Plastic and nonmetallic article shaping or treating: processes – Dental shaping type
Reexamination Certificate
2000-03-24
2001-10-16
Fiorilla, Christopher A. (Department: 1731)
Plastic and nonmetallic article shaping or treating: processes
Dental shaping type
C264S019000, C264S040100, C264S040500
Reexamination Certificate
active
06303059
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of controlling an oven for producing tooth replacement components or dentures, whereby an electric motor moves a piston that acts upon a moldable restoration material that is introduced into a muffle oven having an oven hood that is removable from the muffle.
A method of this type is known from Australian patent 617,064 which also discloses a suitable apparatus, the subject matter of which patent is incorporated herein by reference thereto. With the method of the foregoing patent, an oven for producing a tooth replacement component is controlled in a special manner. A drive mechanism presses upon a piston that deforms a dental material under the effect of heat and presses it into a mold. The mold corresponds to a tooth replacement component and the plastic dental material forms this component upon curing. Whereas with earlier techniques air pockets were frequently formed, and also problems resulted for different geometries of the tooth replacement components, the aforementioned publication taught the improvement of detecting movement parameters of the piston and establishing an alteration of the piston movement velocity as a measure for shutting off the oven.
Even though with these features the quality of the tooth replacement components were significantly improved relative to previously known solutions, a further improvement would be desirable especially for filigree tooth replacement components. A further problem results with the use of in particular lithium disilicate glass ceramics. Although this material is very suitable for the manufacturer of tooth replacement components, it reacts very significantly at high temperatures with the matrix material of the muffle. In order nonetheless to achieve a good surface of the tooth replacement component, it is already known to clean the finished tooth replacement component with aqueous hydrofluoric acid.
However, this known method is not desired for two reasons. For one thing, the handling of aqueous hydrofluoric acid requires special protective measures since hydrofluoric acid is very corrosive. In this connection, the disposal problem is also relevant, since a regeneration directly in a dental lab would be too expensive.
On the other hand, the corrosive etching by the aqueous hydrofluoric acid removes a small amount of material, so that the etched tooth replacement component has slightly smaller dimensions than does the unetched tooth replacement component.
It has furthermore been known for a long period of time to control dental ovens via prescribed programs. With such control methods, a plurality of parameters can be prescribed, whereby for example even complexity of the tooth replacement component can be taken into account. However, the control is affected in particular by the type of heating, and it is theorized that the heating-up curve is very important to the quality of the tooth replacement part that is produced.
It has furthermore already been proposed to allow the pressure or force that acts upon the tooth replacement part to continuously increase at the beginning of the pressing or molding process. However, this measure taken alone leads for large volume tooth replacement components merely to a prolongation of the required molding time.
It is know that a temperature increase of the restoration material during the pressing or molding can shorten the molding time. However, this has a negative effect upon the surface and physical characteristics of the finished tooth restoration component. Therefore, a low temperature and as short a molding time as possible would be ideal, whereby with a practical realization compromises must be made depending upon the type of dental material.
It is therefore an object of the present invention to provide a method of controlling an oven for the production of tooth replacement components as previously described, with such a method being better suitable for different types of tooth replacement parts and in particular permits surfaces of the tooth replacement components to be improved such that the involvement of etching acid can at least be reduced if not entirely eliminated.
SUMMARY OF THE INVENTION
This objective is inventively realized in that a compactibility curve is established as a function of the type of dental material utilized, and after conclusion of the mold time the motor is turned off and the oven hood is removed.
In the following, the present invention is described for a ceramic material, especially for a ceramic blank. However, pursuant to the present invention it is also possible to use polymeric materials, metals and alloys in the form of powder or solid bodies.
Pursuant to the present invention it is particularly expedient that with the inventive features dental replacement components result that have a high quality surface not only for large volume molds but also for filigreed molds. It is particularly advantageous pursuant to the present invention if a compactibility curve is used that has a pressing force that preferably initially rises slowly then achieves a relatively high maximum value, which is maintained, whereby the reduction of the penetration speed of the piston and/or the pressure increase are relied upon as an immediately effective turnoff signal. The relatively strong pressing surprisingly also results in a quite rapid penetration of the dental material into finely branched mold channels and into the mold, so that pursuant to the present invention it is for example readily possible to mold three and multi-element bridges in the filigreed front toothed region of the lower jaw. To the extent that the detected perimeters indicate that the filling process is concluded, the motor is shut off. Depending upon the type of tooth replacement component, it is also possible to institute a retention time, which, however, should also be as short as possible; immediately thereafter, the oven hood is removed so that removal to the cooling process can take place.
Pursuant to one particularly advantageous specific embodiment of the invention, it is proposed that the oven hood be automatically removed. This can be effected in various ways, whereby it is preferred that the oven hood be raised and that the muffle then be pivoted out of the pressing or mold region, so that the muffle can be cooled on a rest surface and if necessary the next muffle with the next prepared tooth replacement components can already be subjected to pressing and molding.
It is particularly expedient pursuant to the present invention to keep the reaction time between the possibly finely branched tooth replacement components and the matrix material as short as possible. In this way, in an inventively surprisingly advantageous manner, matrix materials, for example phosphate-containing matrix materials that are suitable for the high temperature processing, can also be used for new dental ceramics, such as lithium disilicate glass ceramics.
Pursuant to a further, particularly expedient point of view, the occurrence of air cushions can inventively be nearly entirely avoided. Air cushions are inventively avoided by reducing the force of pressure in the beginning for filigreed tooth replacement components, or for large volume tooth replacement components by filling then rapidly without bubbles or pockets, being formed.
It is furthermore particularly expedient pursuant to the present invention to avoid as much as possible the reaction of the matrix material with the ceramic during the temperature dependent viscous flowing process. By minimizing the time of the pressing process, at most a very short reaction time takes place, because due to the relatively high flow velocity the dental material rapidly reaches the objective, where it remains static, so that the possible reaction and possible influence upon the viscosity have no further effects upon the flow process.
Pursuant to another particularly expedient point of view, it is inventively ensured that a bursting or cracking of the matrix material and/or of the muffle is avoided. Since the compa
Foser Hans-Peter
Holand Wolfram
Lorunser Johannes
Rohner Gottfried
Schweiger Marcel
Fiorilla Christopher A.
Ivoclar A.G.
Korman Alan S.
Thompson John C.
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