COVID-19 infection rates of dentists remain lower than other health professionals

AMERICAN DENTAL ASSOCIATION

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CHICAGO, May 24, 2021--More than a year after COVID-19 appeared in the U.S., dentists continue to have a lower infection rate than other front-line health professionals, such as nurses and physicians, according to a study published online ahead of the June print issue in the Journal of the American Dental Association. The study, "COVID19 among Dentists in the U.S. and Associated Infection Control: a six-month longitudinal study," is based on data collected June 9 - Nov. 13, 2020.

According to the study, based on the number of dentists with confirmed or probable COVID-19 infections over more than six months, the cumulative infection rate for U.S. dentists is 2.6%. The monthly incidence rate varied, ranging from 0.2% to 1.1% per month. By comparison, in June 2020, the cumulative COVID-19 prevalence rate for other U.S. health professionals ranged from 3.3% (Chicago-based hospital physicians) to 35.3% (U.S. based emergency medicine services).

"We're pleased to see that dentists have demonstrated continued low monthly incidence of disease despite several regional and national COVID-19 rate spikes during the study period," said American Dental Association (ADA) Science and Research Institute Chief Executive Officer Marcelo Araujo, D.D.S., M.S., Ph.D., the senior author of the report.

Dr. Araujo added, "This study shows high rates of pre-appointment screening of patients and appropriate infection control measures throughout the study period, demonstrating that adhering to very strict protocols for enhanced infection control helps protect their patients, their dental team and themselves."

In addition to Dr. Araujo, other authors of the report include researchers from the ADA Science and Research Institute and Health Policy Institute based in Chicago, as well as Maria L Geisinger, D.D.S., M.S. with University of Alabama at Birmingham in Birmingham, Ala., and Effie Ioannidou, D.D.S., M.D.S., with the University of Connecticut in Farmington, Conn., and a member of the ADA Council on Scientific Affairs.

This study is a continuation of the first large-scale report of incidence rates of COVID-19 among dentists in the U.S published in October 2020. The present six-month longitudinal study aimed to:

• Determine the cumulative prevalence rate of COVID-19 among dentists;

• Calculate the monthly incidence rate for the same population over the course of the study; and

• Assess the level of engagement in specific infection control practices among dentists over a six-month period of time.

The results of this present study, as well as the earlier study, show that prevalence and incidence rates among dentists continue to be very low when compared to the population as a whole and to other health care professionals.

"This study reinforces that the dental care sector is up and running safely," said Chief Economist and Vice President of the ADA Health Policy Institute Marko Vujicic, Ph.D. "Nowhere is this proof point more evident than by the fact that more than 90% of patients surveyed indicate they have already visited the dentist or soon will."

The authors plan future research projects on the barriers and facilitators to wearing Personal Protective Equipment (PPE) according to CDC recommendations, and levels of protection against COVID-19 provided by different levels of PPE use and infection control procedures.

A gentler strategy for avoiding childhood dental decay

By targeting the bonds between bacteria and yeast that can form a sticky dental plaque, a new therapeutic strategy could help wash away the build-up while sparing oral tissues, according to a new study by a team from the University of Pennsylvania

UNIVERSITY OF PENNSYLVANIA

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The combination of a carb-heavy diet and poor oral hygiene can leave children with early childhood caries (ECC), a severe form of dental decay that can have a lasting impact on their oral and overall health.

A few years ago, scientists from Penn's School of Dental Medicine found that the dental plaque that gives rise to ECC is composed of both a bacterial species, Streptococcus mutans, and a fungus, Candida albicans. The two form a sticky symbiosis, known scientifically as a biofilm, that becomes extremely virulent and difficult to displace from the tooth surface.

Now, a new study from the group offers a strategy for disrupting this biofilm by targeting the yeast-bacterial interactions that make ECC plaques so intractable. In contrast to some current treatments for ECC, which use antimicrobial agents that can have off-target effects, potentially harming healthy tissues, this treatment uses an enzyme specific to the bonds that exist between microbes.

"We thought this could be a new way of approaching the problem of ECCs that would intervene in the synergistic interaction between bacteria and yeast," says Geelsu Hwang, an assistant professor in Penn Dental Medicine and senior author on the study, published in the journal mBio. "This offers us another tool for disrupting this virulent biofilm."

