Speaker 1: Welcome to Brainstuff from house stuff works dot com where
Speaker 1: smart Happens. Hi Am Marshall Brain with today's question, why
Speaker 1: is it that biting on aluminum foil can be painful?
Speaker 1: Biting on aluminum foil can be painful, and it's usually
Speaker 1: noticed if you have metal in your mouth from things
Speaker 1: like fillings or crowns. Basically, when you bite on foil,
Speaker 1: you set up a battery in your mouth and the
Speaker 1: electrical current stimulates nerve endings in your tooth that generates pain. Specifically,
Speaker 1: here's what happens. First of all, the pressure from biting
Speaker 1: brings two different metals, in this case aluminum foil and
Speaker 1: mercury in your fillings or gold in your crowns, in
Speaker 1: contact with each other in a moist salty environment. The
Speaker 1: salty environment is provided by your saliva. The two metals
Speaker 1: have an electric chemical potential difference between them, or a
Speaker 1: voltage that gets generated because they're coming into contact with
Speaker 1: each other. The electrons flow from the foil into the tooth,
Speaker 1: so you have this electrical current created by this little
Speaker 1: battery flowing into your tooth. The current gets conducted into
Speaker 1: the tooth's root, usually by the filling or crown, and
Speaker 1: the current sets off nerve impulses in the roots nerve.
Speaker 1: Those nerve impulses go to your brain, and then finally,
Speaker 1: the brain interprets those impulses as pain. The production of
Speaker 1: the electric current between two dissimilar metals like this is
Speaker 1: called the Voltaic effect after Alessandro Volta, who discovered it
Speaker 1: long ago when he was creating early batteries. He made
Speaker 1: them by stacking dissimilar metal discs with blotterer paper soaked
Speaker 1: in salt water between them. This was called a voltaic pile,
Speaker 1: and it was an easy way to create a simple
Speaker 1: and very low power battery. If you have no metal
Speaker 1: dental work in your mouth, you're not going to feel
Speaker 1: this effect. You've got to have these two dissimilar metals
Speaker 1: coming together for you to feel the pain that aluminum
Speaker 1: foil causes. Be sure to check out our new video podcast,
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