Hyperdontia is an oral condition characterized by having an excess number of teeth. The standard number of primary teeth is 20 and the standard number of permanent teeth is 32. Primary teeth are the first set of teeth that erupt in a person’s mouth, generally by the age of 36 months, and are shed by the time the person is about 12 years old. Permanent teeth then take the place of the primary teeth and are usually fully erupted by the time the person reaches 21 years of age. A person who develops more than 20 primary teeth or more than 32 permanent teeth has hyperdontia. The additional teeth are referred to as supernumerary teeth.
Supernumerary teeth can occur in any part of the dental arch, but the most common supernumerary teeth are permanent, anterior incisors, in the maxillary (upper) arch. After maxillary incisors, maxillary and mandibular (lower arch) fourth molars are the next most common supernumerary teeth. These generally appear as extra impacted wisdom teeth. An extra maxillary incisor is called a mesiodens, and an extra fourth molar is referred to as a distodens or distomolar. Extra primary teeth present at or shortly after birth are called natal teeth.
The prevalence of hyperdontia is between 1% and 4% of the population with a male to female ratio of 2:1; the majority of cases are limited to a single tooth. There have been reported cases of over 30 supernumerary teeth in one person, but such large numbers are rare. When a person does develop multiple supernumerary teeth, it often is associated with a variety of conditions or sydromes such as cleidocranial dysplasia, Ehler-Danlos syndrome, Gardner syndrome, and cleft lip and palate. The cause of hyperdontia is not entirely clear. It is believed that there may be a genetic factor in hyperdontia consisting of an autosomal dominant trait with low penetrance (only sometimes producing supernumerary teeth in a carrier of the mutated gene). Other possible causes are environmental factors and overactivity of the dental lamina during tooth development. The dental lamina is a zone of cells that initiates the formation of the tooth germ, which forms the tooth. It is important to detect, evaluate, and treat supernumerary teeth as soon as possible since the additional teeth will present both cosmetic and functional problems for the affected individual. As a majority of supernumerary teeth cause clinical problems, treatment generally consists of removal of the teeth when possible. Supernumerary teeth may cause delayed eruption of adjacent teeth or significant crowding which will often require orthodontic treatment to correct. If retained, the teeth can lead to the development of cysts or tumors. It is generally not necessary to remove natal teeth unless the supernumerary teeth are loose and present a risk for aspiration due to passage into the lung.