Dentistry – Apparatus – Having static product shaping surface
Reexamination Certificate
2000-05-25
2001-06-19
Lucchesi, Nicholas D. (Department: 3732)
Dentistry
Apparatus
Having static product shaping surface
C433S047000
Reexamination Certificate
active
06247925
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a tray for taking dental impressions. More particularly this invention concerns such a tray used for making impressions used for the manufacture of false teeth.
BACKGROUND OF THE INVENTION
As described in German patent document 3,344,774, a standard tray for taking a dental impression from a jaw having mobile and immobile gum tissues separated at an action line has a body formed with a U-shaped outer or buccal wall having an edge and a U-shaped inner or lingual wall spaced inwardly from the outer wall and defining therewith a U-shaped cavity adapted to fit over the jaw. The U-shaped cavity is dimensioned to fit with some play over the jaw.
In use the cavity is partially filled with impression material and then is forcibly pressed down on the jaw whose impression is to be taken. The impression material is quite viscous so that, when forced against the gum tissues, it push back the mobile tissues and, as a result, the impression will in effect be of the hard tissues of the jaw. The fit is as close as possible so that the impression material is, in effect, pressurized and forced into intimate contact with the immobile tissues of the jaw.
A common problem with such trays is that the impression material pulls out of them. Thus when the material has hardened sufficiently and the tray is lifted, instead of stripping off the patient, the material pulls out of the tray. Then the impression must be peeled off the patient, a procedure that normally damages it and requires that it be taken again.
One solution to this problem has been the use of special bonding agents in the tray that cause the impression material to stick to the tray. While such a system is in theory quite effective, in reality it has numerous drawbacks. The bonding agent must be applied carefully, and must be made of some safe material as it is being put in the patient's mouth. Furthermore if the finished impression is too solidly bonded to the tray, it is itself damaged on removal.
Accordingly U.S. Pat. No. 4,368,040 of Weissmann proposes a tray with numerous cutouts and ridges that cause the impression to interlock with the tray. This purely mechanical coupling is in part effected by causing the impression material to flow out through the tray. As a result the pressure applied to the material to force it against the tissues of the jaw is substantially reduced and the impression is inaccurate.
German published patent application 3,837,585 describes another system where thin slots are cut through the walls of the tray adjacent their edges. Such a system allows the impression mass to be pressurized and does indeed couple the impression to the tray. Nonetheless the material can still pull rather easily out of the tray. In addition the tray itself does not always form a particularly good fit and seal with the jaw.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved dental-impression tray.
Another object is the provision of such an improved dental-impression tray which overcomes the above-given disadvantages, that is which produces a highly accurate impression and which securely holds the thus produced impression so that, when separated from the patient, it stays with the tray.
SUMMARY OF THE INVENTION
A tray for taking a dental impression from a jaw having mobile and immobile gum tissues separated at an action line. The tray is formed of a body formed with a U-shaped outer wall having an edge formed as a thickened bead, a U-shaped inner wall spaced inwardly from the outer wall and defining therewith a U-shaped cavity adapted to fit over the jaw with the edge projecting past the action line, a plurality of throughgoing slots on the outer wall immediately adjacent the outer-wall edge and extending generally parallel to the outer-wall edge.
With this system the only place for the material to escape from the tray is at or adjacent the edge. Thus the material will be highly pressurized in the critical center region, but when the tray is pulled off the jaw the impression will be sure to come with it. The combination of a thickened edge bead and slots immediately adjacent it thus not only improves the quality of the impression, but makes it hold better in the tray.
According to the invention the tray is intended for a lower mandible and its inner wall has an edge and is also formed with a plurality of throughgoing slots immediately adjacent the inner-wall edge and extending generally parallel to the inner-wall edge. The inner-wall edge is also formed as a thickened bead. Thus there is a controlled fit and controlled leakage at the inner edge too.
The slots in accordance with the invention are elongated parallel to the outer-wall edge. They have a length of 0.5 cm to 2 cm, preferably 0.8 cm to 1.7 cm and most preferably of 1.2 cm to 1.6 cm. They have a width of between 1 mm and 3 mm, preferably bout 2 mm. There are two to six, preferably, four such slots on the outer edge and two on the inner edge. The thickened edge has a thickness of from 2 mm to 5 mm, preferably 3 mm.
In use there will therefore be a form of leakage through the slots and, normally, at the small gap between the edge and the jaw tissue. These two leakage flows will typically unite and harden outside the tray so that, when the tray is extracted, it will have a solid bead of impression material around its edge, solidly securing the impression in place. Since the slots are in the action region of the gums the impression will be very accurate once the patient, whose impression is being taken, moves these mobile tissues as is normally done, for instance by extending the tongue when the lower-jaw impression is being taken.
Such a tray can be used with a dentate human jaw. When there are not teeth, a shallower cavity is needed, but even so the system of this invention is highly effective in that it builds up pressure at the critical regions to form an accurate negative impression of these regions.
REFERENCES:
patent: 2352545 (1944-06-01), Jefferies
patent: 2611959 (1952-09-01), Baum
patent: 4146963 (1979-04-01), Schreinmakers
patent: 4368040 (1983-01-01), Weissman
patent: 4375965 (1983-03-01), Weissman
patent: 5551872 (1996-09-01), Mena
patent: 5890894 (1999-04-01), Mio et al.
patent: 5890895 (1999-04-01), Tucker
patent: 33 44 774 (1985-06-01), None
patent: 38 37 585 (1990-05-01), None
Dubno Herbert
Lucchesi Nicholas D.
Wilford Andrew
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