teeth whitening?

2 of my teeth have gone a greyish colour.. theyve been like this for a while now. Is there any way i could get them whitened or bleached?
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Before looking at teeth Whitening I'd see a dentist to make sure the tooth is healthy it could be related to your diet. I have a friend who had one of his teeth whitened by using a product i suggested from this site http://www.teeth-whitening.com.au but go see a dentist first - let us know what he/she says
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