Endodontic instrument for drilling root canals

The invention relates to an endodontic instrument (20) for drilling root canals in a tooth. Said instrument comprises a working area (21) arranged so as to form and/or shape and/or cut the inner wall of the root canal. To this end, it is provided with a plurality of flutes wound around a central axis in the form of a spiral, within a conical envelope (25) having a cross-section that becomes narrower from one end (23) to the other end (26) of the instrument. Said working area (21) is sub-divided into adjacent segments (S) wherein the flutes alternately have a straight section and a section that is twisted in the form of a spiral and are arranged in such a way that the edges thereof are located either on the conical envelope (25) or inside said envelope on the straight sections or on the twisted sections.