Establishment Of The Early Diagnostic Model For Stress Change Of Abnormal Disc-condyle Relationship In Patients With Mandibular Deviation

Objective:To analyze the features of the position change and stress change of the condyle and articular disc in the TMJ under the condition of mandibular deviation by CAE,and to establish the early diagnostic model according to these features,which is intended to give advice on clinical treatment of patients with mandibular position abnormality in the early stage.Methods:Head CT images and TMJ MRI images of 10 normal volunteers in ICP and the condition of mandibular deviation were collected and imported into Mimics 17.0 software in DICOM format for 3D reconstruction.The 3D finite element model of TMJ was established after mesh division through registration and optimization with Abaqus 6.14 software,then simulate muscle load to analyze the stress distribution status.The same method was used to analyze the stress distribution characteristics of TMJ in patients with mandibular deviation,and the model was compared with the one in simulated state to verify the effectiveness of the model,and establish the early diagnostic model of mandibular deviation.Results:Twenty one 3D digital and finite element models of TMJ including bilateral condyle,fossa and disc were established.The stress distribution of normal and mandibular deviation was obtained by CAE.Under the condition of the mandibular deviation of 3mm to the left,the position of the oblique condyle did not change significantly,and the stress distribution was centralized.The displacement of articular disc was not obvious,and the stress compacted area moved outward.The condyle of the opposite side moves inward,downward and forward,and the stress compacted area moved outward obviously.Inward and backward movement occurred in the articular disc,and the stress compacted area moved outward.The volume,anteroposterior diameter and height of the oblique condyle in the patient with mandibular deviation were significantly smaller than that of the opposite side.The oblique condyle was shifted backward,upward and outward,while the opposite condyle was shifted forward,downward and inward.The stress compacted area of the oblique condyle was medial,and the stress area of the articular disc was lateral and relatively diffuse.The stress area of the articular disc on the opposite side was medial and relatively centralized.The stress distribution of normal volunteers under the condition of simulated mandibular deviation was similar to that in the patient with mandibular deviation in multiple joints.Conclusion:1.The position change and the abnormal stress distribution of the condyle and the articular disc would appear at the early stage of the mandibular deviation,which is more obvious in the opposite side than in the oblique side,with a tendency to develop into skeletal mandibular deviation.2.The position of the oblique condyle may not change significantly,the stress compacted area maybe unchanged either,while produces a compacted point.There may be no obvious displacement of the articular disc,with its stress compacted area moves outward.The opposite condyle may shift forward,inward or downward,with its stress compacted area may move outward.And the articular disc may shift inward or outward,with its stress compacted area may move outward.3.If abnormal position changes of condyle and articular disc were found in the imageological examination of a patient in clinic,vigilance should be aroused to check the reasons timely,and advocate early treatment as far as possible,so as to correct the structure in TMJ in time,and relieve abnormal stress,to prevent the symptoms of TMD and more serious craniofacial asymmetry.