How Rare Is Hyperdontia? The Prevalence of Extra Teeth

Hyperdontia, the development of extra teeth beyond the normal set, affects roughly 0.1% to 3.4% of people depending on the population studied and how the count is done.¹ That range sounds wide, and it is, because prevalence shifts with geography, ethnic background, whether the study used routine X-rays or clinical exams, and whether it included baby teeth or only permanent ones. The condition is uncommon enough that most dentists will see only a handful of cases each year, yet common enough that it is one of the better-studied dental anomalies in the literature.

Putting the Numbers in Context

Most large surveys place the prevalence of supernumerary teeth somewhere between half a percent and about two percent. A study of more than 3,300 Iranian orthodontic patients found extra teeth in 0.72% of cases, with a 95% confidence interval stretching from 0.4% to 1.0%.² That figure lines up well with the broader literature on permanent-dentition hyperdontia. Numbers at the higher end of the range tend to come from studies that include primary (baby) teeth or use cone-beam CT scanning, which catches impacted extra teeth that a standard dental exam would miss entirely.

Importantly, supernumerary teeth show up far more often in the permanent dentition than in primary teeth.³ When extra baby teeth do appear, they are easy to overlook because they tend to be small and may shed before anyone notices. That matters clinically, because extra baby teeth can sometimes predict extra permanent teeth or interfere with the eruption of normal teeth later on.

Who Gets Extra Teeth

Textbooks and older reviews consistently report that males develop supernumerary teeth more often than females, usually at a ratio of about two to one. But the picture is not quite that clean. A survey of more than 7,300 people found that females were actually more commonly affected, at a ratio of about 1.28 to 1, a result the authors themselves acknowledged contradicted the prevailing literature.⁴ The Iranian orthodontic study, meanwhile, found an almost even split between males and females.²

The inconsistency probably reflects differences in study design and population. Orthodontic samples skew toward people who already have crowding or alignment issues, which may inflate or distort the apparent sex ratio. Population-based screening studies, which catch people who never sought orthodontic care, sometimes tell a different story. The safest summary is that males are affected slightly more often, but the gap is smaller and less consistent than older sources suggest.

Where Extra Teeth Show Up and What They Look Like

The most common type of supernumerary tooth is the mesiodens, a small extra tooth that appears between the two upper front incisors. After the mesiodens, the next most frequent locations are the premolar region and the area behind the last molar. A study from a dental institution in Rajasthan documented 82 supernumerary teeth across 58 patients and found that parapremolars (extra premolars) were the single most common type, followed by mesiodens, paramolars, distomolars, and supplementary lateral incisors.⁵ These proportions vary across studies, but the upper jaw is almost always more involved than the lower jaw.

Shape matters for treatment planning. Extra teeth tend to fall into three categories:

Conical: small, peg-shaped teeth, the most common form, accounting for about 48% in one analysis of 248 supernumerary teeth.
Supplemental: teeth that roughly mimic the shape of a normal neighboring tooth, making up about 42%.
Tuberculate: barrel-shaped teeth with multiple cusps, the least common at around 10%.⁶

Conical supernumerary teeth usually erupt or at least partially emerge into the mouth, which makes them easier to spot. Tuberculate ones are more likely to stay buried in the bone, where they can silently push neighboring teeth off course or block their eruption.

Extra Molars Behind the Wisdom Teeth

A subgroup that gets less attention is the distomolar, an extra tooth situated behind the third molar (the wisdom tooth). A large study examining 10,000 patients found distomolars in 0.37% of cases and paramolars, which sit beside a normal molar rather than behind it, in 0.12%.⁷ Among those with distomolars, nearly half had them on both sides of the jaw. Most of these teeth remain impacted and symptom-free, discovered incidentally on panoramic X-rays taken for other reasons. When they do cause problems, it tends to involve interference with wisdom tooth eruption or cyst formation around the unerupted tooth.

