Three-dimensional Evaluation Of The Glenoid Fossa And Mandible In Adults With Skeletal Class Ⅱ Mandibular Deviation

Objective:1.Mimics software was used to study the three-dimensional structure of the glenoid fossa and mandible in adults with skeletal Class Ⅱ deviation,skeletal Class Ⅱ symmetry and skeletal Class I symmetry,and to explore the causes of skeletal Class Ⅱ mandibular deviation in adults;2.To investigate the correlation between the three-dimensional structure of glenoid fossa and mandible of skeletal Class Ⅱ mandibular deviation and the degree of deviation.Methods:Sixty patients who visited the Department of Orthodontics at Shanxi Provincial People’s Hospital from September 2018 to September 2022 were selected,including 20 patients with skeletal Class Ⅱ mandibular deviation(skeletal Class Ⅱ deviation group),20 patients with skeletal Class Ⅱ symmetry(skeletal Class Ⅱ symmetry group),and 20 patients with skeletal Class I symmetry(skeletal Class I symmetry group),The skeletal Class Ⅱ deviation group were divided into the deviation side and the non-deviation side according to the direction of the Me point deviation.CBCT scans were obtained for all patients before treatment.Three-dimensional reconstructions of the DICOM images were generated using Mimics 21.0 software,and the reconstructed models were output by3-Matic software.The maxilla and mandible were distinguished using different colors and the condyles,glenoid fossa,and other important anatomical structures were isolated to display them clearly.Measurements of the articular fossa and mandible were were performed on models of the four groups(skeletal Class Ⅱ mandibular deviation groupdeviation side,skeletal Class Ⅱ mandibular deviation group non-deviation side,skeletal Class I symmetry group,and skeletal Class Ⅱ symmetry group)to assess differences between the two sides of each group and among the each four groups.The width of anterior articular fossa,width of posterior articular fossa,length of articular fossa,depth of articular fossa,angle of articular fossa,superior articular space,anterior articular space,posterior articular space,condylar width,condylar length,condylar neck height,condylar angle,sagittal angle of condylar neck,coronal angle of condylar neck,elevation of mandibular raum,length of mandibular body,and angle of mandibular angle were measured.Results:1.There were statistically significant differences(P<0.05)in bilateral glenoid fossa length,glenoid fossa angle,condylar length,condylar neck height,condylar angle,condylar neck coronal angle,mandibular ramus height,mandibular body length,and mandibular angle between the deviation side and non-deviation side in skeletal Class Ⅱ deviation group.2.There were no significant difference(P>0.05)between the bilateral measurements in the skeletal Class I symmetry group and the skeletal Class Ⅱ symmetry group.3.There were significant differences(P>0.05)in glenoid fossa length,glenoid fossa angle,condylar length,condylar neck height,condylar angle,condylar neck coronal angle,mandibular ramus height,mandibular body length,and mandibular angle among the four groups(skeletal Class Ⅱ mandibular deviation group deviation side,skeletal Class Ⅱ mandibular deviation group non-deviation side,skeletal Class I symmetry group,and skeletal Class Ⅱ symmetry group).There were also significant differences(P<0.05)in the measurements of anterior fossa width,fossa length,condylar length,condylar neck height,mandibular ramus height,and mandibular body length of skeletal Class I symmetry group mean and skeletal Class Ⅱ symmetry group mean,with the mean values of skeletal Class I symmetry group being greater than skeletal Class Ⅱ symmetry group.In the linear indicators describing the size of the articula fossa,condyle,mandibular ramus and mandibular body,there was no significant difference(P>0.05)between the mean values of the skeletal Class Ⅱ symmetry group and the deviation side of the skeletal Class Ⅱ deviation group.There were also no significant differences(P>0.05)in the measurements between the mean values of the skeletal Class I symmetry group and the contralateral deviation of the skeletal Class Ⅱ deviation group.4.In skeletal Class Ⅱ deviation group,there was a certain correlation between the differences in bilateral glenoid fossa angle,condylar angle difference,condylar neck coronal angle,mandibular body length,mandibular ramus height,condylar neck height between the two sides and the severity of Me point deviation.Conclusions:1.In the vertical direction,the condylar neck of the oblique side,the ramus of the mandible and the mandibular body are shorter.The mechanism of skeletal class Ⅱ mandibular deviation in adults is caused by insufficient development of the condyle,ramus and mandibular body on the side of the deviation,rather than excessive development on the opposite side.2.In the transverse and sagittal directions of adult skeletal Class Ⅱ deviation group,the mandibular angle on the deviation side was rotated backward,upward,and outward.The condyle rotates backward and inward.There was no significant difference in bilateral joint space,and the articular fossa adjusted and rotated inward with the condyle.3.There is a correlation between the degree of mandibular deviation and the degree of mandibular deviation in adults with skeletal class Ⅱ deviation.