| 摘要 |
PURPOSE:To obtain an investment casting material having an adequately stabilized coefft. of thermal expansion for dental purpose by compounding gypsum, salt and cristobalite as well as quartz at a specific weight ratio each, adding further alumina thereto at a specific weight ratio and kneading the mixture with water. CONSTITUTION:30-40%, by weight, gypsum which permits easy adjustment of the coefft. of thermal expansion and exhibits substantially a binder effect, 0.6-1.5%, by weight, salt which suppresses the shrinkage of the gypsum, 40-52%, by weight, cristobalite which has a large coefft. of thermal expansion and fills the inside of a casting mold together with the quartz and 4-20%, by weight quartz are compounded. <=8%, by weight, alumina which contributes to an improvement in fire resistance is further added thereto and the mixture is kneaded with water. The investment casting material produced by such compounding is usable as a good casting mold for dental purpose and contributes to a considerable increase in applicable kinds of casting alloys. |
