RESUMO
Different rotary NiTi systems have been introduced for root canal cleaning. This study was performed to compare the effectiveness of a manual file [K file] with two rotary systems [ProTaper and Mtwo] for root canal preparation in the first permanent molar teeth. India ink was injected to 140 of 150 mesiobuccal root canals of human mandibular first permanent molars, which were randomly divided into three experimental [including 40 canals] and three control groups [10 canals]. In each of these first, second and third subgroups, either the manual instrument [K-file] or the rotary system [ProTaper and Mtwo] were used to prepare the root canals. Canals in group 4 were irrigated with normal saline. In group 5 and 6 no instrumentation was performed. After clearing the teeth, the root canals were observed with the help of a stereomicroscope and the data were analyzed by SPSS, Kruskal-Wallis and Friedman tests [p<0.05]. There was no significant difference between manual and rotary instruments. There was a significant difference between cleaning of the apical, middle and coronal areas of the canals prepared with K-file with a better performance at the apical area compared with the coronal and middle parts. While there were no significant differences in any of the three root canal regions ProTaper or Mtwo systems. The ProTaper and Mtwo rotary systems showed acceptable cleaning ability and efficacy in permanent molar root canals