The buildup of bacteria deep in our teeth can cause infections in difficult-to-reach areas, and scientists at the Indian Institute of Science have developed a set of tiny cleaning robots they believe can tackle this problem. The nano-sized machines can be steered with a magnetic field into microscopic channels in the teeth and kill bacteria with heat, offering a safe and potent way to improve the success of standard root canal treatments.
The robots came about through the team's pursuit of new and improved ways to tackle the bacteria that reside in what are known as dentinal tubules. These microscopic channels start at the pulp inside of the tooth and continue outwards, stopping just short of the enamel on the outer. The bacteria that builds up in these channels can cause infections requiring a root canal, but some bacteria are able to evade this treatment.
“The dentinal tubules are very small, and bacteria reside deep in the tissue," explained team member Shanmukh Srinivas. "Current techniques are not efficient enough to go all the way inside and kill the bacteria."
Root canal treatments involve flushing out the tooth with chemicals that kill off the bacteria, but antibiotic-resistant species can withstand the attacks, and others might escape their clutches altogether. In earlier work, the scientists had some success using lasers and ultrasound to supercharge these treatments, creating shockwaves in the fluid to better wash away the bacteria. These approaches had their limitations, only being able to penetrate about 800 micrometers into the tooth.
The scientists have now taken a markedly different route, tapping into the world of miniaturized robots to come up with an even deeper-cleaning solution. The team's tiny droids are helically shaped and made from silicon dioxide with an iron coating. This enables them to be controlled by a magnetic field and taken to depths of up to 2,000 micrometers, where the field can be tweaked to make the robots generate heat and kill off the bacteria.
This was demonstrated by injecting the robots into extracted tooth samples, with the scientists successfully moving them about so they penetrate deep into the dentinal tubules to take out the bacteria. Importantly, they also showed that they could retrieve the robots, drawing them out of the tooth sample once the job was done.
“No other technology in the market can do this right now,” said team member Debayan Dasgupta.
There are similarities between this approach and others being developed for cancer treatment. We've seen numerous examples of magnetic nanoparticles that can infiltrate cancer cells and be heated up to destroy them, with one interesting take on this coming earlier this year that involved spherical seeds designed to take out tough-to-treat tumors. We've also seen this type of thinking applied to dental hygiene before, with a research team in 2019 demonstrating a type of microbot designed to break up the bacteria biofilms coating our teeth.
Having tested the robots on mouse models and proven them safe and effective, the authors of this new study are looking to commercialize the technology through a spin-off company called Theranautilus. They are are also working on a purpose-built medical device dentists can use to deploy and control the robots inside the mouth during root canal treatment.
"We are very close to deploying this technology in a clinical setting, which was considered futuristic even three years ago," says Ambarish Ghosh, co-founder of Theranautilus. "It is a joy to see how a simple scientific curiosity is shaping into a medical intervention that can impact millions of people in India alone."
The research was published in the journal Advanced Healthcare Materials.
Source: Indian Institute of Science
