Removable functional appliances such as a bionator/activator/twin block/Fraenkel improve severe bite issues in young patients, usually as a first phase (early treatment) of a comprehensive orthodontic treatment. They can either be made from separate upper and lower parts, which interlock, placing the lower jaw in a different position, or of one piece. Removable appliances such as a “plate” are used to improve the alignment of a couple of teeth or to expand an upper jaw.
Removable appliances are, in general, less precise and effective than fixed appliances; the success of treatment with removable appliances depends on the compliance of daily wear and the growth pattern/growth amount. Alternative devices and treatments are available and may include full fixed braces combined with headgear, teeth extractions, or severe cases, possibly jaw surgery when growth is finished.