Hypodontia: aesthetics and functions part 1: aetiology and the problems

The term hypodontia refers to the developmental absence of one or more primary or secondary teeth, excluding third permanent molars.1 Hypodontia is a common dental anomaly with a prevalence that ranges from 2.6–11.3% worldwide.2 In the UK, however, studies are relatively consistent and suggest a prevalence rate of 4–4.5%.2^,3 It is generally accepted that hypodontia occurs as a result of both genetic and environmental factors. Females tend to be more frequently affected than males.4 Mandibular second premolars are most commonly absent, followed by maxillary lateral incisors and second premolars.4 The primary dentition tends to be less affected with a prevalence of only 0.1–0.9%.5

Whilst hypodontia may occur in isolation, likely as a result of genetic mutation, it is also commonly associated with conditions such as cleft lip and palate, Down's syndrome and ectodermal dysplasia.6 Patients with absent teeth are referred to as having hypodontia and this can be classified as simple (one or two absent teeth), moderate (one or more absent teeth per quadrant) and severe (more than one absent tooth in all quadrants).7 Historically, the term anodontia refers to complete absence of teeth and oligodontia to when six or more teeth are missing. Regardless of the type, however, treatment aims are the same – to provide patients with a healthy, functional and aesthetic outcome throughout life.6