Gypsum-bonded investment and dental precision casting (III) Composition of investment for the quick casting technique.
A simultaneous differential thermal analysis and thermogravimetry method previously established was used to estimate the composition of gypsum-bonded investment marketed for the quick casting technique. Three commercial investments of this type were heated to 700 degrees C at 10 degrees C/min and the hemihydrate content was estimated by the mass decrease reached at 300 degrees C after subtracting the mass decrease at 100 degrees C as moisture content. The hemihydrate contents were between 25% and 30%, which appears to be the range also chosen for the conventional gypsum-bonded investment of cristobalite type over 70 years by the industry. However, the new type of investment contained both cristobalite and quartz. The small sample size is a disadvantage of the present method but this can be overcome by more frequent use of the method by investigators.
Mori
Toshiko
T
Department of Dental Biomaterials, College of Dentistry, Kyungpook National University, Samduk-dong, Jung-gu Daegu, South Korea. mori@knu.ac.kr
Aghajani
Farzaneh
F
D002133:Calcium Sulfate; D003734:Dental Casting Investment / Q000737:chemistry*; D003735:Dental Casting Technique; D004055:Differential Thermal Analysis; D006358:Hot Temperature; D011791:Quartz; D012822:Silicon Dioxide; D013818:Thermogravimetry; D013997:Time Factors; D014867:Water
D003734:Dental Casting Investment; D014867:Water; D011791:Quartz; D012822:Silicon Dioxide; D002133:Calcium Sulfate