Evidence grows for vaping’s role in gum disease

Research confirms unique community of bacteria and immune responses among people who use e-cigarettes

A series of new studies by researchers at NYU College of Dentistry highlights how e-cigarettes alter oral health and may be contributing to gum disease. The latest, published in mBio, finds that e-cigarette users have a unique oral microbiome—the community of bacteria and other microorganisms—that is less healthy than nonsmokers but potentially healthier than cigarette smokers, and measures worsening gum disease over time.

 

“To our knowledge, this is the first longitudinal study of oral health and e-cigarette use. We are now beginning to understand how e-cigarettes and the chemicals they contain are changing the oral microbiome and disrupting the balance of bacteria,” said Deepak Saxena, who led the research with Xin Li; both are professors of molecular pathobiology at NYU College of Dentistry.

 

Gum disease affects nearly half of U.S. adults over 30 years of age. Smoking cigarettes is a known risk factor for developing gum disease, but less is known about the impact of e-cigarettes—which vaporize nicotine and other chemicals—on oral health, especially the long-term consequences of vaping.

 

The researchers studied the oral health of 84 adults from three groups: cigarette smokers, e-cigarette users, and people who have never smoked. Gum disease was assessed through two dental exams six months apart, during which plaque samples were taken to analyze the bacteria present.

 

Changes to gum health

All participants had some gum disease at the start of the study, with cigarette smokers having the most severe disease, followed by e-cigarette users. After six months, the researchers observed that gum disease had worsened in some participants in each group, including several e-cigarette users.

 

A key indicator of gum disease is clinical attachment loss, measured by gum ligament and tissue separating from a tooth’s surface, leading the gum to recede and form pockets. These pockets are breeding grounds for bacteria and can lead to more severe gum disease. In a study of the same participants published in Frontiers in Oral Health, the research team found that clinical attachment loss was significantly worse only in the e-cigarette smokers—not non-smokers and cigarette smokers—after six months.

 

A unique microbiome

The researchers then analyzed the bacteria found in the plaque samples and determined that e-cigarette users have a different oral microbiome from smokers and nonsmokers—building on findings the team previously reported in iScience and Molecular Oral Microbiology.

 

While all groups shared roughly a fifth of the types of bacteria, the bacterial makeup for e-cigarette users had strikingly more in common with cigarette smokers than nonsmokers. Several types of bacteria, including Selenomonas, Leptotrichia, and Saccharibacteria, were abundant in both smokers and vapers compared to nonsmokers. Several other bacteria—including Fusobacterium and Bacteroidales, which are known to be associated with gum disease—were particularly dominant in the mouths of e-cigarette users.

 

When plaque samples were gathered and analyzed in the six-month follow-up, the researchers found greater diversity in bacteria for all groups studied, yet each group maintained its own distinct microbiome.

 

“Vaping appears to be driving unique patterns in bacteria and influencing the growth of some bacteria in a manner akin to cigarette smoking, but with its own profile and risks to oral health,” said Fangxi Xu, a junior research scientist in Saxena’s lab and the study’s co-first author.

 

An altered immune response

The researchers found that the distinct microbiome in e-cigarette users was correlated with clinical measures of gum disease and changes to the host immune environment. In particular, vaping was associated with different levels of cytokines—proteins that help regulate the immune system. Certain cytokines are linked to an imbalance in oral bacteria and can worsen gum disease by making people prone to inflammation and infection.

 

TNFα, a cytokine that causes inflammation, was significantly elevated among e-cigarette users. In contrast, cytokines IL-4 and IL-1β were lower among e-cigarette users; IL-4 tends to be reduced in people with gum disease and increases after treatment, which suggests that certain bacteria in the mouths of e-cigarette users may be actively suppressing immune responses.

 

The researchers concluded that the distinct oral microbiome of e-cigarette users elicits altered immune responses, which along with clinical markers for gum disease illustrate how vaping presents its own challenge to oral health.

