There are a few metallic-type things dentists use ... bridge, spacer, braces, retainers ... any of these strike a chord?
Crown? Those aren't generally silver, though - they're meant to match the colour of your teeth.
Grillz? It doesn't have to be silver though, it can be gold, or platnum.
yess! i thought they said crayon lol
its start with a c...
A sealant?
Sealant.