Aim: To determine the efficacy of sonic or Er,Cr:YSGG laser activation of irrigation protocols on Enterococcus faecalis biofilms in vitro.

Materials and methods: E. faecalis biofilms were generated in instrumented root canals (n = 120), and randomly divided into six groups (n = 20) based on the irrigation/activation protocol. Three percent sodium hypochlorite (NaOCl) was used during instrumentation. The six groups included G1: 3% NaOCl /sonic activation; G2: 3% NaOCl/Er,Cr:YSGG laser activation; G3: 17% EDTA- 3% NaOCl/ sonic activation; G4: 17% EDTA- 3% NaOCl/Er,Cr:YSGG laser activation; G5: 3% NaOCl; and G6: saline. Bacterial viability was assessed by confocal microscopy. Dentin powder was obtained for analysing the colony forming units (CFU/ml). Data were analysed by appropriate statistical analyses with P = 0.05.

Results: The biofilm along the root canal wall was completely destroyed by all groups except saline. G4 (EDTA-NaOCl / Er,Cr:YSGG activation) showed maximum bacterial destruction within the dentinal tubules of 200 μm depth (P < 0.05). At 400 μm within the dentinal tubules, there was no significant difference between the groups (P > 0.05). Culture analysis showed no growth in any of the groups at 200 μm except the saline control.

Conclusions: Activation of irrigants using Er,Cr:YSGG laser brought about a significant reduction of bacteria within the dentinal tubules at 200 μm depth.