Background: The aim of this study was to evaluate the whitening efficacy and long-term stability of different in-office bleaching agents containing high concentrations of hydrogen peroxide (HP). Methods: Records of 50 patients who underwent in-office bleaching treatment at the Department of Restorative Dentistry, Ege University, were retrospectively analyzed. Five bleaching agents were evaluated: Opalescence (40%HP), FGM Whiteness HP (35%HP), FGM Whiteness HP Blue (35%HP), Biowhiten (40%HP) and Powerbright (35%HP). Color measurements were obtained using a spectrophotometer (VITA Easyshade V, VITA Zahnfabrik, Bad Säckingen, Germany) and standardized intraoral photographs at baseline, immediately after treatment, at 1 week, 6 months, 12 months, and 18 months. Color change (ΔE00) was calculated using the CIEDE2000 formula, and shade differences were assessed using ΔSGU values. Statistical analyses were performed using repeated-measures ANOVA and Kruskal–Wallis tests, followed by post hoc comparisons where appropriate (p 0.05). At 18 months, ΔE00 values remained within a clinically acceptable range (3.56–4.74), with no significant color regression in most groups (p > 0.05), except for a significant decrease in the FGM Whiteness HP group (p < 0.05). Conclusions: High-concentration (35–40%) in-office bleaching agents demonstrated effective short-term whitening and maintained clinically acceptable and stable color outcomes over 18 months. Although material-dependent differences were observed, bleaching efficacy and long-term color stability appear to be influenced by multiple factors beyond hydrogen peroxide concentration alone. These findings support the clinical reliability of in-office bleaching procedures and highlight the importance of long-term follow-up.
Gönüllü et al. (Fri,) studied this question.