whitening

Pool Boy has offered to get my teeth whitened for a present. I've always had rather yellow teeth, the whole famly kind of has yellow teeth. I just don't know if this really works or not. My denist is a really nice guy, but honestly, it's a lot of money and I've read it can take many...

There have been gum on the market for a while now, that claim it will make your teeth become whiter. Is this just some market trick, or does it actually whiten teeth in time? And if so, how long will the effect last? Permanently? Peter :)