‘Artificial tongue’ detects and inactivates common mouth bacteria

 

Peer-Reviewed Publication

AMERICAN CHEMICAL SOCIETY

From the fuzzy feeling on your teeth to the unfortunate condition of halitosis, bacteria shape mouth health. When dental illnesses take hold, diagnosis and treatment is necessary, but identifying the microorganisms behind an infection can be a lengthy and expensive process. Now, researchers reporting in ACS Applied Materials & Interfaces have designed a chemical sensor array, or an artificial tongue, that distinguishes dental bacteria and can inactivate them.

When bacteria are suspected as the agent behind dental disease, such as cavities or periodontitis, the first step is to identify the source. Traditional detection and identification methods can involve culturing or looking for specific DNA markers belonging to different species using sophisticated equipment. So, Na Lu, Zisheng Tang and coworkers wanted to investigate a simple and less expensive alternative: sensor arrays known as electronic or artificial tongues. Previously developed artificial tongues have detected and measured several types of bacteria, similar to how a real tongue can taste multiple flavors at once. And the researchers wanted to add in the capability of reducing the effects of, or inactivating, the identified dental bacteria.

The researchers turned to a nanoscopic particle that mimics natural enzymes, called a nanozyme, and made them from iron oxide particles coated in DNA strands. When hydrogen peroxide and a colorless indicator were added in solution, the presence of nanozymes caused the indicator to turn bright blue. However, bacteria that adhered to the DNA decreased the nanozyme’s reactivity, reducing the amount of blue color produced. The researchers coated nanozymes with different DNA strands so that each type of bacteria could be linked to a unique change in color signals. To test the DNA-nanozyme system, as an artificial tongue, the researchers created samples of 11 different dental bacteria species. The sensor array was able to identify all the bacteria in artificial saliva samples. Then, using the DNA-encoded nanozyme sensor array, the researchers were able to distinguish whether a dental plaque sample came from a healthy volunteer or from a person with cavities.

In addition, the DNA-encoded nanozyme sensor array had antibacterial effects on the dental bacteria species tested. Compared to controls without the nanozymes, three typical bacterial species were inactivated in solutions containing the nanozyme system. Scanning electronic microscopic images suggest to the researchers that the nanozyme system destroyed the bacteria membranes. They suggest that this sensor system could also be used in the future to diagnose and treat bacterial dental diseases.

When it comes to bad breath, some bacterial interactions really stink

 

Researchers from Osaka University find that a metabolite produced by the commensal oral bacterium Streptococcus gordonii activates another bacterial species, Fusobacterium nucleatum, to produce the malodorous compound methyl mercaptan

Peer-Reviewed Publication

OSAKA UNIVERSITY

 

IMAGE: 

SCHEMATIC REPRESENTATION OF OBSERVED METABOLIC FLOW OF BACTERIAL METABOLISM F. NUCLEATUM AND S. GORDONII COCULTURES.

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CREDIT: © 2024 HARA ET AL. THIS IS AN OPEN-ACCESS ARTICLE DISTRIBUTED UNDER THE TERMS OF THE CREATIVE COMMONS ATTRIBUTION 4.0 INTERNATIONAL LICENSE.

Osaka, Japan – Having bad breath really stinks! Now, researchers from Japan report that a particular combination of bacteria in our mouths may be responsible for producing some very unpleasant smells.

In a study published last month in mSystems, researchers from Osaka University revealed that the interaction between two common types of oral bacteria leads to the production of a chemical compound that is a major cause of smelly breath.

Bad breath is caused by volatile compounds that are produced when bacteria in the mouth digest substances like blood and food particles. One of the smelliest of these compounds is methyl mercaptan (CH3SH), which is produced by microbes that live around the teeth and on the surface of the tongue. However, little is known about which specific bacterial species are involved in this process.

“Most previous studies investigating CH3SH-producing oral bacteria have used isolated enzymes or relatively small culture volumes,” explains lead author of the study Takeshi Hara. “In this study, we aimed to create a more realistic environment in which to investigate CH3SH production by major oral bacteria.”

To do this, the researchers developed a large-volume anaerobic co-culture system that enabled them to test interactions between multiple different types of bacteria that live in the mouth. This system was able to test both direct, physical interactions among the bacteria, as well as whether these species could affect each other from a distance, for example by secreting active substances.

“The results were very intriguing,” says Masae Kuboniwa, senior author. “We found that Fusobacterium nucleatum produces large quantities of CH3SH in response to Streptococcus gordonii, another oral bacterium.”

