Stopping tooth decay before it starts—without killing bacteria

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tooth decay nanoparticles
Photo: Karel Joseph Noppe – 123rf

US scientists report a treatment that could someday stop plaque and cavities from forming, using a new type of cerium nanoparticle formulation that would be applied to teeth at the dentist’s office and would not involve killing bacteria. 

The group presented their progress toward this goal at the recent American Chemical Society (ACS) Fall 2020 Virtual Meeting & Expo.  

The mouth contains more than 700 species of bacteria. They include beneficial bacteria that help digest food or keep other microbes in check. They also include harmful streptococcal species, including Streptococcus mutans. 

Soon after a cleaning, these bacteria stick to teeth and begin multiplying. With sugar as an energy source and building block, the microbes gradually form a tough film that can’t easily be removed by brushing. As the bacteria continue metabolising sugar, they make acid byproducts that dissolve tooth enamel, paving the way for cavities.

Dentists and consumers can fight back with products to inhibit plaque—but the problem is these agents are not selective, so they kill many types of oral bacteria, even good ones.

So, the scientists led by Russell Pesavento, from the University of Illinois in Chicago, wanted to find an alternative that wouldn’t indiscriminately kill bacteria in the mouth and that would help prevent tooth decay, rather than treat cavities after the fact. 

He and his research group turned to cerium oxide nanoparticles which they produced by dissolving ceric sulfate salts in water. When they then seeded polystyrene plates with S. mutans in growth media and fed the bacteria sugar in the presence of the cerium oxide nanoparticle solution, they found that the formulation reduced biofilm growth by 40 per cent compared to plates without the nanoparticles, though they weren’t able to dislodge existing biofilms. 

Under similar conditions, silver nitrate—a known anti-cavity agent used by dentists—showed no effect on biofilm growth.

“The advantage of our treatment is that it looks to be less harmful to oral bacteria, in many cases not killing them,” Pesavento said. 

Instead, the nanoparticles merely prevented microbes from sticking to polystyrene surfaces and forming adherent biofilms. In addition, the nanoparticles’ toxicity and metabolic effects in human oral cells in petri dishes were less than those of silver nitrate.

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