The invention relates to an instrument for treating root canals, said instrument including an end section (3) and an operative area (1) that includes a talon, adjacent to the end section, and a tip, the operative area having the general shape of an upside-down cone, a diameter of a section of the operative area near the tip being greater than a diameter of a section of the operative area near the talon, the instrument being characterized in that the operative area has a smooth outer surface. The invention can be used for cleaning canals and measuring the apical diameter.