The work builds off findings from a 2017 paper by Hwang and colleagues, including Hyun (Michel) Koo of Penn Dental Medicine, which found that molecules call mannans on the Candida cell wall bound tightly to an enzyme secreted by S. mutans, glycosyltransferases (Gftb). In addition to facilitating the cross-kingdom binding, Gftb also contributes to the stubbornness of dental biofilms by manufacturing gluelike polymers called glucans in the presence of sugars.

While some cases of ECC are treated with drugs that kill the microbes directly, potentially reducing the number of pathogens in the mouth, this doesn't always effectively break down the biofilm and can have off-target effects on "good" microbes as well as the soft tissues in the oral cavity.

Hwang and colleagues wanted to try a different approach that would directly target the insidious interaction between yeast and bacteria and opted to target the mannans in the Candida cell surface as a point of contact.

Using three different mannan-degrading enzymes, they applied each to a biofilm growing on a tooth-like surface in a human saliva medium and left it for five minutes. Following the treatment, they noted that the overall biofilm volume was reduced. Using powerful microscopy, they also observed drastic reductions in the biofilm thickness and interactions between bacteria and yeast. The pH of the surrounding medium was higher when exposed to the enzymes, indicating an environment that is not as acidic and thus less conducive to tooth decay.

They also measured how easy it was to break up the biofilm after treatment, using a device that applies a stress, akin to tooth brushing.

"The biofilm structure was more fragile after the enzyme treatment," Hwang says. "We were able to see that the biofilms were more easily removed."

To confirm the mechanism of their approach--that the mannan-degrading enzymes were weakening the binding between yeast and bacteria--the team used atomic-force microscopy to measure the bonds between Candida and Gftb. The therapy, they found, reduced this binding force by 15-fold.

Finally, they wanted to get a sense of how well-tolerated these enzymes would be when used in the oral cavity, especially since children would be the patient group targeted.

Applying the enzymes to human gingival cells in culture, they found no harmful impact, even when they used a concentrated form of the enzymes. In addition, they observed that the treatment didn't kill the bacteria or yeast, a sign that it could work even if the microbes developed mutations that would lend them resistance against other types of therapies.

The researchers kept the application time relatively short at five minutes though they hope to see activity in an even shorter time, like the two minutes that is recommended for tooth brushing. Hwang says they may consider a non-alcohol-based mouthwash with these enzymes added that could be used by children as a preventive measure against ECC.

The researchers hope to continue pursuing this possibility with additional follow up, including testing these enzymes in an animal model. With more successes, they aim to add another tool for fighting the public health threat of ECC.

Dental procedures during pandemic are no riskier than a drink of water

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 A new study's findings dispel the misconception that patients and providers are at high risk of catching COVID-19 at the dentist's office.

SARS-CoV-2 spreads mainly through respiratory droplets, and dental procedures are known to produce an abundance of aerosols - leading to fears that flying saliva during a cleaning or a restorative procedure could make the dentist's chair a high-transmission location.

Ohio State University researchers set out to determine whether saliva is the main source of the spray, collecting samples from personnel, equipment and other surfaces reached by aerosols during a range of dental procedures.

By analyzing the genetic makeup of the organisms detected in those samples, the researchers determined that watery solution from irrigation tools, not saliva, was the main source of any bacteria or viruses present in the spatter and spurts from patients' mouths.

Even when low levels of the SARS-CoV-2 virus were detected in the saliva of asymptomatic patients, the aerosols generated during their procedures showed no signs of the coronavirus. In essence, from a microbial standpoint, the contents of the spray mirrored what was in the office environment.

"Getting your teeth cleaned does not increase your risk for COVID-19 infection any more than drinking a glass of water from the dentist's office does," said lead author Purnima Kumar, professor of periodontology at Ohio State.

"These findings should help us open up our practices, make ourselves feel safe about our environment and, for patients, get their oral and dental problems treated - there is so much evidence emerging that if you have poor oral health, you are more susceptible to COVID," Kumar said.

The study was published Wednesday, May 12, in the Journal of Dental Research.

