Why does it hurt when you touch a filling with something metal??

Question

Why does it hurt when you touch a filling with something metal eg. a spoon??

Answer 1

Probably because a nerve is exposed if there is deep decay in it.

Answer 2

Galvanic shock

When aluminium foil makes contact with some amalgam fillings, saliva in the mouth can act as an electrolyte. This can generate small electrical currents which are felt through the nerves in the tooth as (often extremely painful) electrical "jolts" or shocks.

from wikipedia

Answer 3

that sucks....you have a 'silver' filling?  i have the white ones  and a tongue ring .. never experience any pain ...  

Answer 4

The two metals creates static electricity that shoots to the nerve and causes pain.