Ask A Scientist General Science Archive

Author:     ranger
Text:       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)?

Response #:  1 of 1
Author:      Joe Schultz
Text:        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.