Also found in: Dictionary, Medical.
the condition in which the forward protrusion of the upper jaw in relation to the total frontal surface of the face is absent or greatly reduced; the term is contrasted with “prognathism.” The degree of protrusion of the jaw is loosely dependent on the length and breadth of the face. The facial angle in orthognathism ranges from 85° to 92.9°. Within the same range, “orthognathism” is conventionally used to designate the degree of straightness of the midfacial section and of the alveolar part of the upper jaw. Orthognathism is an exclusive morphological characteristic of human beings and is the result of the predominance of the cerebral portion of the skull over the facial portion.