Antimicrobial effect of endodontic solutions used as final irrigants on a dentine biofilm model

Aim To evaluate the residual biovolume of live bacterial cells, the mean biofilm thickness and the substratum coverage found in mixed biofilms treated with different endodontic irrigant solutions. Methodology Twenty-five bovine dentine specimens were infected intraorally using a removable orthodontic device. Five samples were used for each irrigant solution: 2% chlorhexidine, 1% sodium hypochlorite (NaOCl), 10% citric acid, 17% EDTA and distilled water. The solutions were used for 5min. The samples were stained using the Live/Dead technique and evaluated using a confocal microscope. Differences in the amount of total biovolume (μm ³), number of surviving cells (μm ³), mean biofilm thickness (μm) and substratum coverage (%) of the treated biofilms were determined using nonparametric statistical tests (P<0.05). Results Similar values of biovolume total, biovolume of live subpopulations and substratum coverage were found in 2% chlorhexidine, 10% citric acid, 17% EDTA and distilled water-treated biofilms (P>0.05). The lower values of the studied parameters were found in 1% NaOCl-treated dentine (P<0.05) with the exception of the mean biofilm height criteria that did not reveal significant differences amongst the irrigant solutions (P>0.05). Conclusions One per cent sodium hypochlorite was the only irrigant that had a significant effect on biofilm viability and architecture.