| Objective: By using MRI and CBCT imaging examinations,this study aims to investigate the relative position relationship between the disc and condyle of the asymptomatic temporomandibular joint in young people,and to explore the range of disc condyle angle,symmetry of bilateral joints,and differences in disc condyle angle of the same joint at different levels on magnetic resonance imaging.The aim is to clarify the normal position of the temporomandibular joint disc and determine the standard for determining the normal position of the temporomandibular joint disc,Provide theoretical basis for the selection of measurement planes for the disc condyle angle of the temporomandibular joint in clinical practice and for the imaging diagnosis of temporomandibular joint disorders.Methods: A total of 3120 new students from Qingdao University were subjected to oral examination,and 1095 individuals were selected according to the inclusion criteria of the experiment.100 individuals were randomly selected and 200 joints were scanned with MRI and CBCT.Observing the bone tissue morphology of the temporomandibular joint of the subject through CBCT,measuring the disc condylar angle of TMJ in the central layer of the oblique sagittal position of the MRI T1 sequence using the condylar apex method,and conducting paired t-tests on the recorded data using SPSS19.0 software.Among the 100 volunteers mentioned above,33 of them were able to clearly present the condylar process and joint disc structure in the oblique sagittal MRI T1 sequence at 5 layers or above,and measured the disc condylar angle.66 joints of these 33 individuals were measured at the middle 5 layers of the disc condylar angle,and the results were analyzed using one-way ANOVA.Results: The CBCT results of 100 young volunteers showed that 99 of them had symmetrical bilateral joints and normal condylar morphology;One person experienced abnormal changes in the unilateral condyle and joint nodules,resulting in bilateral condylar asymmetry.Paired t-tests were performed on the measurement results of MRI central layer data,and there was no statistically significant difference in the left and right disc condylar angles(P=0.862).However,the bilateral articular discs and condyles of the same individual were not completely symmetrical;The average disc condylar angle of 100 asymptomatic young volunteers was 18.96 °,with 95% of disc condylar angles ranging from 0 ° to 31.49 °;The angles of the joint discs of the same joint measured at five levels were different,but overall,there was no statistical difference in the measurement results between different levels(P=0.322).Conclusions: This experiment measured that 95% of asymptomatic young volunteers had a disc condylar angle between 0 ° and 31.49 °.For most asymptomatic temporomandibular joints,the joint disc is located in the front and upper part of the transverse crest of the condyle,which is adapted to the forward tilting shape of the condyle.For the asymptomatic young population,there is no statistical difference in the left and right disc condyle angles overall,but the bilateral joints of the same individual are not completely symmetrical,and some individuals even have significant differences.In clinical practice,the measurement of the disc-condylar relationship should choose a layer with a clear structure,and the central layer is not the only choice.But when comparing a specific joint before and after treatment,selecting the same layer can more accurately reflect the changes in disc condyle position before and after treatment.Abnormal changes in the imaging of the epicondylar joint nodules may not necessarily indicate clinical symptoms and signs of TMD,which may be related to the balance of the temporomandibular joint occlusal relationship masseter muscle group.The degree to which the posterior edge of the articular disc deviates from the transverse ridge of the condyle is not a sufficient condition for the occurrence of joint bouncing.The mechanism and treatment of joint bouncing still need more exploration. |
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