It is normal to have 20 primary teeth and 32 permanent teeth. Hyperdontia is a condition characterized by the presence of extra, or supernumerary, teeth. The extra teeth can be located in any part of the mouth and can develop from separate tooth buds or from the splitting of permanent tooth buds.
Supernumerary teeth can occur in both primary (deciduous) and permanent teeth, but they are much more common among permanent teeth. There can be either one or several supernumerary teeth present. Most cases involve a single tooth. The most common supernumerary teeth are permanent anterior incisors in the upper arch, followed by upper and lower fourth molars.
About 1 to 4 percent of people have at least one extra tooth. Supernumerary teeth are equally common among males and females in deciduous teeth, but among permanent teeth they are twice as common in males as in females.
Supernumerary teeth are divided into several groups. Conical teeth are peg-shaped and are usually located in the front of the mouth. Tuberculate teeth have two or more tubercles, or cusps. They are very rare and usually occur in pairs. Supplemental teeth occur as duplicates in the series of normal teeth. They are generally located in the lateral incisor, premolar, and molar regions. Odontoma teeth can be completely disorganized or can resemble the normal teeth structure.
The cause of hyperdontia is not clear, but dentists have several theories. Some believe the extra teeth are caused by abnormal division of a tooth, while others believe they are caused by hyperactive dental lamina. Supernumerary teeth may also be caused by genetics.
Extra teeth can cause many problems. They can displace adjacent teeth, prevent normal teeth from erupting through the gums, or lead to crowding in the mouth. All of these problems require that the supernumerary teeth be removed.
Cysts can form if a person has extra teeth. Supernumerary teeth can also cause resorption of the adjacent teeth’s roots in some parts of the mouth. In those cases, the extra teeth need to be removed immediately.
Supernumerary teeth are not always problematic. If they do not cause any of these issues, they can be left alone.