The purpose of this pilot study was to evaluate the long-term skeletal and dental stability in patients who underwent maxillo-mandibular counter-clockwise rotation and mandibular advancement, comparing two different methods for internal fixation.
Methods: This retrospective and randomized study consisted of six patients who underwent orthognathic surgery. All patients were operated at private hospital, Brazil, by one surgeon. They were divided in two groups based in type of internal fixation for mandible. Group I had only miniplates with screws and group II had miniplates with screws and bicortical screws in addition. The average post-surgical follow-up was 17.1 months. To assess the skeletal stability, 18 preoperative (T1), recent post-operative (T2) and late postoperative (T3) lateral cephalograms were digitized. All points and planes were determined three times and computer in randomized method did the measurements.
Results: During surgery, the occlusal plane angle decreased 9.7°. The maxilla moved forward and upward. The posterior nasal spine moved downward and forward. The mandible advanced 7.37 mm (range 6.53–8.22 mm) at the lower incisor tips, 10.8 mm (range 9.8–11.8 mm) at Point B, 18.27 mm (range 18.51–18.03 mm) at menton and 17.05 mm (range 17.3–16.8 mm) at pogonion. Vertically, the lower incisors moved upward 5.03 mm. At the longest follow-up post surgery, the maxilla showed minor horizontal changes. Point A (0.73 mm) and PNS (2.37 mm) showed a backward change. Mandibular points had more stability for horizontal changes in group II (1.45 mm) and for vertical changes in group I (0.1 mm). However they showed significant changes in mandibular horizontal position at point Me (4.27 mm) and at pogonion (4.15 mm).
Conclusion: It was observed that the counter-clockwise rotation of the maxillo-mandibular complex produces more stable results in maxilla surgery and in hybrid rigid fixation in mandible.
Key words: rigid internal fixation; orthognathic surgery; stability