The effect of different temperature and concentration of sodium hypochlorite on the elimination of E.Faecalis using rotary instrumentation and intermittent passive ultrasonic irrigation

OBJECTIVE: The purpose of this study was to compare the intracanal bacterial reduction using rotary instrumentation and intermittent passive ultrasonic irrigation (IPUI) with different concentrations and temperatures of NaOCl in different canal tapers. MATERIALS and METHODS: The root canals of seventy-two extracted single-rooted teeth were instrumented up to size #20k file and inoculated with E. faecalis. The teeth were divided into 5 experimental groups and one control. The root canals in the control group were shaped to a 0.04 taper using ProFile rotary files, with 1.5 minute of IPUI by NaOCl at a concentration of 2.5% and room temperature of 25°C for 30 seconds at a time at three intervals. In Group I, the canals were shaped to a 0.06 taper, and in Groups II and III - the temperature of NaOCl used was 37°C and 45°C respectively, and in Groups IV and V - the concentrations of NaOCl were 1% and 5% respectively. The canals were incubated at 37°C for 48 hours and bacterial samples were obtained using paper points and plated on agar plates. The zones of bacterial growth were measured and statistical analysis was performed. RESULTS: There was significantly more bacterial growth in the control group than in Groups I, II, III and V. Furthermore, there was a significant reduction in bacterial growth in Group V compared to Group IV. CONCLUSIONS: The result of this study showed that significant bacterial reduction in contaminated root canals could be obtained using intermittent passive ultrasonic irrigation combined with 2.5% NaOCl at 37ºC in canals prepared to a taper of 0.06. In addition, complete bacterial eradication could be obtained using IPUI with2.5% NaOCl at 45ºC or 5% NaOCl at room temperature (37ºC).