Prognathism

Prognathism, also called Habsburg jaw or Habsburgs' jaw primarily in the context of its prevalence amongst members of the House of Habsburg, is a positional relationship of the mandible or maxilla to the skeletal base where either of the jaws protrudes beyond a predetermined imaginary line in the coronal plane of the skull. In general dentistry, oral and maxillofacial surgery, and orthodontics, this is assessed clinically or radiographically (cephalometrics). The word prognathism derives from Greek πρό (pro, meaning 'forward') and γνάθος (gnáthos, 'jaw'). One or more types of prognathism can result in the common condition of malocclusion, in which an individual's top teeth and lower teeth do not align properly. Prognathism in humans, particularly alveolar prognathism, can occur due to normal variation among phenotypes. In human populations where prognathism is not the norm, it may be a malformation, the result of injury, a disease state, a hereditary condition, or, if not pathological, may simply be a minority trait within a population. Prognathism is considered a disorder only if it affects chewing, speech or social function as a byproduct of severely affected aesthetics of the face. Clinical determinants include soft tissue analysis where the clinician assesses nasolabial angle, the relationship of the soft tissue portion of the chin to the nose, and the relationship between the upper and lower lips; also used is dental arch relationship assessment such as Angle's classification. Cephalometric analysis is the most accurate way of determining all types of prognathism, as it includes assessments of skeletal base, occlusal plane angulation, facial height, soft tissue assessment and anterior dental angulation. Various calculations and assessments of the information in a cephalometric radiograph allow the clinician to objectively determine dental and skeletal relationships and determine a treatment plan. Prognathism should not be confused with micrognathism, although combinations of both are found.