Patent ID: 7753942

Claim:
A fixture shaped and configured to be screwed firmly into bone tissue, said fixture comprising: a generally cylindrical anchoring portion formed with an insertion end and having an external screw thread, a cavity which opens out at said insertion end, and a plurality of through-penetrating slots extending from said insertion end, wherein each said slot connects the cavity with the outside of said anchoring portion and wherein each said slot is defined by a leading slot wall surface facing each said slot and a trailing slot wall surface facing each said slot, where said leading and trailing wall surfaces relate to the direction of rotation defined by said screw thread when screwing in the fixture, such that said leading slot wall surface is the one that is ahead of each said slot and said trailing slot wall surface is behind each said slot in said direction of rotation, wherein at least the radially outermost part of said trailing slot wall surface defines a cutting edge at an angle α with the radial direction and slopes obliquely forwardly from within and outwardly in said direction of rotation, whereby the cutting edge formed between said at least the radially outermost part of said trailing slot wall surface and the outside of said anchoring portion define an acute angle, and wherein substantially all portions of said trailing slot wall slope obliquely forwardly from within and outwardly in said direction of rotation, and wherein the portion of said anchoring portion that lies between said trailing slot wall and said leading slot wall of the adjacent slot compresses radially when the anchoring portion is screwed into bone tissue to resist distortion of the shape of said anchoring portion.