An endodontic instrument includes a plurality of flutes and a plurality of lands extending helically around a working portion. Each flute includes a curved concave flute surface, a pair of flute shoulders at the peripheral edges of the flute surface, a flute width defined by a distance between the flute shoulders, and a flute depth defined by a point of maximum depth between the flute shoulders. Each land is positioned between a pair of axially adjacent flutes and includes a curved concave land surface, a pair of land shoulders at the peripheral edges of the land surface, a land width defined by a distance between the land shoulders, and a land depth defined by a point of maximum depth between the land shoulders. The land width is less than the flute width and the land depth is less than the flute depth in the upper region of working portion.
