First Premolar Extractions and Fixed Appliances in the Class II Division 1 Malocclusion

This cephalometric study investigates the changes in the facial skeleton and dento-alveolar structures which occur during orthodontic treatment of the Class II Division 1 malocclusion by extraction of four first premolars followed by fixed appliances. The Begg and edgewise appliances are compared, and both are contrasted with a group of untreated Class II Division 1 subjects. The main effects of treatment were in the dento-alveolar structures, the changes in the overall facial pattern being small and largely due to extrusion of the molars during overbite reduction. Molar extrusion tended to interrupt forward growth rotation of the mandible, temporarily making it more backwards in direction, and increasing the lower anterior face height. An increase in the posterior lower face height was also noted in the edgewise group. Whilst SNA, and therefore ANB, reduced significantly during treatment, this was probably the result of palatal root torque to the upper incisors. The Begg appliance was more successful than edgewise in this respect.