Crest Whitening Strips have been clinically proven to whiten teeth and from experience, I have to say they really do! Just two weeks and my teeth were shining and white. Its almost effortless and it gives you so much more self-confidence. Have you stopped smiling? Well it's time ti whiten up that smile and to show your teeth again. Its harmless and it worked wonders for me, all I can say is you have to try this. You have nothing to lose and a bright smile to gain.