| Objective: In this study,three-dimensional finite element analysis method and fluid dynamics analysis method were used to compare the airflow field characteristics of the upper airway field in three types of normal non-rhonchus patients with different sagittal skeletal patterns,so as to explore the root cause of soft tissue collapse of the upper airway.In addition,comparing the changes of upper airway airflow field characteristics with skeletal classⅢ patients that before and after orthognathic surgery,in order to study the effect of orthognathic surgery on patients’ upper airway.Materials and Method: Patients selected from the Stomatological Hospital Affiliated to China Medical University,The CBCT scan,Mimics,Geomagic and ANSYS software are combined to build a three-dimensional finite element model of the upper airway.Based on this upper airway model,the upper airway is divided into four sections,the boundary conditions and initial airflow data were set,the cross-sectional area of the five planes of the samples were measured,the gas velocity and pressure were measured,the differential pressure and the resistance of the glossopharynx were measured.Compare the difference between the measured values of different groups of normal people with different sagittal facial patterns,and the difference between the measured values of skeletal classⅢ patients that before and after orthognathic surgery.The measured data were statistically analyzed by SPSS 23.0.Results: Three-dimensional finite element models of the upper airways were successfully established.Morphologically,the volume of the upper pharyngeal and pharyngeal segments of the skeletal classⅢ group is larger than that of the skeletal class Ⅱ group;The cross-sectional area of the lower pharyngeal and upper epiglottic boundaries of the skeletal class Ⅲ population is larger than the cross-sectional area of the lower pharyngeal and upper epiglottic boundary of the skeletal class Ⅱ(P <0.05).Other groups were not statistically significant(P> 0.05).In terms of fluid dynamics,the velocity of gas flow in the plane of the upper palatopharyngeal boundary and the lower palatopharyngeal boundary(the upper glossopharyngeal boundary)of the skeletal class Ⅲ group was lower than that of the skeletal class I group and the skeletal class Ⅱ group.The pressure in the palatopharyngeal(glossopharyngeal)plane of skeletal class Ⅲ group was higher than that in skeletal class Ⅱ group(P<0.05).The volume of the pharyngeal segment of the airway of skeletal class Ⅲ patients decreased by 8.33% than it was before orthognathic surgery,the volume of the laryngopharyngeal segment decreased by 12.12% than it was before orthognathic surgery,and the cross-sectional area of the palatopharyngeal boundary(the upper pharyngeal boundary)decreased by 28.57% than it was before orthognathic surgery(P<0.05).After orthognathic surgery,the air velocity of palatopharyngeal upper boundary and the glossopharyngeal lower boundary(epiglottis upper boundary)in skeletal class Ⅲ patients increased than it was before the operation.The pressure in the palatopharyngeal lower boundary(glossopharyngeal upper boundary)plane was smaller than it was before surgery.The resistance of the tongue and pharynx is larger than that of the airway resistance of the tongue and pharynx before surgery,and the difference with statistically significant(P< 0.05).Conclusions: The upper airways of skeletal class Ⅱ group are narrower and more prone to collapse than skeletal class Ⅲ group.Skeletal class Ⅲ patients have narrowed upper airways and increased airway internal resistance after orthognathic surgery,and have a greater risk of developing OSA than before surgery. |
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