What is a supernumerary tooth?
Simply put, it is one that is present in addition to the normal set of thirty-two permanent ones and can be found in almost any region of the dental arch, although most tend to occur in the front region of the upper arch.
Supernumerary teeth are estimated to occur in around 2% of children and are classified according to their form and their location. Their presence may give rise to a number of problems in the mouth.
They may not erupt and may often only be detected on radiographs of the full dental arches, often by pure chance.
The most common supernumerary tooth is one which appears in the midline of the upper arch and is called a mesiodens. Treatment depends on the type and position of the extra tooth and on its effect on adjacent teeth. If supernumeraries erupt into the palate, they may go unnoticed by the patient or just be accepted. They may however spoil the appearance by crowding out other teeth or by preventing a normal eruption of an adjacent tooth.
What causes a supernumerary?
The generally accepted theory for how supernumerary teeth form is that an abnormal split of the tooth bud occurs for some unknown reason, although others suggest a “hyperactivity of the dental lamina” during tooth development may be responsible.
There appears to be a genetic predisposing factor involved, since supernumeraries are more common in the relatives of affected children compared with the general population.
Supernumerary teeth are classified into four groups based on their morphology and location.
They are described as conical, tuberculate, supplemental or odontome. The odontome type can be “complex, composite or compound-composite”.
- Conical are shaped as the name suggests and most often found anteriorly.
- Tuberculate are similar to conical but have two or more protrusions or cusps. These are rare and usually occur in pairs.
- Supplemental are usually like a duplicate of a normal anterior tooth, or sometimes a posterior.
- An odontome is a less organised kind of dental abnormality which has also been described as a kind of hematoma or tumor. It involves epithelial and mesenchymal differentiation to the point where enamel and dentine are formed but not usually in a recognisable shape. An odontome can reach a fair size and considerably disturb the development of teeth in the adjacent area.
The location for a supernumerary is most commonly anteriorly (mesiodens) but occasionally occurs in the posterior regions of the mouth.
Where a supernumerary is displacing another tooth, preventing eruption, or causing arch-crowding it usually has to be extracted. This can be relatively simple if it’s a small mesiodens fairly superficially placed, but can be a surgical challenge if it’s deep in alveolar bone or takes the form of a large disorganised odontome. There is an added risk of a cyst forming in association with an unerupted supernumerary and this would need to be surgically addressed also.
A proportion of supernumararies may cause no problems, however, and may be safely left; and indeed there is likely to be a proportion which is never detected at all.