Dentistry – Prosthodontics – Tooth construction
Patent
1997-04-15
1999-11-23
Wilson, John J.
Dentistry
Prosthodontics
Tooth construction
4332031, 264 19, A61C 1308
Patent
active
059890312
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention pertains to an artificial tooth of plastic or ceramic material consisting of several layers and used in dental prosthetics.
BACKGROUND OF THE INVENTION
According to DIN 13914, artificial teeth for producing dental prostheses must consist of several layers because of the desired similarity to natural teeth. Such multilayer teeth have previously been produced exclusively by a pressing process, wherein the differently dyed pressing masses are placed by hand in the pressing tool. The pressing of the teeth is very labor-intensive. The distribution of the layers put in place by hand is subject to irregularities. The excess amounts necessary for pressing lead to considerable burr formation at the separating plane of the mold halves. This makes subsequent processing necessary. Thus considerable production effort is connected to the production of conventional multilevel teeth, so that these teeth are relatively expensive.
The present invention is based on the problem of creating an artificial tooth constructed of several layers whose production can be largely automated and in which a reproducible arrangement of layers is guaranteed and, in particular, burr formation is also minimized, so that low production costs result.
SUMMARY OF THE INVENTION
This problem is solved according to the invention in that a tooth body consists of an internal solid core and least one first injection-molded outer layer enveloping the solid core at least in part. It is advantageous in this regard according to the invention if the solid core is also formed by injection molding.
The invention relies upon the recognition that a considerable savings in cost can be achieved by injection molding technology, since injection molding is done completely automatically and hence a reproducible arrangement of layers can be guaranteed. This may involve a multicomponent injection molding process, wherein the material components form layers inside the tooth body so that, by dying the individual material components differently the natural tooth appearance can be optimally approximated.
In particular, one or more material layers, built up on the base of the injection-molded solid core, can be extruded onto it and envelop it. The tooth structure according to the invention in this case is such that the basal tooth side of the solid core is not enveloped, whereas the other sides of the tooth are formed by the material layers enveloping the solid core.
The present invention also pertains to a process for producing layered teeth by a multicomponent injection molding process. In this case, the entire injection cycle runs completely automatically, with the same arrangement of the layers in each cycle due to the nature of the process. Burr formation in injection molding is considerably less by comparison to the pressing process.
The solid core and the layers enveloping it can consist according to the invention of a plastic material made of a transparent (amorphous) plastic. In particular, an impact-resistant modified polymethylmethacrylate (PMMA) is used for this purpose. It can also be advantageous according to the invention if a plastic material consisting of a mixture of plastics with the same refraction index is used.
Alternatively, it is possible according to the invention to use as material a ceramic material consisting of an injection-moldable ceramic mass consisting of a ceramic powder with a plastic material additive serving as a binder.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be discussed in greater detail on the basis of the embodiments show in the attached drawings. These show in
FIG. 1 a section in the sagittal plane through an artificial tooth constructed according to the invention as a front tooth;
FIG. 2 a section in the frontal plane through the tooth of FIG. 1;
FIGS. 3 & 4 perspective views of a side tooth according to the invention; and
FIG. 5 an additional embodiment of a tooth according to the invention in the view of FIG. 2.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
In
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patent: 4134935 (1979-01-01), Quiring et al.
patent: 4155964 (1979-05-01), Aronow
patent: 4265669 (1981-05-01), Starling et al.
patent: 4433959 (1984-02-01), Faunce
patent: 4645455 (1987-02-01), Kosmos
patent: 5151044 (1992-09-01), Rotsaert
Braun Frank Dietrich
Daug Harry
Kura Gunter
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