WebMD poses this question: Are wisdom teeth removal often unnecessary? And answers this rhetorical question in the affirmative:

Teens often have their wisdom teeth removed. But there’s no evidence this painful procedure prevents future trouble.

That’s the conclusion of a careful review of dental studies by a research team including Dirk G. Mettes, DMD, of Radboud University Medical Center in, Nijmegen, Netherlands. Although Mettes and colleagues looked at 40 studies, they found only two controlled clinical trials of wisdom tooth removal.

The bottom line: If impacted wisdom teeth are not causing trouble, there’s no evidence that removing them helps or hurts future health. But there is some evidence that removing teens’ impacted wisdom teeth “to reduce or prevent late incisor crowding cannot be justified,” the researchers conclude.

Read the abstract of the Mettes’ study here.

How controversial is it to remove wisdom teeth that aren’t currently causing problems? Two dentists who spoke with WebMD agree that there’s no reason to remove perfectly healthy wisdom teeth. Both agree that troublesome wisdom teeth should be removed. And both say that there has to be a medical reason to perform such a serious surgery.

Eric K. Curtis, DDS, spokesman for the Academy of General Dentistry and a private-practice dentist in Safford, Ariz., says it comes down to what an individual dentist thinks is best for an individual patient.

“In my practice, about 75% of the asymptomatic (without symptoms), impacted wisdom teeth I see I take out,” Curtis tells WebMD. “It is subjective. There is no decision tree to tell us, ‘If this happens, take the tooth out,’ or ‘If this happens, leave it in.’ It comes down to your own sense of what is right and wrong and to patients’ own preferences.”

Mohamed Bassiouny, DMD, PhD, professor of dentistry at Temple University — the oldest dental school in the U.S. — in June will celebrate his 40th anniversary as a dentist.

But isn’t it normal for teen’s to have their wisdom teeth removed? Not to Bassiouny.

“It is a shame,” Bassiouny tells WebMD. “It should not be considered that way. God gave us a full set of teeth. We should live with it.”

Wisdom tooth removal is so common, Curtis says, that patients have stopped thinking of it as a serious medical procedure.

“In the public’s mind, dentistry is really routine,” he says. “You turn 18 and you think it is time for wisdom teeth to come out. It is almost ubiquitous, a rite of passage. But a dentist has to tell you maybe you should take out wisdom teeth for this, this, and this reason. But there is this, this, and this risk, too. You have to decide if it is worth it.”

Wisdom teeth typically emerge around age 17 to 24 or later. Wisdom teeth can be a problem because the human jaw is shorter than it was early in our evolution. And these teeth are at the very end of the jaw, Curtis notes.

“If the jawbone is straight, the tooth wants to come in straight,” Curtis tells WebMD. “But most people run out of bone. Your jawbone starts its curve upward, and the wisdom teeth on the lower jaw get caught in that curve and tip forward.”

Impacted wisdom teeth may lie fully horizontal. If that’s the case, trouble almost certainly lies ahead. It’s a harder call when a wisdom tooth fully emerges but is only slightly tipped toward the molar next to it. Some worry that, over time, this will cause crowding of the front teeth. The Mettes review, however, suggests this is not the case.

“If a wisdom tooth is completely horizontal, I almost universally recommend taking that out,” Curtis says. “The chances of bone disease are so high that I can predict with pretty good probability that 10 or 20 years down the road that person will have gum problems that will pose a risk to other teeth as well.”

Also risky, Curtis says, is a wisdom tooth that emerges from the underlying bone but comes only part way through the skin. That leaves a person open to high risk of decay and infection.

When a dentist deems wisdom tooth removal necessary, he or she should talk to the patient about possible risks of surgery.

“It is surgery, so there is risk of infection, there is some risk of jaw fracture, and risk of numbness that lingers on because a nerve is damaged in pulling the tooth,” Curtis says. “And that is a really uncomfortable thing to have your lip numb for the rest of your life or even for a couple of years. You have to think of risks.”

What Good Are Wisdom Teeth, Anyway?

We get three sets of molars — and get them at different times of life — because the diet we ate as we evolved into humans was tough on the teeth. A third set of molars — the wisdom teeth — kept us chewing on as our first set of molars wore out.

The modern diet isn’t so tough, so we aren’t as likely to wear out our first two sets of molars.

“Wisdom teeth simply aren’t necessary. I don’t know anyone who can’t get along without them,” Curtis says. “And a wisdom tooth is very difficult to clean. Even when it comes in well, it is far back against the upward curve of the jawbone. Sometimes you can’t get a toothbrush behind it — sometimes not even to it. So if it takes a root canal or crown to fix a decayed wisdom tooth, that is not an unsubstantial cost. So is it worth it to do that?”

Bassiouny says it’s still a good idea to have an extra set of molars.

He points out that the wisdom teeth can take up the slack should other teeth fall out or need to be pulled — as commonly happens as we age. And when a person needs a dental bridge, Bassiouny says, wisdom teeth provide an important anchor.

Check out the good illustrations of wisdom teeth classifications here.

Bottom Line: A good educated discussion with your dentist and oral surgeon can best inform the patient as to the appropriate course of treatment.