Chromium Cobalt. Metal based removeable partial dentures and even sometimes full dentures have frameworks of metal. Usually chromium/cobalt. Fixed dentures such as bridge work is generally a high nobel metal specifically gold.
None usually. Unless it is a partial denture, metal is not used however, for partial dentures the metal is cobalt-chrome.
There are a few... Historically, removable partial and complete denture frames were composed of a gold alloy. This alloy has fallen out of favor due to its high cost. These days, the most popular casting alloys used for this purpose are chromium-cobalt alloys; the prototype was a proprietary product called "vitallium". This alloy combines strength, rigidity, resistance to corrosion, and bio-compatibility.