[Steven Wasmer]

Steven Wasmer  asked the Naked Scientists:
   
Dear Naked Scientists,  

Fantastic program!  

I've been wondering why it is that if a piece of alumium from say, a chocolate wrapper hurts when it comes in contact with a metal tooth filling?  I've be listening to your podcast long enough to for a hypothesis. 

Does it have something to do with an electric current being produced between two different metals in a salt water solution (saliva)?  Keep up the fantastic work.  

Steven   Philadelphia PA      

What do you think?

[Geezer]

Does it have something to do with an electric current being produced between two different metals in a salt water solution (saliva)? 

I believe you are quite correct. Presumably the current is conducted into the nerve in your tooth by the filling, and OUCH!

In India they put quite a lot of metal in food at weddings, but they don't seem to have the problem because they don't have a lot of fillings (or at least that used to be the case).

[Bored chemist]

The metal in decorations is often silver and, since that's a large part of what fillings are made from there's less electricity generated.

[Donnah]

My dentist noticed that while scraping a tooth with his metal tool I got zapped with an electrical charge whenever the tool came into contact with the tooth beside it, which happens to be a gold crown.

You can get a dental compatibility test done which shows what dental materials are most compatible with your body.  I think it's a good investment because dental work is expensive and sometimes unpleasant, so you want best results.  An allergy to dental components can create a medical mystery.

[Donnah]

The metal in decorations is often silver and, since that's a large part of what fillings are made from there's less electricity generated.

I thought silver was a very good conductor of electricity.

[Bored chemist]

The metal in decorations is often silver and, since that's a large part of what fillings are made from there's less electricity generated.

I thought silver was a very good conductor of electricity.

Silver is a very good conductor. But the electricity is created by a pair of different metals an the silver in fillings isn't different from the silver in the decorations.