Antegonial notching of the mandible: an often overlooked mandibular deformity in congenital and acquired disorders.

Mandibular antegonial notching is a concavity of the undersurface of the body just anterior to the angular process (gonion) seen in congenital and acquired disorders. The notch tends to be longer in the congenital than in the acquired state, and the ascending ramus is at a more obtuse angle to the body.