Nanodiamonds Shine in Root Canal Study

Posted on October 31, 2017 by Dr. Francis Collins

Caption: An artistic rendering of nanodiamonds
Credit: Ho Lab

When the time comes to get relief from a dental problem, we are all glad that dentistry has come so far—much of the progress based on research supported by NIH’s National Institute of Dental and Craniofacial Research. Still, almost no one looks forward to getting a root canal. Not only can the dental procedure be uncomfortable and costly, there’s also a risk of failure due to infection or other complications. But some NIH-supported researchers have now come up with what may prove to be a dazzling strategy for reducing that risk: nanodiamonds!

That’s right, these researchers decided to add tiny diamonds—so small that millions could fit on the head of the pin—to the standard filler that dentists use to seal off a tooth’s root. Not only are these nanodiamonds extremely strong, they have unique properties that make them very attractive vehicles for delivering drugs, including antimicrobials that help fight infections of the sealed root canal.

To see how nanodiamond-fortified filler would perform in a real-world setting, the researchers, led by Dean Ho at the University of California, Los Angeles (UCLA), put it to the test in three people who were having root canals. One other person in the study had a root canal using the standard rubber-like filler called gutta percha.

As reported in Proceedings of the National Academy of Sciences [1], the nanodiamond-fortified gutta percha (NDGP) proved easy for dentists to place in the tooth root (of an incisor and two cuspids) and didn’t require any changes to the usual root canal procedure. Tests of NDGP confirmed it was more durable and resistant to buckling and breaking than the gutta percha dentists have used for decades.

When those patients were examined 3 and then 6 months later, they continued to do well. There were no signs that the NDGP had caused any sensitivity or otherwise interfered with tooth function. Importantly, none had further decay or periodontal disease, a potentially serious inflammation of the gums and a leading cause of tooth loss.

These early findings suggest that NDGP is well tolerated in the tooth, but it’s not possible to assess safety and efficacy with just three patients. Now a clinical trial of a total of 30 patients is under way. Time will tell about how this works on a larger scale, but the use of NDGP, perhaps coated with an antimicrobial drug to lower the risk of infection even further, could reduce the 3 percent or more of root canal patients who find themselves back in the dentist’s chair for retreatment [2].

While this could be great news—millions of Americans undergo root canal procedures each year—this is just the first test case for the vast medical potential of nanodiamonds. Though nanodiamonds have been studied for industrial purposes since the 1960s, Ho is among the first to explore their potential uses in healthcare. A decade ago, he showed that clusters of nanodiamonds had potential for safely ferrying a commonly used chemotherapeutic drug into cancer cells [3].

Additional studies have suggested that nanodiamonds could make chemotherapy more effective and less toxic [4]. That’s because nanodiamonds keep the drug contained on their surfaces while they travel through the bloodstream without causing damage to other parts of the body. They also make it harder for cancer cells to resist treatment by pumping the drugs back out into the surrounding tissue.

Ho says he got the idea to evaluate nanodiamonds in root canals after his own chipped tooth became infected. The problem surfaced late on a Friday, forcing him to wait out a very painful weekend. As he held still in the dentist’s chair, Ho typed questions on his smartphone to ask his dentist about the procedure and the gutta percha used to seal the emptied root canal.

Ho realized immediately that root canals could be ideal to begin testing nanodiamonds in people. After all, unlike an internal organ, the mouth is readily accessible, making delivery of the nanodiamonds to the affected tooth straightforward.

While you might expect diamonds—even tiny ones—to be expensive, nanodiamonds are both readily available and cheap. That’s because they are a natural byproduct of the mining industry. They also break up easily into remarkably uniform structures that look more like faceted soccer balls than a traditional diamond cut. Unlike many other nanoparticles, they can be produced in large numbers without any lengthy or sophisticated manufacturing process.

While Ho and his team continue to evaluate root canal patients in the ongoing trial, they are already looking ahead. He expects the first clinical trial of chemotherapy-coated nanodiamonds for use in patients with liver cancer to begin within the next 18 months. His team also showed in animal studies that a nanodiamond-fortified, water-based gel might encourage bone formation and improve outcomes for children undergoing treatment for cleft lip and/or palate [5]. With more research, it may be that nanodiamonds are a girl’s and guy’s best friend.

References

[1] Clinical validation of a nanodiamond-embedded thermoplastic biomaterial. Lee DK, Kee T, Liang Z, Hsiou D, Miya D, Wu B, Osawa E, Chow E, Sung E, Kang M, Ho D. PNAS. 2017 Oct 23. [Epub ahead of print]

[2] Comparison of the success rate of endodontic treatment and implant treatment. Elemam RF, Pretty I. ISRN Dent. 2011;2011:640509.

[3] Active nanodiamond hydrogels for chemotherapeutic delivery. Huang H, Pierstorff E, Osawa E, Ho D. Nano Lett. 2007 Nov;7(11):3305-14.

[4] Nanodiamonds: The intersection of nanotechnology, drug development, and personalized medicine. Ho D, Wang CH, Chow EK. Sci Adv. 2015 Aug 21;1(7):e1500439.

[5] Reducing posttreatment relapse in cleft lip palatal expansion using an injectable estrogen-nanodiamond hydrogel. Hong C, Song D, Lee DK, Lin L, Pan HC, Lee D, Deng P, Liu Z, Hadaya D, Lee HL, Mohammad A, Zhang X, Lee M, Wang CY, Ho D. Proc Natl Acad Sci U S A. 2017 Aug 29;114(35):E7218-E7225.

Links:

Nanomedicine (Common Fund/NIH)

Periodontal (Gum) Disease: Causes, Symptoms, and Treatments (National Institute of Dental and Craniofacial Research/NIH)

Dean Ho (University of California, Los Angeles)

NIH Support: National Cancer Institute