The effects of the use of whitening mouthwash after home bleaching on the color stability and surface hardness of enamel.

Background: To evaluate the effectiveness of whitening mouthwashes, both with and without hydrogen peroxide (HP), after at-home teeth whitening in preserving the achieved whiteness and assessing their impact on enamel surface hardness.

Methods: One hundred extracted human premolar teeth were divided into two groups, and home bleaching agents (Philips Zoom NiteWhite 22% Carbamide Peroxide, Ultradent Opalescence PF 16% Carbamide Peroxide) were applied to the groups. The teeth subjected to home bleaching were further divided into five subgroups, and each subgroup underwent a four-week cycle of application of a coloring agent and whitening mouthwash (Colgate Optic White (COW)(%2 HP), Rocs Black Edition (Rocs) (%1 HP), SPLAT Professional Bioactive gargle white Plus (SPLAT) (Ananas sativus fruit extract containing), Listerine Advanced White (Listerine) (Pyrophsphate containing), and distilled water (DW) (control)). Color and microhardness measurements were recorded at baseline, after home bleaching, and after treatment with whitening mouthwashes.

Results: Compared with those treated with Opalescence PF, the samples treated with Zoom achieved a significantly greater degree of whitening (p < 0.001). When the effects of postwhitening mouthwash were evaluated (ΔE₀₀₂), Listerine presented the lowest ΔE₀₀₂ value in both home bleaching groups, whereas the control group presented the highest ΔE₀₀₂ value. Both home-bleaching agents caused a significant increase in the initial WI_D values (p < 0.05). After home-bleaching, the increased WI_D values (WI_D2) significantly decreased in all mouthwash groups following exposure to the staining and whitening mouthwash cycle (WI_D3) (p < 0.05). The impact of home bleaching agents on microhardness was not significantly different (p = 0.151). When we examined the impact of whitening mouthwashes on microhardness, in the Zoom group, no statistically significant difference was observed in surface hardness (p > 0.05). However, in the Opalescence PF group, only the Listerine group showed a statistically significant increase (p < 0.05).

Conclusions: Higher concentrations of carbamide peroxide provide faster and more effective whitening. Whitening mouthwash containing HP and pyrophosphate is effective in maintaining tooth whiteness after home bleaching; however, its impact on enamel microhardness depends on the formulation. Notably, only Listerine in the Opalescence PF group significantly increased surface hardness. Given the drawbacks of HP, pyrophosphate-based mouthwash may serve as a safer alternative.