 

“E-cigarette use is a relatively new human habit,” said Scott Thomas, an assistant research scientist in Saxena’s lab and the study’s co-first author. “Unlike smoking, which has been studied extensively for decades, we know little about the health consequences of e-cigarette use and are just starting to understand how the unique microbiome promoted by vaping impacts oral health and disease.”

Impact of COVID-19 on dental hygienists

Studies focus on infection and vaccination rates, employment

 –– Nearly two years into the pandemic with widespread availability of COVID-19 vaccines and a decrease in infections, new studies reveal dental hygienists have low COVID-19 infection rates and high vaccination acceptance. In addition, less than half of dental hygienists that left employment early in the pandemic have returned to the workforce in 2021, and staffing challenges, exacerbated by the pandemic, persist.

The research, published in the February issue of The Journal of Dental Hygiene, is part of collaborative research efforts between the American Dental Hygienists’ Association (ADHA) and the American Dental Association (ADA) on the impact of COVID-19 on employment, infection prevention and vaccine acceptance among dental hygienists. The data updated findings from a previous longitudinal study conducted over a 12-month period from September 2020 to August 2021 with a panel of 6,976 dental hygienists across the U.S., Puerto Rico and the Virgin Islands.

“This study of dental hygienists has shown us the profound impact of COVID-19 on clinical practice, as well as the value of disease prevention measures,” said JoAnn Gurenlian, R.D.H., M.S., Ph.D., A.F.A.A.O.M., a lead author of the research and ADHA’s director of education and research. “Workplace safety is of paramount importance to dental hygienists, and it has an effect on employment patterns. This underscores the need to adhere to infection control guidance and proper PPE.” 

Infection and Vaccination Rates

Despite initial concerns that dental hygienists were at increased risk of COVID-19, the updated research shows they have a lower COVID-19 cumulative prevalence (8.8%) than the general U.S. population (11.7%). Results also reveal that 75.4% of U.S. dental hygienists have been fully vaccinated against COVID-19, a higher proportion than the general public and healthcare workers outside of dentistry overall at the time.

“We’re pleased to see that dental hygienists have demonstrated continued low incidence of infection and high vaccination, proving the profession’s ability to mitigate risk while providing care in a safe manner,” said Cameron G. Estrich, M.P.H., Ph.D., health research analyst with the ADA Science & Research Institute. “Increased vaccine availability and greater supplies of personal protective equipment (PPE) should further enable dental teams to continue to follow infection prevention measures to reduce the risk of COVID-19 transmission.”

Challenges Persist in Employment

As of August 2021, less than half of dental hygienists that left employment during the pandemic had returned to work. According to the study, 7.9% of respondents that had been employed in March 2020 were not working six months later in September 2020. When the study concluded in August 2021, that number decreased to 4.9%.

However, the pandemic has impacted staffing levels in industries across the country, and the dental profession is not exempt.

While the number of hygienists that left the workforce rebounded from a high of 7.9% in 2020 to 4.9% in 2021, a total of 1.6% of study participants no longer intended to work as dental hygienists, possibly representing a permanent reduction of 3,300 dental hygienists nationwide.

“Not unlike many other professions in the United States, challenges persist in dental hygienist employment. The COVID-19 pandemic has exacerbated a voluntary reduction in the dental hygiene workforce and may persist, as some dental hygienists are choosing to permanently leave the profession,” said Rachel W. Morrissey, M.A., senior research analyst with the ADA Health Policy Institute (HPI).

Despite recovery in dental practices’ patient volume, dentists in the U.S. continue to report recruitment and retention challenges among dental hygienists due to the COVID-19 pandemic, according to HPI data. The study authors note that future research should examine workforce levels after the pandemic resolves, as well as employment perspectives of dental hygienists from a qualitative perspective to yield greater understanding of the influencing factors that impact decisions to return to or engage in employment in clinical practice settings.

