Antibacterial and substantivity evaluation of 2.5% sodium hypochlorite, 0.2% cholorhexidine and distilled water as root canal irrigants (In - vitro) Dr. S.M. Hasheminiya* - Dr. S.A. Havaee** - Dr. M. Rajabi*** * - Assistant Professor of Endodontics Dept. - Faculty of Dentistry – Isfahan University of Medical Sciences. **- Assistant Professor of Microbiology Dept. - Faculty of Medicine – Isfahan University of Medical Sciences. ***- Dentist. Background and Aim: The use of an irrigating solution during root canal cleaning and shaping is necessary for the elimination of all irritants. The aim of this study was to compare the anti-bacterial efficacy of distilled water, chlorhexidine 0.2% and sodium hypochlorite 2.5% as root canal irrigants on the reduction of Entrococcus fecalis (E.fecalis)colonies in extracted human teeth. Materials and Methods: In this experimental study, 80 extracted human teeth with single ca-nal were selected. After preparation all root canals were contaminated with E. fecalis. Then, filing was done up to file ≠40 and flaring up to ≠70. During filing and flaring procedures irri-gation was done using 20 cc of each solution. Finally, paper points were used to obtain sam-ples which were then sent to laboratory for CFU (colony – forming unit) count after incuba-tion. Sampling was done once after placing teeth in the incubator for one week. Data were sub-jected to Kruskal – Wallis and Duncan tests. Results: The finding of this study showed that sodium hypochlorite and chlorhexidine were more effective in the reduction of microorganisms' counts than distilled water (PV<0.05).Al-though sodium hypochlorite 2.5% had a mean CFU of 12.5 and cholorhexidine had a mean CFU of 22.5, no statistically significant difference was found between them (PV=0.799). The results obtained after one week showed that Naocl had a mean CFU of 42.5 and cholorhexi-dine had a mean CFU of 30, so the mean colony numbers increased in both groups and the dif-ferences were significant comparing to the samples of the first day, however hypochlorite had 240% of elevation and chlorhexidine had 33.3%, distilled water had no substantivity effect. Conclusion: The results have shown that sodium hypochlorite and cholorhexidine can remove E–fecalis and reduce the number of colonies significantly when used as irrigating materials during filing and flaring but distilled water does not have such an effect with higher average of colony numbers. Moreover, chlorhexidine showed more substantivity effect than hypochlorite. Key words: Chlorhexidine – Hypochlorite – Root canal irrigant – Substantivity – Colony – forming unit (CFU) – E. fecalis. | 
