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.[clarification needed]
In the case of mandibular prognathism (never maxillary prognathism) this is often also referred to as Habsburg chin, Habsburg's chin, Habsburg jaw or Habsburg's jaw[2][3] especially when referenced with context of its prevalence amongst historical members of the House of Habsburg.[2]
Mandibular prognathism is typically pathological, whereas maxillary prognathism is often found as a result of normal human population variation.
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]
Presentation
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.
In humans, non-pathological maxillary and alveolar prognathism can occur due to normal variation among phenotypes.
However, mandibular prognathism is usually anomalous, and it may be a malformation, the result of injury, a disease state, or a hereditary condition.[4]
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.
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]
Maxillary prognathism affects the middle third of the face, causing the maxilla to jut out, thereby increasing the facial area.
Mandibular prognathism is a protrusion of the mandible, affecting the lower third of the face.
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 seven-year-old girl.
Not all alveolar prognathism is anomalous, and significant differences can be observed among different ethnicities.[5]
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;[6] 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]
On average, Neanderthals were far more prognathic than modern humans regarding the maxilla. This maxillary prognathism, along with their wide noses, suggests that their faces were not adapted to cold climate.[7]
Mandibular prognathism is a potentially disfiguring genetic disorder where the lower jaw outgrows the upper, resulting in an extended chin and a crossbite. In both humans and animals, it can be the result of inbreeding.[8]
Unlike alveolar or maxillary prognathism, which are common traits in some populations, mandibular prognathism is typically pathological.
In brachycephalic or flat-faced dogs, like shih tzus and boxers, it can lead to problems such as underbite.[9]
In humans, it results in a condition sometimes called lantern jaw, reportedly derived from 15th century horn lanterns, which had convex sides.[10][lower-alpha 1] Traits such as these were often exaggerated by inbreeding, and can be traced within specific families.[8]
Although more common than appreciated, the best known historical example is Habsburg jaw, or Habsburg or Austrian lip, due to its prevalence in members of the House of Habsburg, which can be traced in their portraits.[12] The process of portrait-mapping has provided tools for geneticists and pedigree analysis; most instances are considered polygenic,[13] but a number of researchers believe that this trait is transmitted through an autosomal recessive type of inheritance.[14][12]
Allegedly introduced into the family by a member of the Piast dynasty, it is clearly visible on family tomb sculptures in St. John's Cathedral, Warsaw. A high propensity for politically motivated intermarriage among Habsburgs meant the dynasty was virtually unparalleled in the degree of its inbreeding. Charles II of Spain, who lived 1661 to 1700, is said to have had the most pronounced case of the Habsburg jaw on record,[15] due to the high number of consanguineous marriages in the dynasty preceding his birth.[14][12]
Charles II of Spain showing Habsburg jaw, a severe type of mandibular prognathism.
Prior to the development of modern dentistry, there was no treatment for this condition; those who had it simply endured it. 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.[16]
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.[17]
1 2 Peacock, Zachary S.; Klein, Katherine P.; Mulliken, John B.; Kaban, Leonard B. (September 2014). "The Habsburg Jaw-re-examined". American Journal of Medical Genetics. Part A. 164A (9): 2263–2269. doi:10.1002/ajmg.a.36639. PMID24942320. S2CID35651759.
In vertebrates, the maxilla is the upper fixed bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxillary bones are fused at the intermaxillary suture, forming the anterior nasal spine. This is similar to the mandible, which is also a fusion of two mandibular bones at the mandibular symphysis. The mandible is the movable part of the jaw.
Hypodontia is defined as the developmental absence of one or more teeth excluding the third molars. It is one of the most common dental anomalies, and can have a negative impact on function, and also appearance. It rarely occurs in primary teeth and the most commonly affected are the adult second premolars and the upper lateral incisors. It usually occurs as part of a syndrome that involves other abnormalities and requires multidisciplinary treatment.
The inferior alveolar nerve (IAN) (also the inferior dental nerve) is a sensory branch of the mandibular nerve (CN V3) (which is itself the third branch of the trigeminal nerve (CN V)). The nerve provides sensory innervation to the lower/mandibular teeth and their corresponding gingiva as well as a small area of the face (via its mental nerve).
Orthognathic surgery, also known as corrective jaw surgery or simply jaw surgery, is surgery designed to correct conditions of the jaw and lower face related to structure, growth, airway issues including sleep apnea, TMJ disorders, malocclusion problems primarily arising from skeletal disharmonies, and other orthodontic dental bite problems that cannot be treated easily with braces, as well as the broad range of facial imbalances, disharmonies, asymmetries, and malproportions where correction may be considered to improve facial aesthetics and self-esteem.
In orthodontics, a malocclusion is a misalignment or incorrect relation between the teeth of the upper and lower dental arches when they approach each other as the jaws close. The English-language term dates from 1864; Edward Angle (1855–1930), the "father of modern orthodontics", popularised it. The word "malocclusion" derives from occlusion, and refers to the manner in which opposing teeth meet.
The inferior alveolar artery is an artery of the head. It is a branch of the maxillary artery. It descends through the infratemporal fossa as part of a neurovascular bundle with the inferior alveolar nerve and vein to the mandibular foramen where it enters and passes anteriorly inside the mandible, supplying the body of mandible and the dental pulp of the lower molar and premolar teeth. Its terminal incisor branch supplies the rest of the lower teeth. Its mental branch exits the mandibula anteriorly through the mental foramen to supply adjacent lip and skin.
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 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 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 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.
Overbite is the extent of vertical (superior-inferior) overlap of the maxillary central incisors over the mandibular central incisors, measured relative to the incisal ridges.
In jawed vertebrates, the mandible, lower jaw, or jawbone is a bone that makes up the lower – and typically more mobile – component of the mouth.
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.
Erik Arne Björk was a Swedish dentist famous for his The Face in Profile Analysis which he published in 1947. He is also known to develop the implant radiography.
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.
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 term "open bite" was coined by Carevelli in 1842 as a distinct classification of malocclusion. Different authors have described the open bite in a variety of ways. Some authors have suggested that open bite often arises when overbite is less than the usual amount. Additionally, others have contended that open bite is identified by end-on incisal relationships. Lastly, some researchers have stated that a lack of incisal contact must be present to diagnose an open bite.
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.
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