Evaluation of photodynamic therapy using a diode laser 635 nm as an adjunct to conventional chemo-mechanical edodontic procedures against enterococcus faecalis biofilm: ex-vivo study

The study aimed to evaluate the antimicrobial effect of photodynamic therapy (PDT) with the use of Toluidine Blue (TB) on extracted teeth infected with biofilms of Enterococcus faecalis. Fifty-four extracted teeth with single-roots and single canals were mechanically shaped, autoclaved, and contaminated with E. faecalis. They were randomly divided into six groups: two groups were negative and positive control groups, two groups were subjected to mechanical instrumentation and PDT with different pre-irradiation times and irradiation times, and two groups were subjected to chemo-mechanical endodontic treatment and PDT with different pre-irradiation times and irradiation times. In PDT groups, after the application of TB, the canals were irradiated with a diode laser of wavelength 635 nm, with a fiber diameter of 200 μm and 100 mW of power in continuous mode. The bacterial load was evaluated using a BioTimer Assay protocol. The greatest reduction of bacterial load was observed in groups of combined PDT with chemo-mechanical treatment. The reductions of bacterial load in groups of combined PDT with chemo-mechanical treatment, and in the positive control group, were significant (p < 0.01) when compared to that of the negative control group. Photodynamic therapy as an adjunctive modality may improve the disinfection capacity of conventional endodontic treatment against E. faecalis.