appliances are made using a dental mold representing a patient &# 39 ; s dental configuration . in particular , thermoformable plastic positioning appliances which fit over the patient &# 39 ; s teeth may be formed over a three - dimensional mold of the patient &# 39 ; s dentition . an apparatus and methods which employ a manipulable or reconfigurable mold to model patient dentition and gingiva at each stage of treatment . the apparatus and methods are particularly useful for performing midcourse corrections during orthodontic procedures using a plurality of such appliances in sequence .