Genetic Dentistry: The Tooth Fairy for Grownups

This may sound like dentist-chair sci-fi, but researchers at the University of Texas Health Science Center at San Antonio have already successfully regrown mouse teeth in a petri dish from single mouse cells — and they think humans are next.

"In the next 10 years, we hope to push the research in the direction where we could take initial tissue from a [human] patient, put it in a culture dish and grow a tooth for them," said Univ. of Texas lead researcher Dr. Mary MacDougall.

To accomplish this seemingly futuristic feat, MacDougall and her colleagues need to determine which human genes will induce formation of a new tooth in order to be able to stimulate these genes within the tooth bud cells.

Tooth regeneration research is only one way in which the genetics industry is putting its money where your mouth is.

A more mundane but practical advance: a mail-in genetic test that determines if you are at high risk for periodontitis, a degenerative tooth and gum disease that affects up to 67 million Americans.

Diagnostic genetic test kits that identify cavity-prone children are also in the pipeline. And in the far future, gene therapy could even reprogram babies' DNA so they'll have perfect jaws and cavity-resistant teeth.

"It's almost science fiction that these things are possible," said Dr. Michael McGuire, president-elect of the American Academy of Periodontology. "But I'm convinced that genetic research such as the Human Genome Project is going to revolutionize the way we treat diseases in general, whether heart disease or periodontal disease."

Tissue engineering, such as the teeth regrowth and another related technology are going to play a major role in undoing the ravages of dental diseases and decay, McGuire said.

Perio Prophesies

The periodontitis genetic test, manufactured by Interleukin Genetics Inc., is already helping dentists diagnose this degenerative disease before symptoms are shown.

Periodontal disease, a chronic bacterial infection that damages gums and bone supporting the teeth, is more severe in people whose immune systems overreact to the bacteria (plaque) that gets between teeth and gums.

These people, who make up about 30 percent of the population, according to Interleukin Genetics, have a genetic variation associated with the production of interleukin-1, which regulates immune function.

The test identifies this variation from a simple swab of a patient's cheek cells. Dentists and patients can then decide how aggressive to be with treatment.

"In dentistry, you don't see the onset of periodontal disease until your 30s and 40s," said Dr. Max Anderson, a dental director for Washington Dental Service, a dental insurance plan. "But if you know a patient is susceptible to periodontal disease when he or she is 25 years old, you can intercept with treatment before you need surgery."

Insurance companies have not decided whether to cover the genetic test for periodontitis, which costs about $200, said Anderson.

The picture is complicated by the fact that factors such as smoking, diabetes and oral hygiene affect a person's susceptibility to periodontal disease more than this genetic variation alone.

Knowing the genetic susceptibility can help dentists to figure out how much these other components will affect a given person, McGuire said: "Having the genetic defect is not the kiss of death for your teeth, but for people who smoke and have this genetic defect, it's really bad news."

In looking at 48 people in his practice over 15 years, McGuire determined that people who had the genetic defect were 2.7 times more likely to lose their teeth than those who did not, while smoking alone made people 2.9 times more likely to lose their teeth than nonsmokers, and smokers with the genetic defect were eight times more likely to lose their teeth than nonsmokers without the defect.

"The nice thing about this test is that if you come back positive, forewarned is forearmed and you can still beat the disease," McGuire said. "You just have to work harder than your friends."

The Secrets of Shark Teeth

If you still need surgery or dental implants, it will be some time before you can actually get a new set of living teeth that can be transplanted into your mouth.

But MacDougall and her colleagues have already figured out how to grow cementum, the tooth substance that is normally destroyed with periodontal disease, as well as tooth enamel. They have yet to find how to integrate these lab-produced substances into the bone structure of living teeth.

Even if this integration is possible, another route may prove even more effective. "Now we are looking at repairing a tooth at the cavity site from the bottom up by stimulating cells that are still viable in the tooth," MacDougall said.

To figure out how to stimulate these cells, they are looking at sharks, who regrow their teeth as they lose them.

If researchers can learn how sharks do this — or determine how to turn on the genes in human beings that do this — you may be able to go to the dentist and have your teeth regrown without them ever leaving your mouth.

But these new technological innovations are about 20 years away, according to experts. Meanwhile, it's a good idea to keep caring for the teeth you have.