[Application of gypsum-bonded investment containing niobium carbide on casting of alloy for metal-ceramic restoration].
Experimental gypsum-bonded investments containing 0.5-5.0 wt% NbC were prepared by mechanical mixing of each powder. Setting and thermal expansion measurement, compressive strength and casting accuracy for Ni-Cr alloy for metal-ceramic restoration were investigated. Analysis of NbC during heating was carried out by X-ray diffraction, TG-DTA and SEM. NbC was oxidized to Nb2O5 with a volume change between 300-600 degrees C, as in the following equation: 2NbC + 4 1/2O2----Nb2O5 + 2CO2 The theoretical volume of 1/2Nb2O5 calculated from the lattice constants according to JCPDS file was approximately 4 times larger than that of NbC. The experimental investments of 70 wt% cristobalite and 30 wt% gypsum containing 2.0, 3.0 and 5.0 wt% NbC showed large thermal expansion of 7.0, 10.0 and 13.0% respectively. The investment containing 2.0 wt% NbC showed nearly the same casting accuracy for Ni-Cr alloys for metal-ceramic restoration as the commercial phosphate-bonded investment.
Tsuruta
S
S
Department of Dental Materials Science, School of Dentistry, Aichi-Gakuin University.
Ban
S
S
Hasegawa
J
J
Hayashi
S
S
Iiyama
K
K
Yamamura
Y
Y
D002133:Calcium Sulfate; D002858:Chromium Alloys; D003734:Dental Casting Investment; D003735:Dental Casting Technique; D016876:Metal Ceramic Alloys; D009556:Niobium
D002858:Chromium Alloys; D003734:Dental Casting Investment; D016876:Metal Ceramic Alloys; D009556:Niobium; C073844:niobium carbide; D002133:Calcium Sulfate