"Chinese character face" is also called square face, which can be divided into rectangular face and short square face. The formation of square face is mainly caused by the hypertrophy and heaviness of mandibular angle on one side of mandible. At the same time, it is accompanied by hypertrophy of masseter muscle attached to it, which is extremely obvious when biting teeth. This kind of face shape appears gradually in the development period, and may also be related to excessive masseter activity, which is basically stereotyped in adulthood.