Clear aligners are orthodontic devices that are a transparent, plastic form of dental braces used to adjust teeth.Clear aligners have undergone changes, making assessment of effectiveness difficult. A 2014 systematic review concluded that published studies were of insufficient quality to determine effectiveness. Experience suggests they are effective for moderate crowding of the front teeth, but less effective than conventional braces for several other issues and are not recommended for children. 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 of the jawbone. They are also indicated for patients who have experienced a relapse after fixed orthodontic treatment.