In vitro evaluation of photodynamic therapy associated with irrigation protocols in the control of multispecies endodontic biofilm.

Aim

To evaluate the antimicrobial efficacy of antimicrobial photodynamic therapy (aPDT), either alone or in combination with various irrigation protocols, against mature multispecies biofilms.

Materials And Methods

Multispecies biofilms consisting of nine bacterial species were cultivated on 72 bovine dentin discs and randomly assigned to six groups (n = 12 each): saline (control), saline + aPDT, 2.5% sodium hypochlorite (NaOCl) + 17% EDTA, NaOCl + EDTA + aPDT, 2% chlorhexidine (CHX) + EDTA, and CHX + EDTA + aPDT. aPDT was performed using 0.005% methylene blue and a red diode laser (660 nm, 100 mW, 9 J, 90 s). The antimicrobial efficacy was assessed through colony-forming unit (CFU) counts and confocal laser scanning microscopy (CLSM). The data were analyzed using a significance level of 5%.

Results

The saline control exhibited the highest microbial load, which was significantly reduced when combined with aPDT (p < 0.05). Both NaOCl and CHX, in the absence of aPDT, significantly decreased microbial levels compared to saline (p < 0.05). When used alongside aPDT, NaOCl resulted in the lowest CFU values; however, no additional antimicrobial benefit from light activation was observed. The antimicrobial reduction achieved with saline + aPDT was comparable to 2% CHX. CLSM analysis corroborated these findings.

Conclusion

aPDT enhanced the antimicrobial efficacy of physiological saline, resulting in an antimicrobial effect comparable to that observed with 2% liquid chlorhexidine. Among the irrigation protocols evaluated, 2.5% sodium hypochlorite showed the greatest antimicrobial efficacy, with no significant additional benefit following the application of aPDT.