Humans are built to grow exactly two sets of teeth: 20 baby teeth and 32 permanent adult teeth. A true third full set of teeth doesn’t happen naturally. However, some people do grow extra teeth beyond the normal 32, a condition called hyperdontia, and in rare genetic disorders, dozens of additional teeth can develop. There’s also early-stage research into drugs that could one day stimulate new tooth growth.
Why Humans Only Get Two Sets
Your first set of teeth, called primary or deciduous teeth, starts forming in the womb around five weeks of gestation. By age 3, most children have all 20 baby teeth in place. Around age 6 or 7, those baby teeth begin falling out as the permanent teeth push through. By about age 21, the average person has 32 permanent teeth, including wisdom teeth. Once those adult teeth are in, the biological program for tooth development is finished. There’s no built-in mechanism for a third round.
This two-set system is common across mammals. Some animals, like sharks and crocodiles, continuously regenerate teeth throughout their lives, but human jaw biology simply doesn’t work that way. The stem cells responsible for forming teeth go dormant after the permanent set develops.
Extra Teeth From Hyperdontia
While a complete third set doesn’t occur, growing extra teeth beyond the normal count is surprisingly common. Hyperdontia affects up to 3.8% of people in their permanent teeth and about 0.6% in baby teeth. That means roughly 1 in 26 people develops at least one supernumerary (extra) tooth.
These extra teeth most often appear in the upper front of the mouth, between or behind the two central incisors. They can also show up near the molars or premolars. In most cases, people grow just one or two extra teeth, not an entire additional set. The extra teeth may look normal, peg-shaped, or oddly formed, and they sometimes remain buried in the jawbone without ever breaking through the gum.
Extra teeth can cause real problems. They may block permanent teeth from erupting properly, push neighboring teeth out of alignment, create gaps, or lead to cyst formation around the impacted tooth. For these reasons, dentists typically recommend removing supernumerary teeth, especially when they’re interfering with normal dental development in children. The timing of removal depends on the individual case.
Genetic Conditions That Produce Many Extra Teeth
In certain rare genetic disorders, people can develop far more extra teeth than the occasional single supernumerary, sometimes enough that it loosely resembles a partial third set.
Cleidocranial dysplasia is the most well-known example. This condition, caused by a mutation in the RUNX2 gene, disrupts normal skeletal and dental development. About 70% of people with the condition develop supernumerary tooth germs, meaning their jaws produce additional teeth that crowd in alongside the normal ones. At the same time, their baby teeth often fail to fall out on their own, and their permanent teeth are delayed in erupting. The result can be a mouth containing baby teeth, permanent teeth, and numerous extra teeth all at once, creating significant crowding that requires extensive dental treatment over many years.
Gardner syndrome, a condition linked to intestinal polyps, also involves dental abnormalities in about 30% of affected individuals. These can include supernumerary teeth, impacted teeth, and abnormal tooth shapes. The dental signs sometimes appear before other symptoms, making them useful for early diagnosis.
Could Humans Ever Regrow Teeth?
Researchers in Japan have been developing an antibody drug that targets a protein called USAG-1, which normally acts as a brake on tooth development. In animal studies, blocking this protein allowed mice and ferrets to grow new teeth. The idea is that dormant tooth buds in the human jaw might be reactivated if this biological brake is released.
A humanized version of the antibody has been developed as the final drug candidate, and the framework for a phase 1 clinical trial has been finalized. The initial goal is narrow: helping people born with congenitally missing teeth (a condition called hypodontia) grow the teeth they never developed. This is not yet available as a treatment, and it would be years before it could reach general use for replacing teeth lost to decay or injury, if it proves safe and effective at all.
What “Three Sets of Teeth” Usually Means in Practice
When people report having a “third set of teeth,” they’re almost always describing one of a few situations. Some older adults notice a single new tooth poking through the gum late in life, which is typically a supernumerary tooth that was buried in the jawbone for decades and only migrated to the surface over time. Others with conditions like cleidocranial dysplasia retain their baby teeth well into adulthood while also having permanent and extra teeth present simultaneously, giving the appearance of multiple generations of teeth coexisting.
In every documented case, what’s happening is extra individual teeth forming beyond the normal count, not a coordinated third set replacing the second one the way adult teeth replace baby teeth. The biological signals that trigger a full wave of tooth replacement simply don’t fire a third time in humans. So while growing extra teeth is entirely real and not even particularly rare, a true third set of teeth remains outside the boundaries of normal human biology.