Hypodontia
| Hypodontia | |
|---|---|
| Classification and external resources | |
| ICD-10 | K00.0 |
| ICD-9-CM | 520.0 |
| MeSH | D000848 |
In dentistry, hypodontia is the condition at which the patient has missing teeth as a result of the failure of those teeth to develop (also called tooth agenesis). Hypodontia describes a situation where the patient is missing up to five permanent teeth, excluding the 3rd molars. 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.
The condition of missing over five (six or more) permanent teeth, excluding 3rd molars or wisdom teeth, has been called oligodontia. The condition for missing all teeth, either primary and/or permanent), is called anodontia. A similar condition is hyperdontia, in which there are more than the usual number of teeth, more commonly called supernumerary teeth.
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.
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.
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.
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.
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