A rotatable endodontic file for cleaning/shaping a tooth root canal, comprising: an elongated shaft having a proximal end portion, a distal end and a tapered working portion having a rotational axis, the working portion extending from said proximal portion to said distal end the external surface of said shaft working portion having a plurality of at least two spirals, a plurality of parallelogram-shaped cross sections along the working portion, at least one of the plurality of parallelogram-shaped cross sections two C-shaped or concave geometries along two symmetrical sides or four C-shaped or concave geometries along all four sides, each parallelogram-shaped cross section having an acute angle and a center of mass that is located on the axis of rotation, each parallelogram-shaped cross section, wherein an acute angle of a first parallelogram-shaped cross section is different or the same as an acute angle of a second parallelogram-shaped cross section.