Future Opportunities for Risk Mitigation

Given the ongoing COVID-19 pandemic and emergence of new variants, the study authors believe opportunities exist for hygienists to play an important role in public health and safety. However, there is a need for ongoing and increased education and polices to support the continued use of PPE and infection control and prevention procedures, as recommended by the CDC and required by government regulatory agencies.

“This research collaboration with the ADA marks an important moment in oral health,” said ADHA CEO Ann Battrell, M.S.D.H. “Our shared understanding of what dental hygienists are experiencing provides us with essential evidence-based direction for how we can support safe and supportive workplaces, deliver care safely to patients and help define lasting practice improvements that may emerge from this pandemic.”

The ADHA and the ADA will continue to work together to further understand the impact of COVID-19 on the dental team.

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About the American Dental Hygienists' Association

The American Dental Hygienists’ Association (ADHA) is the largest national organization representing the professional interests of the country’s more than 226,000 dental hygienists. Dental hygienists are preventive oral health professionals, licensed in dental hygiene, who provide educational, clinical and therapeutic services that support total health through the promotion of optimal oral health. To learn more about ADHA, dental hygiene or the link between oral health and general health, visit ADHA at www.adha.org.

About the American Dental Association

The not-for-profit ADA is the nation's largest dental association, representing 161,000 dentist members. The premier source of oral health information, the ADA has advocated for the public's health and promoted the art and science of dentistry since 1859. The ADA's state-of-the-art research facilities develop and test dental products and materials that have advanced the practice of dentistry and made the patient experience more positive. The ADA Seal of Acceptance long has been a valuable and respected guide to consumer dental care products. The monthly The Journal of the American Dental Association (JADA) is the ADA's flagship publication and the best-read scientific journal in dentistry. For more information about the ADA, visit ADA.org. For more information on oral health, including prevention, care and treatment of dental disease, visit the ADA's consumer website MouthHealthy.org.

Less antibiotic use in dentistry gave no increase in endocarditis

 

Sweden is one of the few countries that have removed the dental health recommendation to give prophylactic antibiotics to people at a higher risk of infection of the heart valves, so-called infective endocarditis. Since the recommendation was removed in 2012, there has been no increase in this disease, a registry study from Karolinska Institutet published in the journal Clinical Infectious Diseases shows.

Infective endocarditis is a rare but life-threatening disease caused by bacterial infection of the heart valves that affects some 500 people a year in Sweden. Individuals with congenital heart disease, prosthetic heart valves or previous endocarditis are at higher risk of infection.

People at a higher risk of infective endocarditis in Sweden used to receive the antibiotic amoxicillin as a prophylactic ahead of certain dental procedures, such as tooth extraction, tartar scraping and surgery. This recommendation was lifted in 2012 due to a lack of evidence that the treatment was necessary and to help prevent antibiotic resistance by reducing antibiotic use. A collaborative project involving researchers from Karolinska Institutet has now studied how the decision has affected the incidence of infective endocarditis.

Supports the change in recommendation

“We can only see small, statistically non-significant variations in morbidity, nothing that indicates a rise in this infection in the risk group since 2012,” says the study’s corresponding author Niko Vähäsarja, dentist and doctoral student at the Department of Dental Medicine, Karolinska Institutet. “Our study therefore supports the change in recommendation. This is an internationally debated issue and Sweden and the UK are the only countries in Europe to restrict antibiotic use like this.”

The registry study encompassed 76,762 high-risk individuals and 396,048 individuals at a low risk of infective endocarditis, who were monitored from 2008 to 2018 with the help of the Medical Birth Registry, the National Patient Register and the Swedish Endocarditis Registry.

The recommendation was supplemented in 2016 with an instruction to consider prophylactic antibiotic treatment if prescribed by the patient’s doctor. It is unclear how this addition has influenced the prescription of antibiotics by dentists.

Reduction of amoxicillin prescriptions

After the change in recommendation in 2012, prescriptions of amoxicillin in dentistry declined by approximately 40 per cent. However, the study is unable to demonstrate that this was an effect of the amended recommendation and amoxicillin has other uses in dental medicine.

