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. Clear-aligner treatment involves an orthodontist or dentist, or with home-based systems, the person themselves, taking a mold of the patient's teeth, which is used to create a digital tooth scan. The computerized model suggests stages between the current and desired teeth positions, and aligners are created for each stage. Each aligner is worn for 22 hours a day for one or two weeks. These slowly move the teeth into the position agreed between the orthodontist or dentist and the patient. The average treatment time is 13.5 months. Despite patent infringement litigation, no manufacturer has obtained an injunction against another manufacturer. Uses A 2014 systematic review concluded that there is insufficient evidence to determine the effectiveness of these clear aligners. Opinion is that they are likely useful for moderate front-teeth crowding. In those with teeth that are too far forward or backward, or rotated in the socket, the aligners are likely not as effective as conventional braces. More cases of relapse of the anterior teeth have been found with clear aligners compared with conventional braces. A 2013 Cochrane review found no high-quality evidence with respect to the management of the recurrence of lower-front-teeth misalignment following treatment. Clear aligners are more noticeable than lingual braces, but they can be removed, which makes cleaning of the teeth easier, and they are faster for the dentist to apply. Application Treatment begins with taking x-ray and photographs for diagnostic purposes, followed by capturing the patient's bite, teeth, and gums via a bite registration and polyvinyl siloxane impressions or an intra-oral digital scanner. The latter method has greatly increased in popularity in recent years as digital scanning technology has improved. The dentist/orthodontist completes a written evaluation that includes diagnosis and treatment