Effects Of Upper Airway And Hyoid By Mandibular Asymmetry And Its Orthognathic Surgery In Skeletal Class ? Malocclusion Of High-angle

Objective: The aims of this study were to evaluate the difference of upper airway morphology and hyoid position in skeletal Class ? malocclusion of high-angle patients with and without mandibular asymmetry by 3-dimensional cone-beam computed tomography(CBCT),and to study the effect of upper airway and hyoid position by orthognathic surgery in skeletal Class III malocclusion of high-angle with mandibular asymmetry.Methods:The first part: 30 patients' CBCT documentations were chosen randomly and respectively with skeletal class ? malocclusion of high-angle in Dalian Stomatological Hospital.These patients include 15 without mandibular asymmetry and 15 with mandibular asymemtry.The second part: 29 patients were chosen randomly who underwent orthognathic surgery from 2015 to 2018,including 13 patients in the group with mandibular asymmetry and 16 patients in the group without mandibular asymmetry.MIMICS 20.0 software was used to measure the length,cross-sectional morphology,cross-sectional area,volume in nasopharynx,oropharynx and laryngopharynx.It was also used to measure the vertical and horizontal position of hyoid as well.SPSS 20.0 software was used to conduct statistical analysis on the data of the two parts.A value of P< 0.05 was considered significant.Results:1.The radio of the largest sagittal diameter to the largest transverse diameter,the cross section area and the volume of oropharynx,the volume of laryngopharynx and the total volume in the group without mandibular asymmetry were greater than the group with mandibular asymmetry.And the differences were statistically significant.Compared with group without mandibular asymmetry,the T-Y index of the hyoid increased and the T-X index decreased in the group with mandibular asymmetry,but there were no statistically significant.2.The changes of upper airway and hyoid after patients who were mandibular asymmetry with the skeletal Class III malocclusion of high-angle were performed the orthognathic surgery: the radio of largest sagittal diameter to the largest transverse diameter increased in nasopharynx.The cross-sectional area,the volume of the oropharynx and the total volume decreased,and the differences were statistically significant.The T-Y index of thehyoid was increased and the T-X index was decreased,but there were no statistically significant.3.Comparisons of upper airway and hyoid after patients who were in asymmetry group and symmetry group were performed the orthognathic surgery: the radio of the largest sagittal diameter to the largest transverse diameter in oropharynx was increased in group with mandibular asymmetry,while was decreased in group without mandibular asymmetry.The cross-sectional area,the volume of the oropharynx and laryngopharynx,and the total volume were decreased obviously in group without mandibular asymmetry than the group with mandibular asymmetry.The T-Y index of the hyoid was increased and the T-X index was decreased obviously in group without mandibular asymmetry than the group with mandibular asymmetry.But there were no statistically significant.Conclusions:1.Mandibular asymmetry caused the middle and lower upper airway narrow in patients who were the skeletal Class III malocclusion of high-angle.Which can be reflected by more elliptic of cross section in oropharynx and the decrease of the volume of oropharynx and laryngopharynx in group with mandibular asymmetry.The hyoid position had a tendency to shift back and down.2.After patients who were mandibular asymmetry with the skeletal Class III malocclusion of high-angle were performed the orthognathic surgery,the shape of cross section tended to be round in nasopharynx,the cross-sectional area and the volume of oropharynx and the total volume were decreased obviously.The hyoid position had a tendency to shift back and down.3.Surgical treatment of the mandibular asymmetry had some compensation for the narrowing which were caused by mandibular asymmetry and the orthognathic surgery of the cross section in oropharynx and the volume in oropharynx and laryngopharynx.