Inert metal, resin
Partial dentures are combination of nickel, cobalt molybdenum alloy for the metal and a polymer, monomer resin that is heat polymerized under pressure to make it rigid and dense.
The teeth are also made of resin or ceramic. The materials are highly polished to make them impervious to stain and odors as well as smooth to the tongue. Over time, the polish erodes and materials deteriorate.