I had it done by the dentist years ago using the trays and gel. Had to sleep with them for 2 weeks. Fantastic results.
Lately I tried Crest Premium and saw very little results. The only bonus is that Crest will refund your money if not satisfied.
If you think about it using the dentists method with the gel on your teeth for 8 hours a treatment for 14 days would obviously be more effective than 1/2 hour a day. I wish for miracles.