Lasers heal damaged rodent teeth

To rebuild damaged teeth, just add laser light.

Zaps from a low-power laser boost tooth growth in rodents, researchers report May 28 in Science Translational Medicine. The beams of light set off a molecular chain reaction that ends with the regeneration of dentin, the tough stuff inside teeth.

The findings may change the way dentists think about treating patients, says dental stem cell researcher Peter Murray of Nova Southeastern University in Fort Lauderdale, Fla. “It’s a new application for lasers in dentistry.”

Today, dentists and doctors can use lasers as high-tech scalpels to carve out damaged tissue, slice away overgrown gums or burn away tumors. But for years scientists have had hints that turning down a laser’s power could actually get cells growing.

Light from a low-power laser can spark new growth of heart, skin and nerve tissue, and researchers have speculated that the regeneration somehow involves stem cells, says study coauthor David Mooney, a bioengineer at Harvard University.

“But certainly people did not understand how it worked,” he says. “We wanted to put all the pieces of the puzzle together.”

Mooney and colleagues drilled holes into two molars each in seven rats— down past the hard white enamel and through the tough dentin — to expose the spongy, sensitive pulp at each tooth’s core. The team then hit the pulp of one tooth in each rat with a 5-minute blast from a handheld near-infrared laser, a device that looks like a laser pointer wired to a little power box, and left the other tooth alone.

After filling both drilled teeth with dental composite and waiting 12 weeks, the team saw tiny knobs of dentin growing at the bottom of the hole — in and around the pulps of both teeth. About 20 percent more dentin grew in the tooth treated with the laser than in the untreated one, Mooney says.

“It’s not re-forming the tooth perfectly,” he says. But teeth could benefit from having extra lumps of new dentin protecting the underlying pulp. Damage to dentin by cavity-causing bacteria can leave the pulp open to microbial attack, which can kill the tooth.

The new laser treatment probably works by activating stem cells, the researchers suggest. In lab tests, dental stem cells from human teeth and cells from mice showed signs of turning into dentin-making cells when hit with low-power laser light.

“It’s a surprise to me,” says dental developmental researcher Irma Thesleff of the University of Helsinki. “I never thought that these stem cells could be stimulated with a laser.”

What’s more, she says, Mooney’s team has for the first time mapped out the molecular path linking laser light to switched-on stem cells.

When the laser beam shines, chemicals in the cells absorb the light’s energy and morph into reactive molecules that rev up a growth factor protein, the researchers discovered. This protein then spurs dental stem cells into action and show signs of turning into dentin-forming cells, Mooney says.

Thesleff and Murray both caution that any potential side effects of the low-power laser light still need to be figured out, but they believe the technology could one day be a normal part of dentists’ toolkits.

“Dentists already use lasers,” Thesleff says. “This is just a different kind of laser.”