Interfacial modulus mapping of layered dental ceramics using nanoindentation
The Journal of Advanced Prosthodontics
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Purpose: The aim of this study was to test the modulus of elasticity (E) across the interfaces of dental yttria stabilized zirconia (YTZP) / veneer multilayers using nanoindentation. Methods: YTZP core material (KaVo-Everest, Germany) specimens were either coated with a liner (IPS e.max ZirLiner, Ivoclar-Vivadent) (Type-1) or left as-sintered (Type-2) and subsequently veneered with a pressable glass-ceramic (IPS e.max ZirPress, Ivoclar-Vivadent). A 5μm (nominal tip diameter) spherical indenter was used with a UMIS CSIRO 2000 (ASI, Canberra, Australia) nanoindenter system to test E across exposed and polished interfaces of both specimen types. The multiple point load – partial unload method was used for E determination. All materials used were characterized using Scanning Electron Microscopy (SEM) and X – ray powder diffraction (XRD). E mappings of the areas tested were produced from the nanoindentation data. Results: A significantly (p<0.05) lower E value between Type-1 and 2 specimens at a distance of 40μm in the veneer material was associated with the liner. XRD and SEM characterization of the zirconia sample showed a fine grained bulk tetragonal phase. IPS e-max ZirPress and IPS e-max ZirLiner materials were characterized as amorphous. Conclusions: The liner between the YTZP core and the heat pressed veneer may act as a weak link in this dental multilayer due to its significantly (p<0.05) lower E. The present study has shown nanoindentation using spherical indentation and the multiple point load - partial unload method to be a reliable predictor of E and a useful evaluation tool for layered dental ceramic interfaces.