Supernumerary teeth, or hyperdontia, are the existing of additional teeth to the normal series in the dental arches. It occurs with both primary and permanent teeth, but it is more common with permanent teeth. The rarest form of hyperdontia is the molar type. Hyperdontia can be classified as eumorphic or dysmorphic. Eumorphic supernumerary teeth have the same morphology of the normal teeth, whereas dysmorphic ones are small and conical or tuberculate. Many supernumerary teeth never erupt and these may delay eruption of nearby teeth or cause other dental problems. Delayed in tooth loss, or eruption are possible signs of hyperdontia. Usually, diagnosis can be performed after radiographic assessment. The incidence of hyperdontia ranges from 0.1% to 3.8% depending on the population. In the Caucasian population, the incidence of supernumerary teeth ranges from 1-3%, and the highest frequency has been found in Native American tribes.
As hyperdontia is more common among the relatives of an affected child than the general population, it is suggested that genetic factors play a role in its occurrence. However, the anomaly does not follow a simple Mendelian pattern. Also, it is believed that environmental factors along with hereditary factors are combined to cause the condition.