Dentistry – Prosthodontics – Holding or positioning denture in mouth
Patent
1995-04-26
1996-12-31
Lucchesi, Nicholas D.
Dentistry
Prosthodontics
Holding or positioning denture in mouth
433174, A61C 800
Patent
active
055888380
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to fixtures for dental implants, i.e. the parts of dental implant systems which are to be implanted in the bone tissue, and particularly to fixtures whose outer end or neck are provided with a conically flaring portion intended to at least partly abut the bone tissue.
BACKGROUND TO THE INVENTION
Fixtures having a cylindrical main body and a conically flaring upper portion or neck have been known and used in the art of dental implants for a long period of time. These fixtures are to be inserted into bore-holes in the jaw-bone in order to become osseointegrated to the bone tissue. The cylindrical parts generally osseointegrate correctly provided the proper techniques are used.
There are however some difficulties regarding the osseointegration around the conical neck portion of the implants which portion normally is smooth or polished. For some reason the bone tissue may degenerate around a smooth or polished conical part (bone resorbtion), leaving a pocket in the bone tissue around the conical part. The mechanism behind this is not quite clear. These pockets normally are accepted as inevitable although it is not entirely satisfactory that the implant is not entirely osseointegrated particularly since this pocket is formed in the strongest part of the bone tissue, the cortical bone.
SHORT DESCRIPTION OF THE INVENTIVE CONCEPT
It surprisingly has been found that the provision of a circumferentially or tangentially oriented, defined micro-roughness on the outer side of the conically flaring portion of the fixture having a height which may vary between 0.02 and 0.20 mm alleviates this problem, the risk for pockets in the bone tissue around the conically flaring portion being minimized.
In preferred embodiments the micro-roughness, as set forth in the appended dependent claims, may be in the form of circumferential beads or microthreads.
SHORT DESCRIPTION OF THE APPENDED DRAWINGS
FIG. 1 shows the exterior of a fixture according to the invention,
FIG. 2 shows the fixture in FIG. 1, partly sectioned.
FIG. 3 is a front view of an alternative embodiment of a fixture.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
In the description below, the invention is illustrated by means of micro-threads. It should be noted that the description in the relevant parts (i.e. the parts not relating directly to the helical nature of the threads) also is applicable to the embodiment featuring the circumferential beads and that this choice does not reflect any preference regarding the two embodiments.
Thus, in a preferred embodiment, the invention comprises an implant or fixture having a generally cylindrical body 1 for insertion into a bore-hole into bone tissue. The envelope surface of the body 1 is provided with conventional threads 2. These threads will allow the implant to function as a screw. The forward end or the tip of the screw is provided with three cutting edges 4 together with chip-collecting cavities 3.
The cutting edges 4 and the chip-collecting cavities 3 will allow the screw, if necessary, to function as a self-tapping screw for cutting new threads or adjusting already cut threads in the tissue.
The other end of the screw is, as is quite conventional in the art, provided with a longitudinal bore for the attachment of an abutment for bridging the soft tissue covering the bone tissue and for the attachment of a prosthesis. The inner part 7 of the bore is cylindrical and provided with interior threads 6 and the outer part 5 of the bore, which is located in a portion 10 having a conically flaring outer surface, is conically flaring in order to accommodate a conically tapering attachment part of an abutment. The transitional portion between the conical part and the cylindrical bore comprises a hexagonal socket 8 which is intended to cooperate with a corresponding, hexagonal part of the abutment in order to allow the abutment to be oriented and locked in specific rotational positions relative to the fixture.
As can be seen in FIGS. 1 and 2, the outer surface of the co
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Hansson Stig G. V.
Holmen Anders
Astra Aktiebolag
Lucchesi Nicholas D.
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