Characterization of the Interface Between Zirconia and Veneering Porcelain

Objective: To evaluate the interface between the zirconium oxide core and veneering porcelain using Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and X-ray Photoelectron Spectroscopy (XPS). Methods: Four zirconium oxide discs (e.max ZirCad, Ivoclar Vivadent) were sintered to make square specimens (1mm in thickness). A liner material (e.max Zirliner, Ivoclar Vivadent) was applied to two of the zirconia squares followed by pressable (e.max ZirPress, Ivoclar Vivadent) or manually applied (e.max Ceram, Ivoclar Vivadent) veneering porcelain. The other two squares were veneered as above but without the liner material. The specimens were cross-sectioned using diamond discs on Leica TXP, targeted sectioning and polishing unit (Leica Microsystems Inc). Before the surface analysis, the samples were pre-cleaned with a 1 keV Ar+ ion beam. The chemical composition changes along the interfacial areas of all the specimens were examined using ToF-SIMS (ToF-SIMS IV, ION-TOF Gmbh. Muenster, Germany) complemented by XPS (K-Alpha XPS, Thermo Scientific, East Grinstead, UK). Results: Oxygen was the main element present on both the veneer and core area. Sodium, Silicon and Aluminum were the dominant elements in the veneering porcelain, while Zirconium was the dominant element in the zirconia core. XPS analyses revealed total disappearance of the Aluminum and Sodium at the core region. On the other hand, a significant decrease (but not total disappearance) in the relative atomic percentage of Zirconium in the veneering porcelain region was detected compared to the core region. ToF-SIMS data reveals variations in zirconium chemistry in the interfacial region. Conclusions: The result of this study is indicative of chemical changes of the zirconium along the interface regardless of the veneering porcelain application technique or the usage of the liner. Further investigations are needed to confirm and explain these changes.

Supported by: University of Toronto, Faculty of Dentistry Research Committee Grant and Ivoclar Vivadent