Sodium hypochlorite and laser activation effectiveness against an E.faecalis biofilm

Objectives: It has been shown that laser irradiation in combination with an irrigant creates turbulent and cavitation effects that have been shown to improve the removal of debris from the root canal system. Sodium hypochlorite (NaOCl) is the most commonly used endodontic irrigant due to its antibacterial and tissue dissolving properties. The aim of this study was to establish the effectiveness of various concentrations of NaOCl with and without laser activation, in eradicating an E. faecalis biofilm in vitro. Method: Decoronated single rooted extracted human teeth were assembled within a flow cell. The apparatus allowed a nutrient media to be pumped into the flowcell and through the root canals. The flow cell was inoculated with E. faecalis (ATCC 700802) and cultivated for 4 weeks. There were 6 treatment groups; saline irrigation, 1% NaOCl; 4% NaOCl; 0.5% NaOCl with laser activated irrigation (LAI); 1% NaOCl with LAI; 4% NaOCl with LAI. Following treatment teeth were crushed and colony forming units (CFU) per mL calculated. Results: There were 16 teeth within each group. The median CFU/mL for the 6 groups were: saline 3.9 x 10⁵, 1% NaOCl 3.25 x 10³, 4% NaOCl 2 x 10², 0.5% NaOCl with LAI 5 x 10², 1% NaOCl with LAI 4 x 10², 4% NaOCl with LAI 1.3 x 10². Post-hoc analysis showed a significant difference between the saline irrigation group and the other 5 treatment groups (P < 0.001). Significant differences between 4% NaOCl and 1% NaOCl (P=0.036), as well as 1% NaOCl with LAI and 1% NaOCl (P = 0.045) were shown. Statistical differences were not shown between the other groups. Conclusion: The study concluded that 4% NaOCl is more effective than 1% NaOCl however lower concentrations (0.5% and 1% NaOCl) when laser activated are as effective as 4% NaOCl.