Static molds – Dental prosthodontic type
Patent
1989-01-12
1990-10-16
Housel, James C.
Static molds
Dental prosthodontic type
164 35, 164246, 164DIG4, 249 62, 249149, 249177, 264 19, A61C 1320
Patent
active
049629093
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a casting mold for the production of muffles for use in dental prosthetic manufacture.
2. The Prior Art
Such a casting mold is known from "Das zahnrztiche and zahntechnische Vorgehen beim Teleskopsystem in der Prosthetik", "Dental and Dental Surgery Procedures using the Telescope System in Prosthetics" by Bottger and Grundler, Verlag Neuer Merkur GmbH, Munich, 1978. In order to be able to produce precise casting objects, such as crowns, bridges, inlays, onlays, telescopes and similar items from precious metals, the object must first be modeled in wax or a self-polymerizate. The wax model is subsequently provided with a casting channel, which serves for subsequent injection of the melt. The other end of the casting channel is attached to a funnel shaper in the form of a rubber socket. Subsequently, a pipe-shaped muffle ring is inserted into a depression located in the rubber socket with one part, and this ring then surrounds the wax model. Then the embedding mass is introduced into the casting muffle, with setting expansion occurring when the embedding mass sets, predominantly in the axial direction, since expansion of the embedding mass in a radial direction is prevented by the muffle ring.
After setting or curing of the embedding mass, the funnel shaper is pulled off from the set embedding mass and the muffle ring. The set embedding mass is subsequently heated to a temperature of 200.degree. C. with the muffle ring, in order to drive out the wax. After the wax has been driven off, the mold, i.e. the set embedding mass with the muffle ring, is placed in an oven and is heated until it has reached the temperature desired for subsequent casting, namely 700.degree. C. During this heating, thermal expansion takes place. Since the setting expansion mentioned above and the thermal expansion mentioned now predominantly occur in an axial direction, a distortion of the casting cavity in an axial direction takes place, which results in fitting inaccuracies of the casting object. To eliminate these fitting inaccuracies, other cost-intensive work procedures are then necessary.
SUMMARY OF THE INVENTION
It is an object of the present invention to develop a casting mold for the production of muffles for use in dental prosthetic manufacture in such a way that predominant distortion of the mold or the muffle in an axial direction can be prevented, so that the casting object exactly corresponds to the wax model.
The above object is accomplished in accordance with the present invention, by providing a cylindrical ring which is inserted on the side of the muffle ring which faces the funnel shaper, which ring is removed after the embedding mass has set, and a blind cone is provided on the side of the muffle ring opposite the funnel shaper, expansion of the embedding mass in the area of the casting objects can also take place towards the inside, i.e. towards the center axis of the muffle ring and below the casting objects downwards towards the side facing the casting funnel, so that uniform, three-dimensional enlargement of the casting cavity takes place, and therefore unilateral distortion can be prevented. The expansion is massdependent and the cylindrical ring has the effect that the same amount of mass expands in the vertical, axial and transverse direction. This spatially uniform expansion is equalized by the contraction of the precious metal during the casting cooling process. This makes it possible to avoid cost-intensive reworking of the casting objects. Also, less embedding mass is needed for the mold and the muffle.
Since the blind funnel can also be positioned and fixed as desired in the frontal surface of the muffle ring, according to the invention, a distance which is essentially uniform can be achieved between the wax model and the blind funnel, so that later, approximately the same amount of embedding material will be found in the area of the casting objects. The exact positioning of the blind funnel can also be carried out with a rel
REFERENCES:
patent: 3064309 (1962-11-01), Steinbock et al.
patent: 3698468 (1975-10-01), Hudson
patent: 3768544 (1973-10-01), Padeh
patent: 3985178 (1976-10-01), Cooper
patent: 4825934 (1989-05-01), Kai
Das Zahnarztliche Und Zahntechnische Vorgehen Beim Teleskopsystem in Der Prothetik, of Professor Dr. Hermann Bottger and Zahn technikermeister Horst Grundler, 1978, pp. 119-134.
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