Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
2000-05-09
2001-08-07
Lucchesi, Nicholas D. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
Reexamination Certificate
active
06270346
ABSTRACT:
SPECIFICATION
1. Field of the Invention
The present invention relates to a dental implant. In addition this invention concerns a method of promoting bone regrowth while doing a dental implant.
2. Background of the Invention
A standard dental implant comprises an endosseous root member that is set in the upper or lower jaw, a coronal or head part that is fixed to the root member, and the actual dental prosthetic that is mounted on the head part. Normally the gum or mucosa is cut to reveal the jaw bone and a hole is drilled in the living bone. Then the root member is fitted, normally screwed, into the hole, and is provided with a transmucosal cap dimensioned to project through the gum. Then the incision is sutured up and the site is allowed to heal, with the root member becoming integrated into the jaw bone and the gum healing neatly around the cap. The cap is then normally unscrewed from the root and replaced with a head part or mount of similar dimensions to which the actual prosthesis is mounted.
A significant problem is that typically the implant is needed in a location where a tooth has been missing for quite some time. As a result of the lack of a tooth at this side, the jaw bone has not received the necessary mechanical stimulation to ensure its good health, so it has atrophied and shrunk. Thus the implant must be installed just at a particularly weak point.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved dental implant.
Another object is the provision of such an improved dental implant which overcomes the above-given disadvantages, that is which encourages bone regrowth.
A further object is to provide a method of encouraging bone regrowth at the site of a dental implant.
SUMMARY OF THE INVENTION
A dental implant has according to the invention an inner root part adapted to be seated in a jawbone, an outer root part adapted to be seated in the jawbone outwardly of the inner root part, and a screw for displacing the outer root part outward relative to the inner root part.
Such an implant is used by first drilling in a jawbone from an outer surface thereof a hole extending along an axis and forming in the jawbone a throughgoing first cut generally parallel to the outer surface of the jawbone and traversed by the bore. The implant member is fitted to the bore so that the inner part engages the jawbone to one side of the cut and the outer part engages the jawbone to the other side of the cut. Then the jawbone is cut again generally parallel to the first cut to free from the jawbone a piece of bone engaged by the outer part. Subsequently the core-member parts are periodically axially separated to axially outwardly displace the piece of bone from the jawbone and promote bone growth in the cut until the piece of bone has been moved axially outwardly a predetermined distance from the jawbone. Finally a dental prosthesis is mounted on an outer end of the outer part.
This system makes it possible to promote bone regrowth in the manner used, for instance on serious long-bone fractures. It is known that when for example, a femur is broken with bone loss that the two parts can be periodically pulled apart at the fracture site until the bone has the desired length, the regrown bone filling the gap created as the bone parts are distracted. In this manner a seriously shrunken and atrophied jaw bone can be rebuilt so that it will provide solid support for the dental prosthesis by means of the implant.
According to the invention the root parts have outer surfaces each formed with a screwthread. The screwthread of the inner root part is deeper than the screwthread of the outer root part so that it can better engage in the spongier bone it will be set in. It is possible to eliminate the screwthread on the inner part since it is only subjected to compression when in use.
The parts are provided with axially interengaging formations rotationally coupling the parts together and the outer part is formed with tool-engaging facets. Thus the two-part core member can be screwed into the bore formed in the jaw in the standard manner, care being taken that the outer part only engages the jawbone outward of the cut and the inner part inward thereof. The inner part is internally threaded and engages the screw and the screw has a head bearing axially in both directions on the outer part. Furthermore the outer part includes a retaining nut formed with a central axial passage and bearing axially inward on the screw head and the inner part has an extension tube axially slidable in the outer part. The coupling formations need only be effective when the core member is being screwed in; once installed it is no longer necessary so that it is irrelevant if these formations are pulled apart and rendered ineffective.
To solidly fix the piece of bone to the outer core part a ring is releasably engaged with an inner end of the outer part. This ring bears against the inner face of the piece of bone so that as the outer part is moved axially out, it bears via this ring, which can be set in a groove of the outer part, on the piece of bone. The ring can be provided with a set screw bearing on the outer part and can have a large diameter central hole so it can tip relative to the outer part. In this system the inner end is inwardly flared. Normally the piece of bone is initially separated completely or widely enough by means of the outer part to allow a special instrument to install the ring on the inner end of the outer part, then the parts are reassembled and the piece fitted back relatively tightly in the pocket formed in the jawbone. The ring later assists pulling out the piece, which will adhere fairly strongly as bone regrows so that the extra force needed can be applied via the ring and not solely through the screwthreads of the outer part.
The implant has according to the invention can include a mounting head having an inner face engaging an outer face of the outer face and secured thereto by the screw. These faces can have complementary interengaging frustoconical surfaces to prevent tissue from growing inside the implant. Alternately one of the faces is planar and the other of the faces is flared and has an edge engaging the one face in line contact.
To stiffen the core member, the mounting head has a tubular extension engaging into the outer part.
According to the invention the dental prosthesis is mounted by removing the screw from the core member, mounting a head part on an outer face of the core member, securing the head part to the core member by means of another screw, and installing the prosthesis on the head part. Thus a transmucosal collar that is used while the gums heal and as core-member parts are being distracted to promote bone growth is replaced with a standardized head part whose axial dimension is determined by the thickness of the gum tissue, the depth of the core member, and the type of implant, is mounted on the outer part for securing to it of the dental prosthesis.
REFERENCES:
patent: 5439381 (1995-08-01), Cohen
patent: 5695335 (1997-12-01), Haas
patent: 5961329 (1999-10-01), Stucki-McCormick
patent: 6050819 (2000-04-01), Robinson
patent: 96 29022 (1996-09-01), None
Gaggl Alexander
Grabenhofer Andreas
Dubno Herbert
Lucchesi Nicholas D.
MKE Metall-und Kunststoffwaren Erzeugungs GmbH
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