Endodontic files with cross-cuts

An endodontic instrument for preparing an endodontic cavity space, the endodontic instrument comprising:

• a shank configured for attachment to a motor to drive the endodontic instrument about a first axis;
• and
• a working portion extending from the shank by a length, the working portion having a tip end and a shank end and a working surface between the shank end and the tip end, the working surface including multiple edges, at least a portion of the working portion with the working surface being tapered such that the tip end has a diameter that is less than a diameter of the shank end, the working portion comprising a plurality of transverse cross-sections, each transverse cross-section of the working portion having a center of mass and multiple sides, the working portion having a center of mass path defined by the centers of mass of the plurality of transverse cross-sections of the working portion, each side of the multiple sides intersecting two edges of the multiple edges, wherein at least a portion of the center of mass path between the tip end and the shank end spirals around the first axis along a length of the first axis, and wherein the working portion is configured such that when the endodontic instrument is driven within the endodontic cavity space about the first axis, at each transverse section of at least a portion of the length of the working portion, one or more edges of the multiple edges are out of contact with a wall of the endodontic cavity space,
• wherein the plurality of transverse cross-sections includes a first transverse cross-section and a second transverse cross-section, wherein the first transverse cross-section has a first geometry, and wherein the second transverse cross-section has a second geometry different from the first geometry.

An endodontic instrument for preparing an endodontic cavity space, the endodontic instrument comprising:

• a shank configured for attachment to a motor to drive the endodontic instrument about a first axis;
• and
• a working portion extending from the shank by a length, the working portion being solid and having a tip end and a shank end and a working surface between the shank end and the tip end, the working surface including multiple edges, at least a portion of the working portion with the working surface being tapered such that the tip end has a diameter that is less than a diameter of the shank end, the working portion comprising a plurality of transverse cross-sections, each transverse cross-section of the working portion having a center of mass and multiple sides, the working portion having a center of mass path defined by the centers of mass of the plurality of transverse cross-sections of the working portion, each side of the multiple sides intersecting two edges of the multiple edges, wherein at least a portion of the center of mass path between the tip end and the shank end spirals around the first axis along a length of the first axis, and wherein the working portion is configured such that when the endodontic instrument is driven within the endodontic cavity space about the first axis, at each transverse section of at least a portion of the length of the working portion, one or more edges of the multiple edges are out of contact with a wall of the endodontic cavity space,
• wherein each transverse cross-section of the working portion is defined by a polygonal shape, and
• wherein a ratio of lengths of sides of the polygonal shape varies along the length of the working portion.