1980 Volume 5 Issue 3 Pages 119-126
Until recently porcelain fused to metal had been solely imported goods. Being developed by some Japanese mades, however, a few kinds of porcelain for fused to metal are now available in the market, Therfore, measurement of the bending strength, hardness and thermal expansion were made in three kinds of domestic made porcelain (UNIBOND, METALBOND and CERACHROME) and the clinically acknowledged foreign made VMK68.
The comparative investigation of their results led to the following conclusions.
1) Bending strength: VMK68, opaque colour porcelain was 1,080kg/cm2 and the other kinds UNIBOND and METALBOND were almost eqally strong being 1,120 kg/cm2 and 1,060 kg/cm2 each opaque colour. CERACHROME opaque colour was 860kg/cm2 that was inferior to the three kinds beforementioned. VMK68, UNIBOND, and METALBOND, dentin colour and enamel colour porcelain were inferior to opaque colour, CERACHROME enamel colour was strong to opaque colour and dentin colour porcelain.
2) Hardness: There was no obvious difference in the hardness of these porcelain, opaque colour and enamel colour porcelain were nearly 520Hv, dentin colour porcelain was around 500Hv. It was harder than natural enamel which was approximately 400 Hv.
3) In any porcelain the thermal expansion of opaque colour porcelain was the greatest, dentin colour and enamel colour porcelain were compared with that of the opaque colour was 0.2-0.5% lower.
4) In any porcelain the thermal expansion was smaller than that of metal alloy (KIK) within the range of temperature lower than the transformation point. At temperatures higher than the trnsfomation point, however, porcelain showed greater expansion than the alloy.
5) In the investigation of the physical properties of porcelain fused, VMK68 showed the most favourable results. Whwereas UNIBOND results showed as good as those of VMK68 and CERACHROME, and METALBOND suggested to have some problems.
