Reduction of dual-species biofilm after sonic- or ultrasonic-activated irrigation protocols: A laboratory study

Abstract

Aim: To evaluate the antibacterial effect of sonic- and ultrasonic-activated irrigation on bacterial reduction of a dual-species biofilm in root canals compared to nonactivated irrigation in a laboratory study. Methodology: Two hundred and forty extracted human single-rooted maxillary anterior teeth were divided into two main groups (G, n = 120) according to the initial preparation size of the root canal (G1: size 25, 0.06 taper, G2: size 40, 0.06 taper). Root canals were inoculated with Enterococcus faecalis and Streptococcus oralis. After 5 days, G1 received combined instrumentation (up to size 40, 0.06 taper) and irrigation/activation, whereas G2 received solely irrigation/activation protocols. In both groups, irrigation was performed with sodium hypochlorite (NaOCl 1%) or physiological saline (NaCl 0.9%), using nonactivated syringe irrigation, sonic activation (2 x 30 s) or ultrasonic activation (2 x 30 s). Logarithmic reduction factors (LRFs) of colony-forming units were analysed separately for dentine-adherent and planktonic bacteria immediately after irrigation/activation protocols (time-point 1) or after 5 days of further incubation (time-point 2) by analysis of variance (anova) and post hoc tests (Tukey's HSD, t-test). The significance level was set at 0.05. Results: In G1 subgroups (combined instrumentation with irrigation/activation), LRFs were significantly affected by the applied irrigation solution (p.05; anova). In G2 subgroups (solely irrigation/activation), both, irrigant solution and activation, significantly affected LRFs (p