Do you have a gold restoration next to the tooth that is bothering you?
You might want to go back to your dentist and get it checked out. I've never heard that before. It doesn't sound serious but a possible adjustment/polish might do the trick.
You know how that the silver fillings are sensative to something like putting a fork in your mouth and accidentally scraping it against that filling, well thats what it feels like constantly. I hope I explained it better.
A piece of tin foil? Do you mean that it feels like there's something stuck on the top/bottom of your teeth when they bite like a piece of tin foil? I don't understand how tin foil is sensitive.