Hypodontia is an inherited condition characterized by developmentally missing teeth, without taking the absent third molars into account. In the case where there are six or more missing permanent teeth, the condition is called oligodontia. Anodontia refers to the condition where no teeth are present. Supernumerary teeth refers to conditions where there are more teeth than the usual number.
Missing third molars occur in 9-30% of studied populations. In primary dentition the maxilla is more affected, with the condition usually involving the maxillary lateral incisor.
Many other terms to describe a reduction in number of teeth appear in the literature: aplasia of teeth, congenitally missing teeth, absence of teeth, agenesis of teeth and lack of teeth.
Video Hypodontia
Prevalence
In persons of European ancestry, the most common missing teeth are the wisdom teeth (25-35%), the permanent upper lateral incisors (2%), the lower second premolars (3%), or the upper second premolar, with a higher prevalence in females than in males. The prevalence of missing primary teeth is found at 0.1-0.9%, with a 1:1 male to female ratio. Excluding the third molars, missing permanent dentition accounts for 3.5-6.5%. Similar trends of missing teeth can be seen in approximately 3-10% of orthodontic patients.
30-50% of people with missing primary teeth will have missing permanent teeth, as well.
In a systematic review in the Journal Of Orthodontics, the overall prevalence of hypodontia was found to be 6.4%, with the highest occurrence in Africa (13.4%). There is an increased risk of hypodontia in females than in males.
Maps Hypodontia
Other dental anomalies associated with Hypodontia
- Conical shaped teeth
- Ectopic canines
- Cleft lip and palate
- Diastema
- Delayed eruption
Cause
The cause of isolated missing teeth remains unclear, but the condition is believed to be associated with genetic or environmental factors during dental development. Missing teeth have been reported in association with increased maternal age, low birth weight, multiple births and rubella virus infection during embryonic life.
In a recent study assessing environmental risk factors for hypodontia, it was established that maternal smoking does play a causative role in Hypodontia. Passive smoking and caffeine were also assessed but showed no statistical significance.
There is a possible correlation between tooth agenesis and innervation. A relationship was also postulated between abnormalities of the brainstem and the presence of agenesis.
Hypodontia is often familial, and can also be associated with genetic disorders such as ectodermal dysplasia or Down syndrome. Hypodontia can also be seen in people with cleft lip and palate.
Among the possible causes are mentioned genetic, hormonal, environmental and infectious.
Cause due to hormonal defects: idiopathic hypoparathyroidism and pseudohypoparathyroidism. Exists the possibility that this defect depends on a moniliasis (candidiasis, candida endocrinopathy syndrome).
Environmental causes involving exposure to PCBs (ex.dioxin), radiation, anticancer chemotherapeutic agents, allergy and toxic epidermal necrolysis after drug.
Infectious causes of hypodontia: rubella, candida.
The Journal of the American Dental Association published preliminary data suggesting a statistical association between hypodontia of the permanent teeth and epithelial ovarian cancer (EOC). The study shows that women with EOC are 8.1 times more likely to have hypodontia than are women without EOC. The suggestion therefore is that hypodontia can serve as a "marker" for potential risk of EOC in women.
Also the increased frequency of hypodontia in twins and low birth weight in twins with hypodontia suggests that environmental factors during perinatal are responsible hypodontia.
Genetics
Genetic causes also involve the genes MSX1 and PAX9.
Genetic associations for selective tooth agenesis ("STHAG") include:
Genetics has always played a crucial role in dental aplasia. 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. This multifactorial aetiology involves environmental factor which triggers the genetic anomalies resulting the occurrence of dental agenesis. Common environmental factors include infection, trauma and drugs which predispose to the condition. In hereditary cases, evidence of dental germ developing after surrounding tissues have closed the space required for development may be a huge contributing factor as well.
Another supported aetiological theory would be the polygenic mode of inheritance. The combination of epistatic genes and environmental factors exert influences on the phenotypic expression of genes involved, thus disturbing the initial proliferation of tooth germ. Isolated cases can be autosomal dominant, recessive or even X-linked patterns of inheritance. Mutations in MSX, PAX9 and TGFA genes are known to cause congenitally missing teeth in some racial groups. MSX1 and MSX2 are homeobox genes crucial in mediating direct epithelial-mesenchymal interactions during craniofacial bone and teeth development. MSX1 commonly results in missing second premolars and third molars, with a small percentage of first molars. PAX9 and TGFA are involved in regulating between MSX1 and PAX9 causing hypodontia of the molars.
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.
Restorative management of hypodontia
The oral rehabilitation of hypodontia, especially where a significant number of teeth have not developed, is often a multidisciplinary process, involving a specialist orthodontist, a consultant in restorative dentistry, and a paediatric dentist in the earlier years. The process of treating and managing hypodontia begins in the early years of the patient's dentition where absent teeth are identified and the process of maintaining the remaining teeth begins. This is largely conducted by the paediatric dentist with orthodontic input. Once all the adult teeth have erupted the orthodontist is likely to liaise with the restorative dentist regarding optimal positioning of teeth for subsequent replacement with prosthodontic methods. This may include the utilisation of a resin-retained bridge and implants for spaces or composite resin, veneers or crowns where teeth are diminutive or misshaped.
References
Source of article : Wikipedia
0 Comments