“The scientific name for this condition, which is encountered in daily life and at work, is “temporomandibular joint dislocation”. Many of our friends and patients often ask, “Why does the jaw drop? Before we know the reason, let’s understand “TMJ dislocation” first! Dislocation of the TMJ (temporomandibular joint dislocation) refers to the condylar process of the mandible due to external force or abnormal joint structure, the condylar process exceeds the normal range of motion, and detaches from the joint fossa without being able to reset itself. It can occur unilaterally or bilaterally, and can be categorized into anterior dislocation, posterior dislocation, medial dislocation and lateral dislocation according to the direction of dislocation. Acute anterior dislocations, recurrent dislocations and old anterior dislocations of the mandibular joint are more common in clinical practice. Regarding the causes of TMJ dislocation, the following 7 factors are generally summarized. ① Inadequate treatment of acute anterior dislocation of the mandibular joint can lead to recurrent or habitual dislocation. In the imaging examination, it can be found that the joint capsule, joint ligaments and joint disc attachment are obviously lax, and because of the repeated impact of the condyle on the articular nodes, the condyle and the articular nodes are flattened, the joint fossa becomes shallow, and the masticatory muscles are dysfunctional. ② The elderly, frail and sick or patients with systemic and consumptive diseases are prone to occur, arthrography can be seen in the joint capsule laxity, disc attachment avulsion, joint nodes become flat. (iii) Some “improper” or “excessive” behaviors, such as sudden opening of the mouth too wide, such as laughing, singing, yawning, chewing hard food or nausea and vomiting can easily lead to temporomandibular joint dislocation. Medical factors, such as oral treatment, such as tooth extraction, tooth preparation, inlays, full mouth implantation time is too long (more than 30 minutes); and then for oropharyngeal surgery or examination, the use of the cotter is excessive, so that the condylar eminence is detached from the joint fossa, shifted to the front of the joint joint nodes, and dislocation occurs. Also such as oral tracheal intubation, tracheoscopy, laryngoscopy, esophageal endoscopy, gastroscopy, open-heart device, neonatal use of forceps and other factors that make the opening of the mandible is too large, the condyle over the joint nodes can not be self-recovery; the joint capsule and joint ligament laxity, habitual excessive mandibular movement, rapid jaw movement can increase the probability of anterior dislocation. ⑤ External force factors, fights, car accidents and other accidents and playing basketball, soccer and other confrontational and intense projects, open state, the jaw will be dislocated by external force. (6) Stale dislocation, acute anterior dislocation fails to timely and correct treatment, the time is more than two weeks, the patient has been in the state of temporomandibular joint dislocation for a long time, the dislocated condyle, the joint fossa and the fibrous connective tissue around the joint disk proliferation and the formation of stale dislocation, then the joint reset is even more difficult, usually need surgery to solve. (7) congenital factors, common in the joint ligament or joint capsule development is more “fragile” “congenital insufficiency”. From the above you can see that “laugh off the jaw” is true, often “drop jaw” will affect the quality of life or work, there is this disease early treatment is what should be done, although not many methods, the effect is not certain.