Antimicrobial activity of chlorhexidine in root canals instrumented with the ProTaper Universal™ System

Aim: The purpose of the present study was to evaluate the antimicrobial activity of 0.2%, 1%, and 2% chlorhexidine in root canals instrumented with the ProTaper Universal™ system. Methods: Fifty human mandibular premolar teeth were infected with a mixture of Candida albicans, Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus aureus. The specimens were randomly divided into 5 groups with 10 root canals according to the irrigant used. All root canals were instrumented with the ProTaper Universal™ system. Assessment of the antimicrobial action of the irrigant was performed before, during, and after instrumentation. Data were analyzed statistically by Chi-squared test and the Fisher exact test at 5% significance level. Results: The 0.2% chlorhexidine solution was ineffective against all test microorganisms. The 1% chlorhexidine solution was effective in eliminating P. aeruginosa and C. albicans after the use of the F1 and F3 instruments, respectively. The 2% chlorhexidine solution was effective at killing S. aureus, P. aeruginosa and C. albicans after the use of the S1 instrument. There were statistically significant differences (p