Yeah I react horribly to nickel! Any cheap jewelry causes me to get a rash and itch horribly in about 35 minutes. Even some 14kt gold that has more nickel in it than normal can cause this. Sterling Silver that isn't plated with rhodium will also do this to me. It's terrible! I've basically stopped wearing all jewelry except for my wedding band and engagement ring.

With an old mercury filling you have the risk of it breaking off and swallowing it! My fillings were only 2-3 years old and the dentist said they were already deteriorating.

I personally wouldn't keep any fillings in. =)