A 5-year-old child grinding his teeth at night may be caused by intestinal parasites, indigestion, vitamin D deficiency, emotional factors and so on. 1. Intestinal parasites: when children have roundworms in the small intestine, they will stimulate the intestinal wall to secrete toxins and cause indigestion, abdominal pain, and grinding of teeth at night; pinworms will lay eggs in the anus at night, causing anal itching and grinding of teeth at night. 2. Indigestion: If the child eats more before going to bed, it is difficult to fully absorb, and there will be teeth grinding at night. 3. Vitamin D deficiency: Vitamin D deficiency can lead to decalcification of bones, muscle pain, etc. It can also lead to restlessness at night, easy night sweating, grinding teeth at night, and occipital baldness. 4. Emotional factors: If the child is too excited to play during the day, or watch scary cartoons, etc., it can also cause teeth grinding at night. 5-year-old children grinding teeth at night timely to the hospital, clear causes after active treatment, so as not to delay the condition.