The effect of intermittent passive ultrasonic irrigation and rotary instruments on microbial colonies of infected root canals

OBJECTIVE: To study the effectiveness of reduction of E. faecalis in root canals with passive ultrasonic irrigation (PUI) of 2.25% NaOCl for 1.5 min intermittently during hand instrumentation and continuously after rotary instrumentation. MATERIALS and METHODS: Forty-eight extracted single rooted teeth were filled with E. faecalis suspension and divided into 4 groups. They were either hand instrumented alone using the stepback technique, hand instrumented with PUI of the 2.25% NaOCl intermittently for a total of 1.5 min during the instrumentation, rotary instrumented with ProFile 0.04 alone, or rotary instrumented with PUI of the irrigant for 1.5 min. RESULTS: There was significantly more bacterial growth in the hand instrumented group than in the hand instrumented group with PUI, and marginal significant difference in the hand instrumented group with PUI compared to the rotary instrumented group. No differences were found between the rotary instrumented groups. CONCLUSIONS: It was concluded that intermittent use of PUI of 2.25% NaOCl for a total of 1.5 min (half of the current recommended time) during hand instrumentation reduced bacterial colonies significantly. There was no difference in bacterial reduction when rotary instrumentation was used with or without PUI.