THOUSAND PALMS, Calif. - Nobody likes having to undergo a root canal, but these painful procedures could soon be a thing of the past. The trick: laser light and stem cells.
Researchers at Harvard University found that exposing the cells on the inside of a tooth to weak laser light stimulates the growth of dentin, the substance that makes up much of a tooth's structure.
So far, the experiments have been done in rats and mice but the researchers have tested the technique on human cells in culture, and it seems to work, said Priveen Arany, an assistant clinical investigator at the National Institutes of Health.
"We're using resident stem cells — they are adult cells already present in the tooth pulp," Arany told Live Science. That means that many of the challenges facing stem cell therapies aren't there – there's no need to harvest stem cells at all.
The experiment was simple enough: Drill two holes in a rodent's molar and expose the dentin in one of the holes to laser light.
After 12 weeks, the laser-treated hole showed the growth of tertiary dentin, a type of hard tooth tissue. The untreated hole showed no such growth.
The researchers found that laser light hits the tissue and creates what are known as reactive oxygen species, or ROS. The ROS molecules in turn stimulate a certain amino acid, which then brings out a growth factor called latent transforming growth factor beta, or TGF-beta.
That growth factor stimulates the growth of dentin. It isn't quite the same kind of dentin that teeth start with, but it is good enough to chew with, Arany said.
The researchers tested the same technique on human cells harvested from tooth extractions. The laser light seemed to stimulate the growth of dentin, but more tests are needed before the therapy is tried on human patients. One of the challenges noted in the study is that focusing the laser light onto specific areas to ensure that dentin regenerates precisely where it is needed most can be tricky.
Even if the technique works, it won't completely regenerate teeth, the researchers said. The part of the tooth that gets restored is underneath the enamel. The cells that make enamel are lost when the tooth grows into the mouth. So, any repairs done this way will need some kind of artificial enamel covering or protection to strengthen the tooth, just as dentists use now for fillings and root canals.
Even so, Arany said this laser therapy could mean the end of root canals because the technique would restore the structure of the tooth.
A root canal is necessary when too much of a tooth is infected or damaged, and there isn't any way to prevent the problem from getting worse (other than removing the tooth entirely). The procedure involves hollowing out the tooth, including the blood vessels that connect the roots to the jaw (hence the term "root canal"), filling the crevices with an artificial material, and then covering the site with a "crown," or tooth-shaped cap. Anyone who has had a root canal done will likely agree that in the aftermath, the procedure can be quite painful.
The longer-term problem is that the tooth lacks a blood supply to replenish nutrients and moisture. As a result, the restored tooth can't take as much stress as a healthy one. If a tooth's dentin could be restored, then a root canal wouldn't be necessary anymore, and the tooth could remain viable, the researchers said.
But there are also implications for other tissues, Arany said. TGF-beta is a growth factor involved in the regeneration of cells in other organs, so it's possible laser light treatments could have other useful applications, the researchers said.
The detailed findings of the study were published online today (May 29) in the journal Science.