Abstract:
Currently, feldspathic porcelain for dental restoration has been imported and its demand has increased every year. In this research, the dental porcelain was attempted to synthesize. Two parts of experiment were provided for this study. The first section concentrated on selecting the raw materials and their sources. The main materials such as potash feldspar, clay, quartz and frit were investigated on their chemical components, phase and firing properties, i.e. color, fusion and thermal expansion. The second part was to synthesize the feldspathic porcelain from the selected raw materials by changing the compositions and firing schedule to achieve Leucite phase as obtained from the commercial VMK95 dental porcelain. In addition, the coefficient of thermal expansion, the chemical solubility in vinegar and thermal shock resistance of synthesized porcelain and VMK95 were compared. The results showed that Nepheline Syenite, potash feldspar KM85, Ranong china clay, Frit FP606, FP660 and 502000 were used to synthesize the feldspathic porcelain. This selection was based on %K2O,%total flux and its fusion. In this research, synthesized Leucite determined from XRD could be obtained from the composition of 84 %Nepheline Syenite, 6%quartz, 5%Ranong china clay and 5%FP606. The optimum firing schedule was 1185-1210 degrees celsius and then slowly to 1000 degrees celsius before quenched down to below the temperature of quartz inversion. To achieve the transformation of cubic to tetragonal Leucite, slow cooling was required from 500-270 degrees celsius. The solubility of synthesized feldspathic porcelain in 5% distilled vinegar was less than 0.1% as compared to that of VMK95, only 0.006%. For the thermal shock resistance by quenching from 200 degrees celsius ice water, the microcracks appeared in both of synthesized feldspathic porcelain and VMK95.