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Objectives To test the wear of enamel against Yttria Tetragonal Zirconia Polycrystals (Y-TZP) in comparison to the wear of enamel against a noble white high Palladium alloy. Methods A total of 20 specimens were used, 10 of Y-TZP and 10 of High Palladium alloy, both were subjected to 202,800 contacts against an enamel rod 2 × 2 mm in cross section under a mean load of 475.04 g leading to a mean force of 4.66 N in a Wilson Wear Machine. The specimens were kept in Dulbecco's phosphate buffered saline at a pH of 7 and the enamel rods were measured before and after the experiment for loss of enamel height (mm). Results The mean wear caused by the Y-TZP and the High Palladium alloy tested was 0.0912 mm, and 0.0113 mm respectively. This difference was statistically significant (p = 0.012 (p Significance It is recommended that Y-TZP is not to be used to form the occlusal surfaces of indirect restorations due to its high abrasive potential with respect to dental enamel.

In the course of contract research at our laboratory several investigations of metal-hydrogen systems have been carried out. The experience from these constitutes a major part of our reserach background for present work on metal hydrides for storage purposes. This paper gives a short account of some of our findings which have not been published or have been reported superficially only in a different context. A procedure for hydriding Zirconium and Zirconium alloys is described and results from development of Hydrogen-permeable Palladium-Boron alloys are presented.

The feasibility of using palladium alloy membranes in a diffusion cascade in order to separate the H, D and T in the exhaust stream of a fusion reactor is discussed. Values of the permeation separation factor are estimated for Pd - 20% Ag from available data and corresponding estimates for the necessary number of stages and the total membrane area are given for the required isotopic purification. The results show the advantage of operating at low temperatures and pressures and show that the method is perfectly feasible. The use of Pd - 8% Y will probably further improve the performance.