Prognathism

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Prognathism
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Prognathism 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.[ citation needed ]

Contents

Presentation

Prognathism in humans can be 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 or a hereditary condition. [1]

Prognathism is considered a disorder only if it affects chewing, speech or social function as a byproduct of severely affected aesthetics of the face.[ citation needed ]

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.[ citation needed ]

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.[ citation needed ]

Prognathism should not be confused with micrognathism, although combinations of both are found. It affects the middle third of the face, causing it to jut out, thereby increasing the facial area, similar to the phenotype of archaic hominids and apes. Mandibular prognathism is a protrusion of the mandible, affecting the lower third of the face. Alveolar prognathism is a protrusion of that portion of the maxilla where the teeth are located, in the dental lining of the upper jaw.[ citation needed ]

Prognathism can also be used to describe ways that the maxillary and mandibular dental arches relate to one another, including malocclusion (where the upper and lower teeth do not align). When there is maxillary or alveolar prognathism which causes an alignment of the maxillary incisors significantly anterior to the lower teeth, the condition is called an overjet. When the reverse is the case, and the lower jaw extends forward beyond the upper, the condition is referred to as retrognathia (reverse overjet).[ citation needed ]

Classification

Alveolar prognathism

Alveolar prognathism, caused by thumb sucking and tongue thrusting in a 7-year-old girl. Alveolprog.jpg
Alveolar prognathism, caused by thumb sucking and tongue thrusting in a 7-year-old girl.

Not all alveolar prognathism is anomalous, and significant differences can be observed among different ethnic groups. [2]

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.[ citation needed ]

Alveolar prognathism can also easily be corrected with fixed orthodontic therapy. However, relapse is quite common, unless the cause is removed or a long-term retention is used.[ citation needed ]

Maxillary prognathism

In disease states, maxillary prognathism is associated with Cornelia de Lange syndrome; [3] however, so-called false maxillary prognathism, or more accurately, retrognathism, where there is a lack of growth of the mandible, is by far a more common condition.[ citation needed ]

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. The same can be said for mandibular prognathism.[ citation needed ]

Mandibular prognathism (progenism)

15th-century lantern with a jutting base. OHM - Geburt Christi 1e.jpg
15th-century lantern with a jutting base.

Pathologic mandibular prognathism is a potentially disfiguring genetic disorder where the lower jaw outgrows the upper, resulting in an extended chin and a crossbite. It is most often the result of inbreeding. [4]

This condition is sometimes colloquially known as lantern jaw (the OED defines lantern jaw differently, as "long thin jaws, giving a hollow appearance to the cheek", [5] like an old lantern with concave horn sides), and Habsburg jaw, Habsburg lip, or Austrian Lip (as depicted in portraits of Charles V of the House of Habsburg), due to its prevalence in that bloodline. [6] The trait is easily traceable in portraits of Habsburg family members. [7] This has provided tools for people interested in studying genetics and pedigree analysis. Most instances are considered polygenic. [8]

It is alleged to have been derived through a female from the Mazovian branch of the princely Polish family of Piast. The deformation of lips is clearly visible on tomb sculptures of Mazovian Piasts in the St. John's Cathedral in Warsaw. However this may be, there exists evidence that the trait is longstanding. It is perhaps first observed in Vlad Dracula (1431–1476/77) and Maximilian I (1459–1519).[ citation needed ]

Traits such as these that were common to royal families are believed to have been passed on and exaggerated over time through royal intermarriage which caused acute inbreeding. Due to the large amount of politically motivated intermarriage among 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. [9] Many dog breeds have underbite, particularly those with short faces, like shih tzus and boxers. This too might be due, as in the case of bulldogs, to severe inbreeding.

Treatment

Example of mandibular prognathism, where teeth have almost reached their final, straight position by dental braces. This makes the prognathism more obvious, and it will take an operation, moving the jaw backwards, to give the ultimate result. Pre-surgery.PNG
Example of mandibular prognathism, where teeth have almost reached their final, straight position by dental braces. This makes the prognathism more obvious, and it will take an operation, moving the jaw backwards, to give the ultimate result.

