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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.

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    $\begingroup$ It's basically setting up a galvanic cell that involves a nerve root in your tooth. The term for it is actually "galvanic shock"! $\endgroup$ – airhuff Apr 4 '17 at 6:15
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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.

(one reference)

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  • $\begingroup$ Slightly off topic, but possibly based on similar electrochemical interactions in the mouth, some people have even reportedly picked up radio signals with their teeth & dental fillings! skeptics.stackexchange.com/questions/3638/… $\endgroup$ – theo Apr 5 '17 at 2:56
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    $\begingroup$ @theo I'm unaware if the gate-shaped metal detectors at the airport may be attuned to catch passengers with metal fillings in their teeth, yet this comment prompts me to think if other objects then the metallic filling of a tooth may be susceptible to electrochemical interaction. What about braces and dental bridges? What about voluntary piercing (across tongue, lip, cheek, etc), equally made of metal? Simply I do not remember if people invested in the later remove this decoration / attire, potentially acting as an electrode, prior to eating, drinking, kissing because of electrochemistry. $\endgroup$ – Buttonwood Apr 5 '17 at 10:18

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