The question of how many wisdom teeth a person grows is common, as these teeth are perhaps the most unpredictable members of the human mouth. Known scientifically as third molars, they represent the final set of adult teeth to develop, often arriving long after the rest of the permanent dentition is complete. The confusion surrounding these teeth stems from the wide variation in their presence, timing of eruption, and potential for causing problems.
The Standard Number of Third Molars
For most people, the standard count for third molars is four, completing the full set of 32 adult teeth. This arrangement includes one wisdom tooth positioned at the back of each of the four quadrants of the mouth. Specifically, an individual typically develops one third molar in the upper right, upper left, lower right, and lower left jawbone.
These molars are the most posterior teeth in the dental arch, situated behind the first and second molars. Their presence brings the total number of molars to 12, with three on each side of the upper and lower jaws. When all four third molars develop properly, they contribute to the powerful chewing and grinding surfaces necessary for breaking down food.
Timing of Eruption and Evolutionary Context
Third molars earned the common name “wisdom teeth” because they typically emerge much later than other teeth, at a time when an individual is thought to be gaining maturity. The general age range for their eruption is between the late teenage years and the early twenties, usually spanning from about 17 to 25 years old. This timing can vary significantly from person to person due to genetics and the physical space available in the jaw.
From an evolutionary standpoint, third molars once served a functional purpose for early humans. Our ancestors consumed a tough, abrasive diet that caused significant wear and tear on their teeth. The late eruption of the third molars provided a set of replacement grinding teeth later in life, which was an adaptation for maintaining chewing function.
As human diets softened with the advent of cooking and agriculture, the intense pressure for large, powerful chewing surfaces decreased. Over thousands of years, the size of the human jaw has gradually reduced. Consequently, many modern individuals lack sufficient space to accommodate all four third molars, a phenomenon that often results in the teeth being trapped beneath the gum line, known as impaction.
Why Some People Grow Fewer or More
The number of wisdom teeth a person develops is not fixed at four and is subject to significant genetic variation. A common scenario is dental agenesis, which refers to the congenital failure of teeth to develop. Third molars are the teeth most frequently affected by agenesis, with studies indicating that between 10% and 41% of populations worldwide may be missing at least one.
Some individuals are born without the tooth buds for one, two, three, or even all four wisdom teeth. The likelihood of missing third molars is highly influenced by genetics, with specific genes such as PAX9 and WNT10A playing a role in tooth development. The prevalence of this absence also shows variation across different ethnic groups, with some Asian populations exhibiting higher rates of third molar agenesis.
In contrast to agenesis, a small percentage of the population experiences hyperdontia, a condition where supernumerary teeth develop. While rare, some individuals may grow a fifth or even a sixth molar positioned behind the standard third molar, sometimes called a distomolar or fourth molar. When these extra teeth occur in the molar region, they add to the potential number of wisdom teeth.