Influence of different photosensitizers on the internal bleaching response of aPDT-induced coronal discoloration: an...

Purpose this study aimed to evaluate the effectiveness of the conventional walking bleaching (CWB) method in treating coronal discoloration caused by different photosensitizers used in antimicrobial photodynamic therapy (aPDT). Methods sixty extracted maxillary central incisors were randomly allocated into four groups (n = 15): methylene blue (MB), toluidine blue (TB), curcumin (CUR), and a negative control (NC). In the NC group, neither photosensitizer application nor light activation was performed. Following root canal treatment and aPDT procedures, intracoronal bleaching was performed using the conventional walking bleaching (CWB) technique with 35% hydrogen peroxide. Color measurements were obtained at baseline, one month after aPDT, and on days 4, 8, and 12 of bleaching. Color differences were calculated using the CIEDE2000 (ΔE00) formula. Data were analyzed using Robust Mixed ANOVA with Holm-adjusted multiple comparisons (α = 0.05). Results no significant main effect of photosensitizer type was observed on the overall ΔE00 values (p = 0.097), whereas time had a significant effect on bleaching response (p < 0.001). A significant photosensitizer × time interaction was also identified (p = 0.003). Although no differences were observed among the groups at ΔE002, the TB group exhibited significantly lower ΔE00 values than the MB, CUR, and NC groups during the later evaluation periods (ΔE003 and ΔE004), indicating a reduced bleaching response over time. Conclusion different photosensitizers produced comparable levels of overall bleaching response following aPDT-induced coronal discoloration. However, the temporal bleaching pattern differed among the photosensitizers, with TB-induced discoloration demonstrating a lower bleaching response during the later stages of treatment. These findings suggest that the bleaching behavior of aPDT-related discoloration may vary according to the photosensitizer used.