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.
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.
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.
Do you have a gold restoration next to the tooth that is bothering you?