Aim: To examine the effect of single jaw surgery (mandibular setback) on the vertical relationships of skeletal class III patients and also examine the relationship between these probable changes and occlusal plane angle.
Material and methods: The measurements were evaluated on the preoperative and postoperative cephalometric radiographs of 33 skeletal class III Patients, that preoperative lateral cephalograms were taken before surgery and after insertion of surgical stabilizing arch wires and the postoperative lateral cephalograms were taken before the starting of postoperative orthodontic treatment. Vertical relationships were measured by the analysis of Legan and Burstone.
Results: The results showed that sagittal correction of mandibular prognathism caused significant reduction of lower anterior facial height (p< 0.001, mean =1.8mm ±1.44mm), and no significant correlation was found between lower anterior facial height change and occlusal plane angle and the amount of setback lonely and with together.
Conclusion: After mandibular setback surgery lower anterior facial height was reduced significantly, but it is not possible to find a significant correlation between lower anterior facial height changes and occlusal plane angle and/or amount of mandibular setback, so no prediction is possible for lower anterior facial height changes after mandibular setback surgery. These issues have to be considered to reduce the incidence of this problem in a developing country such as ours (1.10 2006;1: 158-62).