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Speaker 1: Welcome to Brainstuff from house stuff works dot com where

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Speaker 1: smart Happens. Hi Am Marshall Brain with today's question, why

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Speaker 1: is it that biting on aluminum foil can be painful?

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Speaker 1: Biting on aluminum foil can be painful, and it's usually

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Speaker 1: noticed if you have metal in your mouth from things

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Speaker 1: like fillings or crowns. Basically, when you bite on foil,

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Speaker 1: you set up a battery in your mouth and the

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Speaker 1: electrical current stimulates nerve endings in your tooth that generates pain. Specifically,

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Speaker 1: here's what happens. First of all, the pressure from biting

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Speaker 1: brings two different metals, in this case aluminum foil and

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Speaker 1: mercury in your fillings or gold in your crowns, in

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Speaker 1: contact with each other in a moist salty environment. The

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Speaker 1: salty environment is provided by your saliva. The two metals

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Speaker 1: have an electric chemical potential difference between them, or a

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Speaker 1: voltage that gets generated because they're coming into contact with

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Speaker 1: each other. The electrons flow from the foil into the tooth,

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Speaker 1: so you have this electrical current created by this little

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Speaker 1: battery flowing into your tooth. The current gets conducted into

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Speaker 1: the tooth's root, usually by the filling or crown, and

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Speaker 1: the current sets off nerve impulses in the roots nerve.

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Speaker 1: Those nerve impulses go to your brain, and then finally,

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Speaker 1: the brain interprets those impulses as pain. The production of

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Speaker 1: the electric current between two dissimilar metals like this is

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Speaker 1: called the Voltaic effect after Alessandro Volta, who discovered it

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Speaker 1: long ago when he was creating early batteries. He made

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Speaker 1: them by stacking dissimilar metal discs with blotterer paper soaked

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Speaker 1: in salt water between them. This was called a voltaic pile,

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Speaker 1: and it was an easy way to create a simple

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Speaker 1: and very low power battery. If you have no metal

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Speaker 1: dental work in your mouth, you're not going to feel

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Speaker 1: this effect. You've got to have these two dissimilar metals

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Speaker 1: coming together for you to feel the pain that aluminum

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Speaker 1: foil causes. Be sure to check out our new video podcast,

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Speaker 1: we explore the most promising and perplexing possibilities of tomorrow.

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