Orthodontic Retainers: Orthodontic appliances, fixed or removable, used to maintain teeth in corrected positions during the period of functional adaptation following corrective treatment. These appliances are also used to maintain the positions of the teeth and jaws gained by orthodontic procedures. (From Zwemer, Boucher's Clinical Dental Terminology, 4th ed, p263)Tooth Migration: The movement of teeth into altered positions in relationship to the basal bone of the ALVEOLAR PROCESS and to adjoining and opposing teeth as a result of loss of approximating or opposing teeth, occlusal interferences, habits, inflammatory and dystrophic disease of the attaching and supporting structures of the teeth. (From Boucher's Clinical Dental Terminology, 4th ed)Orthodontic Appliance Design: The planning, calculation, and creation of an apparatus for the purpose of correcting the placement or straightening of teeth.Orthodontic Wires: Wires of various dimensions and grades made of stainless steel or precious metal. They are used in orthodontic treatment.