Bactericidal Efficacy of Photodynamic Therapy and Chitosan in Root Canals Experimentally Infected with Enterococcus Faecalis: An In Vitro Study

Objective: To evaluate the antibacterial efficacy of photodynamic therapy (PDT) and chitosan against Enterococcus faecalis and assess the possible enhancive effect of chitosan on the photosensitizer methylene blue in experimentally infected root canals of extracted human teeth in vitro.

Background Data: E. faecalis is frequently found in persistent endodontic infections. In this context, the antimicrobial PDT or newer antibacterial alternatives such as chitosan could become modern alternatives to existing antibacterial treatment approaches.

Methods: One hundred two single-rooted extracted teeth were used. The teeth were contaminated with 0.1 mL E. faecalis (3 × 10 cell/mL). These were randomized into six treatment groups (n = 17 teeth): Group 1 (2.5% NaOCl); Group 2 (PDT); Group 3 (chitosan 3 mg/mL); Group 4 (PDT+chitosan 3 mg/mL); Group 5 (positive control, no treatment); and Group 6 (negative control, no inoculation, no treatment). The canal content was sampled with sterile paper points. The samples were cultured on blood agar plates to determine the number of colony-forming units (CFU)/mL. Five teeth in each group were analyzed by scanning electron microscope (SEM) to determine the percentage of area with contamination and debris.

Results: The positive control group showed the highest number of CFU/mL, with statistically significant differences in comparison with the other treatment groups (p ≤ 0.05). Group 4 (PDT+chitosan) showed the lowest CFU/mL count, followed by Group 2 (PDT alone), which obtained similar results to Group 1 (NaOCl), but there was no significance between the treated groups. SEM images showed that Group 4 (PDT+Chitosan) showed the lowest area of contamination.

Conclusions: Combination of PDT and chitosan showed antibacterial potential against endodontic infection by E. faecalis.