If you want a whitening system that is professional level strength, your choice is limited to Crest Professional Effects, or Crest 3D White strips. Both strips are strong whitening agents that you would not be able to purchase at the dental prices. The strips that are currently being sold were an earlier version of the White Smiles strips (5 strips per package) and they provided tremendous whitening benefits with long lasting effects without a dentist. Crest Professional Effects uniquely adheres to your teeth. The adhesive bonds together strongly to maintain a close position between the strip and the teeth. The flexibility of the strips allow them to accommodate the surfaces of your teeth. The adhesive ability allows the strips to be effective and not displace during usage. In as little as 30 minutes a day in less than a month, results that are comparable to the dentist will be achieved. Complete results are noted after 20 days and a difference can be observed in less than 3 days.