The Study Of Mandibular Movement And Hyperpathia Of Painful Myofascial Temporomandibular Disorders

Temporomandibular disorders(TMD)are a group of pathologic conditions involving the temporomandibular joint and masticatory muscles.For TMD patients the main concern is pain,which is the most common reason for medical consultation;and also a great challenge for clinicians.The main symptoms of TMD are pain in the face and the anterior ear area,limited mandibular movement,and noise in the temporomandibular joint during mandibular movement.For TMD patients,pain and mandibular movement disorders are the most easily perceived clinical symptoms and the most common cause of treatment.However,due to the unknown cause of TMD,the clinical treatment of the disease is not yet satisfactory.The most common types of TMD include pain related functional disorders(TMD induced muscle pain,headache,and joint pain)and articular related functional disorders(mainly including joint disc displacement and degenerative diseases).Myofascial pain is a type of muscle pain caused by TMD.It is the most common type of oral and maxillary pain.The temporomandibular joint disorder characterized by myofascial pain is called myofascial pain type temporomandibular joint disease(MTMD),belonging to pain-related functional disorders.Although there are a lot of studies in related fields,the exact pathophysiological mechanism of TMD is still unclear.It is believed that TMD is a disorder syndrome caused by multiple factors,and the sensitization of the central and peripheral nervous system may be an important mechanism for the occurrence of TMD-related oral and maxillofacial pain.Pain is a subjective feeling,and is resulted by the interaction between the stimulation of the body and the pain transmission system.In themaxillofacial area,noxious stimuli first excite specific receptors,and the receptors receive signals that are transmitted from specific afferent nerve fibers to the brain stem,resulting in pain sensation through central analysis and feedback.Like other parts of the body,the free nerve endings in the maxillofacial are the basis of the peripheral structure that feels pain.Many free endings act as receptors and respond to traumatic stimuli in the maxillofacial.Free nerve endings are widely found in maxillofacial tissues such as facial skin,oral mucosa,temporomandibular joints,periodontal membranes,dental pulp,periosteum,and muscles.They are connected to small diameter medullary nerve fibers Aδ and myelineless nerve fibers C.Therefore,the noxious stimulation of the oral and maxillofacial area is transmitted by small diameter nerve fibers at the outer circumference.TMD-related maxillofacial pain is mainly related to small nerve fiber lesions in the body,and conventional neurological examinations can not detect small nerve fiber diseases.Quantitative sensory testing(QST)is a psychophysiological method for evaluating the function of somatic nerve fibers and is currently the only method for evaluating small nerve fiber lesions.QST method can be used to evaluate the function of coarse sensory fiber,fine sensory fiber and its central transitional pathway,which has the advantages of non-invasive and quantitative.Standard QST tests are divided into mechanical stimulation tests and thermal stimulation tests.At present,TMD patients with maxillofacial pain have been confirmed by mechanical stimulation tests,while the results of thermal stimulation tests have not been consistent.Besides pain,mandibular movement disorder is also the main clinical symptom of TMD patients,mainly limited in anterior extension,open and lateral movement of mandibular.The mandibular kinesiograph can be used to record the mandibular movement track of TMD patients,but it is difficult to generalize in clinical examination because of the complicated operation.The DC/TMD checklist developedby the International Dental Research Institute is a specialist checklist for clinical examinations of temporomandibular joint disorders.It can record mandibular motor functions in detail and can be used to analyze the mandibular movement characteristics of TMD patients.In this study,a quantitative thermal testing method and a DC/TMD checklist are proposed to test the thermal perception threshold,temporal summation effect and mandibular movement index of healthy subjects and MTMD subjects,and compare the differences between the two groups of subjects.This study is aimed to explore whether there is peripheral and central sensitization in MTMD patients and analyze the changes of mandibular movement in MTMD patients,in order to provide a basis for better diagnosis and treatment of myofascial pain temporomandibular joint disorder.The results show that:1.There are no gender in mandibular movement and thermal perception in healthy subjects,while the thermal detection and cold pain perception were more sensitive in trigeminal region than extra-trigeminal region,and there was no difference between two sides of trigeminal region.2.MTMD patients are more sensitive in both trigeminal and extra-trigeminal regions in thermal pain and cold pain perception.There are no gender difference in mandibular movement and thermal perception in MTMD patients;while the cold pain perception is more sensitive in trigeminal region than in estra-trigeminal region.3.Temporal summation can be induced in healthy subjects with supra thermal stimuli.There are no gender differences but region differences in temporal summation with more sensitive in trigeminal region.4.Temporal summation can be induced in MTMD patients with supra thermal stimuli.MTMD subjects are more sensitive than healthy subjects in both trigeminal andextra-trigeminal regions.In summary,by testing the mandibular movement function and quantitative sensory function of MTMD patients and healthy subjects,the gender and site characteristics of the mandibular movement and quantitative temperature perception thresholds of the two groups were obtained.By comparing thermal perception threshold and inducing temporal summation with supra thermal pain stimuli,the peripheral and central sensitization mechanisms of MTMD patients were confirmed,which provide a basis for further diagnosis and treatment of myofascial pain temporomandibular joint disorders.