Abstract
Permeadility of eight dental casting investments was measured at high temperature by the equipment described in the second report.Also thermal expansion, which is essential to the production of correct dental castings, was measured by thermal mechanical analizer(TMA).In this report, the correlation between permeability and thermal expansion was investigated.The obtained results were as follows:(1)Permeability correlated to expansion during the heating.(2)Higher powder-liquid(water)ratios gave higher permeadility values.(3)Phosphate-bonded investments had little permeability in heating up to 200℃.(4)The colloidal silica mixes of investments and the addition of carbon to investments increased permeability.
