Aim: The aim of this study was to evaluate the number of bacteria extruded from the tooth apex after root canal instrumentation using three nickel-titanium rotary systems.
Materials and methods: A total of 55 mandibular premolars were extirpated and inserted into glass bottles. The root canals were contaminated with Enterococcus faecalis. The teeth were divided into four groups: ProTaper Universal, ProTaper Next, ProTaper Gold (all Dentsply Sirona, Charlotte, NC, USA) and the control group. For the first three groups, comprised of 15 teeth each, preparation was implemented with ProTaper Universal, ProTaper Next and ProTaper Gold files, respectively. No instrumentation was performed in the control group, comprised of 10 teeth. The solution in the bottles was investigated using the classical bacteria-counting technique. Data were analysed using a Kruskal-Wallis one-way analysis of variance and Mann-Whitney U tests.
Results: The mean number of colony-forming units in the ProTaper Universal and ProTaper Gold groups was significantly higher than in the ProTaper Next group (P < 0.05). The difference between the ProTaper Universal and ProTaper Gold groups was not statistically significant (P > 0.05).
Conclusions: All instrumentation techniques caused extrusion of intracanal bacteria. The ProTaper Universal and ProTaper Gold groups produced significantly more bacterial extrusion than the ProTaper Next group.