EDA gene defects cause ectodermal dysplasia, which is also known as X-linked hypohidrotic ectodermal dysplasia. Common dental features of ectodermal dysplasia are multiple missing teeth and microdontia.PAX9 and TGFA are involved in regulating between MSX1 and PAX9, causing hypodontia of the molars.Hypodontia can be found in isolated cases too. The familiar or sporadic type of isolations are more frequently reported than the syndromic type. Isolated cases of autosomal dominant, autosomal recessive, or X-linked inheritance patterns may have an impact on the isolation conditions in expressing variation of both penetration and expressivity of traits. Mutations in MSX, PAX9 and TGFA genes are known to cause congenitally missing teeth in some racial groups. Research
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. Impact
There are numerous studies and research reports on the prevalence, aetiology, and treatment of hypodontia and the dentoskeletal effect of hypodontia. A few studies have investigated Oral Health-related Quality of Life (OHRQoL) in individuals with hypodontia and provided some evidence that hypodotia may have an impact on quality of life. Psychosocial
Cosmetic dentistry has become more notable and prevalent in modern society. Interpersonal relationships and perceived qualities, such as intelligence, friendliness, social class, and popularity can be affected by dentofacial appearance.
A delay in tooth development may also serve as an indication, whereby the absence of an adult successor slows down the normal resorption of the roots of the baby teeth, which is the progressive loss of parts of the tooth. Misplaced (ectopic) positioning of the adult teeth may be discovered upon examination or a radiograph. One of the consequences may be an adult tooth intercepting with a baby tooth, causing premature loss or wrong positioning. This can be due to either the absence of neighboring teeth acting as a guide during eruption or the lack of space in the jaw for them to erupt into because of malocclusion. Skeletal features
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. Occurrence of hypodontia can be associated with reduced anterior lower facial height and lip protrusion. This can be linked to lower maxillary to mandibular plane angles. A more acute mandibular angle and flatter chin may develop as a result. These characteristics become more prominent as the condition becomes progressively severe, particularly when more than one tooth is missing. Other dental and radiographic features
Data derived from principal component analysis of radiographic images show that children with mild hypodontia may display significant increase of the interincisal angle and decrease in the maxillary and mandibular incisor angles. Cephalometric tracing is commonly used to study a patients dentofacial proportions in the craniofacial complex.