GB754375A - Improvements in or relating to impression taking compositions - Google Patents

Abstract

A plastic composition for taking dental impressions comprises a gel-forming component, or a mixture of gel-forming components, selected from a water-soluble alginate, a gellable pectin material, and sodium, potassium, or ammonium carboxymethyl cellulose, a metallic salt component, e.g. calcium sulphate, reactive with the gel-forming component or mixture in solution to form an elastic gel, and zinc fluoride uniformly distributed within the composition so that when a plaster cast is made of a dental impression formed in the surface of the composition, the zinc fluoride facilitates the formation of a hard plaster surface. The metallic salt may comprise calcium sulphate decahydrate, dihydrate or hemi-hydrate, or lead monosilicate, disilicate, basic sulphate, basic carbonate or other lead salt, or a salt of zinc or strontium. To retard the reaction between the gel-forming component and the metallic salt the composition may contain, either singly or in admixture, sodium carbonate, an alkali metal phosphate or polyphosphate, e.g. trisodium phosphate or polyphosphate or sodium ortho-, meta-, or pyrophosphate, or a metal salt of a tetracarboxy acid of ethylene diamine, as described in U.S.A. Specification 2,657,971. The composition may also include a filler such as powdered talc, clay, diatomaceous earth, calcium carbonate or silica.ALSO:A plastic composition for taking dental impressions comprises a gel-forming component or a mixture of gel-forming components selected from a water-soluble alginate, a gellable faction material, and sodium, potassium, or ammonium carboxy methyl cellulose, a metallic salt component, e.g. calcium sulphate reactive with the gel-forming component or mixture in solution to form an elastic gel, and zinc fluoride uniformly distributed within the composition, so that when a plaster cast is made of a dental impression formed in the surface of the composition the zinc fluoride facilitates the formation of a hard plaster surface. The gel-forming component is preferably sodium or potassium alginate, and the metallic salt may comprise calcium sulphate, decahydrate, dihydrate, or hemi-hydrate, or lead monosilicate, disilicate, basic sulphate, or basic carbonate, or other lead salt, or a salt of zinc or strontium. To retard the reaction between the gel-forming component and the metallic salt the composition may contain, either singly or in admixture, sodium carbonate, an alkali metal phosphate or polyphosphate, e.g. trisodium phosphate or polyphosphate, or sodium ortho, meta or pyrophosphate, or a metal salt of a tetracarboxy acid of ethylene diamine as described in U.S.A. Specification 2,657,971. The composition may also include a filler such as powdered talc, clay, diatomaceous earth, calcium carbonate, or silica. In an example 0.5 gm. of zinc fluoride is added 72 gm. alkali metal alginate, 220 gm. diatomaceous earth, 7 gm. tetrasodium pyrophosphate and 40 gm. calcium sulphate hemi-hydrate.