Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
1999-08-13
2001-04-10
Lucchesi, Nicholas D. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
C433S174000
Reexamination Certificate
active
06213775
ABSTRACT:
The present invention relates to a method of fastening an implant to a bone.
It is known to insert an implant in a bore or recess formed in a jawbone so that an artificial tooth may be mounted at the outer end of the implant. The outer surface of the implant may have grooves or channels formed therein so that the implant is efficiently fastened to the jawbone when bone tissue eventually grows into intimate contact with the outer surface of the implant. Infection may cause destruction of bone tissue in contact with the implant to such an extent that the implant has to be removed from the jawbone. Such removal of the implant and reinsertion of a new implant is a complicated operation involving removal of bone tissue and enlargement the bore or recess in which the new implant is inserted.
It is also known to insert an implant into the medullary cavity of a bone. Such implant may for example include part of an artificial hipjoint. The insertion of known implants in medullary cavities normally involves the use of so-called bone cement. Bone cement may decompose so that the implant gets loose. Consequently, the patient has to undergo a new surgical operation.
The present invention provides a method allowing an improved and more efficient fastening of an implant to a bone.
Thus, the present invention provides a method of fastening an implant to a bone, said implant comprising a core member and a radially expandable outer tubular member, which includes a helically wound elongated member, said method comprising forming a bore or recess in the bone, arranging the radially expandable tubular member in said bore or recess, positioning the core member so as to at least partly extend into the expandable tubular member, releasably fastening the core member in this position in relation to the tubular member, and allowing bone tissue to grow into intimate contact with the outer surface of the tubular member.
When the tubular member has been inserted into the bore or recess formed in the bone the tubular member may be radially expanded, for example by means of the core member which is inserted into and fastened to the tubular member. This means that the outer surface of the tubular member may be moved into engagement with the inner surface of the bore or recess formed in the bone, whereby a good initial fastening of the implant to the bone may be obtained. Furthermore, as explained below the tubular member may later rather easily be removed from the bone, if necessary.
The core member may be moved into and releasably fastened to the tubular member in any suitable manner. As an example, outer thread-like formations formed on the core member may be engaged with inner tread-like formations formed in the tubular member.
An anchoring member may be arranged at the inner end at the bore or recess in the bone and may be releasably connected to an adjacent end of the tubular member and/or the core member. Such anchoring member, which is arranged at the inner end of the recess or bore may usually remain in the recess or bore in case it is necessary to remove and replace the tubular member and the core member. A new tubular member and core member may then be inserted in the recess and efficiently fixed when they are fastened to the already fixed anchoring member. The anchoring member may have any size and shape. Usually, it is preferred that the maximum radial dimension of the anchoring member exceeds that of the adjacent end of the tubular member.
In a preferred embodiment an outer thread-like formation formed on the core member at the inner end thereof is engaged with an inner thread-like formation at an inner surface part of the anchoring member. The core member may then be moved axially in relation to the tubular member by screwing the core member into the anchoring member.
The helically wound elongated member forming part of the tubular member is preferably a string or wire. The windings of the helically wound elongated member may be in mutual abutting engagement. In this case the helically wound elongated member may form a tubular member having a substantially closed peripheral wall. Alternatively, adjacent windings of the helically wound elongated member may be slightly spaced in the axial direction of the tubular member. In order to obtain an unbroken peripheral wall of the tubular member adjacent windings of the helically wound elongated member may be interconnected by preferably thin, tearable wall parts.
When the implant is mounted in the bore or recess of the bone the tubular member may be inserted first and the core member may thereafter be inserted into the tubular member. Preferably, however, the core member is positioned within the tubular member prior to arranging the tubular member in the bore or recess. The core member may thereafter be moved axially in relation to the tubular member.
The outer surface of the tubular member may have any suitable shape and may, for example, be generally cylindrical. However, in order to facilitate a possible later removal of the implant the outer surface of the tubular member may be tapered toward the inner end of the bore or recess formed in the bone. As an example, the tapered outer surface of the tubular member may be frustoconical.
The outer surface of the core member and the inner surface of the tubular member cooperating therewith are preferably such that the tubular member arranged in the bore or recess formed in the bone is expanded radially by moving the core member axially inwardly into the expandable tubular member. As an example, the core member may comprise an outer, generally conical surface of the core member cooperating with a corresponding inner, generally conical surface of the tubular member.
The implant comprising an anchoring member, an outer tubular member, and an inner core member preferably forms a unit which is inserted into the bore or recess of the bone. Therefore, the anchoring member is preferably releasably connected to the tubular member and/or the core member prior to inserting said members into the bore or recess in the bone.
The bore or recess may, for example, be formed in a jawbone, and an artificial tooth may be fastened to the outer end portion of the core member. Alternatively, the bore or recess may at least partly be formed by the medullary cavity of a bone. In the latter case part of an artificial hipjoint may be connected to the core member. When the implant has been inserted in the medullary cavity of a bone the expandable tubular member may be expanded as described above, whereby the implant may be effectively fastened to the bone to such an extent that the use of bone cement may become unnecessary. If an implant which have been mounted by the method according to the invention should get loose it would be possible later to further fastened the implant by tightening the thread connection between the core member and the tubular member or the anchoring member so as to further expand the tubular member into intimate contact with the inner walls of the medullary cavity. Such tightening would involve only a minor surgical operation.
The tubular member, the anchoring member, and/or the core member should be made from physiologically tolerable materials which may be accepted by the human or animal body in which it is to be used. Such materials include titanium, plastic, and any other material conventionally used for implants.
If, for some reason, the implant has to be removed from a bone in which it has been embedded for a shorter or longer period of time the core member is first released from the tubular member and the tubular member is subsequently removed from the bore or recess in the bone. Bone tissue may have grown into depressions or grooves formed in the outer surface of the tubular member, whereby a strong adherence has been established between the tissue and the tubular member. However, because the tubular member is at least partly formed by a helically wound elongated member the tubular member may be removed by pulling the outer end of the elongated member so as to unwind or straightened the elongated memb
Lucchesi Nicholas D.
Reipur Technology A/S
LandOfFree
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