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Brace yourself: These shapeshifting microrobots can clean your teeth

06 July 2022

Image: Minjun Oh/Penn Dental Medicine
Image: Minjun Oh/Penn Dental Medicine

Microrobots have been developed that can help treat tooth decay.

A shapeshifting robotic microswarm may one day act as a toothbrush, rinse, and dental floss in one. The technology, developed by a multidisciplinary team at the University of Pennsylvania, is poised to offer a new and automated way to perform the mundane but critical daily tasks of brushing and flossing. It’s a system that could be particularly valuable for those who lack the manual dexterity to clean their teeth effectively 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 away dental plaque from the broad surfaces of teeth, or elongated strings that can slip between teeth like a length of floss. In both instances, a catalytic reaction drives the nanoparticles to produce antimicrobials that kill harmful oral bacteria on site.

Experiments using this system on mock and real human teeth showed that the 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 a proof-of-concept for the robotic system in the journal ACS Nano.

“Routine oral care is cumbersome and can pose challenges for many people, especially those who have [a] hard time cleaning their teeth,” says Hyun (Michel) Koo, Professor at Penn’s School of Dental Medicine and co-corresponding author of the study. 

“You have to brush your teeth, then floss your teeth, then rinse your mouth; it’s a manual, multi-step process. The big innovation here is that the robotics system can do all three in a single, hands-free, automated way.”

“Nanoparticles can be shaped and controlled with magnetic fields in surprising ways,” says Edward Steager, a Senior Research Investigator in Penn’s School of Engineering and Applied Science and co-corresponding author.

“We form bristles that can extend, sweep, and even transfer back and forth across a space, much like flossing. The way it works is similar to how a robotic arm might reach out and clean a surface. The system can be programmed to do the nanoparticle assembly and motion control automatically.”

Disrupting oral care technology
“The design of the toothbrush has remained relatively unchanged for millennia,” says Koo.

While adding electric motors elevated the basic ‘bristle-on-a-stick format’, the fundamental concept has remained the same. “It’s a technology that has not been disrupted in decades.”

“It doesn’t matter if you have straight teeth or misaligned teeth, it will adapt to different surfaces,” adds Koo. “The system can adjust to all the nooks and crannies in the oral cavity.”

The researchers optimised the motions of the microrobots on a small slab of tooth-like material. Next, they tested the microrobots’ performance in adjusting to the complex topography of the tooth surface, interdental surfaces, and the gumline, using 3D-printed tooth models based on scans of human teeth from the dental clinic. Finally, they trialled the microrobots on real human teeth that were mounted in such a way as to mimic the position of teeth in the oral cavity.

On these various surfaces, the researchers found that the microrobotics system could effectively eliminate biofilms, clearing them of all detectable pathogens. The iron oxide nanoparticles have been FDA approved for other uses, and tests of the bristle formations on an animal model showed that they did not harm the gum tissue.

Indeed, the system is fully programmable; the team’s roboticists and engineers used variations in the magnetic field to precisely tune the motions of the microrobots as well as control bristle stiffness and length. 

The researchers found that the tips of the bristles could be made firm enough to remove biofilms but soft enough to avoid damage to the gums.

The customisable nature of the system, the researchers say, could make it gentle enough for clinical use, but also personalised, able to adapt to the unique topographies of a patient’s oral cavity.

To advance this technology to the clinic, the Penn team is continuing to optimise the robots’ motions and considering different means of delivering the microrobots through mouth-fitting devices.

They’re eager to see their device help patients.

“We have this technology that’s as or more effective as brushing and flossing your teeth but doesn’t require manual dexterity,” says Koo. “We’d love to see this helping the geriatric population and people with disabilities. We believe it will disrupt current modalities and majorly advance oral health care.”


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