Dentistry – Prosthodontics – Holding or positioning denture in mouth
Patent
1996-05-30
1999-11-30
Lucchesi, Nicholas D.
Dentistry
Prosthodontics
Holding or positioning denture in mouth
433214, A61C 800
Patent
active
059932112
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to ball attachment devices, in particular for overdentures in which posts or abutments carrying a ball part are attached to a fixture in the jawbone and complementary snap fasteners or ball housings are mounted in the overdenture, and more particularly to a temporary coping for use during the preparation of a overdenture having ball attachment devices.
BACKGROUND TO THE INVENTION
The preparation of overdentures involves a series of positive and negative impressions and casts which are used so as to adapt the overdenture to the shape of the oral cavity and so as to orient the fastener elements in the jaw and in the overdenture correctly in relation to each other. During this casting-impression procedure, a temporary coping is placed upon the ball abutments in the jaw and moulded into an impression in an impression spoon. The copings have a bore which is complementary to the ball parts of the ball attachment devices. The copings, which now are located in the impression, are then utilized to hold ball abutment replicas which are moulded into a positive model of the jaw cast into the impression. The snap fasteners or ball housings are then attached to the temporary ball abutment replicas and moulded into or otherwise attached to the overdenture.
The copings normally have an interior bore which is circular in cross-section. This means that the fit between the coping and the ball part has to be very exact. If the bore is too small, it will be difficult to press the coping onto the ball part, and if the bore is too wide, there will be no or insufficient friction to hold the ball abutment and the abutment replica securely. Furthermore, special arrangements have to be made in order to allow the air in the bore to escape, such as channels to the outside etc.
It thus is desirable that there is a specified friction between the bore in the coping and the ball parts of the respective ball abutment This sets a high standard in regard of the dimensional precision of the bore. It furthermore is desirable that any air present in the interior of the coping has a possibility of escaping when the coping is pushed down onto the ball part in order to allow the coping to be fully seated on the ball part.
DISCLOSURE OF THE INVENTION
We have now found that the above disadvantages with known copings may be overcome by using a ball impression ball coping in which the interior bore has a cross-section which is polygonal in shape.
Thus, according to the present invention there is provided a temporary ball impression coping for use during the preparation of a overdenture having ball attachment devices for attaching said overdenture to fixtures in the jaw, said coping being provided with a bore for cooperation with a ball part on said ball attachment device, characterized in that said bore has a cross-section which is polygonal in shape.
Such a ball impression coping can overcome the disadvantages inherent in the prior art whilst still being simple and inexpensive to manufacture.
The bore may be any type of polygon. However, preferably the bore has a polygonal cross-section which is regular. In a further preferred embodiment, the polygonal shape is hexagonal.
The sides of said polygonal shape may be curved inwardly. The sides of the polygonal cross-section may also be formed of two parts having the same length and being angled inwardly in relation to each other so as to form a star shape.
Preferably the mouth of the bore is provided with a conically flaring part for cooperation with a corresponding conical part on said ball attachment abutment.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention will now be described, by way of example, with reference to the attached drawings in which
FIG. 1 is a perspective view of a impression coping according to the invention,
FIG. 2 is a plan view of the coping in FIG. 1, and
FIGS. 3-10 illustrate the use of the ball impression coping.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
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REFERENCES:
patent: 4955811 (1990-09-01), Lazarra et al.
patent: 5040983 (1991-08-01), Binon
patent: 5071350 (1991-12-01), Niznick
patent: 5073110 (1991-12-01), Barbone
patent: 5194000 (1993-03-01), Durg
patent: 5417570 (1995-05-01), Zuest et al.
patent: 5520540 (1996-05-01), Nardi et al.
Astra Aktiebolag
Lucchesi Nicholas D.
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