The invention relates to a reamer (1) with improved blade (2； 3) for Ni-Ti instruments for endodontic preparation, said blade (2； 3) having a growing pitch and a not active tip (4), characterised in that an interruption (5) of the blade (2； 3) spiral is provided at a set height along the extension of the same blade (2； 3), said spiral, after said interruption (5), starting again its development.
