Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1992-01-17
1994-06-21
Bradley, Paula A.
Metal founding
Process
Shaping liquid metal against a forming surface
164 98, 164DIG4, 433183, 433208, 433224, B22D 1900, A61C 1308
Patent
active
053221109
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a dental prosthetic casting-on process and to a dental prosthetic primary part, which is suitable for the casting-on process.
2. Description of the Related Art
As an alternative to soldered, welded, cemented and precision-fitted connections, dental prosthetic components can be connected by casting-on. If a metallic connection with a closed joint is required for this, the joint component which is to be cast-on to (hereinafter designated the "primary part") and the joint component (hereinafter designated the "secondary part") which is to be cast-on, consist of an alloy which is made up of pure precious metals. As a rule high-carat, copper-free platinum- and iridium-containing gold alloys are used (cF. Lindigkeit in: G. K. Siebert: Dentallegierungen in der zahnarztlichen Prosthetik [Dental alloys in dental prosthetics], 1989, p880). If oxidizing alloys, e.g. a cobalt- or nickel-based alloy, are used, then provided the joint elements possess sufficiently retentive form, a tight connection is created initially. Due to the separating effect of the oxide layers on the joint elements, however, this latter exhibits an open metal joint apart from a few welded fusion points. This latter is soon attacked by crevice corrosion in the mouth and is enlarged. In the course of time the originally tightly-fitting elements can develop a distinctly visible and palpable loose fit which destroys the precision fit of the prosthesis.
Numerous dental objectives cannot be fulfilled by a single-casting process. As opposed to soldering or welding, the casting-on process avoids the additional problems associated with the transfer of sources of error involved in the production of a model for positioning and supporting the segments to be soldered; this results in a saving in both time and costs. The metallic cast-on connection using oxidising dental non-precious alloys is not considered possible in the-current state of the art.
SUMMARY OF THE INVENTION
It is, therefore, an objective of the invention to make available a dental prosthetic casting-on process which avoids the occurrence of a disruptive oxide or inactivating layer of oxide-forming alloys (base metals) under casting-on conditions.
This objective is fulfilled in the present invention by a dental prosthetic casting-on process in which a metal secondary part is cast-on to a metal primary part where the primary part used consists of an oxide-forming metal alloy whose casting-on surface is alloyed, prior to casting, with a reducing metalloid. Boron, silicon or phosphorus are the preferred reducing metalloids used. Such a metalloid is made to diffuse into the surface lattice of the primary element prior to casting. This process is advantageously enhanced with the aid of a halogenide, e.g. lithium fluoride, Lif. For the metalloids, boron or silicon can be used in the elementary form. The metalloid can, however, also be used in the form of a reactive compound.
The objective is further realized by means of a primary part which is characterized therein that it comprises an oxide-forming dental alloy (base metal) which in its surface casting-on zone exhibits a boron and/or silicon and/or phosphorus content.
The following advantages can be achieved by implementation the invention:
It is possible to produce a metallic cast-on joint between a primary part made of a base-metal alloy and secondary element made of a base-metal alloy.
It is, however, also possible to produce a metallic cast-on joint between a base-metal alloy primary part and a precious metal secondary part.
Pre-treatment of the base-metal alloy primary part prior to the casting-on of the base-metal alloy secondary part and the casting-on process itself can be performed in any dental laboratory.
Pre-treatment of the primary part prior to casting-on can, however, also be per formed on a mass production basis on the premises of the primary part manufacturer.
Further advantages of the invention can be deduced from the following description, illustra
REFERENCES:
patent: 3337956 (1967-08-01), Lirot
patent: 4450886 (1984-05-01), Enomoto
patent: 4494287 (1985-01-01), Cruzen
patent: 4895516 (1990-01-01), Hulten
Lutzman Manfred
Wall Giselher
Bradley Paula A.
Pelto Rex E.
Wall Giselher
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