After nightfall, most people have been sound asleep. However, there are some people (especially children and adolescents), in the sleep will grind up teeth. As no food in the mouth when grinding teeth at night, the amount of saliva secretion is correspondingly reduced, the teeth are not lubricated, so that the formation of the “dry grinding teeth” like pushing the empty mill. Night grinding teeth is what is going on? Is it harmful to the human body? Can be prevented? Why do some people grind their teeth at night? It turns out that the action of grinding teeth is caused by the continuous contraction of the muscles of mastication. The chewing muscle is managed by the motor branch of the third branch of the trigeminal nerve. As for why the motor branch is so excited, the mechanism is not particularly clear as to why the chewing muscle is ordered to keep contracting at night when the body neither eats nor drinks. However, from a clinical point of view, examples of teeth grinding caused by dental disease, ascariasis and gastrointestinal dysfunction are often seen. Ascaris lumbricoides parasitic in the human intestine can secrete a variety of toxins, such as neurotoxins, allergic toxins, hemolytic toxins, and enzymatic toxins. In addition, some of the metabolites discharged by the worms will also constantly stimulate the corresponding parts of the sleeping human brain, so that some people continue to contract the chewing muscles at night, thus causing the phenomenon of teeth grinding. In addition, if children play too excited during the day, or those who work too much during the day, the night before bedtime is also busy, too tired people, after sleep, although most of the cerebral cortex in a state of inhibition, but there will be part of the region (such as the trigeminal nerve of the brain bridge) in a state of excitement. Thus, it will send a “signal” to order the chewing muscles of the face for a short period of continuous contraction. So the sleeping person will show that the jaw involuntarily up and down, left and right back and forth movement, so that the “squeaky” grinding sound. This night grinding, others can hear clearly, but the teeth grinder himself is completely unknown. He is not a disease, as dreaming, talking in their sleep. In summary: the causes of night grinding are: (1) genetic genes; (2) neurological disorders; (3) dental misalignment; (4) intestinal parasitic infections; (5) drugs, such as antidepressants, caffeine, etc.; (6) teething; (7) excessive emotional tension or excitement; (8) smoking, drinking alcohol. Is grinding teeth at night harmful to the human body? If you often “dry grinding”, the wear and tear on the teeth is quite serious. Over time, the worn teeth will be different degrees of soreness or pain, and sometimes the formation of jaw joint disorder. Severe night grinding will speed up the wear and tear of the teeth to appear the symptoms of tooth hypersensitivity, and even cause periodontal tissue damage, chewing muscle fatigue and temporomandibular joint dysfunction. The prevention and treatment of night grinding should start from the cause in order to receive good results. (1) Eliminate tension, remove unnecessary worries, be open-minded and arrange study and work reasonably. (2) Develop good living habits, regular living and living, dinner should not be too full. Avoid alcohol and coffee before going to bed, and it is best not to eat or do strenuous exercise. (3) Develop good habits of hygiene to prevent and control intestinal parasitic infections. If intestinal parasites are suspected, deworming should be carried out under the guidance of a physician to reduce intestinal parasite peristalsis and stimulate the intestinal wall. (4) Check for digestive system diseases and treat promptly. (5) Correct poor biting habits, such as unilateral chewing and pencil biting. (6) Sleeping in the side-lying position can reduce and alleviate nocturnal teeth grinding than in the supine position. (7) The above treatment still does not improve, especially those who have a family history of night grinding should go to the dentistry department to make a dental pad, wear it on the teeth at night before going to bed and take it off in the morning to prevent tooth wear.