What a wisdom tooth is and where it sits
A wisdom tooth is a third molar. Adults who have a full set can have up to four: one at the back of each side of the upper jaw and one at the back of each side of the lower jaw. They sit behind the second molars, the last teeth you would normally count when you run your tongue along the arch.
Wisdom teeth are the last teeth to form and the last to come through, which is where the name comes from: they appear at an age when a person is supposed to have gained some wisdom. In most people they start to show between the late teens and the mid twenties, though some come through later, and some never come through at all.
A wisdom tooth may be fully through the gum, partly through, or stay buried in the bone. Which of these it is matters far more than the fact that it exists.
Because they come last, wisdom teeth also meet the most crowded conditions. The second molars, which erupt years earlier, have already settled into the space. That timing difference is the root of nearly every wisdom tooth problem, and it is why the same tooth can be trouble-free in one person and painful in another.
How many people have them, and why some do not
The number varies from person to person. Some people have all four, some have one, two or three, and some have none. A tooth that was never formed will not show on an X-ray at all, so the only way to know how many you have is to have an X-ray taken.
This runs in families and between populations, so a sibling or parent having fewer or more than you is not unusual. Having a missing wisdom tooth is not a sign of a problem, and it does not affect how your other teeth work.
A tooth that is present but buried can sit silently for years. It is often found by chance when an X-ray is taken for some other reason.
Dentists usually confirm the count and position on a panoramic X-ray (OPG), which shows all the teeth in one image. If you have never had one, it is a quick way to find out what is happening behind the gum.
Why there is often no room for them
The usual explanation is that human jaws have become smaller over many generations, while the number of teeth has stayed the same. Early humans ate tough, coarse food that wore teeth down and demanded a lot of chewing surface. Those extra molars were useful to them.
Modern diets are softer and our jaws are generally smaller, so by the time the third molar is ready to come through, the arch may already be full. The tooth then has to find a way in at an angle, push against the second molar, or stay trapped under the gum.
A tooth blocked from coming in fully is called an impacted tooth. It is common with wisdom teeth, though it is not the case for everyone.
Some people have enough jaw length for all four teeth to come through straight, and for them wisdom teeth behave like any other molar. Jaw size, tooth size and the angle at which the tooth forms all play a part, which is why you cannot judge your own mouth by looking at a friend's.
When a wisdom tooth is useful
A wisdom tooth that has come through fully, sits upright, meets a tooth in the opposite jaw and can be reached by a brush works like any other molar. It adds chewing surface, and it is a real tooth that can be kept and cared for.
A wisdom tooth can also be useful if another back molar has been lost, because it can sometimes be used as a support tooth for a replacement. That is a decision for your dentist and depends on how healthy the tooth is.
A wisdom tooth that has no problem and is not at risk of one does not need to be taken out only because it is a wisdom tooth.
When a wisdom tooth causes trouble
Trouble comes when the tooth is partly through or tilted. A flap of gum can trap food and bacteria and become infected, which is pericoronitis. A tilted tooth can press on the second molar and cause decay on it. Occasionally a cyst forms around a buried tooth without any pain.
Not every wisdom tooth is a problem, and not every problem is the tooth's fault. Whether a particular tooth should stay or go depends on its position, its angle, whether it can be kept clean, and what it is doing to its neighbour. Do wisdom teeth need removing goes through that decision.
If you have pain, swelling or a bad taste at the back of your mouth, the wisdom tooth pain page covers the causes. Call the clinic to ask how a particular case would be handled.
Common questions
At what age do wisdom teeth come in?
Most people see them between the late teens and the mid twenties. Some come through later in adulthood, and some never come through. The timing is not a reliable guide to whether a tooth will cause trouble.
Is it normal not to have wisdom teeth?
Yes. Some people are born without one or more of them, and some have none at all. An X-ray is the only way to know whether a tooth is missing or simply buried under the gum.
Are wisdom teeth good or bad?
Neither by default. A fully erupted, cleanable one is a working molar. A partly erupted or tilted one can cause infection or decay. It depends on the individual tooth, which is why each one is judged on its own position and condition.
Why are they called wisdom teeth?
They come through much later than other teeth, at an age when a person is expected to be more mature. The dental name is third molar. The link with wisdom is only a naming tradition and has no connection to intelligence.
Do wisdom teeth push the other teeth out of line?
The evidence does not support wisdom teeth crowding the front teeth. Crowding tends to change with age whether or not wisdom teeth are present. They can press on the tooth beside them if tilted, which is a different problem.
About this page
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