Effect of photodynamic therapy in combination with various irrigation protocols on an endodontic multispecies biofilm ex vivo.

AIM: To analyse the antibacterial effect of photodynamic therapy (PDT) in combination with various irrigation protocols on a multispecies biofilm in root canals ex vivo.

METHODOLOGY: A total of 160 extracted human single-rooted teeth were divided into four groups (n = 40). In group G1, root canals were instrumented up to size 60 (control group), whereas in G2 to G4 canals were enlarged up to size 40. All root canals were inoculated with a multispecies biofilm (Enterococcus faecalis, Streptococcus oralis, Prevotella intermedia) for 5 days. In G2 to G4, instrumentation up to size 60 was performed using 0.9% sodium chloride (NaCl) (G2), 1% sodium hypochlorite (NaOCl) (G3), 1% NaOCl and a final irrigation with 2% chlorhexidine (CHX) (G4), respectively. In all groups half of the specimens received adjunctive PDT using phenothiazine chloride as photosensitizer and a diode laser (wavelength 660 nm). Counts of colony-forming units (CFUs) in each group were analysed separately for planktonic and dentine-adherent bacteria immediately after therapy (T1) and after 5 days of further incubation (T2). Descriptive statistics and two-way analysis of variance were carried out to analyse reduction of planktonic bacteria and nonparametric tests were used to analyse dentine-adherent bacteria.

RESULTS: CFU reduction in planktonic bacteria was significantly affected by the irrigation protocol at T1 and T2 (P < 0.0001), but PDT significantly reduced CFUs only at T2 (P = 0.01; anova). Irrigation using NaOCl, CHX and adjunctive PDT significantly reduced CFUs at T2 (P < 0.0001; Tukey HSD) compared to the control group. In 85.6% of all samples the same categories of CFU counts in both planktonic and dentine-adherent bacteria were detected at T1 and T2.

CONCLUSIONS: Adjunctive photodynamic therapy in combination with an irrigation protocol including NaOCl and CHX was an effective method for reduction of bacterial biofilm inside the root canals of extracted teeth.