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KMID : 0362220130400030205
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Journal of The Korean Research Society for Dental Materials
2013 Volume.40 No. 3 p.205 ~ p.213
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Effect of complete firing cycle, rebake and holding condition on the hardness and microstructure of the Au-Pd-Ag metal-ceramic alloy
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Cho Mi-Hyang
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Abstract
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The aim of present study is to evaluate the changes in hardness and microstructure of the Au-Pd-Ag metal-ceramic alloy for fusing porcelain after simulated complete firing with controlled cooling rate, rebake and holding treatment at various condition by means of a Vickers hardness test, microscopic observation, X-ray diffraction study, and dispersive X-ray spectrometry analysis. The hardness value increased by the oxidation treatment, and then decreased slightly during simulated complete firing. The hardness value of the specimen rebaked by three times after simulated complete firing was similar with that of the specimen after complete firing, therefore the hardness decrease was irrelevant to repetitive firing. The particle-like precipitate increased from the oxidation stage, and it was maintained during the complete firing, the repetitive firing and the holding treatment. The hardness increased when the specimens were holding-treated at the temperatures of 400℃, 500℃, 600℃ and 70 0℃ for 35 min after complete firing. For the specimen treated at the holding temperature of 700℃, the holding time was efficient under 25 min, because the hardness began to decrease after 25 min by a rapid atomic diffusion at the temperature. In the process of making a prosthesis, the efficient application of the holding time and the holding temperature further enhance the mechanical properties of the material, ultimately, it can contribute extending the life of the prosthesis.
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KEYWORD
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cooling rate, firing cycle, hardness and microstructure, holding time, rebake
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