Abstract A composition and method for preparing model bases in the manufacture of dental prostheses, in which the model base is made of a castable-refractory composition that is stable at high temperatures and is compatible with commercially available dental porcelains and gold alloys, as well as with the implaced dies and dowels. The catable-refractory composition of the invention is made by a dry blend consisting essentially of 40-50 weight percent of a refractory oxide, 6-8 percent by weight of an alkali phosphate, and 42-47 percent by weight of an alkaline-earth fluoride, and then mixing that dry blend with a colloidal silica sol of 40 weight percent content, using a ratio of 4 to 5 parts of blend to 1 part of sol.
The composition of claim 1 wherein the dry blend also consists of up to about 1 weight percent of a metal oxide as colorant.
Claim 2
Dependent Claim
177 words
In the making of dental prostheses by a method including the casting of dies of castable-refractory material capable of maintaining its physical integrity when solidified and then heated to 2,000* F, the positioning in said castable-refractory material while in its fluid state of dowels, the subsequent solidification of said castable-refractory material, and the casting about said dies and dowels of a model base composition to form a structure, the steps of preparing a model base of castable-refractory composition consisting essentially of a mixture of (a) 4 to 5 parts of a dry blend consisting essentially of about 43 weight percent of magnesia, about 10 weight percent of alumina, about 7 weight percent of ammonium dihydrogen phosphate, about 38 weight percent of calcium fluoride, and (b) 1 part of a colloidal silica sol of about 40 weight percent solids content, casting said model base composition about said dowels and dies, permitting said model base composition to solidify, heating said structure to a temperature of ranging from about 1, 800* F. to 1,850* F., and cooling to room temperature.
Claim 3
Dependent Claim
24 words
The method of claim 3 wherein the dry blend also consists of up to about 1 weight percent of a metal oxide as colorant.