貴金属と非貴金属を下地とする焼付陶材冠の色調変化

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Ceramo-metal restorations are well established by effectively combining the advantages both of the esthetical appearance of porcelain and the high strength of metal structure. Precious alloys have been used successfully as metal substructure for these two decades. Recently, nonprecious Ni-Cr alloys have been developed as substitute for precious alloys, and many investigations are being pursued on the substitute alloys in relation to fabrication, marginal fit, bond strength and esthetics. Particularly great interests and demands are now directed to the esthetics. This study, therefore, was designed to find the effect of the substructure metal on color performance of the porcelain. Substructure was fabricated with a precious or nonprecious commercial alloy. Two brands of porcelains were fired individually on each substructure. Both of the porcelain powders were of the same shade guide number. On opaque firing, two different procedures, i. e., one-firing technique and Stein's skim technique, were employed. The thickness of the fired opaque layer was settled to 0.1, 0.2 or 0.3 mm. Dentin and enamel layers were built up in different proportion of thickness so as to be 1.2 mm thick in total. Specimens having precise thickness were prepared by careful grinding after firing. Data obtained from color analyses were converted into CIE standard colorimetric notations and Hunter color difference values. Skim technique was found to be more effective than one-firing technique for the opaque to hide the color of the substructure metal. Almost the maximum color hiding effect was obtained by the opaque of 0.2 mm in thickness and no marked differences could be detected with increase in thickness more than 0.2 mm. The body porcelain was significantly affected in color by the thickness proportion of the dentin and enamel layers as well as the thickness of the opaque. The color of the substructure metal seemed not to be completely eliminated by the opaque up to 0.3 mm in thickness, seemingly the maximum thickness for opaque layer in practice, and the inherent color of the alloy was still reflected in the color appearance of the finished porcelain. Delicate differences were also observed between the two different brands of the porcelains, although they were of the same shade guide number. It should be noted that these various factors may unexpectedly lead the ceramometal restoration to a different color from the indication of the shade guide.
九州歯科学会の論文
1983-02-25

著者

郭明毅
九州歯科大学歯科補綴学第2講座

貴金属と非貴金属を下地とする焼付陶材冠の色調変化

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