A shapeshifting robotic microswarm could one day double as a toothbrush, a rinse, and a dental floss. The technology, developed by a multidisciplinary team at the University of Pennsylvania, is poised to deliver a new, automated way to perform the mundane but critical daily tasks of brushing and flossing. It is a system that could be particularly useful for those who lack the manual dexterity to effectively clean their teeth themselves.
The building blocks of these microrobots are iron oxide nanoparticles that have both catalytic and magnetic activity. Using a magnetic field, researchers could direct their motion and configuration to form either bristle-like structures that sweep dental plaque from the broad surfaces of teeth, or elongated cords that can slip between teeth like a length of dental floss. In both cases, a catalytic reaction drives the nanoparticles to produce antimicrobials that kill harmful oral bacteria on the spot.
Experiments using this system on both fake and real human teeth have shown that robotic assemblies can conform to a variety of shapes to nearly eliminate the sticky biofilms that lead to cavities and gum disease. The Penn team shared their findings establishing proof of concept for the robotic system in the review ACS Nano.
“Routine oral care is tedious and can pose challenges for many people, especially those who have difficulty cleaning their teeth,” says Hyun (Michel) Koo, a professor in the Department of Orthodontics and Penn’s School of Community Oral Health and Pediatric Dentistry divisions. of dentistry and corresponding co-author of the study. “You have to brush your teeth, then floss, then rinse your mouth; it’s a manual, multi-step process. The big innovation here is that the robotic system can do all three in one way, hands free and automated.
“Nanoparticles can be shaped and controlled with magnetic fields in surprising ways,” says Edward Steager, principal investigator at Penn’s School of Engineering and Applied Science and corresponding co-author. “We form hairs that can reach out, sweep and even transfer through space, much like dental floss. The way this works is similar to how a robotic arm might reach and clean a surface. The system can be programmed to automatically do nanoparticle assembly and motion control.”
Revolutionary oral care technology
“Toothbrush design has remained relatively unchanged for millennia,” says Koo.
While the addition of electric motors has elevated the basic ‘bristles on a stick’ format, the fundamental concept has remained the same. “It’s a technology that hasn’t been disrupted for decades.”
Several years ago, Penn researchers at the Center for Innovation & Precision Dentistry (CiPD), of which Koo is co-director, took steps towards a major breakthrough, using this microrobotics system.
Their innovation was born out of a bit of serendipity. Research groups at Penn Dental Medicine and Penn Engineering have taken an interest in iron oxide nanoparticles, but for very different reasons. Koo’s group was intrigued by the catalytic activity of nanoparticles. They can activate hydrogen peroxide to release free radicals that can kill bacteria that cause tooth decay and break down dental plaque biofilms. Meanwhile, Steager and fellow engineers, including Dean Vijay Kumar and CiPD co-director Professor Kathleen Stebe, were exploring these nanoparticles as the building blocks of magnetically driven microrobots.
With support from Penn Health Tech and the National Institutes of Health’s National Institute of Dental and Craniofacial Research, Penn collaborators have married the two applications in ongoing work, building a platform to electromagnetically control microrobots, allowing them to adopt different configurations and release antimicrobials. on site to effectively treat and clean the teeth.
“It doesn’t matter if you have straight teeth or misaligned teeth, it will adapt to different surfaces,” says Koo. “The system can fit into every nook and cranny of the oral cavity.”
The researchers optimized the movements of the microrobots on a small plate of tooth-like material. Next, they tested the performance of the microrobots by adjusting to the complex topography of the tooth surface, interdental surfaces and gum line, using 3D printed tooth models based on human tooth scans from the dental clinic. Finally, they tested the microrobots on real human teeth mounted to mimic the position of teeth in the oral cavity.
On these different surfaces, the researchers found that the microrobotics system could effectively remove biofilms, ridding them of all detectable pathogens. Iron oxide nanoparticles have been approved by the FDA for other uses, and tests of hair formation in an animal model have shown that they do not damage gum tissue.
Indeed, the system is fully programmable; The team’s roboticists and engineers used variations of the magnetic field to fine-tune the movements of the microrobots as well as to control the stiffness and length of the hairs. The researchers found that the tips of the bristles could be made firm enough to remove biofilms but soft enough to avoid gum damage.
The customizable nature of the system, the researchers say, could make it gentle enough for clinical use, but also personalized, able to adapt to the unique topographies of a patient’s oral cavity.
To advance this technology in the clinic, Penn’s team continues to optimize robot movements and is considering different ways to deliver the microrobots through mouth-adaptive devices.
They are eager to see their device help patients.
“We have this technology that is as effective or more effective than brushing and flossing, but does not require manual dexterity,” Koo explains. “We would like to see this help the geriatric population and people with disabilities. We believe it will disrupt current modalities and significantly advance oral health care.”
Hyun (Michel) Koo is a professor in the Department of Orthodontics and the Divisions of Community Oral Health and Pediatric Dentistry in the School of Dentistry and co-director of the Center for Innovation and Precision Dentistry at the University of Pennsylvania .
Edward Steager is a Principal Investigator at Penn’s School of Engineering and Applied Science.
Koo and Steager’s co-authors on the article are Min Jun Oh of Penn Dental Medicine, Alaa Babeer, Yuan Liu and Jingyu Wu of Zhi Ren and Penn Engineering, David A. Issadore, Kathleen J. Stebe and Daeyeon Lee.
This work was supported in part by the National Institute of Dental and Craniofacial Research (grants DE025848 and DE029985), Procter & Gamble, and the Sungkyunkwan University Postdoctoral Research Program.