Over the counter and dentist supervised at home products usually contain a lower strength bleaching agent. Usually, these products will have only 10 percent to 25 percent carbamide peroxide, which is the whitening agent, compared to 15 percent to 43 percent carbamide peroxide in whitening products professionally applied at the dental office.
Dentist supervised at home whitening trays are fabricated using an impression of your mouth. Each tray is custom made to fit your mouth exactly. This customization allows the whitening gel maximum contact with your teeth. However, over the counter tray whiteners use a “one size fits all” approach. The trays are not designed to fit your mouth exactly. Too large or too small of a tray can cause gum and soft tissue irritation and the whitening gels may not whiten teeth evenly.