Evaluation of antimicrobial activity of association of chlorhexidine to photosensitizer used in photodynamic therapy in root canals infected by Enterococcus faecalis

Introduction: The aim of the present study was to evaluate, in vitro, the influence of the addition of chlorhexidine to photosensitiser in the antimicrobial activity of photodynamic therapy in root canals infected by Enterococcus faecalis. Methods: The root canals of 50 single-rooted human extracted teeth were enlarged up to a file F3 of Pro-Taper system, autoclaved, inoculated with Enterococcus faecalis and incubated for 14 days. The samples were divided into five groups (n = 10) according to the protocol of decontamination: G1 (control group) - no procedure was performed; G2-photosensitiser (0.01% methylene blue); G3-2% chlorhexidine gel; G4-photodynamic therapy; and G5-photodynamic therapy with photosensitiser modified by chlorhexidine. Microbiological test (CFU counting) was performed to evaluate the effectiveness of proposed treatments. Data were subjected to one-way ANOVA followed by post-hoc Tukey test (alpha = 0.05). Results: Group 3 (CHX) showed the lowest mean contamination (2.03 log(10) CFU/mL), being statistically different from all other all groups (p < 0.05). There was no statistically significant difference between groups 4 (PDT) and 5 (PDT + CHX) (p < 0.05), being more effectives against E. faecalis when compared to groups 1 (NT) and 2 (MB), and less effective when compared to group 2 (CHX). Conclusions: The addition of chlorhexidine to photosensitiser did not result in a better decontamination potential of photodynamic therapy alone over root canals infected by E. faecalis.