Supernumerary teeth are extra teeth that grow beyond the normal set of 20 baby teeth or 32 adult teeth. The condition is formally called hyperdontia, and it can produce one extra tooth or, less commonly, several. These extra teeth may look perfectly normal, appear as small peg-shaped growths, or stay completely hidden beneath the gums where only an X-ray reveals them.
Types of Supernumerary Teeth
Extra teeth fall into two broad categories based on their shape. Supplemental teeth look like normal teeth in both size and form. They essentially duplicate a tooth that already exists in the arch. Rudimentary teeth, on the other hand, are smaller and abnormally shaped. Rudimentary forms include conical, tuberculate, and molariform types.
The most common supernumerary tooth is the mesiodens, a small conical tooth that appears between the two upper front teeth. Conical types are generally small, often peg-shaped, and tend to develop a full root. Tuberculate types are wider, barrel-shaped, and topped with multiple bumps. Unlike conical teeth, tuberculate ones often have stunted roots or no roots at all, which changes how they behave and how they’re treated.
Location also matters. About 63% of supernumerary teeth show up in the upper jaw, with the remaining 37% in the lower jaw. The front of the upper jaw, around the incisors, is the single most common spot.
Why Extra Teeth Develop
No one can point to a single cause. The leading theory involves the dental lamina, a band of tissue in the jaw that gives rise to tooth buds during development. If this tissue becomes overactive, it can produce more tooth buds than needed, and those buds develop into extra teeth. Genetics clearly play a role: hyperdontia runs in families and is more common in males, who account for roughly 56% of cases.
There’s also an evolutionary angle. One hypothesis, called atavism, suggests that supernumerary teeth may be a resurfacing of traits from early human ancestors who needed extra grinding surfaces to process raw plants and nuts. It’s a theory that’s difficult to prove, but it fits the pattern of extra molars and premolars that sometimes appear.
Conditions Linked to Hyperdontia
Most people with a single extra tooth have no underlying syndrome. But when multiple supernumerary teeth appear, especially if they’re impacted beneath the gums, the pattern can signal a genetic condition. Cleidocranial dysplasia is one of the most well-known associations. People with this skeletal disorder often develop numerous extra teeth, particularly in the premolar region of both jaws.
Familial adenomatous polyposis, a condition that causes polyps in the colon, also has a dental connection: supernumerary teeth appear in 11% to 27% of affected patients, typically embedded in the bone near the front teeth or canines. Other conditions where extra teeth are a recognized feature include Nance-Horan syndrome (which emphasizes extra upper incisors), Rubinstein-Taybi syndrome, and Robinow syndrome. Cleft lip and palate, even without a broader syndrome, increases the likelihood of supernumerary teeth in the area near the cleft.
Problems Extra Teeth Can Cause
A supernumerary tooth doesn’t always cause trouble. Some sit quietly in the bone for years without symptoms. But when problems do develop, they tend to follow a predictable list:
- Delayed or blocked eruption. The extra tooth physically blocks a permanent tooth from coming in on schedule. This is the most noticeable issue in children, often discovered when an adult tooth simply doesn’t appear.
- Spacing and alignment issues. A mesiodens between the front teeth can push them apart, creating a visible gap, or force neighboring teeth into crooked positions.
- Root damage to neighboring teeth. An impacted supernumerary tooth pressing against the root of an adjacent tooth can cause resorption, where the root gradually dissolves.
- Cyst formation. Tissue surrounding an unerupted extra tooth can develop a fluid-filled sac (dentigerous cyst) that slowly expands and damages surrounding bone.
- Prolonged retention of baby teeth. The extra tooth can prevent a baby tooth from falling out naturally, disrupting the normal transition to adult teeth.
How Supernumerary Teeth Are Found
Many supernumerary teeth are discovered incidentally on a routine dental X-ray, especially when they haven’t erupted. A dentist may also suspect the condition when a child’s permanent tooth is significantly late coming in, or when teeth are erupting in unusual positions.
Standard dental X-rays can identify that an extra tooth exists, but they flatten a three-dimensional structure into two dimensions. That makes it hard to tell exactly where the tooth sits relative to the roots of neighboring teeth. Cone beam computed tomography (CBCT), a type of 3D dental scan, is significantly better at pinpointing the exact location of the extra tooth, detecting root resorption on adjacent teeth, and planning a surgical approach. Studies comparing the two methods found CBCT was statistically superior for all of those tasks. The trade-off is a slightly higher radiation dose, so it’s typically reserved for complex cases rather than every routine screening.
Treatment: Removal vs. Monitoring
Not every supernumerary tooth needs to come out. If the tooth is deep in the bone, not causing symptoms, and not interfering with the development or position of other teeth, a dentist may recommend periodic monitoring with X-rays to make sure it stays harmless.
Removal is recommended when the extra tooth is blocking or delaying the eruption of a permanent tooth, causing crowding or spacing problems, showing signs of cyst formation, or resorbing the roots of adjacent teeth. For children, the timing of removal matters. Extracting too early can risk damaging developing permanent tooth buds, while waiting too long can allow complications like misalignment to become established and harder to correct.
The procedure itself depends on whether the tooth has erupted or remains buried in the bone. An erupted supernumerary tooth can often be extracted like any other tooth. An impacted one requires a surgical approach, where the overlying gum and sometimes bone are carefully opened to access and remove it. Recovery is similar to a wisdom tooth extraction in most cases, with swelling and discomfort subsiding over a week or so. After removal, orthodontic treatment is sometimes needed to guide the permanent teeth into their correct positions, especially if the extra tooth created a gap or shifted the alignment of the arch.
In cases where multiple supernumerary teeth are present due to an underlying genetic condition, treatment planning becomes more involved and typically requires coordination between a dentist, an oral surgeon, and sometimes an orthodontist to map out a staged approach.