Hyperdontia is a developmental dental condition characterized by the presence of supernumerary teeth—teeth that exceed the normal count found in the dental arch. Humans typically develop 20 primary (baby) teeth and 32 permanent teeth, including the third molars. Any tooth structure forming beyond these standard counts is considered a supernumerary tooth. The condition is far more common in permanent dentition, with a prevalence ranging from 0.1% to 3.8% in the general population. A person may have only a single extra tooth, but multiple supernumerary teeth can also occur in one or both jaws.
Types of Supernumerary Teeth
Supernumerary teeth are classified according to their morphology (shape) and their specific location within the jawbone. Morphologically, they are broadly categorized into four main types.
Morphological Classification
Conical supernumeraries are the most frequent type, characterized by a small, peg-shaped crown and single root, often appearing in the front of the mouth.
Tuberculate teeth have a barrel shape and a complex crown and root structure, and they often do not erupt.
The supplemental type is an almost exact duplication of a normal tooth in the arch, such as an extra lateral incisor.
An odontoma is a disorganized mass of dental tissue, which can be compound (small, tooth-like structures) or complex (a random, unorganized mass).
Location Classification
Classification by location indicates where the extra tooth is positioned relative to the normal dentition. A mesiodens is the most common supernumerary, found specifically between the two maxillary central incisors. Paramolars are situated next to a molar, often on the cheek or tongue side. A distomolar, or fourth molar, is positioned behind the third molar at the end of the dental arch.
Origins of Hyperdontia
The cause of hyperdontia is often unclear, but it is widely accepted to be multifactorial, involving a combination of genetic and developmental factors. The most prevalent theory points to localized hyperactivity of the dental lamina, the tissue responsible for forming tooth buds during embryonic development. This hyperactivity is thought to lead to the formation of an extra tooth bud.
Other developmental explanations include the dichotomy theory, which suggests a single tooth bud splits into two, resulting in one normal and one supernumerary tooth. The atavism theory proposes that supernumerary teeth are an evolutionary throwback to the dentition of ancestral primates, which possessed more teeth.
The condition frequently has a genetic component, often appearing in family members. Hyperdontia is also a recognized feature of several genetic syndromes, including Cleidocranial Dysplasia, which affects bone and tooth development, and Gardner’s Syndrome, which involves multiple polyps and growths.
Detecting Extra Teeth
Supernumerary teeth are frequently asymptomatic and are often discovered incidentally during routine dental checkups. The primary way to identify these extra structures is through radiographic examination, such as a panoramic X-ray, which provides a comprehensive two-dimensional view of the jaws.
When symptoms occur, they are generally related to the extra tooth disrupting the alignment or eruption of normal teeth. Clinical signs include the delayed or complete failure of a permanent tooth to erupt, the displacement or rotation of adjacent teeth, or the presence of a gap. A more serious complication is the formation of a dentigerous cyst, a fluid-filled sac that develops around the crown of an impacted tooth.
For definitive diagnosis and treatment planning, dental professionals often rely on Cone-Beam Computed Tomography (CBCT). This advanced imaging technique provides a detailed three-dimensional view of the extra tooth’s exact position. A CBCT scan is essential for assessing proximity to surrounding structures and determining if the supernumerary tooth is causing complications like root resorption.
Treatment Approaches
The management of hyperdontia is individualized based on the supernumerary tooth’s location, morphology, and its potential impact on surrounding teeth. The primary decision involves choosing between surgical extraction and periodic observation.
Observation is recommended when the extra tooth is not causing complications, adjacent permanent teeth have erupted satisfactorily, and removal carries a significant risk of damaging a nearby tooth’s vitality.
Extraction is typically recommended when the supernumerary tooth is causing or is likely to cause complications. Reasons for surgical removal include:
- Inhibited or delayed eruption of a permanent tooth.
- Displacement or severe crowding of teeth.
- Development of associated pathology, such as a dentigerous cyst.
- Need to create space before planned orthodontic treatment.
- Location in a site designated for a dental implant.
The timing of removal is important, especially for a mesiodens impacting a central incisor. Early extraction, often in childhood, is performed to allow the permanent tooth to erupt into its correct position. Following removal, approximately 75% of impacted permanent incisors will erupt spontaneously. However, many cases require subsequent orthodontic treatment to align the teeth and close any remaining spaces.