In a proof-of-concept study, University of Pennsylvania researchers proved that a hands-free device may successfully automate the treatment and removal of dental plaque and germs that cause tooth decay.

A shape-shifting robotic microswarm may one day act as a toothbrush, rinse, and dental floss all in one. The technology, developed by a multidisciplinary team at the University of Pennsylvania, has the potential to give a whole new, automated technique for doing the mundane but essential everyday tasks of brushing and flossing. This device might be highly useful for folks who lack the physical dexterity to clean their teeth properly on their own.

These microrobots are made up of catalytic and magnetic iron oxide nanoparticles. Using a magnetic field, the researchers were able to manipulate their movement and arrangement to make bristle-like structures that remove dental plaque from the large surfaces of teeth or elongated threads that can slip between teeth like floss. In both cases, the nanoparticles are propelled by a catalytic reaction to release antimicrobials that kill hazardous oral germs on the spot.

The magnetic and catalytic characteristics of iron oxide nanoparticles, as well as their assembling into bristle and floss-like forms, are explained in an infographic. Photographer: Melissa Pappas/Penn Engineering

Experiments on mock and genuine human teeth with this technique revealed that the robotic assembly can adjust to a range of geometries, almost eliminating the sticky biofilms that cause cavities and gum disease. The Penn researchers published their findings in the journal ACS Nano, demonstrating a proof-of-concept for the robotic system.

“Routine oral care is time-consuming and can be difficult for many people, especially those who have difficulty cleaning their teeth,” says Hyun (Michel) Koo, a professor in the Department of Orthodontics as well as the divisions of Community Oral Health and Pediatric Dentistry at Penn’s School of Dental Medicine and a co-corresponding author on the study. “You must brush your teeth, floss your teeth, and rinse your mouth; it is a laborious, multi-step process.” The key breakthrough here is that the robots system can accomplish all three tasks hands-free and automatically.”

“Nanoparticles may be sculpted and manipulated in surprising ways with magnetic fields,” says co-corresponding author Edward Steager, a senior research investigator in Penn’s School of Engineering and Applied Science. “Like flossing, we build bristles that can expand, sweep, and even transmit back and forth over an area.” It functions in the same manner that a robotic arm could reach out and clean a surface. The device may be configured to autonomously assemble nanoparticles and regulate motion.”

Disrupting oral care technology

“The toothbrush design has stayed basically unaltered for millennia,” adds Koo.

While the addition of electric motors enhanced the original ‘bristle-on-a-stick format,’ the underlying premise remained the same. “It’s a technology that hasn’t changed in decades.”

Using this microrobotics technology, Penn researchers at the Center for Innovation & Precision Dentistry (CiPD), of which Koo is a co-director, took the first steps toward a big disruption some years ago.

Their breakthrough was the result of a stroke of luck. Iron oxide nanoparticles piqued the curiosity of researchers at Penn Dental Medicine and Penn Engineering, but for very different reasons. The catalytic activity of the nanoparticles piqued Koo’s interest. They can cause hydrogen peroxide to be activated, releasing free radicals capable of killing tooth decay-causing bacteria and degrading dental plaque biofilms. Meanwhile, Steager and his engineering colleagues, notably CiPD co-director Dean Vijay Kumar and Professor Kathleen Stebe, were investigating these nanoparticles as building blocks for magnetically operated microrobots.

Penn collaborators married the two applications in the current work, constructing a platform to electromagnetically control the microrobots, allowing them to adopt different configurations and release antimicrobials on site to effectively treat and clean teeth with support from Penn Health Tech and the National Institutes of Health’s National Institute of Dental and Craniofacial Research.

“Whether you have straight or crooked teeth, it will adjust to varied surfaces,” adds Koo. “The system is capable of adapting to all of the nooks and crannies of the mouth cavity.”

On a tiny slab of tooth-like material, the researchers tuned the actions of the microrobots. They then used 3D-printed tooth models based on scans of real teeth from the dental clinic to assess the microrobots’ performance while responding to the complicated geometry of the tooth surface, interdental surfaces, and gumline. Finally, the microrobots were tested on genuine human teeth that were placed in a fashion that mimicked the location of teeth in the mouth cavity.

The researchers discovered that the microrobotics system could efficiently eradicate biofilms on these diverse surfaces, eliminating all detected infections. The iron oxide nanoparticles have been cleared by the FDA for various purposes, and testing on an animal model showed that they did not impair the bristle forms.

The device is totally programmable; the roboticists and engineers employed magnetic field fluctuations to precisely adjust the movements of the microrobots as well as regulate bristle stiffness and length. The researchers discovered that the bristle tips might be made strong enough to clear biofilms while being soft enough to minimise gum injury.

According to the researchers, the system’s configurable nature might make it soft enough for therapeutic usage but being individualised, able to adapt to the specific topographies of a patient’s mouth cavity.

The Penn team is continuing to refine the robots’ movements and investigating other methods of distributing the microrobots through mouth-fitting devices in order to bring this technology to the clinic.

They’re excited to see how their technology can aid people.

“We have this technology that is as effective as or more effective than brushing and flossing your teeth but does not require physical dexterity,” Koo explains. “We’d want to see this benefiting the elderly and individuals with disabilities.” We believe it will upend present practises and significantly progress oral health care.”