Another option, instead of investing in expensive treatments, is to use a simple and safe at home remedy from products you may already have in your pantry or medicine cabinet.
Baking soda and hydrogen peroxide are both known for their whitening abilities. To get the most of benefit from baking soda, use it only twice a week, and mix it with some water and a touch of salt or lemon juice. Brush your teeth as you normally would and rinse immediately, this is definitely important if you use lemon juice, as it is acidic. To use hydrogen peroxide to whiten your teeth, mix it with water and use as a mouthwash.