When Juan M. Taboas, PhD, wants to explain hydrogels, he turns to different kinds of pasta as an analogy.
“Think about making spaghetti out of regular pasta, or that squid pasta that’s black, you have two different colors of pasta,” he explains.
“If you strain your spaghetti and you let it sit for a while, it all sticks together wherever the strands touch. Both kinds of spaghetti are bound together; that is a single polymer network. But when only the squid black pasta sticks to itself and only the white pasta sticks to itself, that’s an interpenetrating polymer network. And that gives you an exponential or synergistic increase in mechanical properties. And we do that to create hydrogels that can support load bearing,” an important function in joints like the knee or the temporomandibular joint of the jawbone.
Hydrogels, while not naturally present in the body, are a gel-like material that can be created to have specific molecular characteristics and structures for use in biomedical applications like tissue engineering.
Building hydrogels is the key to Taboas’ work in helping keep children’s damaged teeth alive. Funding through the Michigan-Pittsburgh-Wyss Regenerative Medicine Resource Center is helping his team develop Vital-Dent, a drug-free implant that would revitalize teeth treated with root canal procedures to support continued tooth growth and prolong tooth survival. It’s an example of bench research that could make a direct difference in the clinic, he said.
Taboas is an associate professor in the Department of Oral and Craniofacial Sciences at the University of Pittsburgh School of Dental Medicine. He has a secondary appointment in the Department of Biomedical Engineering in the Swanson School of Engineering and the Clinical and Translational Science Institute. He is also a member of the McGowan Institute for Regenerative Medicine.
Taboas’ research focuses on regenerating bone and soft tissues that interface with bone, like cartilage and pulp tissue, the soft, connective tissue found in the center of a tooth.
“We have five different projects going on in the lab right now that fall under that theme,” he said. “Ones that relate directly to clinical work in our school would be our work in regenerative endodontic therapy. We’re working on a revitalizing therapy for pulp and teeth for juvenile applications.”
He said that the Vital-Dent research aims to serve children with pulpitis, or inflammation of the dental pulp. The standard procedure is to remove the infected pulp and fill the tooth with a bio inert material, which Taboas said works for adults but is not ideal in children, whose teeth are not fully developed.
“We’ve applied platform technologies with the biomaterials we’ve developed in the lab. We have an acellular, drug-free approach for regenerative and endodontic therapy in that application.” The work has been tested in dog models so far, both adult and juvenile, but not yet in humans. “There is no commercial device in the marketplace or available to clinicians to provide pulp regeneration,” Taboas said.
While it’s possible to fill the tooth with a blood clot of some type, Taboas said it is not practical. He said typically, dentists either “extract blood from the patient on the chair side, and spin it down to form platelet-rich fibrin, or they just poke into the space beyond the tooth to induce bleeding.”
This procedure is called revascularization, or the restoration of blood flow to a specific area of the body—in this case, the tooth’s dental pulp.
While this procedure could be performed in a facility like the Pitt School of Dental Medicine, “Dentists don’t really want to be extracting blood from a patient in the clinic, and the quality of clots is variable,” he said. “It’s really unlikely to see that in general practice.”
“[Dentists] want something that they can handle off the shelf, straight out of the box, and that’s what this material is. It’s a hydrogel that’s supplied as a powder. At the bedside, we just mix with saline and when you inject it into the tooth, it initially provides a barrier for blood not to get into that canal space in the tooth.”
That’s important, he said, because as blood cells die over time, they release heme and other iron-based groups that produce radicals and activate the immune system, which are detrimental to healing.
“This stops that from happening, and then later, it allows for cells to migrate right in on that scaffold railroad, get in there and start regenerating tissue. What we found compared to revascularization therapy is that we have a doubling in the rate of continued root growth. That’s 100% greater outcomes in the most critical measure: Does the tooth keep growing?”
Taboas said: “My passion in the therapies I work on is for treating kids because I think they’re underserved in regenerative medicine. A great example of this is that the Department of Health and Human Services and the White House have come out with this ARPA-H [Advanced Research Projects Agency for Health] program to drive forward medical therapies and really empower them, just like the DARPA projects of the DOD [Department of Defense] drove through railguns and all of these high-tech military advances.”
Taboas and colleagues are pursuing ARPA-H funding through a program called NITRO, for Novel Innovations for Tissue Regeneration in Osteoarthritis. While osteoarthritis is not typically associated with pediatrics, he said, “We use these large mechanisms to develop the technology that we can give to kids.”