The Study On Skeletal Structure Characteristics Of TMJ By CBCT For Skeletal Class ? Malocclusion Female Adults With Different Vertical Patterns

Objective The purpose of this study was to find out the skeletal structure characterastics of TMJ in different vertical facial types of skeletal Class ? malocclusion by comparing the reconstructed temporomandibular joint 3D CBCT of different vertical facial types of skeletal Class ? malocclusion with normal occlusion,so as to provide some references for orthodontic clinical treatment plan.Methods We selected 20 female adults with skeletal Class ? malocclusion in high vertical facial types,20 female adults with skeletal Class ? malocclusion in low vertical facial types as the experimental group,and 20 female adults with normal occlusion as a control group,which are both captured images by CBCT in Tianjin Stomatological Hospital Orthodontic Department.The original images scaned by CBCT imaging were reconstructed with Invivo Dental 5.4 software.The maximum area of the condyle in the axial view was used to be the reference plane of the reconstruction,then sagittal position perpendicular to the long axis of condyle and coronary position paralleled to the long axis of condyle were reconstructed.Some parametres were measured including the value of long and short axis of condyle,distance between the geometric condyle center and mid-sagittal line,horizontal angle of condyle,depth and width of glenoid fossa,width and height of condyle head,length of condyle,the anterior,superior and posterior joint space,gradient of articular tubercle.All data were analyzed by SPSS 19.0.Results 1.No statistically significant differences were observed between the right and left sides in three groups(P>0.05);2.Some of the skeletal structures of TMJ were different between normal sample and skeletal ? samples in different vertical facial types;statistically significant difference(P<0.05)was observed.3.In the normal group,the percentage of condylar positions in the glenoid fossa respectively were 72.5% concentric,10% anterior,and 17.5% posterior,the difference was not statistically significant between the anterior and posterior joint space(P>0.05);in high angle group,the percentage of condylar positions respectively were 45% concentric,40% anterior,and 15% posterior,the difference was statistically significant between the anterior and posterior joint space(P<0.05);in low angle group,the percentage of condylar positions respectively were 32.5% concentric,10% anterior and 57.5% posterior,the difference was statistically significant between the anterior and posterior joint space(P<0.01).Conclusions: 1.The structures of bilateral TMJs were relatively symmetry in three groups;2.Compared with the normal group,there were significant differences in the skeletal structure of TMJs in female adult patients with skeletal Class ? malocclusion in different vertical facial types;in high angle group,the condylar head was narrow and long,the articular fossa was low and smooth;in low angle group,the condylar head was broad and short,the articular fossa was high and steep;skeletal ? Class malocclusion and different vertical facial types affected condylar and fossa morphology.3.The condylar positions in the glenoid fossa were different between the normal occlusion group and each group of skeletal Class ? malocclusion in different vertical facial types.In the normal group,most of the condyles were in concentric in the glenoid fossa;in high angle group,most of the condyles were in concentric and anterior in the glenoid fossa;skeletal Class ? malocclusion and different vertical facial types affected condylar position.