chiN

Chin refers to the forward-most part of the lower face. Anatomically it is defined by the mental eminence of the mandible, with the pogonion as the most forward point and the menton as the lowest border point. The overlying skin contains subcutaneous fat, and the chin is muscularized by the mentalis and adjacent muscles. The mental nerve, a branch of the inferior alveolar nerve, traverses the chin region and supplies sensation to the chin and lower lip.

Developmentally, the chin is part of the mandible formed by intramembranous ossification. Growth of the chin contributes to the contour of the lower face and is influenced by dental occlusion and jaw relationships. There is considerable variation in chin size and projection between individuals and populations; on average males have a more prominent chin than females.

Clinically, chin morphology contributes to facial balance and aesthetics. Abnormal projection can accompany skeletal jaw relationships: micrognathia (small chin), macrogenia (enlarged chin), retrognathia (receding chin), and prognathism (forward-positioned mandible). Fractures of the chin or surgical alteration may affect sensation and contour. In orthodontics and plastic surgery, the chin is a focal point in cephalometric analysis and facial augmentation planning.

Treatment options range from non-surgical fillers for mild augmentation to surgical genioplasty or alloplastic implants for repositioning or enlarging the chin. Risks include numbness from mental nerve injury and asymmetry.