To determine whether the mouth is convex or not is mainly to see whether the tip of the nose, upper lip, chin in a straight line. To determine the convexity of the mouth, you can take a ruler or wool judgment, with a ruler or wool directly connected to the tip of the nose, upper lip, chin, under normal circumstances, the three points in a straight line. If they are not in a straight line, the human mouth may be concave or convex. If the lips are projected forward, especially more than 2mm, it should be considered that a convex deformity may be present. At the same time, the patient’s lifestyle habits may also indicate a convex mouth. When the patient sleeps, he or she often opens his or her mouth to breathe because of poor nasal breathing, which tends to cause adenoidal facies, leading to a protruding mouth. To know for sure if you have a protruding mouth, you can go to a specialized dental institution to have lateral radiographs taken or a professional examination, etc.