Hypodontia
This condition can be genetically-linked and in severe cases, may present themselves in the form of ectodermal dysplasia, cleft lip or palate or Down Syndrome.
[2] Several studies have discovered that anteriorly missing teeth can accompany retrognathic maxilla, also known as an underbite, prognathic mandible, where the lower jaw protrudes out more than normal, and smaller posterior cranial base length.
Coupled with that, findings consistent among individuals include: Several theories regarding the aetiology of hypodontia have been proposed in existing literature.
[7] Preliminary studies focused on an evolutionary approach which suggested shortening of the intermaxillary complex and thus shorter arches may contribute to a decrease in number of teeth.
This was also suggested in 1945 by Dahlberg using Butler's Field Theory that focused on evolution and development of mammalian teeth into human dentition in an attempt to analyse different of agenesis.
[9] A subsequent theory hypothesised the teeth at the end of each region were possibly "vestigial bodies" that became obsolete during the evolutionary process.
At present, it has been theorised that evolutionary change is working to decrease the human dentition by the loss of an incisor, premolar and molar in each quadrant.
[10] Theories focusing on anatomical principle, hypothesised that specific areas of the dental lamina are especially prone to environmental effects during tooth maturation.
[7] Svinhufvud et al. (1988) suggested that teeth that were more prone to absence developed in areas of initial fusion of the jaw.
[12] Commonly affected regions were found to undergo innervation last, this might imply the developmental relationship between nerve and hard tissue.
Thalidomide (N-phthaloylglutamine) was also discovered to have a causative effect on mothers who took the drug during pregnancy, resulting in congenitally missing teeth in their children.
[30][31][32] The pattern of congenitally missing teeth seen in monozygotic twins is different, suggesting an underlying epigenetic factor, which may be due to the simultaneous occurrence of two anomalies.
[33] This multifactorial aetiology involves environmental factors which trigger the genetic anomalies, resulting in the occurrence of dental agenesis.
[40][41] A study showed that single nucleotide polymorphisms in PAX9 were highly associated with missing upper lateral incisors.
[42] Its polymorphic variant may be associated with hypodontia such as missing lower incisors or in a more severe form of agenesis like oligontia (lack of six or more permanent teeth).
In the 1960s and 1970s, several studies were conducted sponsored by the U.S. Atomic Energy Commission, with the aim of finding a link between genetics and hypodontia.
[57] Interpersonal relationships and perceived qualities, such as intelligence, friendliness, social class, and popularity can be affected by dentofacial appearance.
[57] Some studies have shown that the extent of complaints made by patients[further explanation needed] was associated with the severity of the condition and the number of missing permanent teeth.
[58] Therefore, a divergence from perceived ideal dentofacial aesthetic, particularly in children, might adversely affect self-esteem and self-confidence besides attracting mockery from peers.
[61] It has been found that individuals with hypodontia experience more difficulty during mastication or functioning movements due to smaller occlusal table available.
[74] It should also be noted that spaces within the dental arch should be monitored, especially in younger patients, as teeth are more likely to drift, tilt or over-erupt.
The primary molars present also functions as a space maintainer, prevent alveolar bone resorption and delays future prosthodontic space replacement by acting as a semi permanent solution going into adulthood[72] Previous studies also shown a good prognosis of retained primary molars going into adulthood.
[81] It can be an option for hypodontia management in the case of missing maxillary lateral incisors through the reshaping, and mesial re-positioning of the adjacent canine.
[80] This management is indicated in hypodontia cases of Class I molar relationship with severe crowding in the mandibular anterior region where the extraction of lower premolar leads to a predictable outcome, and Class II molar relationship in the absence of crowding and protrusion of the mandibular anterior dentition.
These include facial profile, size and dimension of canine, the shade of colour of the teeth and the gingival contour and height.
[80] However, the alteration in appearance during orthodontic treatment (e.g. creating diastema for placement of prostheses) before the filling up the space, although temporary, can negatively impact the oral health-related quality of life in adolescents.
[87] Removable partial dentures are known to be an effective interim method for maintaining functional and aesthetic demands in a growing patient, where definitive fixed restorations are not suitable yet.
[75] Removable dentures act as a space maintainer and also prevent the migration of adjacent or opposing teeth, thereby preserving the face height.
[75] Removable prosthetic devices are also known to cause damage to the remaining teeth if worn over a long period of time.
[33] Placing dental implants has proven to be a predictable and reliable method of treating hypodontia, along with bringing excellent aesthetic results.
