| Background and Objectives:Skeletal classⅢis a common malocclusion due to the abnormal growth of jaw size,shape,and position.Adult patients with no growth potential of severe skeletal class Ⅲ malocclusion often need to reconstruct the spatial relationships through combined orthodontic and orthognathic therapy.In recent years,Surgery-First Approach(SFA)has been gaining popularity.Compared with the traditional way of treatment,SFA has the advantage to improve the appearance in the early stage,and help patients cooperate during the entire course of treatment.In addition,the entire treatment cycle is shortened.And by accelerating the orthodontic tooth movement,it reduces both the time and difficulty of orthodontic treatment stage.In orthognathic surgery,the lower jaw requires wide movement.Therefore,the change of position of the upper airway can make differences to the morphology and function of the upper airway.It is pretty common in the clinic setting to find patients having symptoms similar to OSAHS.Previous studies mostly focused on the upper airway changes of patients undergoing orthognathic surgery after orthodontic treatment.However,studies on the influence of the upper airway ventilation function of patients who underwent orthodontic surgery first(SFA)were not well assessed.This experiment utilizes CBCT to observe upper airway of adult skeletal ClassⅢ patients with preoperative and postoperative and surrounding tissues and to study the changes of the upper airway between pre-and post SFA surgery.The purpose is to provide important theoretical basis for the upper airway respiratory function improvement through clinical treatment of malocclusion.Materials and Methods:In this study,11 patients with skeletal Class Ⅲ malocclusion were selected randomly from Taiwan Fenghua Plastic Surgery Hospital.Among them,there were 4 males and 7 females,ages between 20-28.These patients all received orthodontic treatment with orthognathic surgery first(SFA).Orthognathic surgery:maxillary LeFort I osteotomy + mandibular sagittal split osteotomy(SSRO)+ genioplasty.Each patient received a CBCT scan one week before operation(T0),and 12 months after operation(T1).All Dicom data acquired from CBCT were exported to Mimics17.0 to build a 3D reconstructive model.STL format data were exported.And subsequently,the STL data were imported into ANSYS 16.0 software,and the upper airway morphology was modified and divided into grids.3D models were constructed to analyze fluid dynamics and simulation.Statistical analysis was performed using SPSS 19.0 software.Paired samples t test was used to compare the data of TO and T1 group.The correlation between pharyngeal pressure drop and morphological parameters of airway was analyzed by Pearson correlation test.Results:1.The volume and cross-sectional area of nasopharyngeal and pharyngeal segment were increased in the skeletal classⅢpatients with the bimaxillary surgery(SFA)(P<0.05),but the volume and cross-sectional area of the glossopharyngeal and hypopharynx segment were decreased(P<0.05).The LR/AP values of nasopharynx and velopharyngeal airway were increased(P<0.05)and the airway morphology was closer to a circle after surgery.However,the LR/AP values of glossopharyngeal and larynx decreased,and its shape was closer to the oval.The most obvious changes were in the glossopharyngeal segment.All of changes were statistically significant.2.After numerical simulation of airflow,we found that the velocity of the nasopharyngeal and pharyngeal segment slowed down in the skeletal class Ⅲpatients with the bimaxillary surgery(SFA),the velocity of the nasopharynx and the velopharyngeal were lower than pre-surgery by 5.04± 1.51%(P<0.05)and 11.48± 1.91%(P<0.05)respectively.The velocity of the glossopharyngeal and hypopharynx segment were increased compared with pre-treatment by 29.16±3.57%and 13.26±2.56%(P<0.05).The pressure drop of the nasopharyngeal and the velopharyngeal were decreased.However,the pressure drop of the glossopharyngeal and the hypopharyngea were increased.The overall pressure drop of the upper airway compared to the pre-treatment was increased by 7.71%.There was a significant negative correlation between the glossopharyngeal pressure drop,minimum cross-sectional area,volume and morphology changes.Conclusion:One year after the treatment of skeletal classⅢ patients with bimaxillary surgery(SFA),the upper airway morphology still shows a narrowing trend,increasing flow resistance.Among the increasing of glossopharyngeal resistance is the most significant sections.Compared with preoperative,the ventilation function of the upper airway is decreased. |
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