There are two types of whitening toothpastes: those that will maintain whiteness, and those that will actually remove stains. Most of the whitening tooth pastes on the market are really only suitable for maintaining whiteness; although they might remove a little bit of stain, it will not be very noticeable.
Some whitening toothpastes do actually remove a significant amount of stains. These toothpastes contain a bleaching agent, such as hydrogen peroxide, and usually guarantee drastically whiter teeth in two weeks. These toothpastes are very easy to use, very inexpensive, and are able to white even the rather hard-to-reach parts of crooked teeth. However, the whitening chemicals do come into contact with the gums, and it is easy to accidentally swallow the toothpaste.
Talk to Your Dentist
If you are worried about the possible risks associated with teeth whitening, or if you are just not sure which option is best for you, consult you dentists.