Short-term pharyngeal airway changes after mandibular advancement surgery in adult Class II-Patients-a three-dimensional retrospective study

The purpose of this study was to investigate volume changes in posterior airway space (PAS) after bilateral mandibular advancement surgery. Measurements were taken based on three-dimensional (3D) records available for a large and homogeneous cohort of patients. Pre- and postoperative CBCT scans of 102 adult patients with Class II dysgnathia were visualized and analyzed using 3D software (MimicsA (R) Innovation Suite 14.1; Materialise, Leuven, Belgium). The PAS was divided into three segments by three planes parallel and one plane perpendicular to the Frankfort horizontal plane. Total volume, partial volumes, and cross-sectional areas were calculated from the pre- and postoperative scans. Dahlberg coefficients were obtained to verify each parameter for the measurements' reliability. The statistical significance of the changes observed was analyzed by Wilcoxon's rank-sum test. Highly significant (p=0.000) increases in total posterior airway volume (+32.0%) were noted as an effect of mandibular advancement surgery, amounting to 45.6% in the lower PAS third compared to 38.8% in the middle and 12.5% in the upper PAS third. We also obtained highly significant (p=0.000) increases in all the cross-sectional areas investigated, amounting to 48.5% on the soft-palate level compared to 21.6% on the level of the epiglottis tip, and 14.6% on the hard-palate level. These results demonstrate that bilateral mandibular advancement surgery in Class II-Patients leads to significant increases in PAS volume and significant widening of the narrower sites inside the pharynx.