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These shapeshifting microrobots can brush and floss teeth, kill bacteria

The technology provides a new automated way of brushing that could help people with mobility issues.

A multidisciplinary team of researchers at the University of Pennsylvania has developed shapeshifting microrobots that can brush, rinse and floss teeth, and kill bacteria.

This new technology uses a magnetic field to control the iron oxide nanoparticle-based microrobots to form antimicrobial bristle and floss shapes.

It offers a new, automated way of performing the routine daily tasks of brushing and flossing. Research shows that it can effectively automate the treatment and removal of tooth decay-causing bacteria and dental plaque. The microrobots  may act as a toothbrush, rinse, and floss all in one in the future. 

This new hands-free system could be particularly valuable for those who lack the manual dexterity to clean their teeth properly by themselves and struggle to get dental care.

Microrobots could also be applied to healthcare in other ways. The technology is targeted at people who have disabilities or dexterity issues that prevent them from cleaning their teeth effectively. 

Triple shapeshifting action

The researchers from the UPenn team configured the microbes’ motion to form bristle-like structures that sweep away dental plaque from the broad surfaces of teeth using a magnetic field.

The microbes are formed from iron oxide nanoparticles that have both catalytic and magnetic activity. They can also form elongated strings that can sweep between the teeth like dental floss. In a catalytic reaction, the nanoparticles produce antimicrobials that kill harmful oral bacteria on site.

The researchers performed tests on mock and real human teeth. They found that the microrobots can conform to a variety of shapes to eliminate sticky biofilms that lead to cavities and gum disease. They shared these findings in the journal ACS Nano.

Hyun (Michael) Koo, a professor in the Department of Orthodontics and divisions of Community Oral Health and Pediatric Dentistry in Penn’s School of Dental Medicine and co-corresponding author on the study, said routine oral care can be cumbersome and challenging for many people. 

Caring for one’s teeth is a manual, multi-step process that involves brushing, flossing, and then rinsing your teeth and mouth. Those who have a hard time cleaning their teeth have it worse, so this is refreshing news for them. 

Hyun (Michael) Koo, Department of Orthodontics, University of Pennsylvania School of Dental Medicine

With the robotics system being able to do all the  three in a single, hands-free automated way, anyone who feels insecure about their teeth may have a respite. Those who visit the dentist regularly and keep their teeth healthy could also experience tooth stains and look for ways to whiten sensitive teeth naturally.

Co-corresponding author Edward Steager, a senior research investigator in Penn’s School of Engineering and Applied Science, believes tiny machines can be programmed. 

The nanoparticle assembly and motion control can be programmed automatically, like a robotic arm that can reach out to clean a surface. “We form bristles that can extend, sweep, and transfer back and forth across a space like flossing,” Steager said.

Disrupting oral care technology

The design of the toothbrush has relatively remained unchanged and undisrupted for millennia. Electric motors elevated this design and many indigenous people use traditional techniques to clean their teeth, but the fundamental concept has remained the same.

But the researchers – housed at UPenn’s Center for Innovation and Precision Dentistry (CiPD) – are looking to cause  a major disruption in the oral care industry using this microrobotics system.

Their innovation came about by a lucky accident. Research groups in both Penn Dental Medicine and Penn Engineering had developed an interest in iron oxide nanoparticles, which was approved by the United States’s Food and Drug Administration, for different reasons. 

On the one hand, CiPD Director Koo’s dental medicine group was intrigued by the catalytic activity of the nanoparticles. They can activate hydrogen peroxide to release free radicals that can kill tooth decay-causing bacteria and degrade dental biofilms.

On the other hand, Steager and his colleagues, including Dean Vijay Kumar and CiPD co-director Professor Kathleen Stebe, examined the nanoparticles as building blocks of magnetically controlled microrobots.

The UPenn collaborators married the two applications together to birth their current work. They had support from UPenn Health Tech and the National Institutes of Health’s (NIH) National Institute of Dental and Craniofacial Research. 

With this support, they constructed a platform to electromagnetically control the microrobots. This enabled them to adopt different configurations and release antimicrobials on site to effectively treat and clean teeth.

The beauty of the resulting technology was a system that can adjust to all the nooks and crannies in the oral cavity. That way, it doesn’t matter if a person has straight or misaligned teeth; it will adapt to different shapes and surfaces.

How the system works

For the microrobots to work effectively, the researchers optimized their motions on a small slab of tooth-like material. They then tested their performance using 3D-printed tooth models based on scans of human teeth from the dental clinic.

They also adjusted their performance to the complex topography of the tooth surface, interdental surfaces, and the gumline. Finally, they tested the microrobots on real human teeth mounted to mimic the position of teeth in the oral cavity.

On these surfaces, the researchers found that the microrobotics system could eliminate biofilms and clear the teeth of all detectable pathogens. Tests of the bristle formations on a model showed that there were no harm done to the gum tissue.

The system is fully programmable and customizable, making it gentle enough for clinical and personalized use. It can also adapt to the unique topographies of a patient’s oral cavity. However, for this technology to advance, the UPenn team needs to optimize the robots’ motions to find ways of delivering the microrobots through mouth-fitting devices.

Researchers believe the technology will disrupt current modalities and help advance healthcare. “We’d love to see this helping the geriatric population and people with disabilities,” Koo said. 

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