title: Porosity determination of cast investment by a wax-infiltration technique.
abstract: A reproducible method of determining the porosity (pore volume) of cast investment materials is described. This procedure, requiring no highly specialized equipment, involved the infiltration of a test sample with paraffin wax and the weighing of the wax-infiltrated sample in both air and water. Pore-volume wax is then extracted with chloroform and the sample reweighed. The difference in weight is used to calculate the porosity of the investment material. Pore-volume data thus obtained are comparable to those resulting from standard techniques and far more sophisticated (and expensive) instrumentation. The porosities of hand-mixed samples of gypsum-bonded, phosphate-bonded and silica-bonded investments were 53.9 per cent, 36.9 per cent and 31.4 per cent and those of the vacuum-mixed samples were 52.5 per cent, 31.3 per cent and 26.9 per cent, respectively. The results show that gypsum-bonded investments were more porous than phosphate-bonded investments while silica-bonded investments were the least porous. Hand-mixed samples appeared to have greater porosity than vacuum-mixed samples.
authors.forename: M I
authors.initials: MI
authors.lastname: Abu Hassan
authors.forename: J C
authors.initials: JC
authors.lastname: Jones
authors.forename: A S
authors.initials: AS
authors.lastname: Hallsworth
mesh_terms: D002133:Calcium Sulfate; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003734:Dental Casting Investment; D010710:Phosphates; D012822:Silicon Dioxide; D013499:Surface Properties; D014618:Vacuum; D014885:Waxes
chemical_list: D003734:Dental Casting Investment; D010710:Phosphates; D014885:Waxes; D012822:Silicon Dioxide; D002133:Calcium Sulfate