Normal breathing is done through the nasal cavity, if suffering from rhinitis, turbinate hypertrophy, nasal polyps, adenoid hyperplasia, and tonsil hypertrophy, etc., resulting in nasal obstruction, have to use the mouth breathing instead of nasal breathing. There are also a few people who do not have nasal disorders, but just habitually use mouth breathing. Mouth breathing will endanger the nasal cavity, oral cavity, tongue, lips, cheeks, teeth, as well as the upper and lower jaws, maxillofacial muscles, and eventually cause oral and maxillofacial dysfunction and jaw morphology abnormalities, such as nasal root septum, nasal atrophy; lip short, thick and ectropion; frontal cover high arch, upper dental arch narrow, front teeth protrusion, front teeth can not cut food, at this time, not only facial shape abnormal, but also the function is affected. When breathing, the air is directly inhaled by the mouth without nasal filtration, which has caused upper respiratory tract infections and colds; dry and inflamed mouth and gums, even affecting pronunciation, slurred bite and incoherent speech. In order to determine whether mouth breathing is possible, first of all, an ENT doctor should be invited to examine and treat various nasal disorders, so that the nasal cavity is open and can perform normal breathing functions. After the nasal disorders are ruled out, the necessary training should be conducted to change the habit of breathing through the mouth. Specific training methods are as follows: 1, when doing exercises or jogging, pay attention to the closed mouth and nose breathing. 2, wear a thick mask when sleeping, covering only the mouth and not the nasal cavity. 3.Do upper and lower lip and cheek muscle training every day. For example, repeatedly use the upper and lower lips to hold a piece of hard paper and draw it out quickly, 3 times a day for 5-10 minutes each time. You can also clip the magnetic card with the upper and lower lips until fatigue. 4, often closed mouth puffing, whistling, blowing trumpets, eating lollipops, chewing gum and blowing bubbles, and tongue and cheek muscle movement to promote oral and dental cleaning. 5.If the above self-training still does not improve, you must seek treatment from a dental specialist. Such as making a vestibular shield to block mouth breathing, or making orthodontic appliances to expand the dental arch and correct the deformity. Even after the orthodontic appliance, but also with functional training, in order to receive results.