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  • Title: Surface analysis of porcelain fused to metal systems.
    Author: Johnson T, van Noort R, Stokes CW.
    Journal: Dent Mater; 2006 Apr; 22(4):330-7. PubMed ID: 16087227.
    Abstract:
    OBJECTIVE: The effect of four different, commonly performed, metal-ceramic alloy, surface preparation stages, were investigated to observe surface compositional changes. METHODS: Two metal-ceramic alloys were examined (Pd/Ag alloy and a Ni/Cr alloy). Discs 12 mm diameter and 2mm thick were produced using the lost wax casting process. Prior to casting alloy ingots were examined using X-ray fluorescence spectrometry (XRF) to determine bulk composition. The four preparation stages were (1) devesting and Al2O3 blasted; (2) ground smooth and Al2O3 blasted; (3) oxidation firing; (4) firing cycle for opaque porcelain application. X-ray photoelectron spectroscopy (XPS) surface analysis was performed after each surface preparation stage to determine changes in surface composition. SEM with EDS was also used to identify surface composition. RESULTS: XRF and manufacturers compositional analysis of the alloys showed similar findings for the major elements. XPS analysis showed that at preparation stages 3 and 4 evidence of elemental migration to the surface (In with Pd/Ag alloy and Cr and Mn with Ni/Cr alloy). Alumina was also seen on the alloy surfaces, with SEM/EDS confirming Al2O3 particles embedded in the surface of the alloys. SIGNIFICANCE: Surface composition is very different from the batch composition. Surface preparation stage 3 is essential in bringing to the alloy surface elements which could be directly involved in the metal-ceramic bond. Elements and their oxides, in various forms, cover the surface of the alloys. Al2O3 particles can remain embedded in the alloy surface during porcelain application.
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