Objective  To compare the effect of Protaper nickel-titanium file and Orodeka Plex-v nickel-titanium file on the preparation of root canal of molars.

  Methods  A total of 74 maxillary and mandibular molars for root canal preparation were collected and divided into group P with 131 canals and group O with 138 canals according to visiting order, and they were treated with Protaper and Orodeka Plex-v nickel-titanium files respectively. The effects of root canal treatment were compared between the two groups.

  Results  The preparation time for single root canal in group P was (5.09±0.67) min, which was significantly longer than (3.10±0.43) min in group O (P < 0.05). No instrument separation, transportation, apical blockage and ledge were observed in group O, whereas instrument separations occurred in 1 instrument, apical blockage in one case, ledge in one case and no transportation were observed in group P, and there were significant differences in above complications between two groups (P < 0.05). There was no significant difference in the ratio of adequate filling of root canal between two groups (P>0.05).

  Conclusion  Both Protaper and Orodeka Plex-v nickel-titanium files can achievea high performance in the root canal preparation of molars, but Orodeka Plex-v nickel-titanium file is more shorter in time of use and higher in security.