Study On The Correlation Of Mandibular Deviation With Cervical Posture And Cervical Muscle Chain

Objective:The subjects of this study were adult patients with skeletal mandibular deviation and normal subjects.The experiment adopts CBCT to explore the degree of skeletal mandibular deviation and the change of mandible position in patients with mandibular deformity and its correlation with cervical posture in patients with jaw deformity.And using EMG to detect the muscle activities of the head,neck and shoulder muscles in different mandibular movements in patients with mandibular deviation and to investigate the changes in the symmetry and coordination of those muscle movements,in order to provide the reference for clinical diagnosis and treatment planning on patients with facial asymmetry malformation.Methods:CBCT images from 30 adult patients with skeletal mandibular deviation and 30 adult individuals with facial symmetry were analyzed and imported in Invivo 5 to reconstruct a3 D hard-tissue surface model.A reference frame was set up and 20 measurements of the mandible and cervical vertebrae were performed to calculated.The difference between the three-dimensional position of the mandible and the posture of cervical spine were analyzed in patients with mandibular asymmetry and normal people.Electromyography was performed in the subjects mentioned above.Muscle activities were recorded with surface electrodes in the cranial and maxillofacial muscles such as bilateral anterior temporalis(TA),masseter muscles(MM),sternocleidomastoid(SCM)and trapezius(TRAP)areas during different mandibular movements such as mandibular resting position,mandibular forward extension,mouth opening as wide as possible,biting in the position of maximum intercuspation,mastication and lateral movements using Bio EMG III.Muscle activity intensity and asymmetric index of muscular activity were calculated and analyzed using ttests and the Pearson correlation method with P<0.05 chosen as significance level.Results:1.Compared with the normal maxillofacial symmetry groups,there were significant differences in the degree of skeletal mandibular asymmetry and cervical deviation in the mandibular deviation groups(P<0.05),and the degree of cervical deviation was positively connected with that of mandibular asymmetry.2.There were continuous muscle activities in the head,neck and shoulder muscles during the resting position in both groups.With the increase of bite force,the EMG activities in the head,neck and shoulder muscles in the facial symmetry groups also increased,while this activity pattern was not obvious in the mandibular deviation groups.During the middle movements,the discrepancy rates of EMG activities of bilateral muscles in the mandibular deviation groups were higher than those in the normal maxillofacial symmetry groups(P<0.05),but the differences were lower than those in the normal maxillofacial symmetry groups(P<0.05)in the mandibular lateral movements.These results indicated that the symmetrical muscle activity of normal people’s bilateral homonymic muscles was better than that of people with facial asymmetry.In the normal groups,the activity intensity of bilateral sternocleidomastoid,anterior temporalis and masseter muscles showed a trend of simultaneous growth during mandibular movements with occlusal contact such as biting and chewing,but no such pattern was found in the mandibular deviation groups.It was suggested that the coordination and adjustability of head,neck and shoulder muscles in normal subjects were better than those in patients with mandibular deviation.Conclusion:1.There is an inherent correlation between the occurrence of mandibular deviation and the deflection of cervical posture,and they interact on each other.The deformity of mandible affects the three-dimensional posture of the cervical vertebra and can cause different degrees of cervical deflection.Compared with the patients with normal jaw,the deformity among the patients with skeletal mandibular asymmetry has a tendency to tilt forward and bend forward.The abnormal posture of the cervical spine will also affect the three-dimensional position of the mandible,causing the lower 1/3 of the face to appear facial asymmetry with the deflection of the head and neck posture.2.The head,neck and shoulder muscles can play an important synergistic role in the mandibular rest positions and mandibular movements among normal people.The symmetry and coordination of muscle activities in patients with skeletal mandibular asymmetry are not as good as those in healthy adult subjects.