[Chlorhexidine as a root canal irrigant--antimicrobial and scanning electron microscopic evaluation].

Introduction: Selection of irrigant is very important for long-term success of root canal therapy.

Objective: This study was undertaken to evaluate the antimicrobial effects of 2% chlorhexidine digluconate solution (CHX) against five selected microorganisms and to evaluate its efficacy in root canal cleaning.

Methods: In this study, by agar diffusion test, were evaluated antimicrobial effects of three root canal irrigants: 5.25% NaOCl, 2.5% NaOCl and 2% CHX. The microorganisms tested in this study were Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis, Escherichia coli and Candida albicans. A scanning electron microscope was used to evaluate root canal cleaning ability of 5.25% NaOCl, 2.5% NaOCl, 2% CHX and 15% EDTA. Twelve extracted single-root human teeth were divided into four groups depending on the irrigant used during instrumentation. Mechanical preparation was performed with Step back technique and K files. Data were analysed statistically by Student's t-test.

Results: 5.25% NaOCl was the most effective against all tested microorganisms. 2.5% NaOCl and 2% CHX showed antimicrobial effects against all tested microorganisms but zones of inhibition were smaller.The best results in root canal walls cleaning were obtained in the group where the irrigant was 15% EDTA (score 2.33). In 5.25% NaOCl, 2.5% NaOCl and 2% CHX groups, there was more smear layer (score 4 and 5).

Conclusion: 2% chlorhexidine digluconate showed strong antimicrobial effect on the tested microorganisms, but was not effective in cleaning root canal walls.