MTAD combined with endosonic irrigation as a new approach for the disinfection of Enterococcus faecalis biofilm

Abstract

Background/purposeEnterococcus faecalis plays a major role in continuing refractory apical periodontitis. The purpose of this study was to investigate the antibacterial effects of sodium hypochlorite (NaOCl) combined with MTAD [a mixture of tetracycline isomer (doxycycline), an acid (citric acid), and a detergent (Tween 80)] as an endosonic irrigation protocol against E. faecalis biofilm. Materials and methodsThe dentin blocks were incubated with E. faecalis and randomly assigned to five irrigation groups (n = 10): MTAD, 1.3% NaOCl with MTAD, 1.3% NaOCl, 5.3% NaOCl, and 5.3% NaOCl with 17% EDTA using Endoactivator oscillation for 30 seconds and 1 minute, respectively; saline without agitation as a control. The bacterial samples were measured by colony-forming counting. The percentage of viable cells and the thickness of the biofilms were evaluated using confocal laser scanning microscopy. Specimens were observed via scanning electron microscopy. ResultsWhen Endoactivator was applied for 30 seconds, viable counting of the 5.3% NaOCl/17% EDTA group and 1.3% NaOCl/MTAD group were lower than the MTAD group (P < 0.05), whereas the differences between the former two are not significant. There were no statistically significant differences in the number of colony-forming counting unit between 30 seconds and 60 seconds (P > 0.05). The 1.3% NaOCl/MTAD group and the MTAD group appeared to preserve the structure of the dentin surface and cause efficient removal of the smear layer. ConclusionEndoactivator could improve the synergistic antimicrobial action of 1.3% NaOCl and MTAD against E. faecalis biofilm and removal of the smear layer with less erosion of the dentin surface. The combination could be a safe and efficient irrigation regimen.