The invention relates to a reamer with an improved blade for use in root canal preparation, the blade being spiral-shaped with a pitch increasing towards the tip, and with a cutting or non-cutting tip. At given points along the length of the spiral of the blade, there is a plurality of gaps, the spiral starting again beyond the gaps, wherein the portion where the spiral is interrupted has either a constant or decreasing cross section linking the two diameters before and after the gap.
