1) Mental overexcitement Children, playful by nature, play too much during the day, too excited or fatigued, or frightened, restless and anxious, or learning tension, so that the excitation and inhibition process of their cerebral cortex out of balance, inducing the movement of the chewing muscle to occur in a momentary irregular spasm or contraction, resulting in night grinding. 2) Intestinal parasitic disease Ascaris lumbricoides likes to move around in the intestine after the child falls asleep and secretes many kinds of toxins. The toxins stimulate the intestine and speed up intestinal peristalsis, causing indigestion, pain around the umbilicus and restless sleep; if the toxins stimulate the nerves, the nerves become excited and cause teeth grinding. Similarly, pinworms also secrete toxins and cause anal itching, affecting the child’s sleep and making teeth grinding sounds. However, it is important to note that a child cannot be judged to have worms simply by grinding his teeth, and if necessary, he should go to the hospital to have his doctor examine him. 3) Digestive disorders If a child eats too much before bedtime, a lot of food fills the gastrointestinal tract and stimulates the digestive tract, the nerves transmit these stimuli to the brain, so that the brain cells that manage digestion are excited, through reflex action, causing teeth grinding. 4) Unbalanced nutrition Some children have the habit of picky eating, especially do not like to eat vegetables, forming a nutritional imbalance, resulting in calcium, phosphorus, various vitamins and trace elements deficiency, causing involuntary contraction of the facial chewing muscles at night, the teeth will grind back and forth. For example, children with rickets are likely to grind their teeth, and after giving vitamin D supplements, the phenomenon of grinding teeth will improve. 5) Dental disease The dental development during the period of tooth replacement causes dental occlusion disorders, chronic periodontitis and other dental diseases. 6) Other: psychomotor epilepsy, hysteria, or dreaming and eating can cause teeth grinding at night. 7) In a few cases, the cause is not found and may be related to heredity.