Prognathism
From Wikipedia, the free encyclopedia
| ICD-10 | K07.1 |
|---|---|
| ICD-9 | 524.10 |
| DiseasesDB | 29354 |
| MeSH | D011378 |
The word prognathism derives from Greek pro (forward) and ganathos (jaw). If strictly applied, this word refers to conditions where the mandibular (lower) dental arch seems to be more protruded with respect to the maxillary (upper) dental arch. Prognathism refers to one possible way that the maxillary and mandibular dental arches can relate together. Orthodontists often refer to this type of maxillofacial relationship as Skeletal Class III. It is popularly called an underbite.
Prognathism in all its kinds can be a hereditary condition which develops during growth or may be, more seldomly, the result of injury or disease.[1]. It exists to varying degrees and takes different forms.
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[edit] Medical definitions
[edit] Alveolar prognathism
An alveolar prognathism is limited to the dento-alveolar region of the jaw. It can be limited to one jaw or to both of them (biprotrusion). In these cases the front teeth are inclined forward. Alveolar prognathism can be combined to maxillary or mandibular prognathism.
Harmful habits, such as thumb sucking or tongue thrusting can result in or exaggerate an alveolar prognathism, causing teeth to misalign. Functional appliances can be used in growing children to help modify bad habits and neuro-muscular function, with the aim of correcting this condition.
Alveolar prognathism can be easily corrected also with fixed orthodontic therapy. However, relapse is quite common, unless the cause is removed or a long term retention is used.
[edit] Maxillary prognathism
Maxillary prognathism is a protrusion of the maxilla, and is also a common feature of many populations. It affects a large area of the face, causing it to jut out, thereby increasing the facial area. In disease states, it is associated with de Lange Syndrome[2]. False maxillary prognathism, where there is a lack of growth of the mandible, is by far a more common condition.
Prognathism, if not extremely severe, can be treated in growing patients with orthodontic functional or orthopaedic appliances. In adult patients this condition can be corrected by means of a combined surgical/orthodontic treatment, where most of the time a mandibular advancement is performed.
[edit] Mandibular prognathism (Progenism)
Mandibular prognathism is a disfiguring, genetic disorder where the lower jaw outgrows the upper, resulting into an extended chin.
The condition is colloquially referred to as Habsburg jaw, Habsburg lip or Austrian Lip (see Habsburg) due to its prevalence in that bloodline. The trait is easily traceable in portraits of Habsburg family members. This has provided tools for people interested in studying genetics and pedigree analysis.
It is alleged to have been derived through a female from the princely Polish family of Piasts, its Masovian branch. The deformation of lips is clearly visible on tomb sculptures of Mazovian Piasts in Warsaw. However this may be, we have at least good evidence that the remark is of old date. It is perhaps first observed in Maximilian I (1459-1519).
Traits such as these that were common to royal families are believed to have been passed on and exaggerated through royal intermarriage which caused massive inbreeding. Due to the large amount of politically motivated intermarriage between Habsburgs, the dynasty was virtually unparalleled in the degree of its inbreeding. Charles II of Spain is said to have had the most pronounced case of the Habsburg jaw on record (his jaw was so deformed that he was unable to chew).
Many dog breeds have underbite, particularly those with short faces. These can get caught in their jowls.
[edit] Racial or ethnic anthropology
Most types of prognathism in humans as well as orthognathous profiles are normal variations among phenotypes and occur frequently in various populations with a greater number of intra-group variations (differences between sub-groups within the groups) than inter-group variations (physical differences between groups). Nevertheless, a number of anthropologists of the nineteenth-century believed that a classification in racial categories and their social development could be determined by measuring the facial angle, jaw structure and the shape of the head of humans, and claimed that people with a more orthognathous profile were superior to other cultures because they had "evolved" more than other races.
After Darwin popularized the idea that humans are descended from apes, the prognathous (protruding) jaw became a sign of lower development and of a closer relationship to primitive man. It also became the basis of much racial stereotyping of the Irish, and racial anthropologists argued that working class people were more prognathous than their social superiors- who were- self-flatteringly described as also biologically superior. In his very influential book, The Races of Man (1862), John Beddoe, the future president of the Anthropological Institute, emphasized the vast difference between the prognathous (protruding) and orthognathous (less prominent) jawed people of Britain. These were terms originally The Irish, Welsh, and significantly, the lower class people, were among the prognathous, whereas all men of genius were orthognathous. (Beddoe also developed an Index of Nigressence, from which he argued that the Irish were close to Cro-Magnon man and thus had links with the "Africinoid" races!) These activities were reminiscent of Pieter Camper's theory of a 'facial angle'. One should emphasize, however, that such craniological and anthropometric studies "always represented a minority" of the papers presented at the Anthropological Institute, 1871-1899. These late nineteenth-century anatomical and anthropological descriptions of 'races' and their characteristics, measurements etc. were later the inspiration for the sort of mid twentieth-century racial anthropology as promulgated in Nazi Germany. (Anthony S. Wohl [3])
Modern forensic scientists and anthropologists outside the U.S. point out that trends in skeletal dimensions cannot be used for ascertaining racial differences between humans, but facial prognathism is still used by U.S. forensic scientists and U.S. forensic anthropologists as a key metric to estimate to which of the three judicially-enforced, appearance-based U.S. "racial" groups (Black, White, Yellow) human remains would have been assigned in life [4], with European populations estimated to have an orthognathous, or flat profile and northeast Asians having prognathism to a moderate degree. Among some sub-Saharan populations, Nilotic peoples, such as the Dinka of Somaliaas, and some of the people of Melanesia, alveolar and maxillary prognathism is said to be more pronounced, with large incisors and an often more pronouncedly receding chin line.
Maxillary prognathism was also one of the major criteria used by Carleton Coon, 20th-century America's most influential craniofacial anthropometrist, in his now-obsolete studies distinguishing Sub-Saharan "Caucasoids" (the people of Senegal, Gambia, Chad, Niger, Sudan, Ethiopia and Somalia) from what he called "Congoids."
[edit] Notable people with the condition
- Charles II of Spain suffered from the condition and was unable to chew as a result.
- Charles V, Holy Roman Emperor (Charles I of Spain)
- Bill Cowher
- Cymburgis of Masovia, Piast princess through whom the condition was brought into the Habsburg family
- Bruce Forsyth
- Jimmy Hill
- Jay Leno
- Maximilian I, Holy Roman Emperor
- Philip II of Spain
- Philip IV of Spain
- Michael Schumacher
