Hyperdontia is a developmental dental anomaly characterized by the presence of supernumerary teeth, meaning an individual has more teeth than the standard number found in the dental arch. Humans typically develop 20 primary (baby) teeth and 32 permanent teeth; any tooth structure exceeding these counts is considered a supernumerary element. This condition represents a deviation during tooth formation, potentially affecting the alignment and eruption of surrounding normal teeth. While recognized, the presence of extra teeth is generally considered uncommon in the general population.
Defining Hyperdontia and Global Prevalence Rates
Hyperdontia describes the occurrence of supernumerary teeth, which are additional teeth that form within the jawbone beyond the regular dental formula. The condition is relatively infrequent, with global prevalence rates varying by dentition. In the permanent dentition, hyperdontia occurs in approximately 0.1% to 3.8% of the population.
The condition is less common in the primary dentition, observed in about 0.3% to 0.6% of children. Supernumerary teeth are more frequently found in males than in females, often reported at a 2:1 ratio in permanent teeth.
The majority of hyperdontia cases involve a single extra tooth, accounting for an estimated 76% to 86% of all occurrences. Two supernumerary teeth occur in about 12% to 23% of cases, while multiple extra teeth are rare, affecting less than 1% of the population. The anomaly shows a strong predilection for the upper jaw, particularly the anterior region.
Classifying Supernumerary Teeth
Supernumerary teeth are categorized based on their physical appearance (morphology) and their specific position within the dental arch. Morphological classifications help clinicians understand potential complications and include four distinct types.
Morphological Types
- Conical supernumeraries are the most common, characterized by a small, peg-shaped crown and a single root.
- Tuberculate teeth possess a barrel or tube-like shape, often have multiple cusps, and frequently remain unerupted.
- Supplemental supernumeraries closely resemble the shape and size of a tooth in the normal series, appearing as duplicates of adjacent teeth.
- The odontoma is a disorganized mass of dental tissues, sometimes appearing as small, tooth-like structures.
Classification by location identifies where the extra tooth lies. A mesiodens is the most common supernumerary, located between the two upper central incisors in the midline. Distomolars (fourth molars) are positioned behind the last molar, while paramolars are situated buccally or palatally next to a molar.
Etiology and Associated Genetic Syndromes
The precise origin of hyperdontia is often unclear, and most isolated cases are considered idiopathic (occurring without a known cause). Two primary theories attempt to explain the biological basis of supernumerary tooth formation.
The most accepted theory points to the hyperactivity of the dental lamina, the epithelial tissue responsible for initiating tooth development. This concept suggests the lamina does not fully degenerate after forming normal teeth, instead continuing to proliferate and form an additional tooth bud.
An older theory, the dichotomy theory, suggests the supernumerary tooth arises from the splitting of a single tooth bud. This division results in a normal tooth and a smaller, dysmorphic extra tooth.
Multiple supernumerary teeth are frequently linked to specific genetic conditions or syndromes.
Associated Syndromes
Cleidocranial Dysplasia is a rare genetic disorder characterized by numerous impacted supernumerary teeth and skeletal abnormalities, such as absent or underdeveloped collarbones. Gardner Syndrome often includes multiple extra teeth and odontomas alongside a high risk for intestinal polyps. Cleft Lip and Palate also shows an association with the development of supernumerary teeth.
Clinical Management and Treatment Approaches
The presence of supernumerary teeth can lead to various dental problems, making early detection and management important. Common complications include the impaction of a normal permanent tooth, where the extra tooth obstructs the path of eruption. The additional tooth can also cause crowding, leading to the displacement or abnormal rotation of adjacent teeth and resulting in malocclusion.
Rarely, a dentigerous cyst (a fluid-filled sac) may form around the crown of an unerupted tooth. Supernumerary teeth can also cause the root of an adjacent permanent tooth to resorb, potentially leading to its loss. Treatment strategy depends on the specific type, position, and effect of the extra tooth.
If an unerupted tooth is not causing immediate problems, a “watchful waiting” approach with periodic monitoring may be adopted. Removal is generally recommended if the tooth is blocking the eruption of a permanent tooth or causing displacement. Early extraction may allow for the spontaneous eruption of the affected permanent tooth. Delaying removal until adjacent permanent roots are mostly formed can reduce the risk of surgical damage.