The present invention relates to dental implants which are surgically placed in the bone of the jaw to provide an anchoring means for an artificial tooth. Specifically, the present invention is a dental implant which employs shape memory material in the lower portions of the implant to provide self expanding legs, resulting in instantaneous implant stability.
Numerous dental implants found are found in the prior art. Pertinent prior patents are summarized as follows:
U.S. Pat. No. 2,721,387 to Ashuckian discloses an implant having multiple expandable legs. The legs are expanded relative to a spring action apex which is located at the lowermost edge of the implant. Aushuckian also discloses a second embodiment wherein the leg portions are mechanically spread apart using a spreading means between the legs.
U.S. Pat. No. 3,708,883 to Flander discloses an implant having two legs which are mechanically spread apart using wedging means between the legs. Flander does not disclose the use of temperature dependent material to change the relative positions of the legs. Flander also employs the use of exterior projections on the outer surfaces of the legs which are intended to engage the bone. If not completely engaged with the bone, these projections provide gaps between the bone and the legs, allowing encapsulation of the legs by fibrous tissue and preventing osseointegration.
U.S. Pat. No. 4,609,354 to Koch discloses an implant for securing a tooth replacement which uses a shaft implanted in the jaw bone. The shaft has a bore which receives a peg, the peg being the structure which supports an artificial tooth. The diameter of the peg is temperature dependent so that at body temperature the peg diameter is maximized, thus maintaining the peg within the bore. By cooling the peg, the peg can be removed from the shaft. Koch uses a temperature-dependent material to attach different structural portions of the implant to each other. The temperature dependent material is not related to anchoring the dental implant within the jaw.
U.S. Pat. No. 4,832,601 to Linden discloses an implant comprising an upper portion which is pivotably adjustable. The lower portion of the implant is secured within the jaw bone using multiple shingle-shaped members which project into the jaw bone. The projecting members extend from a single shaft and do not appear to be adjustable. Further, Linden does not disclose the use of temperature dependent materials to anchor the implant within the jaw bone.
U.S. Pat. No. 5,219,287 to Nishihara discloses an artificial dental root formed of a shape memory alloy. The implant changes shape upon contact with body heat to engage the jaw bone. There are two disadvantages to using this implant. First, the entire implant is made from the shape memory alloy. Thus, the portion of the implant which extends above the jaw to receive the artificial tooth will be affected and changed each time the patient consumes something hot or cold. Secondly, the curved and branched shape of the root portion provides gaps and spaces between the root and jaw bone. Such spaces provide opportunity for encapsulation by fibrous tissue, preventing osseointegration.