TOYODA Johji Tohoku University, School of Dentistry, Assistant Professor, 歯学部・附属病院, 助手 (00250796)
ISHIBASHI Minoru Tohoku University, School of Dentistry, Assistant Professor, 歯学部, 助手 (40231138)
OKUNO Osamu Tohoku University, School of Dentistry, Professor, 歯学部, 教授 (50014080)
|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1994 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1993 : ¥1,400,000 (Direct Cost : ¥1,400,000)
In recent years, Heratec Crown and Degusint has been realized by the baking of porcelain onto sintered precious metals. These products possess characteristics of both porcelain jacket crowns and porcelain fused to metal crowns, and ceramic crowns (Heratec Crown and Degusint) can be accomplished in a comparatively short period of time. Heretofore, we have performed fundamental research in this field in terms of both the accuracy and the strength of ceramic crowns in which these sintered precious metal are used. As a result, it has become clear the such crowns, compared with porcelain fused to metal crowns, manifest significantly lower strength. Concerning the improvement of crown strength, results of the reserch done in our laboratory show that the strengthening of the inner portion of the crown is more effective than strengthening of the outer portion. It is thus thought that the strength of thesesintered precious metal fused ceramic crowns is a product of insufficient strength of the
precious metal layr and ofthe porcelain and metal joint.
Thus, a detailed study of these strength was conducted this year. Examination of each type of sintered precious metal suggested that the strength of the strength of the crowns involves the differences in tensile strength and elastic modulus. Moreover, with regards to the joint between metal and porcelain, as a result of observations by SEM and EDX,it became clear that even through Heratec Crown have only a simple mechanicaljoint between the metal layr and the porcelain layr, and the Degusint posesses a fusing mechanism, the distribution of Indium involved in the fusion is different from that in porcelain fused to metal crowns.
While the advantages of sintered precious metals are being brought to light, we plan to carry out research and development of these metals with such qualities as a proper degree of elastic modulus, high strength, elongation to some extent, secure fusion to porcelain, etc., with which we can gain sufficient ceramic crown strength, and proceed in research on their accuracy of fit.16FA01 : Veneered Crown Less