Tiny bots that can deep clean teeth

teeth-cleaning nanobots
Left: Nanobots entering a dentinal tubule. Centre top and bottom: Schematic representation and electron microscope image of nanobot moving through dentinal tubule to reach bacterial colony. Right: How locally induced heat from nanobot can kill bacteria. Live bacteria are green and dead bacteria are red. Bottom right shows band where targeted treatment has been done in human teeth. Credit: Theranautilus

Nano-sized robots manipulated using a magnetic field can help kill bacteria deep inside dentinal tubules and boost the success of root canal treatments, a new study by researchers from India shows.

Root canal treatments are routinely performed to treat tooth infections in millions of patients. The procedure involves removing the infected soft tissue inside the tooth, called the pulp, and flushing the tooth with antibiotics or chemicals to kill the bacteria that cause the infection. But many times, the treatment fails to completely remove all the bacteria—especially antibiotic-resistant bacteria such as Enterococcus faecalis—that remain hidden inside microscopic canals in the tooth called dentinal tubules. 

These tubules are very small, and bacteria reside deep in the tissue. Current techniques are not efficient enough to go all the way inside and kill the bacteria.

In the study published in Advanced Healthcare Materials, the researchers from the Indian Institute of Science (IISc) and IISc-incubated start-up, Theranautilus, designed helical nanobots made of silicon dioxide coated with iron, which can be controlled using a device that generates a low intensity magnetic field. These nanobots were then injected into extracted tooth samples and their movement was tracked using a microscope. 

By tweaking the frequency of the magnetic field, the researchers were able to make the nanobots move at will—and penetrate deep inside the dentinal tubules. 

“We have also established that we can retrieve them … we can pull them back out of the patient’s teeth,” Shanmukh Srinivas said.

Crucially, the team was able to manipulate the magnetic field to make the surface of the nanobots generate heat, which can kill the bacteria nearby. 

“No other technology in the market can do this right now,” Debayan Dasgupta said.

Previously, scientists have used ultrasound or laser pulses to create shockwaves in the fluid used to flush out bacteria and tissue debris, in order to improve the efficiency of root canal treatment. But these pulses can only penetrate up to a distance of 800 micrometers, and their energy dissipates fast. 

The nanobots were able to penetrate much further—up to 2000 micrometers. Using heat to kill the bacteria also provides a safer alternative to harsh chemicals or antibiotics, the researchers said. 

“We are very close to deploying this technology in a clinical setting, which was considered futuristic even three years ago,” Professor Ambarish Ghosh added.

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