Hypodontia

Hypodontia (oligodontia), the congenital absence of teeth, represented by the loss of one or two teeth with no apparent associated abnormalities is not uncommon. The most common teeth to be missing are the last in each series. Most surveys, however, show that one or more third molars are missing in approximately one-quarter of the population. A study carried out in an English population and excluding the third molars has shown that the teeth most likely to be missing are the lower second premolars (40.9%) followed by the upper lateral incisors (23.5%) and by the upper second premolars (20.9 %).

The pattern of missing teeth does, however, vary from population to population. A common finding in hypodontia is the presence of small and conically shaped teeth replacing normal units of the dentition . Hypodontia in the primary dentition is a relatively rare occurrence.

The congenital absence of teeth associated with abnormalities of the bone or ectodermal appendages is relatively rare. The dysplasia involved may be attributed to ectodermally derived structures or to more complex syndromes in which there are both dermal and bony abnormalities.