ABSTRACT
PURPOSE: The aim of this study was to test the modulus of elasticity (E) across the interfaces of yttria stabilized zirconia (YTZP) / veneer multilayers using nanoindentation. MATERIALS AND 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 5 µm (nominal tip diameter) spherical indenter was used with a UMIS CSIRO 2000 (ASI, Canberra, Australia) nanoindenter system to test E across the 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<.05) lower E value between Type-1 and Type-2 specimens at a distance of 40 µm 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. CONCLUSION: 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<.05) lower E. The present study has shown nanoindentation using spherical indentation and the multiple point load - partial unload method to be reliable predictors of E and useful evaluation tools for layered dental ceramic interfaces.
Subject(s)
Ceramics , Elastic Modulus , Hot Temperature , Methods , Microscopy, Electron, Scanning , Powder DiffractionABSTRACT
To measure the release of ions from fluoroaluminosilicate glasses, LG125, into deionised water and to compare the ion release from raw and acid washed glasses, taking account of the effect of acid wash on the ion release. Randomized Control Trials [RCT] Study was conducted at Department of Biomaterials in relation to Dentistry, Queen Mary University of London from Nov 2004 to Jun 2005. Specimens of experimental glasses, LG125 raw and acid washed [aw], were stored in polyethylene [PE] tubes at 37 °C in deionised water for a storage period of 1 to 28 days. Glass free solutions were collected after 1, 3, 7, 14, 21 and 28 days. The ions released were analyzed by Inductively Coupled Plasma-Optical Emission Spectroscopy [ICP-OES]. ICP-OES is a very powerful tool for trace metal analysis that uses the phenomenon of atomic and ionic excitation to determine concentration of ions in aqueous solutions. [a] Ions releases from the glasses were observed at all time intervals. The amounts of ion release were decreased over time and minimal quantities were seen in week four. [b] After acid wash the amount of release of fluoride [F] and aluminum [Al] ions were increased from the glasses while the release of Strontium [Sr] and Calcium [Ca] were decreased. [c] It was also seen that the acid washing enhances the release of F ions more than Al ions. Although the amount of Al was increased after acid wash but the concentration was too lower as compared to F ions. [a] Under both conditions substantial amounts of ions were released from the glasses but the release of ion were decreased after reaching a peak value. [b] F and Al were released more from aw glasses as compared to raw. [c] Release of Sr and Ca were greater from raw than aw