Why Does Chewing Tin Foil (AKA Aluminum Foil) Hurt Your Teeth?

Some dental amalgams contain up to five dissimilar metals. Galvanic action between the metals different electrical potentials creates a electric cell in the tooth, which can generate currents of up to 10 microamps, a huge spike over normal body nerve currents of 3 microamps. People with extensive fillings can actually measure a weak voltage in their mouth from this action. This is all fine and dandy, until an outside element is introduced.

When the aluminum is introduced by the foil, it acts as an anode to the filling's cathode. The natural electrolytes present in saliva create a 'salt bridge' and the magic happens. The contact essentially short circuits the cell. A weak current flows between the electrodes (tooth and tinfoil) and is detected by the sensitive nerve of the tooth as an unpleasant sensation. Zap. To accompany the shock, a metallic taste can also be generated by tin ions released by the reaction.

Another interesting dental electrical reaction is the reason that it is rare for people to have both gold and amalgam fillings at the same time. In this case, a gold filling would act as a cathode, and the amalgam would be the anode. Zap again, with the added bonus of having the anode filling corrode each time. It would soon need replacement.

...the pain tinfoil creates feels like an electric shock in the sensitive root nerves of the filled tooth. This description is very accurate. It is an electric shock, of up to 2 volts.

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