BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to apparatus used in making a dental model from a dental impression whereby the patient's teeth are accurately replicated in the dental model. In particular, the present invention relates to novel improvements in trays used in casting the dental models and articulation systems used in association with the trays and the models which are cast in the trays.

2. State of the Art

In order to fabricate a dental prosthetic, such as a crown, inlay, bridge, etc., a negative impression of a patient's teeth is taken using an impression material, and a reproduction of the impression is made as a model in the dental laboratory. The reproduction is a solid, positive model or replication of the gums and at least several adjacent teeth in the mouth of the patient. It is necessary to support the replication or dental model on an articulation device to determine proper size, fit and movement of the restorative prosthetic relative to the other teeth of the patient.

The process of forming dental models is widely known and is described in U.S. Pat. No. 5,207,574 and will not be repeated here. Generally, the reproduction of the patient's teeth corresponding to the upper and lower teeth are formed in separate casting steps. The models of the respective upper and lower teeth are then affixed to an articulation device during the preparation of a restorative prosthetic.

Tray and articulation systems to which the present invention is closely related are shown in U.S. Pat. Nos. 5,846,076; 5,913,681; and in particular my previous U.S. Pat. No. 8,087,933. In U.S. Pat. No. 5,846,076 a tray is shown having a bottom wall and side walls that extend upwardly from the perimeter of the bottom wall to form an open-topped cavity into which dental casting material is poured. The tray is made of elastomeric material so that the tray can be easily removed from the cast model that is formed in the tray. The tray after being stripped from the cast model is then discarded.

In U.S. Pat. No. 5,913,681 a tray is provided that includes a base wall and upwardly extending side walls at the perimeter of the base wall similar to that of U.S. Pat. No. 5,846,076. However, the tray of U.S. Pat. No. 5,913,681 is formed as a single piece from a non-elastomeric, rigid material, and the cast model must be excised with some difficulty from the tray.

In my previous U.S. Pat. No. 8,087,933 a tray is made of a rigid polymeric material and has (1) a substantially planar base with upstanding side walls integrally attached at the perimeter of the planar base by an easily ripped or torn, frangible membrane or thin film type connector mechanism that integrally connects the lower edge or perimeter of the side walls to the planar base; (2) an articulation system which includes an ell-shaped extension that extends from each of the trays. The distal ends of the ell-shaped extensions have a telescopic type attachment such that the end of one extension can be connected to the end of the other extension whereby the extensions can be pivotally rotated relative to each other about the common axis of the telescopic type attachment.

In another of my previous U.S. Pat. No. 7,425,129 a centric stop mechanism is disclosed and claimed which is attached to the dental model. The centric stop mechanism includes means for adjusting or fine tuning the final vertical positioning of the upper and lower base stones of the dental model. The centric stop mechanism prevents the base stones of a dental model from being moved to an improper position that might otherwise be allowed by improper up and down type flexing of the legs of the associated articulation member.

OBJECTIVES AND BRIEF DESCRIPTION OF THE INVENTION

The principal objective of the invention is to provide several novel improvements in prior art trays that are made of a rigid polymeric material similar to those described in my U.S. Pat. Nos. 7,425,129 and 8,087,933. One improvement consists of providing a substantially planar, relatively thin, ribbon-like extension or flange integrally attached to the upper edge of the upstanding, circuitous side wall so as to provide a relatively narrow table-like surface extending from and around the upper side edges of the upstanding, circuitous side wall, whereby the ribbon-like extension or flange and the upstanding circuitous side walls are removed from the tray by ripping or tearing them from the perimeter of the planar base of the trays using the frangible membrane or thin film type connector mechanism that integrally connects the lower edge or perimeter of the upstanding side walls to the planar base.

A second improvement provides a pair of spaced apart, substantially flat ears that project outwardly from the ribbon-like extension or flange, so that the flat ears extend obliquely outwardly from the front of the tray. Each of the ears are adapted to form a stable flat surface to support wet dental casting material during the procedure of casting and forming a dental model. By including the two respective ears in the tray of this invention, the tray is universal in its ability to be used with either right or left radius quadrant impressions in forming a prosthetic device such as an inlay, crown or bridge.

A third improvement provides an alignment pin that extends upwardly from and perpendicular to the planar base of the tray. The alignment pin is integrally attached to the planar base near the distal end of the tray and is of sufficient length to extend well into an opening corresponding to a distal tooth at the distal end of an quadrant impression when the impression is filled with casting material and assembled on the tray in the process of casting a model of the impression. The alignment pin can be tapered so as to diminish in its cross-sectional size from its end attached to the planar base to its upper free end.

A fourth improvement provides a modification to the centric stop mechanism in which the cylindrical hollow post forming the centric stop is provided with a thin membrane covering over the otherwise open end of the post. The membrane prevents wet material used in casting a dental model from entering and flowing into the cylindrical cavity of the post during casting of a dental model.

A fifth improvement provides a novel modification of the articulation systems disclosed in the prior art and in particular shown in U.S. Pat. Nos. 5,913,681 and 5,847,076. The articulation system of the present invention includes a ridged first leg that is substantially rectilinear and extends from one of the trays used in making the dental model. The other tray has a second leg extending therefrom which is formed in the shape of a flat plate having sufficient thickness to be substantially rigid but which also allows limited torsional movement or bending about its longitudinal length as well as limited flexing about its longitudinal length. The two distal ends of the first and second legs are removably attached such that the first and second legs can be pivotally rotated relative to each other about a common axis that lies in a plane that is substantially perpendicular to the longitudinal axes of the two trays to which the first and second legs are attached.

This allows the dental models formed on the trays to be moved in three distinct movements. The first movement being toward and away from each other, the second movement being from side to side, and the third movement utilizing the limited flex movement of the curved leg to replicate condyle angle during protrusive and lateral protrusive movement of the human jaw.

Additional objects and features of the invention will become apparent from the following detailed description taken together with the accompanying drawings.

