Temporomandibular joint disorder syndrome: It is one of the common diseases of the oral and maxillofacial area, and is the most common among temporomandibular joint diseases. It is not a single disease, but a general term for a group of diseases with the same or similar clinical symptoms whose etiology is not fully understood. Generally, there are three types of symptoms: myalgia in the TMJ area and/or masticatory muscles; abnormal jaw movements and associated dysfunction; and joint popping, crushing sounds and murmurs. TMD is mostly a functional disorder, but it can also involve structural disorders of the joints or even organic damage, but it is generally self-limiting and belongs to musculoskeletal disorders. Etiology: 1. Psychosocial factors. Patients often have emotional anxiety, irritability, nervousness, easily agitated and insomnia and other mental symptoms, some patients can be obvious that there is a causal relationship between mental and emotional factors and the onset of the disease, in patients with chronic prolonged, can also be found in the influence of mental factors on the recurrence of symptoms. 2. Dental factors. Clinical examination of patients with TMD often reveals obvious dental factors, including interference, early cusp contact, severe clenching, deep overdentures, absence of most posterior teeth and excessive wear of the dentition surface resulting in low vertical distance. 3. Immunological factors. Immunological studies have shown that the main components of articular cartilage such as collagen polysaccharides and chondrocytes are antigenic. Because articular cartilage is wrapped in matrix, it is isolated from the vascular system from embryo to adult and becomes a closed antigen, which cannot be recognized by the autoimmune system. Related experimental studies indicate that TMD also involves cellular immunity. 4. Excessive joint loading. Moderate weight-bearing is necessary to maintain the normal structure, function and physiological alterations of the joints and is of great importance. However, excessive weight bearing, beyond the physiological limits can cause degenerative changes or even damage to the joint. 5. Anatomical factors of the joint. From a functional point of view, the TMJ has evolved with human beings to make the joints and jaws more dexterous in order to adapt to the more complex jaw movements of speech and expression. Because of this, the corresponding joints and muscle ligaments have become significantly weaker from an anatomical standpoint, and the weight-bearing capacity of the joints has decreased. This increase in the type, flexibility and range of joint movements in humans is a potential threat to the temporomandibular joint with weakened anatomy. 6. Other factors. Cold stimulation of the joint area, poor posture causing muscle dysfunction that affects the normal position of the mandible and condyle, etc. are also factors that trigger TMJ disorders.