When Five or More Extra Teeth Appear

Having one or two extra teeth is uncommon. Having five or more, in the absence of any genetic syndrome, is genuinely rare. A retrospective review of 9,550 patients found 251 with supernumerary teeth, but only six of those had five or more extras, placing the prevalence of so-called “multiple supernumerary teeth” at 0.06%.¹ All six of those patients were male, and most of the extra teeth clustered in the premolar region. When someone without a known syndrome turns up with that many spare teeth, clinicians often look harder for an undiagnosed genetic condition, because the numbers start overlapping with what syndromic patients experience.

Genetic Syndromes That Cause Supernumerary Teeth

Most extra teeth occur in otherwise healthy people with no identifiable syndrome. But several genetic conditions make hyperdontia much more likely, and recognizing those conditions is clinically important because the extra teeth may be the first visible sign of a broader problem.

Cleidocranial Dysplasia

Cleidocranial dysplasia is a rare skeletal disorder caused by mutations in the RUNX2 gene. People with this condition can develop dozens of extra teeth. A systematic review found that missense mutations within a specific functional region of the RUNX2 gene were strongly associated with supernumerary teeth, along with other skeletal features like underdeveloped collarbones and skull abnormalities.⁸ Mutations concentrated in the gene’s Runt domain were significantly more common in patients who had both supernumerary teeth and jaw abnormalities compared to mutations outside that domain.⁹

Not every person with cleidocranial dysplasia develops extra teeth, though. One documented case involved a patient who had the full skeletal phenotype of the disorder but no supernumerary teeth at all, and no detectable RUNX2 mutation on standard sequencing. That case highlights a complication: only about two-thirds of people with cleidocranial dysplasia show a RUNX2 mutation on conventional testing, which means other genetic mechanisms like large deletions or duplications may also be at play.¹⁰

Gardner Syndrome

Gardner syndrome is a form of familial adenomatous polyposis caused by mutations in the APC gene. It is known primarily for intestinal polyps that carry a high risk of colorectal cancer, but it also causes bony growths (osteomas) in the jaw and skull, soft-tissue tumors, and supernumerary teeth.¹¹ In at least one documented family, a specific APC mutation in exon 15 was directly linked to the formation of both supernumerary teeth and an odontoma, a benign tumor made of tooth-like tissue.¹² Because the dental findings in Gardner syndrome can appear years before intestinal polyps become symptomatic, a dentist who spots unexplained extra teeth along with jaw osteomas may be the first clinician in a position to flag the condition.

The Cleft Lip and Palate Connection

People born with cleft lip and palate have a markedly higher rate of supernumerary teeth than the general population, especially in the area near the cleft. One study found extra teeth in about 18% of children with clefts in the primary (baby tooth) dentition and nearly 6% in the permanent dentition.¹³ These extra teeth are usually lateral incisors, both inside and outside the cleft line, and they vary widely in size and shape.

The type of cleft matters. A German study found that supernumerary teeth were most frequent in patients with cleft lip and alveolus (the less severe form), present in about half of those patients, compared to roughly 29% with unilateral cleft lip and palate and about 18% with bilateral cleft lip and palate.¹⁴ That pattern is somewhat counterintuitive, since wider clefts cause more disruption. The likely explanation is that the disrupted tissue in smaller clefts still has enough structural integrity to attempt tooth formation, sometimes producing extra tooth buds, while more extensive clefts tend to destroy the dental lamina entirely, leading instead to missing teeth.

What Problems Extra Teeth Cause

Many supernumerary teeth never cause any trouble at all. They sit embedded in bone, minding their own business, and get discovered only when an X-ray is taken for some other reason. But when they do create problems, the list is longer than you might expect.

The most common complication is crowding or displacement of neighboring teeth. An extra tooth in the front of the mouth can push the central incisors apart, creating a visible gap or rotating adjacent teeth. When the extra tooth stays impacted, it can physically block a normal tooth from erupting, leaving a gap in the smile where a tooth should have come through on schedule.

