Why does aluminum foil "electrocute" dental fillings? This is probably one of the weirdest questions on here. When I was a kid, I put aluminum foil in my mouth (maybe it was still attached to some food or something, I don't remember.)

Anyway, it made my mouth feel like I'd licked a 9-volt battery. Being the natural born scientist, I repeated the procedure with similar results.

Why does this happen? I really think it has something to do with my dental fillings since the sensation occurred near them.
Ouch...  actually a known phenomenon.  Between the foil of aluminum/Al, and the metal filling of amalgam in your tooth, you created a little electrochemical cell.  Your saliva served as an electrolyte and your nerves around sensibly detected the current. This already "works" with little splinters of Al foil wrapping chocolate (obviously, it was not a small Hershey bar), yet is less powerful than the said 9 V block.

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