Antimicrobial photodynamic therapy combined with conventional endodontic treatment to eliminate root canal biofilm infection

Background and Objective: To compare the effectiveness of antimicrobial photodynamic therapy (PDT), standard endodontic treatment and the combined treatment to eliminate bacterial biofilms present in infected root canals. Study Design/Materials and Methods: Ten single-rooted freshly extracted human teeth were inoculated with stable bioluminescent Gram-negative bacteria, Proteus mirabilis and Pseudomonas aeruginosa to form 3-day biofilms in prepared root canals. Bioluminescence imaging was used to serially quantify bacterial burdens. PDT employed a conjugate between polyethylenimine and chlorin(e6) as the photosensitizer (PS) and 660-nm diode laser light delivered into the root canal via a 200-μ fiber, and this was compared and combined with standard endodontic treatment using mechanical debridement and antiseptic irrigation. Results: Endodontic therapy alone reduced bacterial bioluminescence by 90% while PDT alone reduced bioluminescence by 95%. The combination reduced bioluminescence by > 98%, and importantly the bacterial regrowth observed 24 hours after treatment was much less for the combination (P < 0.0005) than for either single treatment. Conclusions: Bioluminescence imaging is an efficient way to monitor endodontic therapy. Antimicrobial PDT may have a role to play in optimized endodontic therapy.