Most humans have four wisdom teeth, one in each corner of the mouth. They sit at the very back of the jaw, directly behind your second molars, and are the last adult teeth to come in. But “four” is just the standard number. A significant portion of the population develops fewer than four, and a small number develop more.
Where the Four Wisdom Teeth Sit
Your mouth is divided into four quadrants: upper left, upper right, lower left, and lower right. A full set of wisdom teeth means one in each quadrant, for a total of four. Dentists call them third molars because they’re the third and final set of molars to develop. They typically begin pushing through the gums between ages 17 and 25, though some never break through at all.
Not Everyone Gets All Four
About 22.6% of people worldwide are missing at least one wisdom tooth entirely, meaning it never formed in the jaw in the first place. This isn’t a dental problem. It’s a genetic variation called third molar agenesis, and rates vary by ancestry. Asian populations show the highest prevalence at roughly 30%, while other groups tend to fall below the global average.
When wisdom teeth are missing, the pattern isn’t random. The most common scenario among otherwise healthy people is being missing all four, followed by missing both lower wisdom teeth. About 9% of people are missing both lower third molars, and a similar percentage are missing both upper ones. Missing just one is actually less common than missing two or four. If you’re also congenitally missing other teeth (like lateral incisors or premolars), your odds of missing wisdom teeth jump to about 50%.
Can You Have More Than Four?
Yes, though it’s rare. Some people develop a fifth molar, sometimes called a fourth molar or “distomolar,” which grows behind the wisdom tooth. The prevalence of these extra teeth falls between 0.1% and 3.8% of the population, depending on the study. One five-year review at a university dental hospital found a rate of 0.32%. These extra molars are usually small and often remain buried in the jawbone, discovered only on dental X-rays.
Why Humans Have Wisdom Teeth at All
Wisdom teeth made sense for our distant ancestors, who had larger jaws and chewed tougher, unprocessed foods that wore teeth down over a lifetime. A third set of molars arriving in early adulthood served as replacements for heavily worn or lost teeth. Over thousands of generations, the human jaw has gradually shrunk, likely driven by the shift to softer, cooked diets. The teeth, however, haven’t caught up. Four wisdom teeth still develop in most people, but the jaw often doesn’t have room for them.
What Happens When They Don’t Fit
When wisdom teeth can’t fully emerge because of limited space, they become impacted. This affects roughly 22% of people, and the lower jaw is the most common trouble spot. Lower wisdom teeth account for the majority of impaction cases.
Impacted wisdom teeth don’t all get stuck the same way. Nearly half are angled forward, tilting toward the tooth in front of them. About a quarter come in mostly straight but can’t fully clear the gum line. The rest are angled backward or lying completely on their side. The angle matters because it influences whether the tooth will cause problems like infection, crowding, or damage to neighboring teeth.
A partially erupted wisdom tooth is especially prone to issues. The flap of gum tissue covering part of the tooth traps food and bacteria, leading to painful inflammation and infection. Impacted wisdom teeth can also cause cavities on the back surface of the neighboring molar, which is difficult to clean and often hard to repair.
When Wisdom Teeth Need to Come Out
The decision to extract wisdom teeth depends on whether they’re causing problems or are likely to. Clear reasons for removal include recurring gum infections around a partially erupted tooth, cavities that can’t be filled, cysts forming around an impacted tooth, or damage to the adjacent molar.
The trickier question is what to do with wisdom teeth that aren’t causing symptoms. Guidelines from the UK’s National Institute for Health and Care Excellence recommend against routinely removing healthy, symptom-free wisdom teeth, favoring regular monitoring instead. The American Association of Oral and Maxillofacial Surgeons takes a more proactive stance, noting that even asymptomatic wisdom teeth can harbor bacteria that raise the risk of gum disease over time, and that early removal may prevent complications down the road.
If your wisdom teeth have fully erupted, are properly aligned, and you can keep them clean, there’s no automatic need to have them pulled. Many people keep their wisdom teeth for life without issues. The key is consistent monitoring through dental X-rays to catch early signs of decay, cyst formation, or bone loss before they become painful problems.