Effects of Bleaching Protocols on the Esthetic Outcome and Surface Integrity of Enamel Treated With an Ammonia-Free...

To investigate the effects of three bleaching protocols on the color stability and surface roughness of enamel previously treated with a water-based, ammonia-free silver fluoride solution (Riva Star Aqua).

Eighty-eight human enamel/dentin specimens were demineralized and treated with Riva Star Aqua, divided into four groups (n = 22): Control (no bleaching), home bleaching with 15% hydrogen peroxide (HP), in-office bleaching with 40% HP, and laser-activated bleaching with 46% HP. Color differences (ΔE ₀₀) were measured at different stages, and the surface roughness (Ra) was evaluated before and after bleaching. Data were analyzed using two-way repeated measures ANOVA and Fisher's PLSD test (α = 0.05).

The application of Riva Star Aqua caused perceptible discoloration in all groups. Following bleaching, all three active protocols resulted in significant color correction compared with the control group (p < 0.05). The final color differences (ΔE ₀₀ Final) for Opalescence Boost (6.82 ± 0.49), Opalescence Home (8.84 ± 0.42), and Laser White 20 (8.83 ± 0.37) were statistically comparable (p < 0.05). At the same time, the control group showed significantly high ΔE ₀₀ Final (10.75 ± 0.29). Regarding surface roughness, all bleaching groups showed a significant increase in Ra values (p < 0.05) compared to baseline, with significant differences between Laser White 20 and the other bleaching protocols (p < 0.05).

Bleaching effectively reversed the discoloration caused by ammonia-free silver fluoride. While all tested protocols achieved comparable final color correction, the laser-activated protocol resulted in significantly less alteration of surface roughness than the conventional in-office and at-home bleaching protocols.