The Effect Of Recasting On Metal-ceramic Bonding Of The Non-nickel-based Ceramic Alloys

Objective：The aim of this study was to evaluate the effects of recasting on thethe metal-ceramic bond strength, the failure mode and the metal-ceramicinterface of the non-nickel-based ceramic alloys.Methods: The non-nickel-based alloys provided by manufacturers were cast for1-3times without adding new alloys under the circumstance of vacuumcompressive casting with argon. Porcelain was applied on the metal substrate.Half of the specimens from3generations were randomly selected to subject thethermal cycling. Force to failure was evaluated by shear test. The metal surfaceof fractured specimen was examined with a stereomicroscope to classify thefailure mode. The metal-ceramic interface of specimens without thermal cyclingand shear test from3generations was observed with the scanning electronmicroscope (SEM) and the elements diffusion in the metal-ceramic interfacewere analyzed with energy dispersive X-ray spectroscopy (EDS).Results:(1) After casting1-3times, no significant difference was found in bondstrength of Co-Cr, cpTi, Pd-based and Au-Pt alloys (P＞0.05). No significantdifference was found in bond strength of Co-Cr, Pd-based and Au-Pt ceramicalloys after thermal cycling (P＞0.05), while cpTi was significantly decreased(P＜0.05). The interaction terms between the recasting and thermal cycling werenot statistically significant (P＞0.05).(2) No statistical differences in the failuremode of Co-Cr, cpTi, Pd-based and Au-Pt alloys that had been cast for2-3times,when comparing to that of the alloys being cast for1time (P＞0.05). Mostspecimens of Co-Cr and cpTi alloys exhibited the adhesive failure, and a few ofthem exhibited a mixed failure. All specimens prepared from Pd-based alloyshowed mixed failure. The specimens of Au-Pt alloy were mostly mixed failure,and a few of them were cohesive failure. According to the bond strength valuesand the number of specimens in different failure modes, there was no correlation between the bond strength and the failure mode.(3) After casting1-3times, noobvious change was observed in the microscopic structure betweenmetal-ceramic interface of cpTi, Pd-based and Au-Pt alloys. Compared with thefirst generation of Co-Cr alloys, the second generation had no significantdifference in the microscopic structure between metal-ceramic interface, whilethe third generation was local flawed. After casting1-3times, no significantdifference was found in the elements diffusion width at the metal-ceramicinterface of Co-Cr, cpTi, Pd-based and Au-Pt ceramic alloys. In the oxidationlayer of Pd-based alloy, the Ga spectrum peak of third generation was lower thanthe first and second generation.Conclusion: Under the circumstance of vacuum compressive casting with argon,no significant difference was found in the bond strength, failure mode andelements diffusion width of Co-Cr, cpTi, Pd-based and Au-Pt alloys. Nosignificant difference was found in the bond strength of Co-Cr, Pd-based andAu-Pt alloys after thermal cycling, whereas cpTi significantly decreased. Noobvious change was observed in the microscopic structure betweenmetal-ceramic interface of cpTi, Pd-based and Au-Pt alloys after recasting1-3times. After recasting3times, the interface of Co-Cr alloy was local flawed.