Evaluation of apically extruded bacteria associated with different nickel-titanium systems.

INTRODUCTION The aim of this in vitro study was to evaluate the amount of apically extruded bacteria associated with several root canal preparation systems. METHODS Forty-four extracted human mandibular premolar root canals were contaminated with an Enterococcus faecalis suspension. After incubation at 37°C for 24 hours, the root canals were instrumented using the Twisted File (SybronEndo, Orange, CA), OneShape (Micro Mega, Besançon, France), and ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland). During instrumentation, apically extruded bacteria were collected into vials containing 0.9% NaCl. The microbiological samples were taken from the vials and incubated in brain-heart agar medium for 24 hours. The numbers of colony-forming units were determined. The data obtained were analyzed using Welch analysis of variance followed by post hoc Games-Howell tests. RESULTS ProTaper Next extruded the highest amount of bacteria, whereas OneShape extruded the least compared with all the other instruments (P = .004). There was a significant difference between OneShape and ProTaper Next in the number of colony-forming units (P = .007) but not between OneShape and Twisted File (P > .05). CONCLUSIONS All instrumentation systems extruded bacteria beyond the foramen. The OneShape system extruded less bacteria compared with the Twisted File and ProTaper Next systems.