RESUMO
AIM: The aim of this study was to evaluate the number of intracanal bacteria extruded apically after instrumentation with three different nickel-titanium rotary instruments. MATERIALS AND METHODOLOGY: Forty freshly extracted mandibular premolars were selected, access cavities were prepared, and the teeth were mounted in the bacterial collection apparatus. Root canals were contaminated with a suspension of Enterococcus faecalis and incubated for 24 h at 37°C. The contaminated teeth were divided into four groups of 10 teeth each according to the rotary system used for instrumentation: Group 1: ProTaper universal files, Group 2: MTwo files, Group 3: ProTaper Next files, and Group 4: Control group (no instrumentation). Bacteria extruded after preparations were collected into vials. The number of colony-forming units (CFUs) was determined for each sample. STATISTICAL ANALYSIS: The data obtained were analyzed using the one-way analysis of variance followed by post hoc Tukey's test with a P = 0.05 as the level for statistical significance. RESULTS: The results suggested a statistically significant difference in the number of CFUs between four experimental groups (P < 0.001). CONCLUSION: Least amount of bacterial extrusion was seen in ProTaper Next Group while more bacterial extrusion was seen in MTwo Group.