Less commonly, a cyst can form around an unerupted supernumerary tooth. About 5% of dentigerous cysts, fluid-filled sacs that develop around the crown of an unerupted tooth, are associated with supernumerary teeth, most often a mesiodens.¹⁵ These cysts can expand slowly over years, potentially weakening bone and damaging the roots of adjacent teeth before anyone notices.

For children, the psychological dimension can be significant. A case report documented how the aesthetic impact of a supernumerary tooth fused to a neighboring tooth affected a child’s social behavior, with measurable changes on a standardized social avoidance scale. Treatment that restored the appearance of the teeth correlated with improved psychosocial function.¹⁶ Visible extra or misshapen front teeth are especially impactful at school age, when peer appearance norms carry disproportionate emotional weight.

How Extra Teeth Are Found

Routine dental X-rays catch most supernumerary teeth, but standard two-dimensional imaging has real limitations. A panoramic X-ray compresses a three-dimensional jaw into a flat image, which means an impacted extra tooth can overlap with nearby structures or be obscured by the roots of normal teeth. This is where cone-beam computed tomography makes a substantial difference. CBCT provides a three-dimensional view that lets clinicians see the exact position, orientation, and relationship of an extra tooth to surrounding structures like nerve canals and neighboring tooth roots.¹⁷

A direct comparison of CBCT against traditional radiography found that CBCT was statistically better at pinpointing pathology location, detecting root resorption on adjacent teeth, and informing treatment planning for both impacted and supernumerary teeth.¹⁸ In practical terms, a CBCT scan before surgery means the surgeon knows exactly how deep the tooth sits, which direction it faces, and how close it is to structures that should not be nicked. That translates to smaller incisions, less bone removal, and fewer surprises during the procedure.

Timing of Removal

Not every supernumerary tooth needs to come out. If it is not causing crowding, not blocking another tooth’s eruption, and not associated with any cyst, monitoring with periodic X-rays is a perfectly reasonable strategy. But when removal is needed, timing matters. For unerupted supernumerary teeth in the upper front of the mouth, evidence suggests that removal before age six or seven leads to fewer complications and better outcomes for the eruption of normal permanent teeth.¹⁹

After that age window, the roots of the extra tooth tend to be more developed, the tooth may be more deeply embedded, and the normal teeth it is affecting may already be significantly displaced. None of that makes surgery impossible, but it does make it a bigger procedure and reduces the chance that the blocked permanent tooth will self-correct its path into the arch without orthodontic help. For children diagnosed early, the calculus is usually straightforward: get it out and give the permanent teeth room to come in on their own.

Why Dentists Are Interested in the Teeth They Remove

Something unexpected has come out of the research on supernumerary teeth in the last decade or so: the pulp inside these discarded teeth turns out to be an unusually good source of stem cells. Stem cells harvested from supernumerary teeth show a significantly higher proliferation rate than those from normal dental pulp.²⁰ They can differentiate into fat, cartilage, and bone-forming cells, making them potentially useful building blocks for tissue repair.

Beyond regeneration, these stem cells show immunomodulatory properties. Research has demonstrated that stem cells from supernumerary teeth can suppress overactive immune responses in lab models, leading to suggestions that they could serve as a source material for treating autoimmune diseases like lupus.²¹ Additional work has shown that both the dental pulp and the root-tip tissue of supernumerary teeth contain stem cell populations with diverse characteristics, expanding their potential utility for regenerative medicine applications.²² This research is still in early stages, but it has created an unusual situation: a tooth that was always considered purely a clinical nuisance may turn out to be a valuable biological resource.

