An objective, quantitative, dynamic assessment of facial movement symmetry changes after orthognathic surgery

The aim of this study was to generate a quantitative dynamic assessment of facial movement symmetry changes after orthognathic surgery. Twenty-five patients diagnosed with skeletal class III malocclusion with facial asymmetry who underwent bimaxillary surgery were recruited. The patients were asked to perform a maximum smile that was recorded using a three-dimensional facial motion capture system preoperatively (T0), 6 months postoperatively (T1), and 12 months postoperatively (T2). Eleven facial landmarks were selected to analyse the cumulative distance and average speed during smiling. The absolute differences for the paired landmarks between the sides were analysed to reflect the symmetry changes. The results showed that the asymmetry index of the cheilions at T2 was significantly lower than that at T0 (P = 0.004), as was the index of the mid-lateral lower lips (P = 0.006). The mean difference in cheilions was 2.13 ± 1.41 mm at T0, 1.33 ± 1.09 mm at T1, and 1.00 ± 0.98 mm at T2. The facial total mobility at T1 was significantly lower than that at T0 (P < 0.001), while the total mobility at T2 was significantly higher than that at T1 (P = 0.012). The orthognathic surgical correction of facial asymmetry was able to improve the associated asymmetry of facial movements.