The Influence Of Surgical Operation On The Upper Airway And Surrounding Structures In Skeletal Class Ⅱ Patients

Objective:1.In order to obtain a good profile,patients with severe skeletal class Ⅱ malocclusion require orthognathic surgery,which may change their airway space.The objectives of this study are: 1)to determine the effects of different orthognathic surgery on upper airway space and hyoid position in skeletal class Ⅱ patients;2)to evaluate the stability of upper airway space and hyoid position changes after orthognathic surgery.2.The changes of chin shape,upper airway space and hyoid position of skeletal class Ⅱ patients after simple genioplasty were analyzed by cone beam CT(CBCT)and cephalometric lateral radiographs,and the effects of simple genioplasty on the upper airway and adjacent tissues of skeletal class Ⅱ patients were analyzed,so as to guide the screening of clinical treatment techniques for patients with skeletal class Ⅱ malocclusion from the theoretical level.Methods:1.In this study,17 patients with skeletal class Ⅱ malocclusion treated in the Department of Orthodontics and Oral and Maxillofacial surgery of Jilin University Stomatology Hospital from 2016 to 2020 were randomly divided into two groups.The CBCT images of 1 week before orthognathic surgery(T0),1 week after operation(T1)and 6 months after operation(T2)were collected and imported into dolphin imaging software to establish a three-dimensional model of upper airway.Changes in upper airway space and hyoid position were evaluated as the main outcome variables.Measurements were obtained before surgery(T0),one week after surgery(T1),and six months after surgery(T2)using Dolphin Imaging Software version 11.0.Differences in measurements between T1 and T0,and T2 and T0 were calculated and imported into SPSS software for data analysis.2.Thirteen patients with skeletal class Ⅱ malocclusion who were treated in the Department of Oral and Maxillofacial surgery of Jilin University Stomatology Hospital from 2016 to 2020 were treated with simple genioplasty.Cone beam CT scanning and cephalometric lateral radiography were taken 1 week before operation(T0)and 6months after operation(T1).The CBCT data and lateral films were imported into Dolphin Imaging and Sketchpad software respectively,and then the fixed-point description and some parameters of upper airway,hyoid and chin were measured.The data analysis tool was SPSS 23.0.The changes of chin shape,upper airway spatial structure and hyoid position before and after operation were compared with paired ttest as technical support.The correlation among chin shape,upper airway spatial structure and hyoid position was analyzed based on Spearson correlation test.Results:1.The indicators of the patient’s upper airway space,hyoid bone position were changed significantly after the three commonly used orthognathic surgery-mandibular advancement,maxillary setback with mandibular advancement and genioplasty.2.After mandibular advancement(MA),the airway space of the nasopharyngeal segment did not change significantly,while the total volume of the upper airway and the airway space of the oropharyngeal and laryngopharyngeal segments increased by32.6%,43.3% and 39.3% respectively,and the stability was better 6 months after surgery.3.After maxillary setback and mandibular advancement surgery(MAMS),the airway space of the nasopharyngeal segment was reduced by 10%,and the total volume of the upper airway and the airway space of the oropharyngeal and laryngopharyngeal segments were significantly increased 10.4%,17.8% and 15.6% respectively,but there was a recurrence at 6 months after the surgery,and the stability was not good.4.After genioplasty,the volume of the laryngopharyngeal segment increased by 27.6%,and the hyoid bone moved forward and downward.5.The three surgical methods all made the hyoid bone moved forward,and the forward movement of mandible was positively correlated with the horizontal movement of hyoid bone and the change of airway space in pharynx and larynx.Conclusions:1.Mandibular advancement can widen the oropharyngeal and hypopharyngeal airway space and move the hyoid bone forward.Maxillary recession has a negative effect on the long-term stability of the increased upper respiratory tract space.2.Genioplasty not only achieved better cosmetic results by advancing the chin but also exerted a significant positive impact on the posterior airway space for patients with skeletal class Ⅱ by moving the hyoid bone forward,thus helping reduce the prevalence of OSAHS.