The failure of operation may be related to the choice of hospital. The reasons that often lead to such consequences are as follows: first, the length of bone resection is too short, and the mandibular angle bone block is triangular or short arc resection; Secondly; The surgeon's aesthetic defects and his unfamiliarity with the distribution and anatomy of neural tubes in the mandibular marginal region are afraid of cutting off the mandibular marginal bone.