The Role Of The Chemistry Of The Oxide Surface Layer Of Ipsd.Sign Alloys On The Quality Of Ipsd.Sign Glass Ceramic Coatings

Experiments were performed at the NYS College of Ceramics at Alfred University and at Ivoclar North America on a series of Glass Ceramic compositions using three IPSd.SIGN alloys; Alloy I (high gold content), Alloy II (a palladium-based alloy), and Alloy III (a palladium-silver alloy). Of these, Alloy I exhibited anomalous behaviour compared to the other alloys in the series in terms of both measured surface properties and in the integrity of the glass-ceramic opaque layers that are fixed to the alloy to make dental restorations. While alloy I contains about 1% of zinc metal, chemical analysis of the oxidized surface showed that the zinc content exceeded 40%. Zinc oxide semiconductors can be formed by the oxidation of zinc and subsequent heat treatment in the presence of zinc. The hypothesis of the present might be responsible for the defects seen in the opaque layer. Glancing angle X-ray diffraction of the oxidized surface of Alloy I showed, beside the peaks of the alloy crystal structure, an unidentified peak at 33.9 degrees, This peak could only be identified as a major peak in one of two phases; a defect platinum oxide structure or a non-equalibrium phase of ZnO. To further investigate the hypothsis opaques were fired onto varistor grade defect ZnO and pure ZnO pellets manufactured from pressed powder sintered at 1200 degreed C for 3 hours. Some bubbles were observed in the film on the pure ZnO.