Have you ever observed whether your child sleeps with his mouth closed at night. Why is it important to keep your mouth closed when you sleep? Please do a test first. First close your mouth and swallow a little, and there is no abnormal feeling? No, it feels very relaxed and normal. Then you open your mouth to swallow saliva, will not swallow it. Many people open their mouths will not swallow saliva, some have to lift their heads and feel the neck muscles exerting themselves. Imagine if the child sleeps with his mouth open, if you do swallowing action, the muscles of the neck will pull the jawbone, people do not know how many times a day to do the swallowing action. Open mouth breathing for a long time by bad muscle tension, the jawbone will be deformed, and the teeth behind will be over-erupted, that is, the face will be stretched. At the same time air will be inhaled directly into the mouth to stimulate the tonsils, triggering chronic tonsillitis and further aggravating open-mouth breathing. Diseases of the nose can cause nasal breathing disorders, which can also trigger open-mouth breathing. It is also common to see nasal hypertrophy, or paranasal depression, and midface hypoplasia. Relaxation of the labial muscles during open mouth breathing often results in a short upper lip, a condition that is difficult to correct later, and there are few effective plastic surgery methods to address the short upper lip. Early preventive treatment is to find a way to keep the child’s mouth closed. The first thing to do is to find out if there are any nasal respiratory problems causing open mouth breathing, such as rhinitis, tonsillitis, hyperplasia, etc. As the saying goes, “winter illnesses are treated in summer”. These respiratory dysfunctions are not resolved, how can the mouth be closed. Generally when the breathing disorder is solved and you can breathe through your nose, you can start treatment by wearing a myofunctional orthosis.