mean and standard deviation of the Whitening Index for Dentistry (ΔWID), according to the respective treatments and time intervals: (A) immediately after bleaching (T1 – T0), (B) after antioxidant application (T2 – T0), and (C) after 14 days from the procedures (T3 – T0). Different letters indicate statistical differences between groups (p<0.05).

Figure 4. Mean of the pH values of the antioxidant gels according to the evaluation times.

Figure 5. Mean and standard deviation of the antioxidant activity (AA%) values of the antioxidant gels. Same letters indicate no statistical difference (p>0.05).