Instrument for drilling dental root canals

An endodontic instrument comprising:

• a tapered rod, the rod comprising an active portion, the active portion terminating at a distal tip end of the rod and defining a conical envelope, the conical envelope having a longitudinal axis that coincides with an axis of rotation of the instrument;
• the active portion comprising a plurality of helical flutes disposed along at least a segment of the active portion, the plurality of helical flutes comprising a first flute, a second flute, a third flute, and a fourth flute;
• the active portion comprising a plurality of edges, the plurality of edges comprising a first edge intersecting the first flute and the second flute, a second edge intersecting the second flute and the third flute, a third edge intersecting the third flute and the fourth flute, and a fourth edge intersecting the first flute and the fourth flute;
• the active portion comprising a first portion having a length and a second portion having a length, the second portion being disposed further from the tip end relative to the first portion;
• the first portion comprising a plurality of first portion cross-sections, the plurality of first portion cross-sections comprising a first cross-section, wherein a center of mass of the first cross-section is located on the axis of rotation of the instrument, each of the first edge, the second edge, the third edge, and the fourth intersecting the first cross-section, the intersection between the first edge and the first cross-section being located on the envelope;
• the second portion comprising a plurality of second portion cross-sections, the plurality of second portion cross-sections comprising a second cross-section, wherein a center of mass of the second cross-section is offset relative to the axis of rotation, each of the first edge, the second edge, the third edge, and the fourth edge intersecting the second cross-section, the fourth flute being overcut along at least a segment of the second portion such that the third edge and the fourth edge are set back within the envelope along the segment.