Lasers for Growing New Teeth?
While California researchers are working on activating lost segments of our DNA, Harvard scientists hope that lasers might be the answer to growing new sets of teeth.
Researchers are using lasers to activate stem cells, which stimulate teeth growth in rats and human dental tissue. The results of the successful tests were published in the journal Science Translational Medicine.
The Harvard researchers are using stem cells, which exist all throughout the body, because they have the ability to become various types of cells. This means that they could repair or even replace damaged or diminished tissue.
Using lasers to regrow teeth would be ideal because it would be a minimally invasive technique and would only require shining a specified light on the damaged area. Or, in this case, the gap where the old tooth was lost.
But don’t throw out your dentures or pull out your implants just yet. The laser technique to regrow teeth is still in its infancy and hasn’t been used on humans…yet.
Twelve weeks after the low-power laser treatment, more newly formed dentin, marked by yellow hashtags (#), can be seen in the laser-treated teeth (right) than in the controls (left). 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.
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 regeneration of teeth, 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.”
—by Shu Hui Chen, Ph.D.
• Engineering Cartilage
• Stem Cell Therapy Rebuilds Heart Muscle in Primates
• Oral Health
References: Photoactivation of Endogenous Latent Transforming Growth Factor-β1 Directs Dental Stem Cell Differentiation for Regeneration. Arany PR, Cho A, Hunt TD, Sidhu G, Shin K, Hahm E, Huang GX, Weaver J, Chen AC, Padwa BL, Hamblin MR, Barcellos-Hoff MH, Kulkarni AB, J Mooney D. Sci Transl Med. 2014 May 28;6(238):238ra69. doi: 10.1126/scitranslmed.3008234. PMID: 24871130.
Funding: NIH’s National Institute of Dental and Craniofacial Research (NIDCR), National Institute of Allergy and Infectious Diseases (NIAID), National Center for Research Resources (NCRR), and National Center for Advancing Translational Sciences (NCATS); Harvard Presidential Scholarship; Wyss Institute; Harvard Catalyst; and Harvard Clinical and Translational Science Center.
Many dentists now use lasers to cut both hard and soft tissue. But Dr. Praveen Arany at the University of Buffalo (UB) is using them to heal and even regenerate tissue. In fact, his work recently earned him the 2016 Dr. Horace Furumoto Innovations Young Investigator Award from the American Society for Laser Medicine and Surgery.
“It is a true privilege to be recognized by my peers for our work in the area of low-dose biophotonics, which has tremendous potential to transform human healthcare,” said Arany, who is an assistant professor of oral biology at UB’s School of Dental Medicine.
Very low doses of light trigger the generation of reactive oxygen species (ROS), which are chemically reactive molecules that contain oxygen. ROS can lead to aging and, possibly, cancer in large amounts. But very small amounts of ROS are necessary for functions like cell signaling and homeostasis. As amino acids sense the generation of these small amounts of ROS, the common growth factor beta is activated, producing regeneration.
“We have learned a lot about harnessing stem cells. The field appears to be poised at our ability to drive their differentiation,” said Arany. “When you direct differentiation, you get useful tissue, which is either an organ or a functional, structurally normal tissue. We find that we can do that with light.”
Arany’s research began by finding that low-level light therapy, also known as photobiomodulation, was effective in healing extraction wound sockets. Later, he and his colleagues extended their work to pulpal healing as they used light to activate the growth factor that’s naturally present in dental pulp.
“In our specific application, we were able to generate dentine from the dental pulp stem cells,” Arany said, noting that the ability to make dentine would be useful for 2 reasons.
“We would be able to use this technique in deep carious lesions close to the pulp, either indirect or direct pulp capping, and hopefully prevent the need for root canal treatment,” he said. “The other place where you would want to make dentine would be in dentine desensitization or tooth desensitization.”
Current desensitization techniques, Arany said, use an extrinsic barrier that burnishes open dental tubules or deposits heavy metal salts on them to plug them up. But these materials get abraded as patients eat and brush their teeth, binding them to a lifetime of using desensitizing toothpaste.
“So in contrast to that, if you were able to induce dentine from the inside, form an intrinsic dentinal barrier, we would be able to prevent tooth sensitivity,” Arany said. “Those are the 2 direct applications that we are in the process of hopefully converting into clinical therapy.”
These treatments wouldn’t require revolutionary new lasers, either. Many current lasers could be used in photobiomodulation simply by adjusting their wavelength and power settings.
“A lot of existing devices can be adapted with the new protocol, and they can potentially work in this space. We are actually using currently available, FDA-approved clinical devices because we want to translate quickly,” Arany said. “Nonetheless, there is a lot of opportunity, depending on the process you want to use the laser for, to develop new devices as well.”
Arany aims to encourage the development of these techniques as president of the North American Association for Photobiomodulation Therapy, which is dedicated to the use of low-dose biophotonic treatments. The association brings together researchers, physicians, dentists, physical therapists, veterinarians, and even acupuncturists who are interested in applying these technologies and techniques to a variety of cases.
“Phototonics have come center-stage for many applications. But there are many other exciting applications with light per se, including optical imaging. There’s a lot of interest in digital dentistry and CAD/CAM imaging. There is even more excitement about pre-cancer screening and pre-carious lesions treatment with light-based diagnostics,” Arany said.
“There are many other applications for light that I think will be recognized in the next few decades,” Arany said. “You’ll have light being a major tool, just like your handpieces.”