Bacterial colonisation of root canal dentine previously treated with endodontic irrigants

Certain irrigants leave antimicrobial residues on dentine. This study assessed if residues from MTAD, Endo-CHX, Peridex Oral Rinse or 6% NaOCl were inactivated by exposure to simulated leakage. Extracted teeth (15/group) were cut and drilled to produce a cylindrical canal space. They were irrigated, dried with paper points and transferred into 1 mL of simulated leakage (Enterococcus faecalis in tryptic soy broth) every 24 h. After one, two or three transfers, the number of colony forming units was measured by drilling the canal space and recovering the dentine shavings in antimicrobial-inactivating broth. Two-way anova of the log-transformed data showed irrigation method, leakage volume and their interaction were significant factors (P < 0.001). Compared with the positive control, the logarithmic reductions in the number of E. faecalis colonies after the first and third millilitre of leakage were: Endo-CHX 6.2 and 2.4; MTAD 3.4 and 2.7; Peridex 1.6 and 0.4; NaOCl 1.0 and 0.0.