By using stable isotope tracers and analyzing gene expression, the researchers showed that S. gordonii releases a substance called ornithine that prompts F. nucleatum to produce more of a molecule called polyamine. Because F. nucleatum needs methionine to produce polyamine, this enhanced polyamine production activates its methionine salvage pathway, which in turn results in increased CH3SH production.

“Taken together, these findings suggest that CH3SH production in the mouth is driven by the interaction between S. gordonii and F. nucleatum,” says Hara.

Understanding how these two bacterial species work together to cause bad breath could be helpful in developing ways to treat or even prevent bad breath. In addition, given that bad breath is often associated with periodontal disease, treating this symptom early could help prevent more serious damage in the future.

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The article, “Interspecies metabolite transfer fuels methionine metabolism of Fusobacterium nucleatum to stimulate volatile methyl mercaptan production,” was published in mSystems at DOI: https://doi.org/10.1128/msystems.00764-23

Gargling away the bad bacteria in type 2 diabetes

 

Researchers from Osaka University find that gargling with an antiseptic mouthwash can reduce ‘bad’ bacteria in the mouths of people with type 2 diabetes, and may lead to better control of their blood sugar

Peer-Reviewed Publication

OSAKA UNIVERSITY

 

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MECHANISM OF TYPE 2 DIABETES MELLITUS IMPROVEMENT BY GARGLING WITH MOUTHWASH

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CREDIT: SAAYA MATAYOSHI

Osaka, Japan – More than bad breath, there is growing evidence that ongoing inflammation in the mouth, like with gum disease, is associated with serious diseases such as Alzheimer’s disease or type 2 diabetes. Now, researchers from Osaka University have identified an easy way to fight bacteria that might cause such problems.

In a study published this month in Scientific Reports, the researchers reported that when people with type 2 diabetes gargled with an antiseptic mouthwash, the numbers of periodontitis-related bacteria decreased. Excitingly, some patients with reduced bacteria also achieved much better control of their blood sugar, hinting at promising future clinical applications. 

“There are three highly virulent bacterial species that are linked to periodontitis, or diseases of the tissues surrounding the teeth,” explains lead author of the study Saaya Matayoshi. “We decided to see if we could reduce these three species—Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia—in patients with type 2 diabetes using a mouthwash containing the antiseptic chlorhexidine gluconate.”

To do this, the researchers took monthly or bimonthly saliva and blood samples from 173 patients over an entire year. With the saliva, the researchers noted the presence or absence of the three bacterial species, and with the blood samples, they measured HbA1c levels as a marker of blood-sugar control. Importantly, for the first 6 months of the study, the patients gargled with water, whereas for the second 6 months they gargled with the antiseptic mouthwash. In this way, the research team could see whether gargling itself was effective for reducing bacteria, or whether mouthwash was more effective.

“We were unsurprised to see that gargling with water had no effects on bacterial species or HbA1c levels,” explains Kazuhiko Nakano, senior author of the study. “However, there was an overall reduction in bacterial species when the patients switched to mouthwash, as long as they were gargling at least twice a day.”

The researchers also found that, although there were no overall changes in HbA1c levels when patients gargled with the antiseptic mouthwash, there appeared to be large variations in individual responses. For example, when they split the group into younger and older patients, younger patients had greater reductions in bacterial species and significantly better blood-sugar control with the mouthwash compared with water.

Given that poor oral health is linked to serious disease, simple methods to improve oral hygiene have important ramifications. If researchers can identify patients who are likely to respond well to antiseptic mouthwash, this easy-to-use treatment may improve the lives of people with periodontitis-linked diseases such as diabetes, dementia, cardiovascular disease, and respiratory tract infections.

 

New guideline details acute pain management strategies for adolescent, adult dental patients

Nonsteroidal anti-inflammatory drugs (NSAIDs) taken alone or along with acetaminophen are recommended as first-line treatments for managing short-term dental pain in adults and adolescents aged 12 or older, according to a new clinical practice guideline developed by the American Dental Association (ADA), the University of Pittsburgh School of Dental Medicine and the Center for Integrative Global Oral Health at the University of Pennsylvania School of Dental Medicine. The guideline has been endorsed by the ADA and is now available in the February issue of The Journal of the American Dental Association.

Based on review of the available evidence, a guideline panel concluded that, when used as directed, NSAIDs (like ibuprofen and naproxen) alone or in combination with acetaminophen can effectively manage pain after having a tooth removed or when experiencing a toothache when dental care is not immediately available.

