Characteristics of mandibular advancement surgery dependent on lower facial height differences in study of skeletal Class II patients with long-term stability

We studied patients who underwent mandibular advancement surgery and showed a stabilized occlusal condition at 5 years after surgery. The patients were classified into 2 groups [long face type (LF group: 16 cases), short face type (SF group: 10 cases)] according to immediate presurgery face type. To clarify the characteristics of the operative method formulated based on lower facial height, morphological changes during the 5-year postoperative period were compared between the groups.There was no statistically significant difference in amount of advancement between the two groups, though lower facial height showed a tendency to increase in group SF. The proximal segment was advanced to the anterosuperior position in both groups.To determine postoperative stability, in the LF group, there were no statistically significant differences for lower face height. In the SF group, the condylar axis increased in the period from immediately after to 6 months after surgery. Correlation analysis revealed that the backward rotation of the proximal segment was greater during the first 6 months, as the amount of surgical advancement of the chin was larger. As a result, the chin was advanced during surgery and the proximal segment was advanced toward the anterosuperior position in both groups. In the SF group, the characteristics of the operative design increased the lower facial height.