Prior to the development of modern dentistry, there was no treatment for this condition: those who had it simply endured the condition. Today, the most common treatment for mandibular prognathism is a combination of orthodontics and orthognathic surgery. The orthodontics can involve braces, removal of teeth, or a mouthguard.[ citation needed ] None of this, however, removes the predisposing genetic condition.

The surgery required has led, in some cases, to identity crises in patients, whereby the new facial structure has a negative impact mentally on how the patients perceive themselves.[ citation needed ]

In insects

In entomology, prognathous means that the mouthparts face forwards, being at the front of the head, rather than facing downwards as in some insects. [10]

See also

Related Research Articles

Dental braces Form of orthodontia

Dental braces are devices used in orthodontics that align and straighten teeth and help position them with regard to a person's bite, while also aiming to improve dental health. Braces also fix gaps. They are often used to correct underbites, as well as malocclusions, overbites, open bites, deep bites, cross bites, crooked teeth, and various other flaws of the teeth and jaw. Braces can be either cosmetic or structural. Dental braces are often used in conjunction with other orthodontic appliances to help widen the palate or jaws and to otherwise assist in shaping the teeth and jaws.

Malocclusion misalignment or incorrect relation between the teeth of the two dental arches when they approach each other as the jaws close

A malocclusion is a misalignment or incorrect relation between the teeth of the two dental arches when they approach each other as the jaws close. The term was coined by Edward Angle, the "father of modern orthodontics", as a derivative of occlusion. This refers to the manner in which opposing teeth meet.

Palatal expansion Orthodontics

A palatal expander is a device in the field of orthodontics which is used to widen the upper jaw (maxilla) so that the bottom and upper teeth will fit together better. This is a common orthodontic procedure. Although the use of an expander is most common in children 8-18 years of age, it can also be used in adults, although expansion is slightly more uncomfortable and takes longer. A patient who would rather not wait several months for the end result by a palatal expander may be able to opt for a surgical separation of the maxilla. Use of a palatal expander is most often followed by braces to then straighten the teeth.

Veterinary dentistry field of dentistry applied to the care of animals

Veterinary dentistry is the field of dentistry applied to the care of animals. It is the art and science of prevention, diagnosis, and treatment of conditions, diseases, and disorders of the oral cavity, the maxillofacial region, and its associated structures as it relates to animals.

Orthodontic technology is a specialty of dental technology that is concerned with the design and fabrication of dental appliances for the treatment of malocclusions, which may be a result of tooth irregularity, disproportionate jaw relationships, or both.

Occlusion, in a dental context, means simply the contact between teeth. More technically, it is the relationship between the maxillary (upper) and mandibular (lower) teeth when they approach each other, as occurs during chewing or at rest.

Overjet

Overjet is the extent of horizontal (anterior-posterior) overlap of the maxillary central incisors over the mandibular central incisors. In class II malocclusion the overjet is increased as the maxillary central incisors are protruded.

Crossbite

Crossbite is a form of malocclusion where a tooth has a more buccal or lingual position than its corresponding antagonist tooth in the upper or lower dental arch. In other words, crossbite is a lateral misalignment of the dental arches.

Cephalometric analysis is the clinical application of cephalometry. It is analysis of the dental and skeletal relationships of a human skull. It is frequently used by dentists, orthodontists, and oral and maxillofacial surgeons as a treatment planning tool. Two of the more popular methods of analysis used in orthodontology are the Steiner analysis and the Downs analysis. There are other methods as well which are listed below.

Cecil C. Steiner American dentist

Cecil C. Steiner was a dentist and one of Edward H. Angle's first students in 1921. He developed a form of cephalometric analysis, presented in 1953, referred to as the Steiner method of analysis.

A jaw abnormality is a disorder in the formation, shape and/or size of the jaw. In general abnormalities arise within the jaw when there is a disturbance or fault in the fusion of the mandibular processes. The mandible in particular has the most differential typical growth anomalies than any other bone in the human skeleton. This is due to variants in the complex symmetrical growth pattern which formulates the mandible.

