Why does touching tinfoil with your teeth, especially when you have fillings, hurt so much?
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When your metal fillings meet tin foil, the body’s weak electrical impulses create a closed circuit and you have essentially form a weak battery. Remove the foil and it stops. You aren’t electrocuted but you will feel a slight buzzing. Your fillings must be pretty close to the nerve in your tooth so that would explain the hurt.
The same way a battery works- different metals hold their electrons with different strengths- so when your amalgam fillings touch the aluminium foil a current flows, which your nerves react to (contrary to the below it’s not the body producing the current).
Edit: More people need to remember the high school science lesson with the nail and the copper stick and the saltwater and the ammeter. And someone should really see about fixing that shower..
Edit II: The Revenge Of The Edit: I guess it /could/ be the body’s own electrode potential interacting with the foil if no fillings are involved. Also apologies for omitting the electrolyte in form of saliva. Was thinking of galvanic corrosion, which doesn’t require one. Is why aluminium and steel will corrode together over time in direct contact.
The fillings are what essentially forms a conductor, sending electricity through your gums.
Some people experience an extremely cold sensation rather than pain with tin foil, regardless of fillings. This is due to the metal in the foil being very efficient at conducting heat away from your teeth and creating a sudden sense of chill in your teeth. Try it, it’s kinda fun.
This is called [Galvanic corrosion ](https://en.m.wikipedia.org/wiki/Galvanic_corrosion)
The two metals (the aluminum foil and the amalgam filling) have different electric potentials, and in the presence of an electrolyte (ie saliva) a current is generated
You create a tiny galvanic cell (a battery) when you bring dissimilar metals together when they’re both bathed in a liquid conductor (your saliva). Electrons run from your mercury amalgam filling to the aluminium. You feel it as pain.
Two different metals (aluminum and silver) in your saliva creates a simple battery. This battery’s voltage causes a small electrical current that conducts through your tooth. This causes the pain you feel.
You create a galvanic cell in your mouth.
The filling in your teeth (mercury alloy) and the tinfoil (aluminium) are the two electrodes, and the saliva (pH range 6.2-7.6) is the electrolyte running the redox reaction.
In short, you have a battery in your mouth.
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