Study of gypsum-bonded casting investments. Part 2.

The simultaneous differential thermal analysis--thermogravimetry (DTA-TG) method used in Part 1 of this two-part study was extended to analyse two gypsum-bonded dental casting investments, Kerr Cristobalite Inlay and GC Cristobalite Micro. Both investments had a similar cristobalite content of about 70 per cent. The remaining 30 per cent was dental stone in GCM, and a mixture of plaster and dental stone in KCl. Inclusion of plaster in KCl appeared responsible for the greater amount of water required for mixing this investment. The DTA-TG method used in the present study can be applied to identify the type and amount of hemihydrate, and the type of silica, in currently available gypsum-bonded investments.