Under normal circumstances, when the upper and lower teeth are engaged, the upper anterior teeth should be bitten outside the lower anterior teeth. If the opposite is the case, the lower anterior teeth are bitten outside the upper anterior teeth, which is what we often call the anti-jaw, commonly known as “ground pack” day”. The anti-jaw of teeth not only affects the appearance, but also hinders our interpersonal communication, but also greatly affects our health. How is the anti-jaw caused? The anti-jaw can be simply manifested as an anterior tooth reflex, but the posterior teeth are normal, and there is no obvious abnormality in the facial shape. In severe cases, in addition to the anterior teeth reflex, the posterior teeth are mesially misaligned and the l / 3 of the face is underdeveloped, and the mandibular protrusion is deformed. Divided into three types: 1. Dental origin is mostly caused by local obstacles, manifested as a simple anterior tooth reversal, anti-coverage is small, the molar relationship is neutral or near-neutral. The size and shape of the mandible are normal, and the relationship between the upper and lower jaws is normal. The mandible can retreat to the tangential relationship, and the face is basically normal. 2. Functional type Much of the mandibular functional over-extension and anterior teeth inversion caused by poor feeding posture, etc. The size and shape of the mandible are normal, and the mandible can retreat to the anterior incisal bisect relationship. 3. Bone-derived type is mostly caused by genetic and disease factors. In addition to the anterior teeth reflex, the reverse coverage is large, the molars are mesial, and the jaw deformity is manifested as long mandible body, short mandibular branch and blunt mandibular angle, insufficient maxillary development, obvious forehead protrusion, and the mandible cannot be spontaneous. Recession, the face is concave, and sometimes accompanied by opening and closing deformities.