I. Confusion of TMD diagnosis The introduction of various new diagnostic instruments and equipment, as well as various diagnostic reagents, has strongly promoted the understanding and confirmation of thousands of human diseases. However, unfortunately, the diagnosis of TMD still mainly relies on detailed history taking, comprehensive clinical signs examination and imaging examination. Due to the different understanding of TMJ disorders, there are different differences and debates on the diagnosis and management of the disease among different disciplines and specialties and even among different specialists of the same specialty. The lack of a unified “gold standard” for the diagnosis and treatment of TMJ disorders has caused many clinicians to have numerous problems in the diagnosis and treatment of the disease. The first systematic classification of temporomandibular joint disorder syndrome was proposed by Prof. Zhang Zhenkang as early as 1973, which classified the disease into: joint functional disorder, joint structural disorder, and organic joint destruction, and the classification was written into the book of Oral and Maxillofacial Surgery, a unified textbook of national higher medical institutions, in 1977, which is very useful for clinicians in China. In 1997, in order to avoid the confusion in the naming, diagnosis and classification of TMJ disorders, Ma Xuchen-Zhang Zhenkang proposed to change TMJ disorder syndrome into TMJ disorders and proposed a new classification standard to divide the disease into: masticatory muscle disorders, structural disorders, inflammatory diseases and osteoarthropathies. However, since TMD is a group of diseases, and clinically, TMD is often referred to as displacement of the articular disc; therefore, can we consider expanding the extension of TMD and discussing each type of disease separately, so as to guide the treatment? Clinical observations have long revealed that TMD is a self-limiting disease, and most patients can heal spontaneously without the involvement of systemic factors or systemic diseases. Therefore, classical textbooks have emphasized the principles of treatment. The basic principles of TMJ disorder treatment are: 1. a comprehensive treatment based on conservative therapy; 2. a combination of symptomatic treatment and elimination or reduction of causative factors; 3. treatment of local symptoms of the joint should be accompanied by improvement of the systemic condition and the patient’s mental status; 4. patients should be educated about treatment so that they can self-medicate and self-protect the joint; 5. a rational and logical treatment procedure must be followed 5. a rational and logical treatment procedure must be followed; 6. the principle of progressive treatment should be followed. However, this treatment principle is mainly for disc displacement and does not apply to all types of TMD. In addition, there is no standard answer to the question of what treatment and cure criteria are needed for articular disc displacement. sato et al. followed up 44 patients diagnosed with irreducible anterior displacement of the articular disc with no treatment at the initial diagnosis, and the pain was significantly reduced after 6 months, and the degree of opening was significantly improved after 12 months. after 18 months, only 2 cases had joint pressure pain. lundh et al. followed up 26 patients with irreducible anterior displacement of the disc with no treatment, and the pain was significantly reduced after 12 months. Kurita et al. followed 40 patients without treatment for 25 years, and each patient was confirmed to have irreducible anterior disc displacement by MRI; after 25 years, 43% were asymptomatic and 33% had reduced symptoms. Kobayashi et al. studied 41 patients with TMD who had failed to respond to conservative treatment, and first performed MRI and arthrography, which confirmed that all of them had irreducible anterior displacement. However, on MRI review, only one of the 28 asymptomatic patients had a repositioned disc, one had a partial reposition, one had a reversible disc displacement, and 25 still had an irreversible disc displacement. These studies suggest that most patients with TMD can heal themselves or be cured. However, healing is only the disappearance of symptoms, and the discs are not necessarily repositioned. III. Clinical research problems of TMD In the past 10 years, a large number of papers on TMD are basic studies, and there are few important studies on clinical treatment. The limited clinical studies have reported various treatments that are often effective. However, it is difficult to make a definitive conclusion as to which treatment modality is superior, mainly due to the lack of an objective and accepted evaluation system. There are many examples in the literature of evaluating the efficacy of a treatment method based on clinical experience alone, and there are more or less problems in the trial design, evaluation methods, and evaluation indicators of the results, etc. The data lack authenticity and poor credibility. At present, there is no more standardized evaluation system for the efficacy of TMJ disorders in China, and domestic researchers specializing in TMJ disorders should do something about it. IV. TMD and orthodontic treatment problems The occlusal factor as one of the causative factors of TMJ disorders has been controversial, and many studies deny the correlation, but it is accepted by many clinicians. Developmental occlusal abnormalities are a chronic process in which adaptive changes in the muscles and joints may occur without symptoms. However, the adapted anatomy and physiology may be in a state that is not the most conducive to resisting external stresses and other stimuli, and may be susceptible to damage when a variety of stimuli are present. Malocclusion often causes occlusal interference, which disrupts the coordination between the joint, muscles and TMJ, thus affecting the occurrence and development of TMD. Proper orthodontic treatment can not only maintain and promote the function and health of the oromandibular system, but also serve as one of the effective means of joint treatment. The relationship between misalignment and TMD cannot be effectively responded by using the An’s misalignment classification, but should be more focused on the impact of the coaptation type on the function of the oromandibular system. Symptoms of TMD are associated with deep overlap greater than 5 mm and superficial overlap conformation less than 1 mm. There is a clear correlation between posterior retrusion and muscle symptoms. Functional malocclusions such as coincidental interference are more likely to cause TMD if they are present with Ann’s Class II, Class III, anterior open and anticlinal contracts. When TMD is in the stage of masticatory muscle dysfunction, the efficacy of orthodontic treatment is more certain at this time, and the consolidation of the treatment is more stable. In patients with reversible disc displacement, orthodontic treatment can normalize the early disc dysfunction and relieve the symptoms. For patients with loosened disc attachment, the symptoms cannot be completely eliminated. Orthodontic treatment is not recommended for patients with non-reducible displacement of the articular discs resulting in limited jaw movement. Orthodontic treatment can be chosen if the joint organism has been basically stabilized and the problem of disconnection is really needed at this time. Orthodontic treatment should not be used immediately when the bone destruction of the condyle is in the active phase.