Do crest classic tooth whitening strips really work? how white can they get your teeth?

Yes: They can will restore your natural tooth color plus a shade or two whiter.

OTC whitening: In short, yes. Over-the-counter whitening kits do work. Your dentist may be able to provide a better result with a professional whitening system but many patients get good results with otc products.

Usually but...: They work for many but not for all patients. Their ability to whiten teeth varies. The darker the teeth, the less likely you will get the results you desire. There are limitations and precautions. Make sure you have no cavities and your gums are healthy. Fillings and crowns will not whiten. I strongly advise all patients to speak to their own dentist before using any otc products.