silver fillings and aluminum foil

OUCH!

Q. Can any one tell me why we get like electric shocks or whatever when we chew on a piece of aluminum foil (with silver fillings in a couple of teeth)?

A. From Joe Schultz: That is exactly what you get...an electric shock. The filling is
made of an amalgam of mercury and either tin or silver. When the aluminum
foil touches the filling, a galvanic cell is created in the mouth. Aluminum
is the anode, the filling is the cathode and the saliva is the electrolyte
'salt bridge.' The contact essentially short circuits the cell and a small
amount of current flows which is sensed by the nerves in the teeth. There is
the pain you feel.