The antimicrobial effectiveness of photodynamic therapy used as an addition to the conventional endodontic re-treatment: A clinical study

• The addition of the aPDT to the conventional chemomechanical root canal preparation led to the significant further reduction of the number of CFUs or even to complete elimination of bacteria in some cases.
• The addition of the aPDT to the conventional chemomechanical root canal preparation led to the significant of bacteria species from the root canal.
• The combination of chemomechanical preparation and the aPDT was more successful elimination of both gram positive and gram negative bacteria species compared to the chemomechanical preparation alone.

SummaryBackgroundThe purpose of the study was to evaluate the efficacy of antimicrobial photodynamic therapy (aPDT) used as an adjunct to the endodontic re-treatment in the eradication of microorganisms from previously filled root canals.MethodsThe study sample consisted of 21 randomly selected patients with root filled and infected root canal system with chronic apical periodontitis on incisors or canines, who have had previously endodontic treatment. Microbiological samples from the root canals were collected after accessing the canal, following the endodontic re-treatment and after the aPDT procedure. During instrumentation, the root canals were irrigated with 2.5% sodium hypochlorite (NaOCl), and the final irrigation protocol included 17% ethylenediaminetetraacetic acid followed by NaOCl. Root canals were filled with a phenothiazinium chloride and irradiated with a diode laser (λ = 660 nm, 100 mW) for 1 min. Microbiological samples from the root canals were cultivated on selective plates, and the identification was done by micromorphology, macromorphology and different API strips as well as bacterial counts (colony forming units).ResultsFourteen bacteria species were isolated from the root canals initially, with a mean value of 4.57 species per canal. Although endodontic re-treatment alone produced a significant reduction in the number of bacteria species (p < 0.001), the combination of endodontic treatment and aPDT was statistically more effective (p < 0.001). No bacteria were cultivated from the main root canals of 11 teeth.ConclusionThe results indicated that the aPDT used as an adjunct to the conventional endodontic therapy achieved a significant further reduction of intracanal microbial load.