Myoelectric Characteristics Of Masticatory Muscles At Maximum Clenching In Patients With TMJ Anterior Disc Displacement And Its Auxiliary Diagnosis For Anterior Disc Displacement

Background:Temporomandibular disorders(TMD),as a general term for a class of TMJ disease,is characterized by mandibular movement dysfunction,pain in temporomandibular joint(TMJ)area and joint sound,which excludes other clinical or pathological diagnosis such as rheumatism.TMD is divided into two categories,according to diagnostic criteria for TMD(DC/TMD).Class ? consists of painful diseases,including myogenic pain,arthralgia and TMD related pain.Class ? consists of temporomandibular joint anterior disc displacement,degenerative joint disease,and subluxation of joint.Since TMD is a general term for a group of diseases,involving the structure of masticatory muscles,occlusion and temporomandibular joint;and the clinical manifestations of symptoms and signs often overlap,the classification and differential diagnosis of TMD has been difficult.Anterior disc displacement is the most common type of TMD,which can be initially diagnosed by chief complaint,history of present illness and physical examination.However,imaging diagnosis is still essential for a definite diagnosis and classification.Previous imaging examinations included dental orthopantomography,transcranial lateral projection,and transpharyngeal lateral projection.These X-ray examinations have the disadvantage of overlapping images and unclear display of anterior disc displacement;and temporomandibular joint arthrography is an invasive examination,and some patients are allergic to contrast media.With the development of equipment,temporomandibular joint magnetic resonance imaging(MRI)becomes the"gold standard" for the diagnosis of TMD anterior disc displacement.However,MRI equipment is rather expensive and difficult to popularize in primary hospitals.Therefore,it is necessary to establish a diagnosis method that is simple to manipulate,cheap as well as high in diagnostic sensitivity and specificity for the diagnosis of anterior disc displacement.The masticatory muscles and the temporomandibular joints are working together in oral function.Physiological and pathological state of the mucles and joint can be reflected by electromyographic signals from oral functional movements.There is an abnormality of physiological signals,before abnormal manifestation is showed in imaging of temporomandibular joint.And early diagnosis can provide a better prognosis.The Biopak system is used to record physiological signals of stomatognathic system that is capable of simultaneously recording multiple pairs of masticatory muscles,3D movement signals of mandible and joint sound.In this study,the Biopak system was used to record SEMG of the masseter and anterior temporalis,and characteristic value of SEMG was extracted by programs based on Matlab platform.The myoelectric characteristics in anterior disc displacement group and healthy control group were compared in order to investigate the correlation between anterior disc displacement and myoelectricity activity of masticatory muscle.Moreover,the study is also intended to investigate the application value of masticatory muscle SEMG in the diagnosis of anterior disc displacement in order to establish a preliminary diagnostic criteria for anterior disc displacement with the BioPAK system.Objective:This study is intended to investigate the diagnostic value of masticatory muscles myoelectric activity for temporomandibular joint anterior disc displacement by comparing the difference in myoelectric activity of masseter muscles and temporalis muscles between temporomandibular joint anterior disc displacement patients and healthy controls.Subject and Methods:In this study,23 volunteers without TMD signs were included as healthy controls,and 21 patients with temporomandibular joint anterior disc displacement were included as case groups.The surface electromyography signals of bilateral masseter muscles and anterior temporalis at intercuspal position with maximum clenching of healthy controls and patients were collected by BioPAK system and transferred from TRC.file to TXT file.The myoelectric characteristics was extracted by programs based on Matlab and parameters such as the average voltage and kurtosis level of SEMG were calculated to find out their sensitivity and specificity for the diagnosis of temporomandibular joint anterior disc displacement.Results:The surface electromyogram voltage levels of bilateral anterior temporalis regions and right masseter muscle region in the experimental group were significantly lower than those in control group(p<0.05).The sensitivity of the voltage level to the diagnosis of anterior disc displacement is 76.2%?81.0%,and the specificity is 47.8%?60.9%.Kurtosis levels of bilateral anterior temporalis and masseter muscle regions in the experimental group were significantly higher than those in control group(p<0.05),with the sensitivity of 38.1%?61.9%and specificity of 82.6%?100.0%.Conclusion:In patients with temporomandibular joint anterior disc displacement,the average surface electromyogram voltage levels of bilateral masseter and anterior temporalis regions at intercuspal position with maximum clenching is highly sensitive to the diagnosis of temporomandibular joint anterior disc displacement,while the kurtosis level is highly specific.Therefore,taking both of the two parameters into consideration will have diagnostic value for the anterior disc displacement.