Effect of Over-the-counter Whitening Products on Postbleaching Enamel Surface Roughness and Shade Recovery: An In...

To evaluate the effect of over-the-counter (OTC) whitening products on postbleaching enamel surface roughness and the ability to recover the postbleaching shade after a standardized staining challenge under in vitro conditions.

This experimental, longitudinal in vitro study included 40 human enamel specimens. Specimens were subjected to bleaching with 35% hydrogen peroxide (HP) and then immersed in a purple-corn beverage at 37°C for 30 minutes every 24 hour for 28 days; the beverage was renewed daily. Specimens were randomly assigned to four equal groups (n = 10) according to the OTC treatment: Group I, distilled water (control); group II, whitening strips (WS); group III, whitening mouthwash (WM); and group IV, WS + WM. Shade recovery was assessed using the CIEDE2000 color difference (ΔE₀₀) relative to the postbleaching reference shade, and surface roughness (Ra) was measured with a contact profilometer at baseline (post-staining, pre-OTC) and after the assigned OTC regimen. Statistical analyses included paired Student's t-tests, MANOVA, and one-way between-groups ANOVA (p < 0.05).

At baseline, no between-group differences were observed for Ra (p = 0.893) or ΔE₀₀ (p = 0.304). After exposure, Ra increased significantly compared with control in WS (p = 0.026), WM (p = 0.002), and WS + WM (p = 0.025), with no differences among the three OTC regimens (p > 0.05). Within groups, Ra increased in WS (+0.83 μm; p < 0.001), WM (+1.18 μm; p = 0.001), and WS + WM (+0.72 μm; p = 0.005), but not in the control (p = 0.532). For ΔE_00, there were between-group differences (p < 0.001): WS + WM yielded the lowest values and differed from control, WS, and WM (all p < 0.05), while WS and WM did not differ from each other (p > 0.05). Within groups, ΔE₀₀ decreased in WS (-14.62; p < 0.001), WM (-16.47; p < 0.001), and WS + WM (-21.19; p < 0.001), with no change in the control (p = 0.292). A global multivariate effect of OTC whitening was detected [Wilks' Λ, p < 0.001; partial η² (η_p²) = 0.753], with a very large effect size for ΔE₀₀ (η_p² = 0.934) and a moderate one for Ra (η_p² = 0.326).

Under in vitro conditions, OTC whitening regimens increased enamel surface roughness and reduced color difference, with a larger effect on ΔE₀₀ than on Ra. The combined regimen of strips and mouthwash produced the greatest reduction in ΔE_00, while Ra did not differ among OTC protocols. Longer-term randomized clinical trials are needed to determine the clinical relevance of these findings.

After professional bleaching, OTC WS, WM, or both may improve color recovery, but they may also increase enamel surface roughness. Clinicians should advise patients about this esthetic-surface trade-off and recommend judicious use. How to cite this article: Llancari-Alonzo R, Manrique-Guzmán J, Manrique-Chávez J, et al. Effect of Over-the-counter Whitening Products on Postbleaching Enamel Surface Roughness and Shade Recovery: An In Vitro Study. J Contemp Dent Pract 2026;27(2):148-155.