Evaluation of the Effectiveness and Color Stability of In-Office Bleaching Agents: A Retrospective Study

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). Results: Baseline age distribution, initial color parameters, and patient-related behavioral factors were comparable among the groups, with no statistically significant differences observed. All bleaching agents resulted in significant color improvement at the 1-week evaluation (ΔE₀₀ range: 3.67-6.34; p < 0.05), exceeding clinically acceptable thresholds. At 6 months, slight, non-significant reductions in ΔE₀₀ values were observed in the Powerbright, FGM Whiteness HP Blue, and FGM Whiteness HP groups (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.