Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
1998-10-29
2002-03-19
Manahan, Todd E. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
Reexamination Certificate
active
06358050
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to dental implant systems.
BACKGROUND OF THE INVENTION
There are many dental implant systems being marketed today by different manufacturers. The components of these systems are typically incompatible with one another meaning that a “mix-and-match” dental prosthesis is not possible. Clearly there would be many advantages to having the facility to build a dental prosthesis from components of different systems. For example, some systems include components which no other system has an equivalent to, that is to say they are unique, while some systems may have components with advantageous properties compared to the equivalent components of other systems.
The most widespread dental implant system at the present time is that marketed by Nobelpharma AB and known as the Brånemark System®. This system includes a fixture as a component part thereof which is adapted in use to be embedded in the bone tissue of the maxilla or mandible and which presents at the trailing end thereof a male hexagonal projection in which an internally threaded bore opens centrally. A variety of other components of the Brånemark System® are then added temporarily or permanently to the trailing end of the fixture Component to form a dental prosthesis.
For example, the Brånemark System® includes various transmucosal spacers or abutments as component parts for connection to an implanted fixture to bridge the soft tissue layer or gingiva overlying the maxilla or mandible and carry supragingival components of the Brånemark System®. One such abutment includes a sleeve part one of the open ends of which has an inner circumference of hexagonal cross-section for anti-rotational connection of the abutment sleeve to the trailing end of the fixture. An abutment screw then passes through the abutment sleeve to screw into the internally threaded bore in the trailing end of the fixture to secure the abutment sleeve to the fixture.
The trailing end of the abutment presents a profile such that supragingival components of the Brånemark System® can be added temporarily or permanently on the fixture-abutment assembly to complete the formation of a dental prosthesis. For example, in the case of the abutment assembly described hereinabove an internally threaded bore may open in the trailing end of the abutment screw for either a screw threaded projection on a supragingival component to screw into to secure that component to the fixture-abutment assembly or a screw part of a multi-part supragingival assembly to screw into to secure the supragingival assembly to the fixture-abutment assembly.
Abutments may also present anti-rotational surfaces for co-operation with anti-rotational surfaces on the leading end of supragingival components or assemblies for anti-rotational connection of the supragingival components or assemblies to the fixture-abutment assembly or wrench engaging surfaces which enable tightening of the abutment to the fixture but which do not interfere with the connection of the supragingival components or assemblies to the fixture-abutment assembly.
As examples of supragingival components there may be mentioned cylinders which carry a restoration such as a bridge or crown and impression copings which are temporarily connected to the implanted fixture-abutment assembly to enable a model of the implanted fixture-abutment assembly and surrounding dentition to be generated for fabrication of a restoration on a cylinder which will fit in with the surrounding dentition when carried by the fixture-abutment assembly.
In addition to the dental implant systems such as the Brånemark System® which are based on fixtures having male projections at the trailing ends thereof there also exist dental implant systems which rely on a conical seat interface between the fixtures and superstructures carried thereby. In these systems a frusto-conical recess opens in the trailing end of the fixture for a complementary frusto-conical profile at the leading end of the superstructure, for example an abutment, to seat in. The frusto-conical recess typically forms the trailing portion of a socket which at the leading end thereof defines an internally threaded bore. The superstructure is secured to the fixture through a screw connection in the internally threaded bore.
One such system is marketed by Astra Tech AB information about which can be found in inter alia ‘
Dental Implants: A Guide for the General Practitioner’
. Michael Norton, Ouintessence Publishing Co. Ltd., 1995. To prevent rotation of an abutment of this system of the type comprising an abutment sleeve and abutment screw, the socket in the fixture may further comprise a polygonal cross-section portion between the frusto-conical and internally threaded portions with the abutment sleeve being provided with a projection at the leading end thereof having a trailing frusto-conical portion for seating in the frusto-conical portion of the fixture socket and a leading polygonal portion for co-operation with the polygonal portion of the fixture socket. The abutment screw passes through the sleeve into engagement with the internally threaded bore to secure the sleeve to the fixture as for the corresponding abutment of the Brånemark System®.
Tests have shown that a tapered seat interface such as the conical seat interface for a fixture-superstructure assembly, for example a fixture-abutment assembly, leads to an implanted assembly which exhibits greater mechanical stability and strength as compared to the fixtures of the other systems discussed hereinabove.
In addition, the fixture of the Astra Tech system has a unique outer surface characteristic which improves the shear strength of the fixture when implanted and also the ability of the fixture to osseointegrate into the bone tissue of tho maxilla or mandible into which it is implanted.
There is thus a need for the provision of means to enable a fixture of a first dental implant system having a trailing end in which a tapered, for example frusto-conical, recess is provided to support components of a second incompatible dental implant system for the formation of a hybrid dental prosthesis founded on the fixture with the recess.
SUMMARY OF THE INVENTION
With this need in mind, the present invention provides a dental implant system converter structure for enabling a fixture of a first dental implant system having a trailing end in which a tapered recess opens to support components of a second incompatible dental implant system, the converter structure having a leading end which presents a projection having a tapered profile for seating in the tapered recess in the trailing end of the fixture and a trailing end which presents a profile adapted to enable one or more components of the second dental implant system to be carried thereon.
In an embodiment of the invention he tapered recess forms a trailing portion of a socket in the trailing end of the fixture with a leading portion of the socket presenting an internally threaded bore and the tapered profile forms a trailing portion of the projection at the leading end of the converter structure with a leading portion of the projection presenting a screw threaded profile for screw connection in the internally threaded bore portion of the fixture socket.
In an embodiment of the invention the converter structure comprises a sleeve element having a leading end which presents a first part of the projection which comprises the tapered profile and a screw element having a leading end which presents a second part of the projection which comprises the screw thread profile, the screw element adapted to be inserted into the sleeve element for the screw thread profile to be screwed in the internally threaded bore portion of the fixture socket to secure the sleeve element to the fixture. The, converter structure may, on the other hand, be a one-piece component with the projection being formed at the leading end of the component.
In an embodiment of the invention the converter structure comprises anti-rotation means for co-operation with anti-rotation means on the fi
Bergström Nils Gustaf
Lidskog Niklas
Astra Aktiebolag
Manahan Todd #E.
White & Case LLP
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