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 5 min. 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.