Tooth sections stained with Toluidine blue.
Twelve weeks after the low-power laser treatment, more newly formed dentin, marked by yellow hashtags (#), can be seen in the laser-treated teeth (bottom) than in the controls (top). Credit: Harvard's Wyss Institute and SEAS.
A small dose of low-power laser light activated dental stem cells in rat molars to generate dentin, one of the major components of teeth.
The finding may lead to new approaches to develop low-cost, non-invasive therapies for treating dental disease and tooth damage.
by Shu Hui Chen, PhD
Dentists currently use inert materials to repair damaged teeth. Tissue regeneration would be an attractive alternative, because inert materials can fail with time and don’t provide the full function of the tissue.
Stimulating tooth regeneration, however, is a major challenge. Teeth are composed of several parts, including the pulp at the core, dentin in the middle, and enamel on the surface.
Stem cells, found throughout the body, can give rise to specialized cells. Researchers have been able to coax stem cells to transform (differentiate) into many types of cells in the laboratory before infusing them into the body. But these techniques are time consuming and can bring unwanted side effects.
Low-power laser (LPL) therapy has been used to treat inflammation and pain, and to stimulate wound healing, skin rejuvenation, and hair growth. LPL treatment has been noted to promote regeneration in cardiac, lung, and nerve tissues. These regenerative effects may be mediated through stem cells, but a direct link between laser treatment and stem cell biology hadn’t been clearly demonstrated.
A research team led by Dr Praveen Arany of NIH’s National Institute of Dental and Craniofacial Research (NIDCR) and Dr David Mooney at Harvard University set out to investigate whether LPL can induce stem cells to regenerate components in teeth. The work was funded in part by NIDCR and other NIH components. Results appeared on May 28, 2014, in Science Translational Medicine.
The scientists first studied rats that had cavities in 2 molars, each with exposed tooth pulp (the soft inner part of the tooth). One tooth was treated with LPL, and the other wasn’t. Both damaged sites were then filled. The researchers found that dentin was induced in the LPL-treated molar after 12 weeks.
The team used laboratory cell lines to investigate how LPL induced dentin. They found that LPL treatment generated a type of molecule known as reactive oxygen species (ROS). ROS stimulated dentin production by activating transforming growth factor beta (TGF-β), a signaling protein that can promote dental stem cell differentiation.
The researchers also showed that LPL induced adult human dental stem cells to form dentin in the laboratory. Taken together, these results suggest that LPL might be used to direct stem cells in human teeth to regenerate dentin. Effective surgical techniques and optical focusing approaches would first need to be developed for the use of this treatment in people, however.
“Our treatment modality does not introduce anything new to the body, and lasers are routinely used in medicine and dentistry, so the barriers to clinical translation are low,” Mooney says. “It would be a substantial advance in the field if we can regenerate teeth rather than replace them.”