Serial extraction is the planned extraction of certain deciduous teeth and specific permanent teeth in an orderly sequence and predetermined pattern to guide the erupting permanent teeth into a more favorable position.

Human mouth mouth of a human being

In human anatomy, the mouth is the first portion of the alimentary canal that receives food and produces saliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth.

Dentition analyses are systems of tooth and jaw measurement used in orthodontics to understand arch space and predict any malocclusion. Example systems of dentition analysis are listed below.

Clifford Ballard was a British orthodontist. He became England's first Professor of Orthodontics in 1956. He served as the President of BSSO in 1957.

Frankel appliance or Frankel Functional Regulator is an orthodontic functional appliance which was developed by Rolf Fränkel in 1950s. This appliance primarily focused on the modulation of neuromuscular activity in order to produce changes in jaw and teeth. The appliance was opposite to the Bionator appliance and Activator appliance.

Jean Delaire was a French orthodontist known for developing the Delair Facemask or reverse headgear. This facemask is used to treat children who have maxillary retrognathism and mandibular prognathism.

Open bite is a type of orthodontic malocclusion which has been estimated to occur in 0.6% of the people in the United States. This type of malocclusion has no vertical overlap or contact between the anterior incisors. The prevalence varies between different populations, for instance, occurring with 16% in black people and 4% in white people. The term "open bite" was coined by Carevelli in 1842.

Orthodontic indices are one of the tools that are available for orthodontists to grade and assess malocclusion. Orthodontic indices can be useful for an epidemiologist to analyse prevalence and severity of malocclusion in any population.

References

  1. Fotek, Ilona (2018-02-05). "Prognathism: MedlinePlus Medical Encyclopedia". www.nlm.nih.gov.
  2. Vioarsdóttir US, O'Higgins P, Stringer C (2002). "A geometric morphometric study of regional differences in the ontogeny of the modern human facial skeleton". J. Anat. 201 (3): 211–29. doi:10.1046/j.1469-7580.2002.00092.x. PMC   1570912 . PMID   12363273.
  3. "de Lange syndrome definition - Medical Dictionary definitions of popular medical terms easily defined on MedTerms". medterms.com.
  4. Román Vilas, Francisco C. Ceballos, Laila Al-Soufi, Raúl González-García, Carlos Moreno, Manuel Moreno, Laura Villanueva, Luis Ruiz, Jesús Mateos, David González, Jennifer Ruiz, Aitor Cinza, Florencio Monje & Gonzalo Álvarez (2019). "Is the "Habsburg jaw" related to inbreeding?". Annals of Human Biology. 46 (epub ahead of print). doi:10.1080/03014460.2019.1687752. PMID   31786955.CS1 maint: multiple names: authors list (link)
  5. "lantern jaw". Oxford English Dictionary (3rd ed.). Oxford University Press. September 2005. (Subscription or UK public library membership required.)
  6. Online Mendelian Inheritance in Man (OMIM) PROGNATHISM, MANDIBULAR -176700
  7. Chudley, Albert E. (1998). "Genetic landmarks through philately – the Habsburg jaw". Clinical Genetics. 54 (4): 283–4. doi:10.1111/j.1399-0004.1998.tb03729.x. PMID   9831338.
  8. Wolff G, Wienker TF, Sander H (1993). "On the genetics of mandibular prognathism: analysis of large European noble families". J. Med. Genet. 30 (2): 112–116. doi:10.1136/jmg.30.2.112. PMC   1016265 . PMID   8445614.
  9. Yanko Tsvetkov (27 February 2014). Essays on Prejudice: Deep Thoughts on Domesticating Scapegoats and Slapping Labels on Everything That Makes Your Ass Itch. Alphadesigner. pp. 27–28. GGKEY:HS4ZFSTW6JK.
  10. "Prognathous". A Glossary of Entomological Terms. Retrieved 11 September 2019.
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