Dental prostheses are machined from a metallic body instead of being made by lost wax casting. Suitable gold base alloys have only base metal alloying additions which are more readily oxidized than gold and when combined with the gold can be age hardened. Exemplary metals include titanium, zirconium, yttrium and chromium. Scrap from the machining of a dental prosthesis is melted in air so that the base metals are all oxidized and substantially pure gold is reclaimed for reuse in new alloys.