“These teeth are completely impacted,” said Ross, pointing to where they hid in her upper jaw, to explain his recommendation to pull them. “In this position, they probably aren’t going to drop down.”

Or they might. And if they do, my daughter would have two perfectly functioning molars at the back of her upper jaw.

But if the teeth don’t come through or push through only part way, they might cause problems down the road. Ross showed us the X-ray of a 75-year-old man who left in place a wisdom tooth that was now growing sideways, surrounded by a cyst. The man’s jawbone could be in jeopardy, and so the choice was clear: The tooth needed to come out.

For my daughter and me, the decision was not so straightforward. We had to weigh the risks of possibly unnecessary surgery against the advantage of taking the teeth out then, while their roots were less formed and easier to pull, in the hope that she would avoid problems — ranging from infection and damage to adjacent teeth to cysts or even tumors — that might, or might not, happen in the future.

This is the dilemma for those whose wisdom teeth aren’t causing them problems. Dentists often recommend that young people get those teeth pulled, particularly before they head off to college for the first time. Yet, as I discovered when trying to decide what to do with my daughter’s two errant teeth, there just aren’t any etched-in-stone, must-do rules, good scientific studies or even helpful statistics to indicate when it is reasonable to pull a wisdom tooth and when you can leave it.

A controversial 2007 article in the American Journal of Public Health by retired dentist Jay Friedman likened pulling an asymptomatic wisdom tooth to removing a healthy appendix just to prevent the future possibility of appendicitis. “If there’s no evidence to support a surgical procedure, then it should not be done,” he said. But others say that there aren’t enough data to support that conclusion — or any other at this point.

The National Institutes of Health hopes to fill in some of these statistical and clinical gaps through a study it launched a year ago that is following 750 dental patients in five northwestern states. The study will look at the reasons given by general dentists when they recommend either keeping or pulling third molars and what the patients then decide to do. It will follow those patients for two years after their decision to assess rates of complications, according to Greg Huang, principal investigator for the study and head of the Department of Orthodontics at University of Washington School of Dentistry.

“There isn’t any good information about the life cycle of third molars,” said Donald DeNucci, a periodontist with NIH’S National Institute of Dental and Craniofacial Research in Bethesda. “In Great Britain, they have been looking at this closer. They state that if a wisdom tooth has a cavity or is causing swelling of the gum or has periodontal issues, remove it. Then things move into the gray area, where it’s not so clear. In Great Britain, the National Health Service now says if impacted wisdom teeth are not causing problems, don’t remove them.” DeNucci said the NIH study will help oral surgeons and dentists in this country make informed decisions about wisdom teeth based on scientific evidence.

Most people are born with four wisdom teeth, or third molars, which ordinarily begin to come into the mouth between ages 17 and 25. “They are called wisdom teeth, I suppose, because they come in during the late teens and 20s, when a man begins to possess some wisdom,” said DeNucci.

Smaller jaws

They are also considered a remnant of our hunter-gatherer past. “The third molar functioned when the human diet was very coarse,” DeNucci said. “Teeth ground down and wore out. It is possible the third molar came in late to fill in the chewing function. Jaws were larger back then. Now, the human jaw is getting smaller, and our teeth haven’t caught up.”

Thus, wisdom teeth can become impacted — or trapped in the jawbone, unable to grow above the gum — for a variety of reasons, most commonly for a lack of space or because another tooth is in the way. Or the teeth grow in a skewed manner, sideways in the gum or at a slant toward adjacent teeth.

The American Dental Association does not have an official policy about dealing with wisdom teeth, said ADA spokesman Fred Peterson, adding that each case needs to be evaluated on the individual merits. According to its Web site, the ADA believes that “wisdom teeth are a valuable asset to the mouth when they are healthy and properly positioned. Often, however, problems develop that require their removal.”

Chevy Chase dentist Steven Kahan, who has been practicing for 40 years, said: “It is the kind of thing where all of us make a somewhat educated guess. You can’t always predict how a tooth will grow. I have one wisdom tooth locked in my upper arch, and it’s been there forever. The advice of the oral surgeon when I was in dental school was to leave it alone. I’ve never had a problem.”

Yet it is clear that there can be problems.

“Sometimes a sac forms around a wisdom tooth,” said Washington dentist Richard Steinlen, who estimates he has cared for about 4,000 patients a year during his 28-year career. “Mouths are more cyst-prone than other parts of the body. Lots of cysts form around wisdom teeth.”

Partially erupted wisdom teeth also create troubles because they are hard to clean, he said. As a result, food can get lodged in the back of the mouth and create a perfect environment for a bacterial infection called pericoronitis, which can cause pressure, pain and swelling. (Antibiotics are often prescribed to treat it.) In addition, partially erupted wisdom teeth are prone to tooth decay.

Thomas Dodson, a professor of oral surgery at Massachusetts General Hospital and author of an April study in the British journal Clinical Evidence that reviewed other studies on impacted wisdom teeth, found that 25 percent of patients who had wisdom teeth without symptoms had periodontal disease on those teeth. According to Dodson, this shows that the absence of symptoms does not mean the absence of disease. As a result, he said, patients who keep their wisdom teeth should be monitored periodically to assess the health of those teeth.

Often when Dodson tells patients with asymptomatic wisdom teeth that “there are no data” to help them decide whether to pull the teeth, “60 percent elect extraction; 40 percent choose to retain the wisdom teeth and schedule a two-year follow-up visit with me,” he said.

No more hammers

Dodson noted that whatever the patient decides, the surgery has become easier. “One hundred years ago, it was a serious operation with hand instruments and no anesthesia,” he explained. “By the 1950s, power drills were developed, not hammers and chisels, and there was the introduction of antibiotics. Things took off from there.”

Still, pulling a wisdom tooth is surgery, and surgery can lead to problems. Wisdom teeth in the upper jaw can be very close to sinuses, which can get perforated during surgery. The lower teeth, meanwhile, lie very close to several nerves; damaging them can cause temporary or even permanent numbness in the lips, tongue or chin.

“But the most common complication is infection,” Dodson said, and “that happens one in 20 times. Then there can be postoperative bleeding, nerve injury and a host of rare complications, such as a possible break in the jaw. Dry socket [which occurs when the blood clot that is left after a tooth is pulled dislodges and the bone is exposed] and infection can be as high as one in 20.”

In the end, then, how does a patient decide to pull or not to pull. In my daughter’s case, we decided after talking to Steinlen, who is her dentist.

“She only has two upper-jaw wisdom teeth,” he said recently, reviewing her old X-rays. “The roots are barely formed. This is significant [because] a tooth is mostly root. I worry that these two upper wisdom teeth may partially erupt and then begin to cause problems. Usually taking out impacted teeth on teenagers is easier surgery [because the root is only partially formed] and will eliminate problems later. But it is a subjective call. Some people will wait until there are obvious problems, and I don’t disagree.”

And so one day last summer, my daughter and I drove to the office of David Ross and had her teeth pulled.

Ross administered nitrous oxide, or laughing gas, and then made a small incision in her upper gum with a scalpel to create a flap and a passageway to her jawbone.

He scraped away at the bone until he could see the top of her wisdom tooth, and removed the tooth in one piece with a specialized tool. He then repeated the procedure on the other side of the her jaw. For lower wisdom teeth, Ross said, he generally divides the tooth with a drill before extracting it.

The surgery took all of 20 minutes. My daughter didn’t feel great for a few days and her face was swollen, but that was it. She had no complications.

Hambleton is a freelance writer and a documentary filmmaker.