Researchers Trigger Tooth Repair with Low-Power Laser

Yesterday we wrote about a pair of King's College London researcher/dentists who have developed a technique to repair tooth decay using electric currents.

Today we report on a group of researchers at Harvard's Wyss Institute who are working on another way of repairing teeth, this one involving low-powered lasers. The research, which was led by Wyss Institute Core Faculty member David Mooney, PhD, and published in Science Translational Medicine by lead author Praveen Arany, DDS, PhD, lays the foundation for a host of clinical applications in restorative dentistry and potentially in regenerative medicine more broadly, such as wound healing, bone regeneration, and more.

Arany, who is now an assistant clinical investigator at the National Institutes of Health, drilled holes in the molars of rats. Then he treated the tooth pulp that contains adult dental stem cells with low-dose laser treatments, applied temporary caps, and kept the animals comfortable and healthy. After about 12 weeks, high-resolution x-ray imaging and microscopy confirmed that the laser treatments had triggered the enhanced dentin formation.

"It was definitely my first time doing rodent dentistry," said Arany, who faced several technical challenges in performing oral surgery on such a small scale. According to a Wyss Institute release, the rodent dentin was strikingly similar in composition to human dentin, but did have slightly different morphological organization. Moreover, the typical reparative dentin bridge seen in human teeth was not as readily apparent in the minute rodent teeth, owing to the technical challenges with the procedure.

Next the team performed a series of culture-based experiments to unravel the precise molecular mechanism responsible for the regenerative effects of the laser treatment. It turned out that a ubiquitous regulatory cell protein called transforming growth factor beta-1 (TGF-?1) played a pivotal role in triggering the dental stem cells to grow into dentin. TGF-?1 exists in latent form until it is activated. This can be triggered by a number of molecules.

The Wyss Institute release explains that the team observed a chemical domino effect. In a dose-dependent manner, the laser first induced reactive oxygen species (ROS), which are chemically active molecules containing oxygen that play an important role in cellular function. The ROS activated the latent TGF-?1complex which, in turn, differentiated the stem cells into dentin.

Nailing down the mechanism was key, the researchers say, because it places on firm scientific footing the decades-old pile of anecdotes about low-level light therapy (LLLT), also known as Photobiomodulation (PBM).

Stephen Levy is a contributor to Qmed and MPMN.