Functional appliances: mode of action and clinical use.

Functional appliances are frequently used in the treatment of Class II division 1 malocclusions, either in isolation or, more commonly, before a course of fixed appliance therapy. Extensive speculation and investigation into the precise mode of action of these appliances has recently focused on their growth-restraining effect on the maxilla, their growth-enhancing effect on the mandible and dentoalveolar and soft tissue effects. The different types of functional appliances are described in this article, with emphasis placed on practitioners adopting a component approach to design. A checklist is provided to aid identification of the more common problems occurring during treatment.