Cosmetic
The most common type of home teeth whitening involves placing a gel-like whitening solution, which usually contains hydrogen peroxide, in a tray that resembles a Nightguard or mouth guard. Over-the-counter mouthpieces are unlikely to fit correctly and can cause gum irritation if the whitening agent seeps out. The tray is then placed over the teeth for a certain period of time, anywhere from an hour or two to overnight.