The toothbrush is basically a stick with bristles and the concept hasn't changed much as a technology since the ancients of Babylon and Egypt walked the earth over 5,000 years ago. Now scientists at the University of Pennsylvania are preparing to propose brushing teeth with a swarm of microscopic “robots” that can do the work of a toothbrush, floss and mouthwash at the same time.
New research demonstrates the feasibility of a robotic system that could one day be adapted for human use.
“We want to help people with disabilities and the elderly who lack the manual dexterity to perform routine oral care,” says dental scientist and senior author Dr. Hen (Michelle) Koo, Ph.D. “This is an unmet need for oral care and it's time to change the technology.”
The robots are actually nanosized particles of iron oxide, each about 100 times smaller than a pollen grain. When a magnet approaches, the nanoparticles cluster into a series of filaments called bristles that line up along the direction of the magnetic field. By making precise adjustments in the field, the researchers were able to accurately direct the movements of the bristles, adjust their stiffness, and shorten or lengthen them.
“One of the great things about working with magnetic fields is that they penetrate tissue and are harmless at the level at which we use them, which means that the system can reach hard to reach places”, says microrobotics engineer and study co-author Edward Stijer, Ph.D.
The researchers tested the robots' ability to clean on several surfaces, including a 3D printed model of human front teeth, real human front teeth mounted on artificial gums, and part of a pig's jaw that had gums and teeth present.
Nanobots can brush, floss and rinse at the same time./>
As seen in the photo, these robotic structures can be automated and change shapes from bristles to filaments that conform to the surface of the teeth and clean the nooks and crannies between teeth. A separate experiment showed that they were soft enough not to damage the gums, but strong enough to break down biofilms, also known as plaque.
When it comes to destroying biofilms, these robotic nanoparticles have another trick up their sleeve. They have the natural ability to trigger chemical reactions that release germ-killing molecules, essentially creating an antimicrobial rinse in situ. In experiments, this allowed tiny armies of robots to both destroy biofilms and kill the bacteria inside without leaving behind living pathogens.
Left: Biofilms grown on human teeth and stained pink for clarity.
Right: Teeth almost completely cleaned by microbots.
Robots could also sweep and collect debris containing dead pathogens. The microbial content of this material could be analyzed to identify pathogens and other indicators of disease, which could one day be useful in predicting and diagnosing disease in the mouth and other parts of the body, the scientists say.
But before sending a platoon of tiny robots into a human mouth, researchers say clinical trials are needed. To optimize the robotic system and make it affordable for everyday use, the team plans to develop prototypes that fit in the mouth. They are a fully automated system that can adapt to the unique characteristics of the human oral cavity, providing personalized oral care.
The group is exploring other applications. In a proof-of-concept study, the researchers showed that microrobots can magnetically move through a root canal to remove biofilms and possibly carry and deliver drugs. In addition to dentistry, scientists see the technology's role in cleaning the inside of biofilm-contaminated catheters, surgical implants, and even water pipes.
“When you see a result that opens up a whole new field and applications, it's as exciting as it is in research,” Stijer says.