prognathism /prog″nəthiz′əm/ [Gk, pro + gnathos, jaw] , an abnormal facial configuration in which one or both jaws project forward. It may be real or imaginary, depending on anatomical and developmental factors. Real prognathism may exist when both the mandible and the maxilla increase in length or when the maxillary length is normal and the mandibular length increases excessively. Imaginary prognathism may exist when the maxilla is underdeveloped and the mandibular length is normal. −prognathic, adj.
