The whole copper thing goes back to when people thought the green staining from their copper bracelets was somehow curative of arthritis. It isn't. But this has carried over to today where we see ads for copper infused back and knee braces and even copper infused face masks. High copper levels can kill you but this generally a genetic disorder.
On the other hand, silver will kill bacteria (and werewolves) and a silver infused creme is frequently used on severe burns to prevent infections.
Gold is used in dentistry because of its malleability and resistance to corrosion. It only kills your budget.