Evaluation of Nd: YAG and Er: YAG irradiation, antibacterial photodynamic therapy and sodium hypochlorite treatment on Enterococcus faecalis biofilms

摘要

Aim To compare the antimicrobial efficacy of two-high power lasers (Nd:YAG and Er:YAG) and two commercial antimicrobial photodynamic therapy (aPDT) systems with that of sodium hypochlorite (NaOCl) action on Enterococcus faecalis biofilms grown on dentine discs. Methodology Enterococcus faecalis biofilms were grown on dentine discs in a microtiter plate, incubated for 24h and subjected to the following treatments: aPDT (Denfotex and Helbo system), Er:YAG laser irradiation (2940nm, 50mJ or 100mJ, 15Hz, 40s), Nd:YAG laser irradiation (1064nm, 2W, 15Hz, 40s) and immersion in 2.5% (w/v) NaOCl for 1, 5, 10 and 30min. Surviving bacteria were harvested, and the number of CFU per disc was determined by plate counting. Results Significant reductions (anova, P≤0.05) in viable counts were observed for aPDT (Helbo) (2 log 10 reduction), Er:YAG irradiation using 100mJ pulses (4.3 log 10 reduction) and all NaOCl treatments (6 log 10 reduction). NaOCl (2.5%) for 5min effectively eliminated all bacteria. aPDT (Denfotex), Er:YAG irradiation using 50mJ pulses and Nd:YAG treatment caused a reduction in the viable counts of 1log 10 unit; these results were not significantly different from the untreated controls. Conclusion Within the limitations of this particular laboratory set-up, NaOCl was the most effective in E. faecalis biofilm elimination, while Er:YAG laser treatment (100mJ pulses) also resulted in high reductions in viable counts. The use of both commercial aPDT systems resulted in a weak reduction in the number of E. faecalis cells. Nd:YAG irradiation was the least effective.