Extra Teeth in Other Species

Humans are not the only mammals that develop extra teeth. Wild boar examined in Sweden were found to have supernumerary teeth among a range of dental abnormalities, alongside severe tooth wear, periodontal disease, and fractures.²³ A study of invasive North American beavers in South America documented hyperdontia in about 0.4% of skulls examined, with the extra teeth appearing in the upper jaw for the first time in that species.²⁴

Across species, the pattern is similar: extra teeth are uncommon, they tend to show up in predictable locations, and they appear to arise from the same kind of developmental glitch in the dental lamina, the ribbon of tissue that gives rise to tooth buds during embryonic development. Archaeologists have even documented supernumerary molars in human remains from the Chalcolithic period, thousands of years ago, confirming that this is not a modern anomaly.¹ The genetic toolkit for building teeth is ancient and highly conserved, which means the errors that produce extra teeth have been happening for as long as mammals have had complex dentitions.

1
Dentomaxillofacial Radiology. Characteristics and prevalence of non-syndrome multiple supernumerary teeth: a retrospective study
2
PubMed Central. Prevalence and Pattern of Accessory Teeth (Hyperdontia) in Permanent Dentition of Iranian Orthodontic Patients – Section: Results
3
PubMed Central. Supernumerary teeth in primary dentition and early intervention: a series of case reports
4
PubMed Central. Prevalence and characteristics of supernumerary teeth: A survey on 7348 people – Section: Discussion
5
PubMed Central. Prevalence, Characteristics, and Morphology of Supernumerary Teeth among Patients Visiting a Dental Institution in Rajasthan – Section: Results
6
Journal of Dental Sciences. Characteristics of supernumerary teeth among nonsyndromic dental patients – Section: Results
7
PubMed Central. Prevalence and clinical significance of distomolar and paramolar teeth – Section: RESULTS
8
PubMed Central. The impact of RUNX2 gene variants on cleidocranial dysplasia phenotype: a systematic review
9
PubMed Central. Identification of a novel mutation of RUNX2 in a family with supernumerary teeth and craniofacial dysplasia by whole-exome sequencing – Section: Results
10
PubMed. RUNX2 gene status in a cleidocranial dysplasia patient without supernumerary teeth – Section: CONCLUSION
11
PubMed Central. Novel Mutation in APC Gene Associated with Multiple Osteomas in a Family and Review of Genotype-Phenotype Correlations of Extracolonic Manifestations in Gardner Syndrome
12
PubMed Central. A novel mutation of adenomatous polyposis coli (APC) gene results in the formation of supernumerary teeth
13
Journal of Pre-Clinical and Clinical Research. Dental abnormalities in children with cleft lip with or without cleft palate – Section: ABSTRACT
14
PubMed Central. Prevalence of hypodontia and supernumerary teeth in a German cleft lip with/without palate population – Section: RESULTS
15
PubMed Central. Dentigerous Cyst Associated With Impacted Inverted Mesiodens: A Report of Three Cases and a Brief Literature Review – Section: Introduction
16
PubMed Central. Management of a pediatric patient with dental anomalies and its effect on psychosocial status: a case report
17
PubMed Central. Investigation of impacted supernumerary teeth: a cone beam computed tomograph study – Section: Discussion
18
PubMed. Effectiveness of impacted and supernumerary tooth diagnosis from traditional radiography versus cone beam computed tomography – Section: RESULTS
19
Pediatric Dentistry. Determination of the Optimum Time for Surgical Removal of Unerupted Anterior Supernumerary Teeth
20
PubMed. A biological study of supernumerary teeth derived dental pulp stem cells based on RNA-seq analysis – Section: RESULTS
21
PubMed Central. Immune therapeutic potential of stem cells from human supernumerary teeth
22
PubMed. Decoding the multifaceted signatures and transcriptomic characteristics of stem cells derived from apical papilla and dental pulp of human supernumerary teeth
23
PubMed. Caries, Periodontal Disease, Supernumerary Teeth and Other Dental Disorders in Swedish Wild Boar (Sus scrofa)
24
PubMed Central. Dentition Anomalies and Cranial Abnormalities in Invasive Beavers (Castor canadensis) in Tierra Del Fuego, Argentina