“The next step is to examine which dental procedures the individuals in the risk group underwent during the 2008–2018 period, since this is information we lack and it could add to our knowledge of what is to date a poorly studied issue,” says Mr Vähäsarja. “This and the study we’ve just published could inform similar recommendation changes in other countries, resulting in a reduction in antibiotic use.”

The study was financed by Karolinska Institutet, the Swedish Public Health Agency, Folktandvården Stockholm AB, the Steering Committee for Dental Research at Karolinska Institutet and Stockholm City and the Swedish Dental Association. There are no reported conflicts of interest.

Publication: “Infective endocarditis among high-risk individuals - before and after the cessation of antibiotic prophylaxis in dentistry: a national cohort study”. Niko Vähäsarja, Bodil Lund, Anders Ternhag, Bengt Götrick, Lars Olaison, Margareta Hultin, Anna Warnqvist, Carina Krüger Weiner och Aron Naimi-Akbar. Clinical Infectious Diseases, online 4 February 2022, doi: 10.1093/cid/ciac095.

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JOURNAL

Clinical Infectious Diseases

DOI

10.1093/cid/ciac095 

The healthy oral microbiome contributes to jaw bone health by influencing immune cell interactions with bone cells

Microbes colonizing the oral cavity in health can activate immune cells in the jaw bone marrow; ultimately, these activation events lead to increased osteoclast-mediated bone resorption and bone loss.

 

IMAGE: TARTRATE-RESISTANT ACID PHOSPHATASE (TRAP) STAINING WITHIN THE MAXILLARY FIRST MOLAR SHOWS MORE OSTEOCLASTS (PURPLE STAINING) IN ANIMALS TREATED WITH A SALINE ORAL RINSE (TOP) COMPARED WITH A CHLORHEXIDINE ORAL RINSE (BOTTOM). view more 

CREDIT: DRS. CHAD NOVINCE AND JESSICA HATHAWAY-SCHRADER.

It is becoming increasingly clear that the human microbiome – the collection of bacteria, viruses and fungi that live on and within us – significantly contributes to our health. Indeed, several recent studies have demonstrated the contribution of the microbiome to regulating immune cells that influence bone health.

To find out more, researchers at the Medical University of South Carolina (MUSC) who study osteoimmunology, the interface of the skeletal and immune systems, have examined the impact of the oral microbiome on alveolar bone. The alveolar bone, commonly known as the jaw bone, is a unique bone tissue that houses and supports our teeth. Their results, published online on Jan. 25 in the Journal of Clinical Investigation Insight, showed that healthy microbes in the mouth activated a subset of immune cells within the alveolar bone marrow, which in turn promoted osteoclastic cells that are responsible for breaking down bone. They went on to show that depleting the healthy oral microbiome, using an antiseptic mouthwash, protected against this bone loss in preclinical models, demonstrating a direct link between microbes in the mouth and naturally occuring alveolar bone loss.

“The alveolar bone is different from other bone tissues due to its role in supporting the teeth,” said Chad M. Novince, D.D.S., Ph.D., associate professor in the colleges of Medicine and Dental Medicine, who studies the impact of the microbiome on osteoimmunology and skeletal metabolism. “What is most fascinating to me is that we were able to show that the commensal oral microbiota modulates the communication between immune cells and bone cells, separate from other microbiota communities, that impact alveolar bone health.”

“I think this is really only the start to understanding how the commensal oral microbiome can regulate alveolar bone health and homeostasis,” added Jessica D. Hathaway-Schrader, Ph.D., a postdoctoral scholar in the College of Dental Medicine and first author on this study.

Previously, the Novince lab utilized mouse models with a defined microbiota and showed that specific commensal microbes in the gut could influence normal skeletal development and homeostasis. In the current study, they focused on the oral cavity – a unique space in which the microbes colonizing the mouth are in close proximity to the underlying alveolar bone. Little was known about how interactions between microbes and immune cells in the oral cavity, compared with other anatomic sites, influence alveolar bone health.