The guideline also offers clinicians recommendations for prescribing opioid medications in the limited circumstances in which they may be appropriate. These include avoiding “just in case” prescriptions, engaging patients in shared decision-making and exerting extreme caution when prescribing opioids to adolescents and young adults. When prescribing opioids, the guideline suggests advising patients on proper storage and disposal and considering any risk factors for opioid misuse and serious adverse events.

“It’s important to take special consideration when prescribing any type of pain reliever, and now, dentists have a set of evidence-based recommendations to determine the best care for their patients,” said Dr. Paul Moore, D.M.D., Ph.D., M.P.H., the guideline’s senior author and panel chair and professor emeritus at the University of Pittsburgh’s School of Dental Medicine. “Patients are encouraged to discuss pain management expectations and strategies with their dentist so they can feel confident that they are receiving the safest, most effective treatment for their symptoms.”

In 2020, the U.S. Food and Drug Administration (FDA) awarded the University of Pittsburgh and the ADA Science & Research Institute (ADASRI) – now the ADA Forsyth Institute – a three-year $1.5 million grant to develop a clinical practice guideline for the management of acute pain in dentistry in children, adolescents and adults. A group of researchers and methodologists from ADASRI, University of Pittsburgh School of Dental Medicine, Center for Integrative Global Oral Health at the University of Pennsylvania School of Dental Medicine, McMaster University and The Art of Democracy worked together to develop the guideline.

“Providing prescribing guidelines for acute dental pain management is an important step towards improving patient treatment and outcomes,” said Dr. Marta Sokolowska, Ph.D., deputy center director for substance use and behavioral health at the FDA's Center for Drug Evaluation and Research. “We hope this clinical practice guideline will reduce the risk of opioid addiction, overdose and diversion.”

This is the second of two guidelines on acute dental pain management. A previous set of recommendations for pediatric patients was published in 2023. Both guidelines can be found at ada.org/painmanagement.

For more information on how the ADA is working to combat opioid misuse while continuing to help patients manage dental pain, visit ada.org/opioids.

The contents of the guidelines are those of the author(s) and do not necessarily represent the official views of, nor an endorsement by, the FDA, U.S. Department of Health and Human Services or U.S. government.
 

ADA releases updated recommendations to enhance radiography safety in dentistry

 

 The use of lead abdominal aprons or thyroid collars on patients when conducting dental X-rays is no longer recommended, according to an expert panel established by the American Dental Association (ADA) Council on Scientific Affairs. Additionally, dentists should take into consideration the diagnostic information needed from X-rays to benefit patient care or substantially improve clinical outcomes.

The Journal of the American Dental Association published the new recommendations today, which aim to improve radiation protection in dental radiography and cone-beam computed tomography (CBCT). Medical physicists with the U.S. Food and Drug Administration (FDA) supported the panel’s development of these recommendations – the first on dental imaging safety and radiation protection from the Council since 2012. The Council’s recommendations are also aligned with recent recommendations released by the American Academy of Oral and Maxillofacial Radiology.

After reviewing published studies on radiography, the expert panel determined lead aprons and thyroid collars are not necessary to shield patients from radiation exposure. These recommendations apply to all patients, regardless of age or health status (like pregnancy). Evidence indicates that modern digital X-ray equipment and restricting the beam size only to the area that needs to be imaged better protect patients against radiation exposure to other parts of their body. Lead aprons and thyroid collars can also block the primary X-ray beam, preventing dentists from capturing the image they need.

“When this happens, more radiographs need to be taken, and unnecessary X-rays are what we want to avoid,” said Dr. Purnima Kumar, D.D.S., Ph.D., professor of dentistry and chair of the Department of Periodontology and Oral Medicine at the University of Michigan School of Dentistry and chair of the ADA Council on Scientific Affairs. “The central point of these recommendations is that clinicians should order radiographs in moderation to minimize both patients’ and dental professionals’ exposure to ionizing radiation.”

The recommendations also advise dentists to safeguard patients against unnecessary radiation exposure by:

• Ordering radiographs like X-rays to optimize diagnostic information and enhance patient care outcomes and making every effort to use images acquired at previous dental exams;
• Using digital instead of conventional X-ray film for imaging;
• Restricting the beam size during an X-ray exam to the area that needs to be assessed (an approach called “rectangular collimation”);
• Properly positioning patients so the best image can be taken;
• Incorporating CBCT only when lower-exposure options will not provide the necessary diagnostic information; and
• Adhering to all applicable federal, state and local regulations on radiation safety.

“We encourage dentists and their teams to review these best-practice recommendations, comply with radiation protection regulations and talk with their patients about any questions or concerns before ordering dental imaging,” Dr. Kumar said.

To view the complete recommendations, visit JADA.ada.org.