I have had stains from tertracyclene given to me too young and my teth were also naturally very yellow--not my imagination, people would ask about it. When Crest Whitestrips first came on the market, I somehow got in on it as a test product. I loved it, the differnce was dramatic and it actually removed or somehow masked the gray tertacyclene stains.
Since then I have tried many different products in renewing and maintaining my white teeth including two dentist-procured products. I find the best products are indeed Crest Whitestrips and this stuff called "5 minute" something or other that you can get at the grocery store for $5. I use it in my trays from the dentist. for on the go i use whitestrips bcs they ocme in those tiny sealed packets and tak eup no room.
SENSITIVITY - I experienced sensistivity with all of the products I tried. To counteract this I have had thebest luck with ACT flouride treatment, or the store brand. Use the ACT for a few days BEFORE you start whitening and immediatley before you apply the whitening gels. if it still hurts later on, like mine usually does, bring some act with you and rinse with it during the day.