3-year-old children sleep grinding teeth may be caused by periodontitis, parasitic infection, lack of vitamins and other reasons, need to analyze the specific causes. 1. Periodontitis: Oral diseases such as periodontitis can lead to nighttime teeth grinding symptoms, which may be caused by periodontitis stimulating the gums, leading to teeth grinding symptoms at night. 2. Parasitic infections: Parasites such as roundworms and pinworms can be active at night, producing some toxins or metabolites that stimulate the nerves and cause teeth grinding. 3. Vitamin deficiency: Vitamin D deficiency rickets patients, because of the lower blood calcium, can also produce the symptoms of night grinding. 3-year-old children with symptoms of nocturnal teeth grinding, should be timely to the hospital, improve the relevant examination to clarify the cause of the disease, under the guidance of the doctor symptomatic treatment.