How do those teeth whitening kits from Boots work?

And how long do they take?
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I don't know what Boots is, but I assume it's some kind of store. I do know that the over the counter tooth whitening kits do work very well on teeth that are yellowish or brownish, but not very well on teeth with a greyish hue. Our office recommends the Rembrandt or Crest brands, but I did see in another post that someone had good success with the Walmart brand. There are several types. Some kits only take a couple hours, some several weeks. The fast ones cost more. Just go to the store and start reading the instructions on the packages and decide how much you want to spend vs. how long you are willing to treat your teeth.
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