Biting on aluminum foil can be painful. Why?

Key Takeaways

Biting on aluminum foil can be painful because it creates a voltaic battery in your mouth. This happens when the foil comes into contact with metal from dental work in a moist, saline environment like saliva.
This contact generates an electrical current that flows to the tooth's root, stimulating nerve endings and causing pain, especially if you have fillings, crowns or other metal dental work.
The effect, known as the voltaic effect, does not occur in mouths without metal dental work.

Biting on aluminum foil can be painful and is usually noticed if you have metal in your mouth from dental work (e.g. fillings, crowns). Basically, when you bite on foil, you set up a battery in your mouth and the electrical current stimulates nerve endings in your tooth. Here is what happens:

pressure from biting brings two dissimilar metals (aluminum foil, mercury in fillings or gold in crowns) in contact in a moist, salty environment (saliva)
the two metals have an electrochemical potential difference or voltage across them
electrons flow from the foil into the tooth (i.e. electrical current)
the current gets conducted into the tooth's root, usually by the filling or crown
the current sets off a nerve impulse in the root's nerve
the nerve impulse is sent to the brain
the brain interprets the impulse as pain

The production of electric current between two metals in contact is called the voltaic effect after Alessandro Volta, who discovered it. Early batteries were made by stacking metal discs together in a pile called a voltaic pile.

If you have no metal dental work in your mouth, you should not feel this effect.

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Frequently Asked Questions

Can other metals other than aluminum cause similar pain reactions in the mouth?

Yes, contact between other dissimilar metals in dental work and external metals can also create a voltaic battery effect, potentially leading to a similar pain reaction.

Are there any health risks associated with the voltaic effect in the mouth?

While the voltaic effect can cause temporary pain or discomfort, there is no evidence to suggest long-term health risks from occasional contact with dissimilar metals in the mouth.