| 摘要 |
1,270,795. Dental cement. NATIONAL RESEARCH DEVELOPMENT CORP. 6 Aug., 1969 [15 Aug., 1968], No. 38995/68. Heading C3N. A dental cement is produced by mixing a dental cement powder and an aqueous phosphoric acid solution containing dissolved therein a physiologically innocuous metal of Group III of the Periodic Table having an atomic number greater than 13. The mixing provides a plastic mass which rapidly hardens as a dental cement but which remains plastic long enough to be formed into a desired shape. The dental cement powder and the aqueous phosphoric acid solution may comprise separate ingredients of a dental cement pack. The dental cement powder and the aqueous phosphoric acid solution may be mixed together in a proportion of 1À4-1À6 gms. powder to each 0À4 mls. of solution. The dental cement powder is preferably an alkaline earth metal aluminosilicate or a mixed alkali metal alkaline earth metal aluminosilicate which may contain P 2 O 5 and fluorides and preferably has a particle size of less than 40Á, whilst the phosphoric acid is preferably orthophosphoric acid, which may contain 5-25% by weight of free phosphoric acid. The phosphoric acid solutions preferably contain 2-14% by weight of the Group III metal as previously specified and this metal is preferably iridium although gallium and scandium or a rare earth metal are also suitable. The phosphoric acid solution may also contain besides the Group III metal previously specified up to about 3% by weight of aluminium or boron. The phosphoric acid solution may also contain a fluoride, e.g. hydrofluoric acid, in an amount sufficient to give up to 7% by weight of fluorine calculated as hydrogen fluoride or may contain up to 5% by weight of ethylene glycol. |
