The causes of convexity of the mouth mainly include congenital hereditary factors, acquired developmental factors and environmental factors. 1. Hereditary factors: If parents have convex mouth, it may be passed on to the next generation of children. 2. Acquired developmental factors: Commonly, overdevelopment of the maxilla and overdevelopment of the maxillary anterior teeth can cause the teeth to protrude, resulting in a protruding mouth. 3. Environmental factors: For example, having bad habits such as mouthing or breathing through the mouth for a long time may cause protruding mouth. If it is caused by congenital genetic factors, there is no symptom, usually do not need to be treated. It is important to correct bad habits in a timely manner. If you have maxillary bone or maxillary teeth dysplasia, you should consult your doctor for orthodontic treatment.