Written By Kevin Kerfoot / Reviewed By Ray Spotts
The mouth contains more than 700 species of bacteria. Soon after a cleaning, these bacteria stick to teeth and begin multiplying.
Eating sugar or other carbohydrates also causes bacteria to quickly rebuild this tough and sticky biofilm and to produce acids that corrode tooth enamel. The microbes gradually form a tough film that can’t easily be removed by brushing.
As the bacteria continue metabolizing sugar, they make acid byproducts that dissolve tooth enamel, paving the way for cavities.
Oral bacteria even springs into action the moment a dental hygienist finishes scraping plaque off a patient’s teeth. This includes beneficial bacteria that help digest food or keep other microbes in check – as well as the harmful streptococcal species, including Streptococcus mutans.
Cerium Oxide Nanoparticles to stop tooth decay
Scientists now report a treatment that could someday stop plaque and cavities from forming in the first place by using a new type of cerium nanoparticle formulation that can be applied to teeth at the dentist’s office.
The researchers were interested in finding 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 and turned to cerium oxide nanoparticles.
Russell Pesavento, D.D.S., Ph.D., University of Illinois at Chicago and principal investigator, and his team produced their nanoparticles by dissolving ceric ammonium nitrate or sulfate salts in water.
When they 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 percent 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 says. “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.”
The researchers are experimenting with coatings to stabilize the nanoparticles at a neutral or slightly basic pH, closer to the pH of saliva and healthier for teeth than the present acidic solution.
They’ve also begun working with bacteria linked to the development of gingivitis and have found one particular coated nanoparticle that outcompeted stannous fluoride in limiting the formation of adherent biofilms under similar conditions.
Patient safety to stop tooth decay
They will continue to test the treatment in the presence of other bacterial strains typically present in the mouth, as well as test its effects on human cells of the lower digestive tract to gain a better sense of overall safety for patients.
Researchers have also studied nanoparticles made of zinc oxide, copper oxide or silver to treat dental infections. Although bactericidal agents such as these have their place in dentistry, repeated applications could lead to both stained teeth and bacterial resistance.
“Also, these agents are not selective, so they kill many types of bacteria in your mouth, even good ones,” Pesevento added.
Cavity-causing bacteria’s protective microbes on human teeth to prevent tooth decay
When scientists examine the bacteria that causes tooth decay, they find it “shields” itself under blankets of sugars and other bacteria in a crown-like arrangement, helping it evade antimicrobials and concentrate its tooth-damaging acids. They discovered that it's not just the presence of bacteria that can lead to disease, but that their spatial arrangement also matters. The findings were published in the journal Proceedings of the National Academy of Sciences.
Researchers at the University of Pennsylvania School of Dental Medicine and the Georgia Institute of Technology imaged the bacteria that cause tooth decay in three dimensions in their natural environment, discovering that the sticky biofilm known as dental plaque formed on toddlers' teeth that were affected by cavities.
"We started with these clinical samples, which were extracted teeth from children with severe tooth decay," says Hyun (Michel) Koo of Penn Dental Medicine, a co-senior author on the work. "The question that popped in our minds was how these bacteria are organized and whether their specific architecture can tell us about the disease they cause?"
They found that Streptococcus mutans, a major bacterial species responsible for tooth decay, is encased in a protective multilayered community of other bacteria and polymers forming a unique spatial organization associated with the location of the disease onset.
The researchers used a combination of super-resolution confocal and scanning electron microscopy with computational analysis to dissect the arrangement of S. mutans and other microbes of the intact biofilm on the teeth. These techniques allowed the team to examine the biofilm layer by layer, gaining a three-dimensional picture of the specific architectures.
They discovered that S. mutans in dental plaque most often appeared as arranged in a mound against the tooth's surface, but it wasn't alone. While S. mutans formed the inner core of the rotund architecture, other commensal bacteria, such as S. oralis, formed additional outer layers precisely arranged in a crownlike structure.
Supporting and separating these layers was an extracellular scaffold made of sugars produced by S. mutans, effectively encasing and protecting the disease-causing bacteria.
"It's clear that identifying the constituents of the human microbiome is not enough to understand their impact on human health," says co-senior author Marvin Whiteley of Georgia Tech. "We also have to know how they are spatially organized. This is largely under studied as obtaining intact samples that maintain spatial structure is difficult."
"We found this highly ordered community with a dense accumulation of S. mutans in the middle surrounded by these “halos” of different bacteria, and wondered how this could cause tooth decay," added Koo.
To learn more about how structure impacted the function of the biofilm, the research team attempted to recreate the natural plaque formations on a toothlike surface in the lab using S. mutans, S. oralis, and a sugar solution. They successfully grew rotund-shaped architecture and then measured levels of acid and demineralization associated with them.
Effectively killing cavity-causing bacteria to prevent tooth decay
The team applied an antimicrobial treatment and observed how the bacteria fared. When the rotund structures were intact, the S. mutans in the inner core largely avoided dying from the antimicrobial treatment.
Only breaking up the scaffolding material holding the outer layers together enabled the antimicrobial to penetrate and effectively kill the cavity-causing bacteria.
"What we discovered, and what was exciting for us, is that the rotund areas perfectly matched with the demineralized and high acid levels on the enamel surface," Koo continued. "This mirrors what clinicians see when they find dental caries: punctuated areas of decalcification known as ‘white spots.’
“The domelike structure could explain how cavities get their start. It demonstrates that the spatial structure of the microbiome may mediate function and the disease outcome, which could be applicable to other medical fields dealing with polymicrobial infections."
"It's not just which pathogens are there but how they're structured that tells you about the disease that they cause," Whiteley added. "Bacteria are highly social creatures and have friends and enemies that dictate their behaviors."
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With over 30 years of writing and editing experience for newspapers, magazines and corporate communications, Kevin Kerfoot writes about natural health, nutrition, skincare and oral hygiene for Trusted Health Products’ natural health blog and newsletters.
Founder Ray Spotts has a passion for all things natural and has made a life study of nature as it relates to health and well-being. Ray became a forerunner bringing products to market that are extraordinarily effective and free from potentially harmful chemicals and additives. For this reason Ray formed Trusted Health Products, a company you can trust for clean, effective, and healthy products. Ray is an organic gardener, likes fishing, hiking, and teaching and mentoring people to start new businesses. You can get his book for free, “How To Succeed In Business Based On God’s Word,” at www.rayspotts.com.