October 6, 2022

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The future of dental care could have new robotic allies.
A group of researchers from the University of Pennsylvania has developed an automated, hands-free oral hygiene system that adapts to the shape of your teeth.
The researchers claim this system can clean teeth more efficiently than the toothbrush and dental floss, according to an article published by the university in July.
Could this technology eventually replace our current oral health routines? Let's find out.

Penn Dental Medicine 

The official name of the invention is surface topography-adaptive robotic superstructures (STARS). It consists of precision-guided microrobots made of iron oxide nanoparticles that have both catalytic and magnetic activity and can be shaped using a magnetic field.
In the proof-of-concept study, a set of programmable electromagnets are placed on both sides of a vessel containing the iron oxide nanoparticles in an aqueous solution.
These electromagnets, which can be coordinated through a microcontroller, produce the magnetic field that realigns the nanoparticles as needed.
Configured in a swarm-like structure, the nanoparticles react to the magnetic activity generated by the electromagnets, forming bristlelike structures that can sweep away dental plaque from the broad surfaces of teeth or elongated strings that can slip between teeth like a length of floss.
The structures can also be made to move in multiple directions and motion patterns, adjusting to the shape, size, angles, separation, and unique topographic features of the patient’s teeth.
“We form bristles that can extend, sweep, and even transfer back and forth across a space, much like flossing", said Edward Steager, one of the authors of the study.
"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,” added Steager, who is also a senior research investigator in the School of Engineering and Applied Science at the University of Pennsylvania.
Source: Melissa Pappas/Penn Engineering 

The robotic microswarm can have access to pits and fissures (the grooves of the teeth), gingival crevices (the little space between the teeth and the gums), and other difficult-to-reach locations in the mouth.
“It doesn’t matter if you have straight teeth or misaligned teeth, it will adapt to different surfaces,” said researcher Hyun Michel Koo, a professor in the Department of Orthodontics and divisions of Community Oral Health at the University of Pennsylvania.
“The system can adjust to all the nooks and crannies in the oral cavity.”
The bristles can also be made stiffer or softer as desired. Stiffer bristles could be used to clean the hard surface of the teeth while softer bristles are more appropriate for the gums and parts of the teeth that are near them.
The user would also be able to control and program the microrobots according to their own sensitivity, so that they can prevent damage to the gums or gum soreness related to vigorous brushing. This was tested on animal models.
Oral hygiene tools have been used for thousands of years. Although the modern toothbrush wasn’t invented until 1938, precursors can be found even in ancient civilizations.
It is known that the Greeks and the Romans used toothpicks to clean their teeth. Similar artifacts made of twigs were discovered in Qin Dynasty tombs (201-256 BC).
'Chew sticks— thin twigs or roots that were chewed on one end to loosen the fibers, which were then rubbed against the teeth—were found in an Egyptian tomb dating from 3000 BC and in Chinese records from 1600 BC. Chew sticks were also used in Sumer, the earliest known civilization in southern Mesopotamia (now Iraq), by 3500 BC.
The first toothbrush is thought to have been created in China sometime during the Tang Dynasty (619-907). It was made with hog bristles attached to a handle made of bamboo or bones. Although the concept reached Europe in the 17th century, the idea didn't really catch on there until the 1770s, when Englishman William Addis began importing coarse boar bristles from Siberia and northern China to mass-produce high-quality toothbrushes. Eventually, the hog bristles in some brushes were replaced with horsetail hairs to make a softer toothbrush.

Source: Wellcome Images/Wikimedia Commons 

Natural animal bristles would be used until the 20th century, when more resistant and hygienic synthetic fibers, mainly nylon, were added to the design of the tool.
Today, the toothbrush is a mass-produced, essential element that plays an important role in everyday oral hygiene.
The problem is that we all have different teeth and gums, and different sensitivities, while toothbrushes are manufactured in limited, non-customizable shapes.
What the researchers from the University of Pennsylvania realized is that customization is fundamental for the eradication of dental plaque.
Dental plaque is a biofilm full of microbial cells that adhere to the teeth’s surface and can cause dental caries, halitosis (bad breath), and gum disease.

Source: MyUpChar/Wikimedia Commons 

We brush and floss our teeth in an attempt to eliminate that biofilm, but our current tools aren’t able to clean and disinfect every corner of our mouths.
In that sense, the adaptability of the robotic assemblies created by the University of Pennsylvania, as well as their microscale precision, has proved to be effective for biofilm removal in tests with 3D-printed tooth models and real human teeth.
What’s even better, the microrobots’ nanoparticles also have catalytic properties that kill bacteria.
The iron oxide nanoparticles are able to produce hydroxyl free radicals from hydrogen peroxide at the site of mechanical cleaning. This works as an immediate, real-time antimicrobial treatment that, in combination with mechanical cleaning, promises to take the prevention of dental disease to the next level.
The researchers from the University of Pennsylvania expect this innovation to be particularly helpful to the geriatric population and/or people with disabilities who might lack the manual dexterity to brush and floss their teeth themselves.
“Routine oral care is cumbersome and can pose challenges for many people, especially those who have a hard time cleaning their teeth,” added Hyun Michel Koo. “You have to brush your teeth, then floss your teeth, then rinse your mouth; it’s a manual, multistep process. The big innovation here is that the robotics system can do all three in a single, hands-free, automated way.”
Moreover, the system may help dentists with a correct diagnosis when there is an infection. This is because the microrobots can penetrate the biofilm and retrieve samples of it from hard-to-reach places in the mouth. Odontologists can then use these samples to detect the pathogen that is causing the infection and treat it accordingly.
The "surface topography-adaptive robotic superstructures" proved to be effective in detecting bacterial cells, fungal cells, and viruses, which is why this innovation is not only important for localized diagnostic sampling in dentistry, but also for pathogen detection and disinfection in other fields that deal with biofilm-contaminated, hard-to-reach surfaces.
Time will tell how generally useful a product based on this research will be. So far, iron oxide nanoparticles have been approved by the U.S. Food and Drug Administration (FDA) as a treatment for cancer and iron deficiency, as an oral gastrointestinal tract imaging agent, and as a magnetic resonance imaging (MRI) agent.
We’ll have to wait to see if iron oxide nanoparticles will be approved for this use in microrobots and other related applications in the near future.

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