The purpose of this study was evaluation of postoperative counterclockwise relapse of mandible after mandibular setback surgery depending on the amount of intraoperative rotational changes of the proximal segment 30 patients who underwent orthognathic surgery for mandibular setback were included in this study. Rigid fixation was done. The patients were divided into three group using 3D CT depending on the intraoperative rotational direction of proximal segment; Group A: clockwise rotation of the proximal segment, Group B: the original position of the proximal segment, Group C: counterclockwise rotation of the proximal segment. The postoperative stability at 6 months follow up was evaluated using superimposition technique with cephalograms. In the Group A (clockwise rotation: 2.77 ± 1.12°, setback: 7.63 ± 3.51 mm) postoperative anterior movement (relapse) was 2.14 ± 1.31 mm. In the Group B (setback: 4.61 ± 4.01 mm) postoperative relapse was 1.11 ± 1.41 mm In the Group C (counterclockwise rotation: 3.62 ± 0.91°, setback: −7.17 ± 5.12 mm) postoperative relapse was 1.25 ± 0.85 mm. The present study suggests that orthognathic surgery with mandibular setback is more stable when the proximal segment is fixed according its original position. However, minimal amount of postoperative relapse is obligate.
3D evaluation of postoperative counterclockwise-rotation of mandible aftermandibular-setback-surgery depending on the amount of intraoperative rotationof the proximal segment
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