Comparison Study Of TMJ Between Skeletal â…¢Class Malocclusion Adults With High-angle And Normal Occlusion Adults By CBCT Technique

Objective:With comparison of normal occlusion adults,the aim of this study is to analyse the skeletal structure of TMJ (temporomandibular joint, TMJ) of skeletal â…¢ Class malocclusion adults with high-angle by using CBCT (cone-beam computed tomography), making the reference for orthodontic diagnoses and treatment plan.Method:Thirty normal occlusion adults and thirty adults in high-angle of skeletal malocclusion Class â…¢ were selected and undergone CBCT in the intercuspal position. Reconstructed images of TMJ were analysed statistically with Invivo5software and obtained the reference values respectively. The data was input into computer and SPSS19.0software was used to do T test. Condyle positions in two groups were calculated.Results:1. In the normal sample, the measurement results were obtained from CBCT. There was no statistically significant between two sides(P>0.05);2. In normal occlusion adults,both condyles were characterized by nonconcentric positioning; they were anteriorly positioned in the mandibular fossa. There was statistically significant(P<0.01); the condylar positions were48.3%anterior,35%concentric and16.7%posterior, most of the condyles are in anterior and concentric;3. In the Class â…¢ sample, the measurement results were obtained from CBCT. There was no statistically significant between two sides(P>0.05);4. The condylar position within the glenoid fossa was a relative anteriority between two sides in skeletal â…¢ Class malocclusion adults with high-angle, there was statistically significant(P<0.01), the condylar position were81.7%anterior,16.6%concentric and1.7%posterior, most of the condyles are in anterior;5. The skeletal structure of TMJs were different between normal occlusion group and the Class â…¢ group. Statistically significant difference(P<0.01) was observed. Conclusion:1. The structures of bilateral TMJs were relatively symmetry in normal occlusion group;2. The structures of bilateral TMJs were relatively symmetry in the Class â…¢ group; 3. Skeletal structure of TMJs are significantly differences between normal occlusion group and the Class III group;4. In the Class III group, sagittal plane shows that width of condyle is smaller, height of processus condylaris is longer, shape of glenoid fossa is wide and shallow; axial plane shows that anteroposterior distance of the condyle is shorter, mediolateral condylar dimension is longer and ratio of anteroposterior distance of the condyle condyle to mediolateral condyle is smaller. Thus the TMJ condyles in Class III skeletal relationships is more elongated than in the normal occlusion group. Skeletal III Class malocclusion and high angle type affect condylar and fossa morphology.5. The evaluation of condylar concentricity showed that both groups were characterized by nonconcentric position; the Class III group was more anteriorly positioned in the mandibular fossa, most of the condyles were in anterior, superior joint space was smaller, condyles were superior position; most of the condyles were in anterior and concentric in normal occlusion adults, skeletal III Class malocclusion and high angle type affect condylar position.