In order to understand the interplay between microbes and immune cells within the oral cavity more fully, the Novince lab pioneered two new techniques. The first technique involved innovatively collecting bone marrow from the mandible of mice, which enabled the researchers to perform in-depth studies on immune cells within alveolar bone. The second technique involved developing a novel way to deplete microbes from the oral cavity of mice. The team utilized a unique delivery sponge loaded with chlorhexidine, an antiseptic used to treat gingivitis, to perform oral rinses on the mice.

With these innovations in hand, the team used the chlorohexidine rinse to deplete the commensal oral microbiota. Suppressing the commensal microbial load in the oral cavity, while not altering the commensal microbiota at other sites, dampened the immune response in the alveolar bone marrow. This dampened immune response suppressed bone resorbing osteoclast cells, which had an overall protective effect on alveolar bone loss that naturally occurs due to the burden of commensal microbes.

Analysis of the bone marrow within the mandibles of mice revealed that a subset of immune cells were activated by the presence of commensal oral microbes. One important class of activated immune cells were dendritic cells. These cells act like sentinals of the immune system and alert other immune cells that microbial invaders are present. The other important immune cells that were activated by the presence of commensal oral microbes were CD4+ helper T-cells. These cells help to coordinate the immune response during an infection. Ultimately, these immune cells supported osteoclasts.

Together, these data suggest a tightly coordinated pathway in which commensal oral microbes influence alveolar bone health. Furthermore, reducing the burden of commensal microbes in the mouth through oral antiseptic rinses prevented alveolar bone loss, which could have important clinical implications moving forward.

“We were able to show that the commensal oral microbiota influences alveolar bone homeostasis through osteoimmune mechanisms that are distinct from the systemic microbiome,” said Novince. “If we are able to suppress the healthy oral microbiome to lower levels, it could help protect from alveolar bone loss, even in a state of health.”

This report is the first investigation showing that chlorhexidine reduces naturally occurring alveolar bone loss and suggests that antiseptic oral rinses could support alveolar bone health and homeostasis. To ensure that this potential treatment is safe and effective, future studies aimed at better describing the interaction between the microbiome, immune cells and bone is warranted.

“Although we’re broadly suppressing oral microorganisms with the antiseptic rinse, it will be important to determine which specific microbes are really driving this naturally occurring alveolar bone loss,” said Hathaway-Schrader. “The alveolar bone marrow is a unique environment, and this is the first step in understanding interactions between oral microbes and immune cells important for promoting bone health.”

Chewing sugar-free gum reduced preterm births

Each year, an estimated 15 million babies are born prematurely or preterm (defined as delivery before the 37th week of pregnancy), and this number is rising, according to the World Health Organization. Preterm babies are at greater risk of experiencing serious health problems.

Over the last several decades, multiple studies have shown a link between poor oral health and increased occurrence of preterm birth. Researchers have looked at various ways to improve dental health during pregnancy, including doing a “deep-teeth cleaning,” (also called ‘scaling and planing’) which involves removing plaque and tarter on the teeth and below the gum line. However, despite improving periodontitis, deep teeth cleaning approaches have not proven to be effective in the prevention of preterm birth. But now researchers have discovered an easy and inexpensive way to improve oral health and reduce preterm births.

In a new study to be presented today at the Society for Maternal-Fetal Medicine’s (SMFM) annual meeting, The Pregnancy Meeting™, which is being held virtually, researchers will unveil findings that suggest that daily use of xylitol chewing gum starting pre- or early pregnancy significantly reduced the number of preterm births. Xylitol is a naturally occurring alcohol found in fruits and vegetables and is commonly used as a sugar substitute in chewing gum.

The study, the largest of its kind, was conducted over 10 years and included 10,069 women in the South-Central African country of Malawi, which has the highest number of preterm births in the world. Most Malawians live in rural locations, making it especially difficult to conduct of study of this magnitude.

