US Patent 7766657 Endodontic file combining active and passive cutting edges

An endodontic reamer/file for cleaning/shaping a tooth root canal having an elongated shank with a proximal end portion, a distal end and a tapered working portion having a longitudinal axis, the external surface of the shank working portion being defined by a plurality of at least two equally spaced apart continuous concaved helical flutes providing concave flute surfaces, the flute surfaces having therebetween an equal number of spiraled, spaced apart flanges, each flange having in a plane perpendicular the longitudinal axis a single outer end surface having opposed first and second ends, each first end forming an active spiraled leading scraping/cutting edge and each second end forming a passive spiraled edge.