Effect of mandibular setback surgery on the posterior airway size.

Treatment of dentofacial deformities with jaw osteotomies has an effect on airway anatomy, and therefore, mandibular setback surgery has the potential to diminish airway size. The purpose of this study was to evaluate the long-term effect of mandibular setback surgery on the airway size. The material consisted of pre- and postoperative (minimum 1 year) lateral radiograms of 22 individuals (18 females and 4 males) with a mean age of 30 years, who had undergone mandibular setback surgery to correct skeletal Class III discrepancies. Hard and soft tissue points were digitized with a Numonics Accugrid digitizer and analyzed with Xmetrix software. A paired t test was used to evaluate the difference between pre- and postoperative measurements. In addition, Pearson's coefficient correlation was calculated to reveal the possible association between the skeletal change in relation to the change in airway size. The mean value for the initial SNA was 81.3 degrees, 85.4 degrees for SNB, 36.9 degrees for S-Na/MP, and for the posterior airway, 10.5 mm and 12.0 mm retropalatinally and retrolingually, respectively. At the postoperative evaluation, SNB was 80.7 degrees, S-Na/MP 41.0 degrees, and the posterior airway retropalatinally 8.3 mm and retrolingually 9.8 mm. Statistical analysis revealed a highly significant correlation between the change in the ANB angle and in the S-Na/MP angle versus the change in the upper airway size, both retropalatinally and retrolingually. Mandibular setback surgery with posterior rotation may gradually result in increased upper airway resistance in cases where neuromuscular adaptation is insufficient to compensate for the reduction in the airway size. Therefore, large anteroposterior discrepancies should be corrected by combined maxillary and mandibular osteotomies.