Metal-ceramic Specimens Research Articles

赤外線ふく射方式陶材焼成炉に関する研究 第４報 金属・陶材の経時的温度上昇傾向について

The porcelain sintering on “Technomat” is considered to start from the metalceramic interface and proceeds to the surface of porcelain.The purpose of this study is to compare the thermal rising character of metal-ceramic specimen on “Technomat” and conventional furnace.A metal specimen without porcelain and a specimen with 0.5mm opaque and 2.5mm body porcelain powder, were arranged on the tray in each muffle. Three thermal couples (1.0mm wide, 0.15mm thick, CA thermal couple JIS) were set into the specimens (one thermal couple on the metal: 1 channel, one into the metal-ceramic interface: 2 channel and one into the body porcelain powder: 3 channel respectively).Normal firing procedure of each furnace was executed, while each thermal couple's change in temperature was recorded on Data Collector AM 7001 (Anritsu Co.). And we obtained the follwing results.1. On “Technomat” the temperature at the metal-ceramics interface (2 CH) during firing procedure was always higher than that of porcelain powder (3 CH) at the same time.2. As for the conventional furnace “Ace”, the temperature of metal (1 CH) and porcelain powder (3 CH) generally coincide during firing procedure. The temperature of metal cerami interface (2 CH) was always lower than that of porcelain powder (3 CH).3. Measurement of the metal-ceramic specimen's change in temperature during firing procedure revealed the differences of the heating character between two furnaces.

Influence of contraction mismatch and cooling rate on flexural failure of PFM systems.

The interactive influence of cooling rate and the sign and magnitude of thermal contraction difference between metals and ceramic veneers on bond strength have not been extensively analyzed, although numerous bond-test studies have been reported during the past two decades. A previous analytical study of residual incompatibility stress in bond-test specimens indicated that bond strength values may be of relatively little value if the residual stress state of the metal-ceramic specimens is not considered. The objective of this study was to determine the influence of cooling rate and contraction mismatch on the flexural failure resistance of metal opaque-porcelain strips. Specimens were subjected to four-point loading in an Instron testing machine until crack initiation occurred at the metal-ceramic interface. The residual stress states in the ceramic region were estimated from finite element stress analyses of the bond-test specimens by use of dilatometry data obtained at the cooling rate of 3 degrees C/min. The total stress induced from the residual stress and the applied flexural load was also determined for these specimens. Statistical analyses of the experimental data revealed that the slowly cooled specimens exhibited a significantly lower (p < 0.05) flexural strength compared with rapidly cooled specimens. Regardless of the cooling technique, metal-ceramic specimens with a negative thermal contraction difference (alpha m - alpha p < 0) failed at significantly lower (p < 0.05) flexural loads than did specimens with a positive thermal contraction difference.