The main causes of mandibular recession include the following: 1. functional factors: generally due to dental factors or bad oral habits; 2. bony factors: bony factors, i.e. factors affecting the development of the mandible, such as otitis media when some patients had otitis media, which affects the development center of the mandibular condyle after otitis media, because the front of the external ear canal is the mandibular condyle, which is mainly the development center of the mandible. If otitis media affects the developmental center of the mandible, the child’s mandible will be smaller, and the whole face will look like a bird-shaped face, i.e., the upper jaw protrudes and the lower jaw shrinks. In clinical practice, when we meet a patient, we have to trace the cause of the otitis media and find out whether the otitis media had pus as a child, whether the treatment of the otitis media was timely, and whether it spread to the temporomandibular joint, thus causing the underdevelopment of the mandible.