In vitro antimicrobial activity of 0.5%, 1%, and 2.5% sodium hypochlorite in root canals instrumented with the ProTaper Universal system.

Objective: The purpose of this in vitro study was to evaluate the antimicrobial activity of 0.5%, 1% and 2.5% sodium hypochlorite in root canals instrumented with the ProTaper Universal system.
Study Design: Fifty human mandibular premolar teeth with single root canals were infected with a mixture of C. albicans, P. aeruginosa, E. faecalis, and S. aureus. The specimens were randomly divided into 5 groups with 10 root canals each according to the irrigant used: group 1: 0.5% NaOCl; group 2: 1% NaOCl; group 3: 2.5% NaOCl; group 4 (positive control): 0.85% sterile saline solution; group 5 (negative control, without microorganisms): 0.85% sterile saline solution. All root canals were instrumented with the ProTaper Universal system. The assessment of the antimicrobial action of the irrigant was performed before the biomechanical preparation (0), and after instrumentation with S1 (1), S2 (2), F1 (3), F2 (4), and F3 (5) files.
Results: All positive control samples showed microbial growth, whereas negative control samples showed no microbial growth before the biomechanical preparation and after the instrumentation with S1, S2, F1, F2, and F3 files. The microorganisms were eliminated after the instrumentation with S1 file in all tested irrigants, except for 1 sample in S1 at 0.5% NaOCl which showed positive growth. There was no significant statistical difference (P = 1.000) among the tested irrigants.
Conclusion: Sodium hypochlorite, at all tested concentrations, was effective in eliminating C. albicans, P. aeruginosa, E. faecalis, and S. aureus in combination with the NiTi rotary instrumentation with the ProTaper Universal system.