objective: To study the metal ceramic bond of reused surplus alloy of a precious metal ceramic alloy. Methods: The samples in control group for reused surplus alloy were treated by only remelting without adding any fresh alloy up to four generations, those in the test group by adding one third fresh alloy in each generation and up to four generations. Metal ceramic bond strength of the samples was surveied by pull shear test. Results: In control group, the pull shear bond strength (MPa) from generation Ⅰto Ⅳcastings was 47.53?2.02, 33.23?2.03, 25.08?1.88 and 14.61?1.56 respectively( P

Objective: To investigate the influence of repeated infiltrating on the microstucture of In-Ceram alumina substrate. Methods:6 disks of aluminum oxide with the height of 3 mm and diameter of 12 mm were perpared and infiltrated with infiltrating glass for 0～5 times for each disk respectively.The fractured surfaces of the samples were observed by scanning elctron microscope. Results:After sintering,a net -shaped porous coping of alumina was formed. The glass infiltration resulted in a dense ceramic mass. The porous coping matrix was infiltrated with low-viscosity glass in void.3-time-infiltration resulted in the best results. Conclusion: With repeated infiltrating firing,the micro-stucture of In-Ceram alumina substrate may become a dense mass.

Objective: To study the ionic diffusion and the distri bu tion character in the interfacial area of aurogalvano form ceramic crown, and t o discuss the bond mechanism of porcelain fused to 99.9% gold. Method s: The ionic diffusion and the distribution character in the interfac ial area of aurogalvano form ceramic crown were observed by electron probe and scanning electron microscope. Results: The examination wit h electron microprobe showed that from gold to porcelain aluminum ascended from zero to peak value, aurum dropped from the peak value to zero, and the bandwidt h was about 3～4 ?m.There were obvious mechanical table and tuber. C onclusion: There is ionic diffusion and no crack in the interfacial a rea;there are physical and chemical combinations between porcelain and 99.9% gol d.