Anterior retraction using a preadjusted edgewise appliance with interrupted orthodontic force generated by a screw device

The objectives of the present study were to determine the usefulness of interrupted orthodontic force in anterior retraction and to identify its problems. Subjects were three patients (maxillary protraction, bimaxillary protrusion, and mandibular protrusion). As a multi-bracket appliance, the 0.022 preadjusted edgewise appliance was used. After attaching a 0.019 in. × 0.025 in. stainless steel wire, the screw device was placed. With regard to the screw adjustment, each patient was instructed to turn the screw clockwise 360° every three days. In all three patients, anterior retraction was completed in a period of only three months. Cephalograms showed that the tooth axis of the anterior teeth was tilted lingually. When superimposing curves expressed as quartic polynomials at initial examination and during retention, marked constriction at the second premolar region, lateral expansion in the molar region were seen for both the maxilla and mandible. Panoramic radiography did not reveal root resorption. No radiographic abnormalities were seen in the periodontal membrane or dental root. Therefore, the screw device appeared to properly control physiological tooth movement and shorten the duration of orthodontic therapy.