Written By Kevin Kerfoot / Reviewed By Ray Spotts
Researchers at the University of Pennsylvania School of Dental Medicine and the Georgia Institute of Technology have discovered 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 imaged the bacteria that cause tooth decay in three dimensions in their natural environment, the sticky biofilm known as dental plaque formed on toddlers' teeth that were affected by cavities.
The work, published in the journal Proceedings of the National Academy of Sciences.
"We started with these clinical samples, 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?"
Examining Tooth Bacteria
To address this question, the researchers, including lead author Dongyeop Kim of Penn Dental Medicine and co-senior author Marvin Whiteley of Georgia Tech, 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. This approach, of understanding the locations and patterns of bacteria, is one that Whiteley has pursued in other diseases.
"It's clear that identifying the constituents of the human microbiome is not enough to understand their impact on human health," Whiteley says. "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."
In the current work, the researchers discovered that S. mutans in dental plaque most often appeared in a particular fashion: 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.
"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," Koo said.
Tooth Bacteria And Demineralization
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.
"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," says Koo. "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."
In a final set of experiments, the team put the rotund community to the test, applying an antimicrobial treatment and observing 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.
The study's findings may help researcher more effectively target the pathogenic core of dental biofilms but also have implications for other fields.
"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," says Koo. "It's not just which pathogens are there but how they're structured that tells you about the disease that they cause," adds Whiteley. "Bacteria are highly social creatures and have friends and enemies that dictate their behaviors."
Link Between Smoking And Pulp In Teeth
Researchers at the Case Western Reserve University School of Dental Medicine found that smoking also weakens the ability for pulp in teeth to fight illness and disease. In other words, smokers have fewer defense mechanisms on the inside of their teeth.
“That might explain why smokers have poorer endodontic outcomes and delayed healing than non-smokers,” said Anita Aminoshariae, associate professor of endodontics and director of predoctoral endodontics. “Imagine TNF-α and hBD-2 are among the soldiers in a last line of defense fortifying a castle. Smoking kills these soldiers before they even have a chance at mounting a solid defense.”
The results of the study were published in the Journal of Endodontics.
Previously, there was little research into the endodontic effects of smoking - the inside of teeth. Smokers had worse outcomes than nonsmokers, with greater chances of developing gum disease and nearly two times more likely to require a root canal.
This new preliminary research set out to explain the possible contributing factors. Thirty-two smokers and 37 nonsmokers with endodontic pulpitis - more commonly known as dental-tissue inflammation—were included in the study.
“We began with a look at the dental pulp of smokers compared with nonsmokers,” she said. “We hypothesized that the natural defenses would be reduced in smokers; we didn’t expect them to have them completely depleted.”
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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.