From Microstructure to Shade Shift: Confocal and Spectrophotometric Evaluation of Peroxide-Induced Dental Bleaching

Background/Objectives: Tooth bleaching is a widely requested aesthetic procedure in modern dentistry. However, the structural effects of high-concentration peroxide-based bleaching agents on enamel remain insufficiently understood. This study aims to evaluate and compare the effects of three in-office bleaching agents-Opalescence Boost (40% hydrogen peroxide [HP]), Opalescence Quick (45% carbamide peroxide [CP]), and BlancOne Ultra + (35% hydrogen peroxide [HP])-on enamel surface characteristics and color change using confocal laser scanning microscopy (CLSM) and spectrophotometric analysis. Methods: Forty-two extracted human teeth were sectioned and divided into experimental and control halves. Each experimental specimen underwent bleaching according to the manufacturer's protocol. Color measurements were conducted at baseline, immediately post-treatment, at 3 days, 7 days, and 6 months following treatment using the Vita Easyshade^® spectrophotometer. Color differences were calculated using the CIEDE2000 (ΔE₀₀) formula. Enamel surface morphology was assessed by CLSM. Data were analyzed using Wilcoxon and Kruskal-Wallis tests (p < 0.05), performed with SPSS v23. Results: All bleaching agents produced clinically perceptible color changes (ΔE₀₀ > 3.3). Opalescence Boost achieved the highest and most consistent whitening effect (mean ΔE₀₀ > 11), while Opalescence Quick showed moderate efficacy (ΔE₀₀ ~6-8), and BlancOne Ultra+ induced milder changes (ΔE₀₀ ~4-5). CLSM imaging revealed surface alterations in all bleached samples, with more pronounced changes observed in specimens treated with higher peroxide concentrations. Conclusions: All three bleaching systems were effective in improving enamel color, with Opalescence Boost delivering the most substantial and durable effect. CLSM analysis confirmed morphological changes in enamel without evidence of severe damage. These results underscore the importance of selecting bleaching protocols that balance efficacy with enamel safety. Further in vivo studies are recommended to validate long-term structural effects and support clinical decision-making.