To compare the efficacy of an integrated apex locator and an apex locator and endodontic motor assembly in maintaining the working length when operated under autoreverse mode.
Thirty distobuccal roots of intact maxillary first molars were taken and access cavities were prepared. The teeth were divided into Group I: Prepared with TCM Endo V and Group II: Prepared with ProPex and NSK assembly. The instrumentation was ended in ProTaper F3 file, which was cemented in the canal. The roots were sectioned, observed under a stereomicroscope and the distance from instrument tip to the apical foramen was measured.