[Effects of the firing temperature on the color and strength of metal bonded porcelain].

There are many reports on the optical properties of natural teeth and fused porcelain. However, only few studies have been reported on the relationship between the firing temperature, and the optical and mechanical properties of metal bonded porcelain. This is a study of the effects of the firing temperature on the optical and mechanical properties of two groups of porcelain, each of which has five kinds, opaque, body, incisal, transparent and glaze respectively. The results were as follows: 1. The chief ingredient of each porcelain was leucite (K2O . Al2O3 . 4SiO2). Some other components were metal oxides used as pigment and opaque, for regulating the recrystallization of leucite in the fused porcelain, for controlling the thermal expansion, and for diffusing in the both sides of alloy and porcelain. 2. About 40% of each porcelain powder consisted of granular powder, smaller than 10 microns in diameter. 3. Measured by using a color analyser, L, a, and b values of all opaque porcelain did not depend upon the firing temperature. L value of the other porcelain showed decrease in proportion to the increase of the firing temperature. And it slightly decreased over 900-940 degrees C. 4. The firing temperature did not affect the transparency of the opaque porcelain. The transparency of the other porcelain increased in proportion to the increase of the firing temperature. And it also showed slight increase over 900-940 degrees C. The firing temperature did not affect the Heize values of the opaque porcelain. The Heize values of the other porcelain decreased in proportion to the increase of the firing temperature. 5. The compressive and diametral tensile strength of all the porcelain increased in proportion to the increase of the firing temperature to 910-940 degrees C. However, it decreased in proportion to the increase of the firing temperature over 910-940 degrees C. 6. It was confirmed by the SEM observations, microphotographs and X-ray diffraction of the fused porcelain that fully fusing between particles occurred at the firing temperature of 910-940 degrees C. And it was also confirmed by surface roughness.