Comparative Assessment of the Antimicrobial Efficacy of Photoactivated Disinfection Employing Distinct Photosensitizers: A Morphological Analysis Using Scanning Electron Microscopy and Confocal Laser Scanning Microscopy

Abstract

Background The complex morphology of the root canal system and bacterial infiltration to greater depths precludes complete debridement by mechanical preparation alone. Despite promising characteristics of photodynamic inactivation (PDI) and different photosensitizers (PSs), there has been limited research on the antibacterial efficacy of chitosan (CS)-based PS combinations for root canal disinfection. We aimed to evaluate and compare the antimicrobial efficacy of photoactivated disinfection (PAD) using two different PSs as an adjunct to final irrigation in root canal treatment. Methodology Forty single-rooted human teeth were divided into four groups: Group A (positive control) = chemo-mechanical debridement (5.25% sodium hypochlorite (NaOCl)); Group B = chemo-mechanical debridement (5.25% NaOCl) + 15 μg/ml of methylene blue (MB) with T1 = 30 sec + diode laser (650 nm) and T2 = 30 sec; Group C = chemo-mechanical debridement (5.25% NaOCl) + 15 μg/ml of chlorin e6 (Ce6) with T1 = 30 sec + diode laser (650 nm) and T2 = 30 sec; Group D = chemo-mechanical debridement (5.25% NaOCl) + 15 μg/ml of Ce6 and CS with T1 = 30 sec + diode laser (650 nm) and T2 = 30 sec. Bacterial culture, scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM) analysis were used to examine microbial coverage. The data were analyzed using IBM SPSS Statistics software, version 25 (IBM Corp., Armonk, NY); ANOVA followed by Tukey's post-hoc analysis was used to compare colony counts among the four groups. Results While inter-group comparison of pre-irrigation bacterial counts did not reveal a significant difference, post-irrigation counts were greater for NaOCl, followed by MB, Ce6, and Ce6+CS. However, all groups showed a significant reduction in counts post irrigation (Group A = 20.28 vs. 1.36; Group B = 20.12 vs. 1.11; Group C = 20.16 vs. .62; Group D = 20.20 vs. .33; all values in *10). Conclusion Based on colony counts and SEM and CLSM analysis, we found better anti-microbial properties for Ce6+CS, followed by Ce6, MB, and NaOCl, despite not having a difference in their colony counts before irrigation.

Keywords: chlorin e6; clsm; irrigation; lasers; photoactivated disinfection; sem.