Three-dimensional Measurement And Analysis Of The Effects Of Maxillomandibular Expansion On Upper Airway In Different Sagittal Skeletal Pattern

Maxillary arch stenosis is the most common craniofacial bone development problem,which can lead to crowding,anterior crossbite,posterior opening and other types of malocclusion,a series of problems often accompanied by mouth breathing and upper airway stenosis and hearing loss.It is also one of the main causes of obstructive sleep apnea hypopnea syndrome(OSAHS).Rapid maxillary expansion was first proposed by Dr.Angell in nineteenth Century,It is a kind of orthodontic clinical method which was used in the treatment of jaw defects such as crowded dentition,dental arch stenosis,and so on.Its principle is by opening and rapid maxillary palatal suture in stimulating new bone deposition,the movement of the buccal bone plate to expand the width of dental arch,relieve crowding.One hundred years later,Dr.Haas made the Haas arch expander and applied it to the clinic.It has become one of the most common ways to relieve crowding.In recent years,scholars have found that RME can not only expand the crowding of the dental arch,but also increase the nasal ventilation and improve the respiratory function.Therefore,the effect of expanding the arch on the airway becomes a hot topic.Now,we use the mandibular spiral expansion modified by professor Zhao Guizhi to expand mandibular appropriately and flatten the Spee curves or remove a part of congestion.The previous research on airway to two-dimensional,often by cephalometric for its advantages of lower cost,easy operation and lower radiation,but also has its limitations,such as image overlap,magnified image distortion,more artifacts,the projection error of anatomical structure cannot accurately reflect the true anatomical structure of airway.In recent years,high spatial resolution,soft tissue and space enough contrast of CBCT and lower radiation dose compared with traditional spiral CT,have been used to analyze the anatomy of the upper airway in three dimensions,with the emergence of 3D measuring software,we can evaluate the shape and size of airway more accurately.There are many factors that affect the shape and size of the airway,in hard tissue,the domestic and foreign scholars made a lot of research on the relationship between different facial types and airway,we found that the sagittal skeletal pattern and vertical facial affect airway.However,past studies often only on changes before and after a skeletal class expansion airway occurred,but not on the three different sagittal skeletal pattern of longitudinal contrast.This study intends to use CBCT imaging technology,combined with Mimics17.0 software on the reconstruction and measurement of maxillomandibular expansion of the upper airway,evaluate the change of three different sagittal skeletal pattern in adolescent patients after maxillomandibular expansion indexes after treatment,so as to provide some reference for clinical application of this technology.Research PurposesIn this study,we selected 60 adolescent patients who underwent maxillomandibular expansion for the treatment of dental arch stenosis,divided into Class I,II,III three different sagittal sagittal according to the size of the ANB angle,reconstruct the dimensional of the CBCT image data of the patient before and after the expansion.Mimics17.0 software was used to measure the volume of the three-stage airway,the ratio of the sagittal diameter to the transverse diameter of the smallest section of the oropharyngeal airway,compare the size and shape of the airway before and after the expansion of the arch,so as to provide a reference for mandibular arch expansion.Research MethodsSixteen young patients with arch narrow and crowding(27 males and 33 females,aged 9 to 13 years)treated by the technology of maxillomandibular expansion were selected.CBCT images were obtained before and after maxillomandibular expansion.All CBCT images were reconstructed and segmented by Mimics 17.0 image processing software,the volume,the minimum cross-sectional area of the oropharyngeal airway,the sagittal diameter of the smallest cross-section and the ratio of transverse diameter to the diameter of the pharyngeal airway and the pharyngeal airway were measured.SPSS19.0 software package for statistical analysis,three groups of different sagittal skeletal pattern patients before and after treatment group comparison using paired t test,and then three groups of data for one-way analysis of variance,the choice of LSD method between groups of two contrast.ResultsMaxillomandibular expansion of the airway after the indicators of the measurement results show that:1.Nasopharyngeal airway volume of sagittal skeletal Class I after maxillomandibular expansion increased significantly(P <0.05);There was no significant difference in the total airway volume,oropharyngeal and laryngeal airway volume,and there was no significant difference between the minimum cross-sectional area of the oropharyngeal airway and the L-vector / L-transverse value.2.Total volume and oropharyngeal airway volume of Class sagittal facial type ?patients significantly increase the after maxillomandibular expansion(P <0.01);There was no significant difference in the airway volume between the nasopharyngeal and the laryngeal segments(P>0.05)and there was significant difference between the minimum cross-sectional area of the oropharyngeal airway and the L-vector / L-transverse value(P<0.05).3.Nasopharyngeal airway volume of sagittal skeletal Class ? after maxillomandibular expansion increased significantly(P <0.05);There was no significant difference in the total airway volume,oropharyngeal and laryngeal airway volume,and there was no significant difference between the minimum cross-sectional area of the oropharyngeal airway and the L-vector / L-transverse value.Conclusion1.The upper airway of growth skeletal Class and Class patients change in a ? ?short time after maxillomandibular expansion,only nasopharyngeal airway segment volume becomes large,the other measure did not change significantly.2.Total volume and oropharyngeal airway volume of Class sagittal facial type ?patients significantly increase the after maxillomandibular expansion,the minimum cross-sectional area of the oropharyngeal area increased,and the airway morphology changed from elliptical to circular.Maxillomandibular expansion is more suitable for the treatment of mandibular retraction and associated with airway obstruction bone type ? patients3.Through the CBCT three-dimensional reconstruction of the upper airway model,we can directly and comprehensively observe the cavity structure which X-ray film can not be presented on the three-dimensional,so that we measure the airway more accurate and reliable.