Abstract: A dental gypsum composition in the low-dusting powdery form contains (a) hemihydrate gypsum, (b) a setting controlled agent comprising one or more of setting accelerators, setting retarders and setting expansion inhibitors, (c) one or more wetting agents selected from the group consisting of liquid hydrophobic hydrocarbons, liquid hydrophobic fatty acid esters and liquid hydrophobic fatty acids showing a vapor pressure of 3.15 mmHg or below at 20.degree. C., and (d) one or more anionic surface active agents selected from the group consisting of alkylbenzene sulfonates and alkyl sulfates.

Abstract: A dental investement composition in the low-dusting powdery form contains (a) a mixture of a soluble phosphate with magnesium oxide or hemihydrate gypsum as a binder, (b) quartz and/or christobalite as a refractory material, (c) one or more wetting agents selected from the group consisting of hydrophobic liquid hydrocarbons, liquid hydrophobic fatty acid esters and liquid hydrophobic fatty acids showing a vapor pressure of 3.15 mmHg or below 20.degree. C., and (d) one or more anionic surface active agents selected from the group consisting of alkylbenzene sulfonates and alkyl sulfates.

Abstract: An investment for dental casting comprises a mixture of at least one refractory selected from alumina, zirconia, magnesia clinker, quartz, cristobalite and fused quartz with either a mixture of a soluble phosphate with magnesium oxide or hemi-hydrate gypsum, which act as a binder. The investment of the invention further contains 0.5 to 5 parts by weight of raw starch (original starch) and 0.1 to 50 parts by weight of at least one selected from the group consisting of carbides, nitrides, borides, silicides and sulfides of transition metals of Groups IV, V and VI in the periodic table, which are added as expanding agents to 100 parts by weight of the aforesaid mixture. The investment of the invention may still further contain 0.1 to 1 part by weight of soluble starch.

Abstract: A gypsum composition for denture investment comprises 100 parts by weight of a mixture of 50-90 parts by weight of .alpha.-Gypsum hemihydrate (.alpha.-CaSO.sub.4.1/2H.sub.2 O) with 10-50 parts by weight of .beta.-Gypsum hemihydrate (.beta.-CaSO.sub.4.1/2H.sub.2 O) and 0.2-2.0 parts by weight of a soluble potassium salt and 0.5-3.0 parts by weight of mannitol. As the soluble potassium salt, use may be made of one or more of potassium sulfate, potassium chloride and potassium tartrate. The gypsum composition may further include 0.5-5.0 parts by weight of dihydrate gypsum.

Abstract: An investment material for dental casting comprises 100 parts by weight of a mixture of hemihydrate gypsum, quartz and/or cristobalite and 2 to 5 parts by weight of natural starch optionally with 0.1 to 1.0 part by weight of soluble starch.

Abstract: A method for strengthening dental restorative material is disclosed, which comprises depositing one or more inorganic salts of metals selected from rubidium, cesium, and potassium on the surface of a coated material of a dental restorative material obtained by coating and firing a dental porcelain fused to metal material. The dental restorative material is containing leucite and sodium on the surface of a dental alloy substrate, and heat treating the coated material at temperatures of 380.degree. C. or higher but lower than the melting point of the inorganic salt and the strain temperature of the coated material. According to the method of this invention, the coated material can be strengthened with ease while maintaining its translucency and color tone, without using any special device.

Abstract: A method for strengthened porcelain tooth is disclosed, which comprises depositing one or more inorganic salts of metals selected from rubidium, cesium, and potassium on the surface of a porcelain tooth obtained by sintering a dental porcelain material containing feldspar as a main raw material and sodium, and heat treating the porcelain tooth at temperature of 380.degree. C. or higher but lower than the melting point of the inorganic salt and the strain temperature of the porcelain tooth. According to the method of this invention, the porcelain tooth can be strengthened with ease while maintaining translucency and color tone as in a natural tooth, without using any special device.

Abstract: A gypsum composition for denture investment consists of 100 parts by weight of a mixture of 50-90 parts by weight of .alpha.-Gypsum hemihydrate (.alpha.-CaSO.sub.4.1/2H.sub.2 O) with 10-50 parts by weight of .beta.-Gypsum hemihydrate (.beta.-CaSO.sub.4.1/2H.sub.2 O) and 0.2-2.0 parts by weight of a soluble potassium salt. As the soluble potassium salt, use may be made of one or more of potassium sulfate, potassium chloride and potassium tartrate. The gypsum composition may further include 0.5-5.0 parts by weight of dihydrate gypsum.