Removable appliances are usually made from a type of plastic material (acrylic) and are held in the mouth by metal clips within the acrylic that fit over the teeth at the front and back. Although many adults recognise these as "old-fashioned braces" (and mainly kept them in their pockets back in their own school days!) they still have an important role in 21st century orthodontic treatment – indeed Functional appliances are a type of removable appliance.
Before – incisor tooth in crossbite
After 6 weeks of removable appliance treatment – incisor crossbite corrected
Removable appliances are often used to reduce how much the teeth overlap in the vertical plane (known as an overbite) and are also effective at correcting the position of single teeth. In these two photographs you can see the effect that wearing an upper removable brace for 6 weeks has had on the position of the upper incisor tooth in this 7 year old patient.