I tried them without much success, found better results getting Bright Smile at the Dentist and then using a whitening toothpaste to maintain. The bitch about professional whitening is the dull ache you feel for about 12 hours following the procedure and for 24 hours you can only eat white foods and clear liquid until the tooth enamel or film over your teeth is restored, cause the bleaching fucks it up. If you want instant results go for professional whitening, cause your pissing money away with over the counter products, and in allot of cases, especially this time of year Dentist and teeth whitening outfits are offering specials for a couple hundred bucks or about the cost of 3 or 4 Crest kits, I actually just got a e-mail the other day from my Dentist with a whitening special.