Experience suggests they are effective for moderate crowding of the front teeth, but less effective than conventional braces for several other issues[n 1] and are not recommended for children.[further explanation needed] In particular they are indicated for "mild to moderate crowding (1–6 mm) and mild to moderate spacing (1–6 mm)", in cases where there are no discrepancies in the jawbone. They are also indicated for patients who have experienced a relapse after fixed orthodontic treatment.

Hydrogen peroxide (H2O2) is the active ingredient most commonly used in whitening products and is delivered as either hydrogen peroxide or carbamide peroxide. Hydrogen peroxide is analogous to carbamide peroxide as it is released when the stable complex is in contact with water. When it diffuses into the tooth, hydrogen peroxide acts as an oxidizing agent that breaks down to produce unstable free radicals. In the spaces between the inorganic salts in tooth enamel, these unstable free radicals attach to organic pigment molecules resulting in small, less heavily pigmented components. Reflecting less light, these smaller molecules create a "whitening effect". There are different products available on the market to remove stains. For whitening treatment to be successful, dental professionals (dental hygienists or dentists) should correctly diagnose the type, intensity, and location of the tooth discoloration. Time exposure and the concentration of the bleaching compound determine the tooth whitening endpoint.