Long-term stability of surgical mandibular setback

Objective: To test the relationship between positional changes of the proximal segments during surgery and the positional rebound of the mandible during the postsurgical period of orthodontic treatment. Materials and Methods: The sample included records for 34 patients who had received sagittal split surgery for the correction of mandibular prognathism. Data were collected from standardized cephalometric radiographs taken immediately prior to surgery (T2), immediately following surgery (T3), and following the completion of orthodontic treatment (T4). Linear and angular changes in the orientation of the posterior border of the ascending ramus between time points T2, T3, and T4 were measured relative to superimposition on the anterior cranial base. In addition, linear changes in the position of pogonion between T3 and T4 were measured. Results: The magnitude of linear displacement of the posterior border of the proximal segment during surgery (T2 to T3) was statistically significantly correlated (r =.61) with the magnitude of linear displacement of pogonion during the postsurgical phase of orthodontic treatment T3 to T4. There was a strong relationship between the magnitude of angular (r =.67) displacement of the posterior border of the proximal segments during surgery (T2 to T3) and the magnitude of angular rebound of the posterior border of the proximal segments that occurred during the postsurgical phase of orthodontic treatment (T3 to T4). Conclusions: When rigid fixation procedures alter the position of the proximal segments during sagittal split osteotomy of the mandible, the proximal segments tend to go back toward their presurgical positions following surgery.