Dentistry – Apparatus – Having static product shaping surface
Reexamination Certificate
2000-09-06
2001-10-16
Lucchesi, Nicholas D. (Department: 3732)
Dentistry
Apparatus
Having static product shaping surface
C433S037000, C433S041000
Reexamination Certificate
active
06302690
ABSTRACT:
BACKGROUND OF THE INVENTION
Dental impression trays serve to receive a curable material to obtain an impression of a patient's tooth or teeth. By filling the impression, e.g. with gypsum or other materials, a model of the tooth or teeth can be produced which may serve as the working basis for the dental technician.
The precision of the impression is of critical importance for producing high-quality, well fitting dental replacement parts.
Known in the art are impression trays of metal and of synthetic material. Both are widely in use.
Due to the varying sizes and geometries of the human jaws and depending on the specific application, a plurality of tray sizes and shapes, often sold in sets, must be available. Further, since the most frequently needed trays are most frequently with the technician, a plurality of sets of trays must be available to the dentist.
Impression trays of metal are of advantage as their high rigidity and dimensional stability permits the production of very exact impressions and models, from which very exactly fitting dental replacement parts can be prepared. Due to the necessity of having a plurality of sets of trays, the use of metal trays involves high costs. In view of the high costs, the dentist is further faced with the inconvenience of having to control the return of the metal trays from the technician or dental laboratory. In addition, the dentist has to provide for suitable storage of metal trays upon their sterilization to exclude contamination until their reuse.
Another essential disadvantage of metal impression trays resides in the fact that they cannot be individualized. In contrast to trays of materials such as synthetic resin, which can be worked easily, metal trays are unsuited for adapting the tray geometry to the anatomy of an individual patient.
Impression trays of synthetic material, on the other hand, involve low cost and therefore permit disposal. They further allow the cured model to be removed by destroying the tray, which may be useful with certain impressions, e.g., in the case of undercuts, in order to save the model. Furthermore, there is no sterilization and subsequent clean storage. However, the relatively low mechanical strength and dimensional stability of trays made of synthetic material may lead to deformations of the impression while taken. Models prepared from a deformed impression are less accurate and thus of lower quality. If the dimensions of the model differ from those of the teeth from which it was taken, imperfect fitting of the finished dental replacement part will result even if the technician has worked meticulously from the model. In such a case, post-treatment by the dentist will be necessary, if at all possible, and the patient will end up with a dental replacement part that does not fit completely.
German Offenlegungsschrift 196 28 682 discloses a reusable metallic dental impression tray made of several parts that can be disassembled to simplify the removal of the cured impression material.
German Patent Specification 4131 145 shows a dental impression tray made of metal with a thin, flexible insert made of plastic material. Both parts cooperate to receive the impression material and form retentions therefor. Since the flexible insert has virtually no rigidity of its own, it must be supported on all sides by the outer tray.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a dental impression tray which has high overall mechanical strength and dimensional stability without involving high investment or storage costs.
This object is met by a dental impression tray comprising an inner mold shell defining a space for receiving an impression material, and an outer support shell surrounding and supporting the mold shell, the mold shell being completely closed with respect to the support shell to constitute the sole means for receiving impression material.
The object is also met by a dental impression tray comprising an inner mold shell having a peripheral wall and a bottom, the peripheral wall and a bottom defining a space for receiving an impression material, and an outer support shell surrounding and supporting the mold shell substantially only along the peripheral wall.
While the mold shell constitutes the only receptacle for the impression material, the support shell serves to provide the mold shell with sufficient dimensional stability to avoid deformations when the impression is being taken, and also when the tray with the uncured impression material is withdrawn from the teeth and during the curing of the material. While the support shell is reused, the mold shell may be discarded after removal of the cured model by the technician.
The two-part structure of the impression tray has the further advantage that the dentist requires only a small number of differently sized and shaped metal support shells since the exact shape of the space receiving the impression material is determined by the mold shell, and since it is possible 5 to use several different mold shells in combination with one support shell.
The support shell of the present invention can be used for both an upper jaw and a lower jaw. Conventionally, impression trays for upper jaws often differ from those for lower jaws in that the former ones have a palatine plate which does not exist with the latter ones. With the impression tray of the present invention, a support shell with no palatine plate can be used in combination with mold shells for upper jaws and mold shells for lower jaws.
Thus, the number of support shells which a dentist must have available is limited in that it is only necessary to meet different sizes and shapes of human teeth. The technician and dental lab require only one set of support shells to hold the mold shells filled with impression material, no sterilization or cleaning being necessary.
In a preferred embodiment, the mold shell and the support shell are made of different materials; preferably, the mold shell is made of synthetic material and the support shell is made of metal. In this manner, the advantages of a metal impression tray are combined with those of a plastic one without the disadvantages of either.
In another preferred embodiment, the mold shell and the support shell are adapted to be detachably connected by positively engaging means. Preferably, the mold shell and the support shell are provided with slidably engaging means. The support shell may have a peripheral wall, an inner side of which is provided with a groove for engagement with an outward projecting flange provide on the mold shell. Further, the mold shell may have a peripheral wall provided with an outward extending flange for engagement with the free outer edge of the peripheral wall provided on the support shell. Further, the mold and support shells may be provided with mutually engaging locking means.
All these structural features achieve a mechanically strong, yet releasable engagement between the support and mold shells, thus permitting the production of precisely fitting dental replacement parts.
In accordance with another embodiment of the invention, the support shell has a peripheral wall provided with an opening, and the mold shell has an outward projection adapted to extend through the opening and engage an outer portion of the support shell. The extension may be formed by a stock provided with a detent nose spaced from the peripheral wall of the mold shell, for engagement with a step provided on a handle or the support shell. In this embodiment, the impression tray is particularly easy and safe to disassemble without impairing the quality of the impression.
In another preferred embodiment, the mold shell has retention means for engagement with the impression material. Suitable retention structures or shown in U.S. Pat. Nos. 5,772,432 and 5,890,895 and in WO 97/32537.
Further, the inner surface of the mold shell may be provided with a self-adhesive substance or a self-adhesive sheet of woven or non-woven material. This saves the dentist most of the preparatory work necessary with many prior art impression tr
Brandhorst Gerd
Fetz Johann
Wagner Ingo
Zech Joachim
Connolly Bove Lodge & Hutz
Espe Dental AG
Lucchesi Nicholas D.
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