Discussion
Ag–Pd–Cu–Au alloys are clinically used mainly for
inlays, crowns and bridges. The corrosion resistance
of Ag–Pd–Cu–Au alloys generally is lower
than the resistance of high-gold alloys, but
excellent among substitute alloys. The noble
metal contents of 12% Au and 20% Pd by weight
appear to provide adequate corrosion and tarnishing
performance.9 Because of the still relatively
high cost of these alloys, recycling of restorations
is desirable, if it can be accomplished without
degradation of the alloy properties. Such degradation
may result from changes in composition
and microstructure as the alloy is remelted and
recast.