teeth as a result of their failure of development. Anodontia describes the total lack of
teeth of one or both dentitions. Oligodontia is a term used to describe a situation
where multiple⎯usually more than six⎯teeth are missing.
13.2.1 Prevalence
In the primary dentition, missing teeth occur more commonly in the maxilla and
typically the maxillary lateral incisor is the tooth involved. Various studies have
shown the prevalence of missing primary teeth to be between 0.1 % and 0.9 % of
Caucasian populations, with males and females affected equally. Developmentally
missing permanent teeth are seen in both the maxilla and mandible (780HFig. 13.1). In
Caucasian populations the third molars are the most commonly missing teeth,
followed by the mandibular second premolar, the maxillary lateral incisor, and the
maxillary second premolar. A female to male ratio of 4 : 1 has been reported. Missing
third molars occur in 9-30% of individuals. If the third molars are excluded, the
prevalence in the permanent varies between 3.5 % and 6.5 % according to the study
quoted.
Key Points
- Hypodontia
- 0.1-0.9% in the primary dentition;
- 3.5-6.5% in the permanent dentition;
- Missing permanent teeth are seen in 30-50% of patients who have missing primary
teeth.
781H
Fig. 13.1 Hypodontia, absent 41,
retained 81.13.2.2 Aetiology
The cause of an isolated missing tooth is often unclear; this may be genetic in origin
or associated with some environmental insult during development. Missing teeth have
been reported in association with multiple births, low birth weight, and increased
maternal age. Rubella and thalidomide embryopathies may also be associated with
missing teeth.
Single gene disorders have been associated with missing teeth. Multiple missing teeth,
as well as teeth with small crowns, may be seen in a number of syndromes including
X-linked hypohidrotic ectodermal dysplasia (782HFig. 13.2), autosomal dominant and
autosomal recessive cases of ectodermal dysplasia and autosomal recessive
chondroectodermal dysplasia (Ellis-van Creveld syndrome). Down syndrome (trisomy
21) is also associated with hypodontia.