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.