[The mechanics analysis of orthodontic treatment for the impacted inversed upper central incisor].

PURPOSE: To study the treatment on the impacted inversed upper teeth by orthodontic traction. METHODS: Nineteen impacted curved upper teeth were treated with surgical exposure and orthodontic traction after X-ray location and tooth space expansion. RESULTS: Among the 19 impacted teeth, thirteen teeth were successfully treated, four were approximately erupted, two were failed. The average eruption time of the 19 impacted teeth was 6.5 months(3-12 months). All the teeth had vital pulp without root absorption or conglutination. There was labial gingival regression with 2mm and 4mm in 2 teeth, respectively. Marginal bone loss of 1.0 mm was found in one tooth. In 1 case, the tooth couldn't be moved into alignment, and light-cured or porcelain crown treatment was suggested. In 1 case, the tooth couldn't be moved into alignment due to the severely curved root, and then was extracted. In 1 case, the tooth erupted after traction for 3 months, but the patient rejected the treatment. All the other teeth moved into alignment. CONCLUSIONS: Exact location, appropriate traction force and direction decide the movement of impacted teeth.