An endodontic file includes a uniform tapered working length made of shape memory material with at least two helical shaped flutes and narrow spiraled lands in between, having a width no greater than 0.075 mm as measured in a plane perpendicular the central axis of rotation of instrument. The land width is preferably constant along the working length but may vary provided the width of the lands in a waist portion of the file are no greater than those above or below the waist portion. The instrument resists mid-root transportation and exhibits superior fatigue performance and cutting efficiency compared to prior art instruments.
