One day, a microswarm of shape-shifting robots could be a toothbrush, mouthwash and floss all in one. Developed by a multidisciplinary team at the University of Pennsylvania, the technology promises to provide a new automated way to perform mundane but vital tasks such as daily brushing and flossing. This is a particularly valuable system for those who lack the manual dexterity to effectively clean their teeth themselves.
The components of these microrobots are iron oxide nanoparticles that are catalytically and magnetically active. Using magnetic fields, researchers can direct their movements and configurations to form bristle-like structures that remove plaque from the broad surfaces of teeth, or to form long, thin strings that can slide between teeth like dental floss. In both cases, the catalytic reaction drives the nanoparticles to produce antibacterial agents that kill harmful oral bacteria on the spot.
Experiments using the system on simulated and real teeth show that the robotic components can adapt to a variety of shapes, virtually eliminating the sticky biofilm that causes tooth decay and gum disease. Penn team shares their findings building proof-of-concept for robotic system in journal ACS Nano.
“Routine oral care is cumbersome and can present challenges for many people, especially those who have difficulty cleaning their teeth,” said Hyun (Michel) Koo, a professor in Penn’s Department of Orthodontics and Community Oral Health and Pediatric Dentistry, MD, PhD. and the study’s co-corresponding author. “You have to brush, then floss, then rinse; it’s a manual, multi-step process. The big innovation here is that the robotic system can do all three in a single, hands-free, automated way. “
“Nanoparticles can be shaped and controlled in surprising ways by magnetic fields,” said co-corresponding author Edward Steager, a senior researcher in Penn’s School of Engineering and Applied Sciences. “The bristles we formed can extend, sweep, and even in space. It moves back and forth like flossing. It works similar to how a robotic arm reaches out and cleans a surface. The system can be programmed to automate nanoparticle assembly and movement.”
Disrupting Oral Care Technology
“The design of toothbrushes has remained relatively unchanged for thousands of years,” Koo said.
While the addition of an electric motor elevates the basic “bristle-on-stick form”, the basic concept remains the same. “It’s a technology that hasn’t been disrupted in decades.”
A few years ago, researchers at the University of Pennsylvania at the Center for Innovation and Precision Dentistry (CiPD), co-directed by Koo, made a major breakthrough using this tiny robotic system.
Their innovation stemmed from a little accident. The research groups at Penn Dental Medicine and Penn Engineering were both interested in iron oxide nanoparticles, but for very different reasons. Koo’s group is interested in the catalytic activity of the nanoparticles. They activate hydrogen peroxide to release free radicals that kill bacteria that cause tooth decay and degrade plaque biofilm. Meanwhile, Steager and engineering colleagues, including Dean Vijay Kumar and CiPD co-director Professor Kathleen Stebe, are exploring these nanoparticles as building blocks for magnetron microrobots.
With support from Penn Health Tech and the NIH’s National Institute of Dental and Craniofacial Research, Penn collaborators combined these two applications in the current work to build a platform for electromagnetically controlled microrobots that enable them to Capable of effectively treating and cleaning teeth on-site in different configurations and releasing antimicrobial agents.
“Whether your teeth are straight or misaligned, it adapts to different surfaces,” says Koo. “The system can fit into all the nooks and crannies in the mouth.”
The researchers optimized the movement of the microrobot over a small piece of tooth-like material. Next, they tested the microrobot’s ability to adapt to the complex topography of tooth surfaces, interdental surfaces and gum lines using 3D printed tooth models based on scans of human teeth in dental offices. Finally, they experimented with the microrobots on real human teeth, which were mounted in a way that mimicked the position of teeth in the mouth.
On these various surfaces, the researchers found that the microrobotic system could effectively eliminate biofilms, removing all detectable pathogens. Iron oxide nanoparticles are FDA-approved for other uses, and tests on bristle formation in animal models show they do not harm gum tissue.
In fact, the system is fully programmable; the team’s roboticists and engineers used changes in the magnetic field to precisely tune the microrobot’s movement as well as control the stiffness and length of the bristles. The researchers found that the tips of the bristles could be made strong enough to remove biofilm, but soft enough to avoid damaging the gums.
The customizability of the system could make it gentle enough for clinical use, but also personalized, able to adapt to the unique topography of a patient’s mouth, the researchers said.
To bring this technology to the clinic, Penn’s team is continuing to optimize the robot’s motion and considering different ways to deliver microrobots through an oral fit device.
They are eager to see their devices help patients.
“We have this technology that is as good or more efficient as brushing and flossing, but without manual dexterity,” Koo said. “We’d love to see this help the elderly and disabled. We believe it will disrupt the current paradigm and advance oral care significantly.”
Hyun (Michel) Koo is a professor in the Departments of Orthodontics and Community Oral Health and Pediatric Dentistry at the University of Pennsylvania School of Dentistry and Co-Director of the Center for Innovation and Precision Dentistry.
Edward Steager is a senior fellow in the School of Engineering and Applied Sciences at the University of Pennsylvania.
Koo and Steager’s paper co-authors are Min Jun Oh, Alaa Babeer, Yuan Liu, Zhi Ren of Penn Dental Medicine and Jingyu Wu, David A. Issadore, Kathleen J. Stebe and Daeyeon Lee of Penn Engineering.
This work was partially supported by the National Institute of Dentistry and Craniofacial Research (grants DE025848 and DE029985), The Procter & Gamble Company, and Sungkyunkwan University Postdoctoral Research Program.