In vitro study of antimicrobial efficacy of different irrigations on Enterococcus faecalis biofilm formation in root canal

PURPOSE: To compare the antimicrobial effect of different irrigations on Enterococcus faecalis biofilms in extracted teeth and evaluate the antimicrobial activity of irrigating solutions residual against E. faecalis biofilms formation, in order to provide a better strategy for clinician. METHODS: Extracted human premolar teeth with single root canal were clearly autoclaved. These teeth were contaminated with E. faecalis（ATCC33186） and incubated for 60 days. The samples were randomly assigned to 4 experimental groups. During biomechanical instrumentation, the root canal was irrigated with different irrigating agents. The bacteria samples were collected with sterile paper points before and after instrumentation to F2. Then, samples that had been instrumented and autoclaved again were randomly divided into 2 groups treated with normal saline and 1%NaOCl for 30 min. E. faecalis was used to contaminate these root canals. The bacteria samples were collected with sterile paper points after 2, 6, 24, 48 h. SPSS19.0 software package was used for statistical analysis. RESULTS: Group using 1% NaOCI with ultrasound devices was significantly more effective than NS alone groups. 1% NaOCI groups showed a better residual activity than NS group. CONCLUSIONS: NaOCl is still the most important irrigating solutions, and it could be a better choice after biomechanical instrumentation, because of its long time substantivity achieves residual antimicrobial activity. Ultrasound devices is recommended to coordinate with irrigation.