Which of the following is not true about casting gypsum bonded investment material:
A. It is used for cast metal alloys
B. 50 - 65% of gypsum changes to form α-hemihydrateC. The investment material is not heated above 700° temperature
D. Heating above 700° of investment causes formation of sulphur dioxide from copper sulphate.
Ans. (B) 50 -65% of gypsum changes to form
a-hemihydrate:
The essential ingredients of the dental inlay investment
employed with the conventional gold casting alloys are ot-hemihydrate of
gypsum, quartz or crysloballite which are allolropic forms of silica.
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BAWA'S INSTITUTE FOR DENTAL SCIENCES