A reciprocating endodontic hand tool in which the torque applied to an instrument such as a debriding file can be set at or below an endurance limit of the file below which failure of the instrument will not occur. In preferred embodiments the tool can switch between settings in which the torque applied to the instrument is between the endurance limit of the file and an elastic limit of the file, by setting forward and reverse angles of rotation within specified limits. This reduces or eliminates opportunites for plastic distortion, fatigue and breakage of the file during the canal debriding/cleaning/shaping process in a root canal treatment or retreatment. In some embodiments the torque may be set to at or below a durability limit of the file below which failure of the instrument will not occur through repetitive strain over the course of a particular root canal treatment or retreatment.
