Secret to renewed teeth? Lasers show gleam of hope

What if a cavity could fill itself, a broken tooth regrow? That's the promise of work published today in the journal Science Translational Medicine.

By shining light from a low-powered laser – about the brightness of a sunlit day – researchers were able to turn on a natural healing program and regrow dentin, the material inside a tooth. So far, they can only do this in rodents, but they could receive approval to test it in people within a year.

If it succeeds, the approach might also work for regrowing heart tissue, fighting inflammation and repairing bone and wounds, the researchers say.

"There's potential for this to be broadly useful," said David Mooney, the Harvard University bioengineer, who was the paper's senior author.

The promise is fantastic, said Harold Slavkin, a molecular biologist and professor of dentistry at the Ostrow School of Dentistry at the University of Southern California in Los Angeles. By mimicking a process already found in nature, Mooney's work has the potential to eventually transform medical care, enabling people someday to regrow their own livers, hearts or kidneys, he said.

"Twenty or 30 years from now people may say, 'Isn't it ridiculous that they used to transplant organs from one person to the other,'" Slavkin said.

Co-author Praveen Arany, a dentist and pathologist, said he got interested in the potential healing power of light after hearing anecdotes about light's ability to repair wounds and regrow hair. Laser light at very low frequencies does nothing, and at higher frequencies is commonly used to cut and cauterize tissue, so the dose of light has to be carefully delivered, said Arany, who initiated the research while a student in Mooney's lab.

He spent years carefully calibrating light levels to discover an optimal dose.

At appropriate levels, the light appears to trigger a chemical reaction that releases reactive oxygen species, a potentially damaging type of molecule.

In response to the reactive oxygen, the body's natural healing process activates a protein called Transforming Growth Factor (or TGF)-beta, which plays crucial roles in embryonic development, wound healing and the immune system. The TGF-beta stimulates production of new dentin, the material at the center of the tooth.

Arany and Mooney demonstrated that they can trigger this cascade of events and produce dentin by shining a low-powered laser on a rodent's tooth.

What they can't do yet is stimulate an entire tooth to regrow – the new dentin lacks the structure of a tooth, Mooney said. But Arany, now with the National Institute of Dental and Craniofacial Research, is hopeful of finding a way to get the body to rebuild structures, too.

"If we can figure out a way of activating those (processes), that would be really cool," he said.

Anne George, an endowed professor at the University of Illinois at Chicago, College of Dentistry, praised the work as impressive and important.

"If it works in a clinical trial setting, I think it will be great," she said. "No more drilling and filling."