The cluster randomized trial enrolled participants from eight health centers in Malawi and was approved by the Malawi Ministry of Health. Participants enrolled voluntarily and consented to participation before they became pregnant or within 20 weeks of becoming pregnant. All of the eight health centers provided health care messages promoting oral health care and preterm birth prevention and care, while half of the eight centers were randomized to also provide xylitol chewing gum to enrolled research participants.

In the four health centers that served as the control group, 5,520 participants received basic perinatal and oral health education, including things they could do to help lower the chance of delivering a baby prematurely. In the other four centers, the 4,549 enrolled participants also received this same health education. In addition, they were given xylitol chewing gum and instructed to chew the gum for 10 minutes once a day, ideally twice a day, throughout pregnancy.

Out of the 9,670 participants who were available for contact during the up to six years of follow-up, results showed a significant reduction in preterm birth among those who chewed the xylitol containing gum (12.6 percent vs. 16.5 percent) and fewer low birth weight babies, those weighing 5.5 pounds or less (8.9 percent vs. 12.9 percent). Participants also saw an improvement in their oral health.

“Using xylitol chewing gum as an intervention prior to 20 weeks of pregnancy reduced preterm births, and specifically late preterm births between 34 to 37 weeks,” says the study’s lead author Kjersti Aagaard, MD, PhD, a Professor in Maternal-Fetal Medicine and Vice Chair of Obstetrics & Gynecology at Texas Children’s and Baylor College of Medicine in Houston. “When we analyzed by birth weight, instead of estimated gestational age at delivery, we similarly showed a significant improvement in the birth weight with one-third fewer low birth weight babies being born.”

Adds Aagaard, “What’s unique about our study is that we used a readily available, inexpensive, and palatable means to reduce the risk of a baby being born too soon or too small. There is some real science behind the choice of xylitol chewing gum to improve oral health, and our novel application to improving birth outcomes is exciting. This has been a labor of love with our colleagues in Malawi, and we were honored to work side-by-side to demonstrate that xylitol chewing gum in early or pre-pregnancy improved oral health by reducing periodontal disease in pregnancy, which was strongly associated with our observed reduction of preterm and low birthweight birth in Malawi. This fits with longstanding evidence linking oral health with preterm births.”

The next step, say researchers, is to conduct studies in other parts of the world, including in the U.S., to determine whether this invention will be effective in settings where there may be a lower burden of preterm birth tied to oral health. 

At last: a stiff, strong artificial tooth enamel analog

Delivering what has been so challenging to produce, researchers present an engineered analog of tooth enamel – an ideal model for designing biomimetic materials – designed to closely mimic the composition and structure of biological teeth’s hard mineralized outer layer. It demonstrates exceptional mechanical properties, they say. Natural tooth enamel – the thin outer layer of our teeth – is the hardest biological material in the human body. It is renowned for its high stiffness, hardness, viscoelasticity, strength, and toughness and exhibits exceptional damage resistance, despite being only several millimeters thick. 

Tooth enamel’s unusual combination of properties is a product of its hierarchical architecture – a complex structure made up of mostly hydroxyapatite nanowires interconnected by an amorphous intergranular phase (AIP) consisting of magnesium-substituted amorphous calcium phosphate. However, accurately replicating this type of hierarchical organization in a scalable abiotic composite has remained a challenge. Here, Hewei Zhao and colleagues present an engineered enamel that contains the essential hierarchical structure at multiple scales. 

The artificial tooth enamel (ATE) was produced using AIP-coated hydroxyapatite nanowires, which were aligned using dual-directional freezing in the presence of polyvinyl alcohol. According to the authors, this allowed the engineered structures to have an atomic, nanoscale and microscale organization like natural enamel. In a series of tests, Zhao et al. demonstrated that the ATE nanocomposite simultaneously exhibited high stiffness, hardness, strength, viscoelasticity, and toughness, exceeding both the properties of enamel and previously manufactured materials. 

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JOURNAL

Science

DOI

10.1126/science.abj3343