Previous research has shown that dental-procedure aerosols tend to land on providers' faces and the patient's chest, and can travel as far as 11 feet. But the studies, catching the spray in petri dishes placed on people, equipment and around the room, found only that bacteria existed - they rarely identified the organisms and never determined where they came from. Saliva has been the presumptive source for a long time.

When saliva was considered potentially deadly at the start of the pandemic, Kumar decided a long-term answer was needed to settle the question of whether saliva is the source of dental aerosols.

For the study, the team enrolled 28 patients receiving dental implants and restorations using high-speed drills or ultrasonic scaling procedures in Ohio State's College of Dentistry between May 4 and July 10, 2020. Researchers collected samples of saliva and irrigant (the water-based cleaning solutions used to flush out the mouth) before each procedure and, 30 minutes after the procedure, aerosol remnants - condensate - from providers' face shields, the patient's bib and an area 6 feet away from the chair.

Kumar and colleagues then put genome sequencing technology to use that wasn't available in the petri-dish days. This allowed them to first characterize the microbial mix in pre-procedure saliva and irrigants, which they could then compare to organisms in the aerosol samples collected later.

With the analytical method they used, the researchers did not need to characterize the microbes - they instead looked for variations in sequences that provided enough information to identify the family of bacteria or viruses to which they belonged.

"Some species that live in your mouth can closely resemble those in water and the environment. Using this method, we don't even have to know the names of these organisms - you can tell whether they are exactly genetically identical or genetically different," Kumar said. "If you use this granular approach to see these very nuanced differences in the genetic code, you can very accurately identify where they're coming from."

No matter the procedure or where the condensate had landed, microbes from irrigants contributed to about 78% of the organisms in aerosols while saliva, if present, accounted for 0.1% to 1.2% of the microbes distributed around the room.

Salivary bacteria were detected in condensate from only eight cases and of those, five patients had not used a pre-procedural mouth rinse. The SARS-CoV-2 virus was identified in the saliva of 19 patients, but was undetectable in aerosols in any of the cases.

The findings are reassuring, but also make sense, Kumar said: Irrigant dilutes saliva - a "thick, viscous" substance - by an estimated 20- to 200-fold, and the research is validated by a 2020 study that reported a less than 1% COVID-19 positivity rate among dentists.

Kumar noted that dentistry has long been at the forefront of infection-control practices in health care. During the pandemic, new protocols have included strengthened ventilation systems, extra aerosol suction equipment, N95 masks and face shields on top of goggles, and extended downtime between patients. She is hopeful this study's findings will make practitioners and patients feel at ease about being in the dentist's office - with continued stringent protection in place.

"Dental surgeons and hygienists are always at the forefront of the war against bacteria in the mouth, and they of course did not feel safe because they are front-line workers surrounded by aerosol," said Kumar, who has a periodontology practice of her own and was one of the procedure operators in the study.

"Hopefully this will set their mind at rest because when you do procedures, it is the water from the ultrasonic equipment that's causing bacteria to be there. It's not saliva. So the risk of spreading infection is not high," she said. "However, we should not lose sight of the fact that this virus spreads through aerosol, and speaking, coughing or sneezing in the dental office can still carry a high risk of disease transmission."

AI helps predict treatment outcomes for patients with diseased dental implants

UNIVERSITY OF MICHIGAN

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Peri-implantitis, a condition where tissue and bone around dental implants becomes infected, besets roughly one-quarter of dental implant patients, and currently there's no reliable way to assess how patients will respond to treatment of this condition.

To that end, a team led by the University of Michigan School of Dentistry developed a machine learning algorithm, a form of artificial intelligence, to assess an individual patient's risk of regenerative outcomes after surgical treatments of peri-implantitis.

The algorithm is called FARDEEP, which stands for Fast and Robust Deconvolution of Expression Profiles. In the study, researchers used FARDEEP to analyze tissue samples from a group of patients with peri-implantitis who were receiving reconstructive therapy. They quantified the abundance of harmful bacteria and certain infection fighting immune cells in each sample.

Patients who were at low risk for periodontal disease showed more immune cells that were highly adept at controlling bacterial infections, said Yu Leo Lei, senior author and assistant professor of dentistry.

The team was surprised that the types of cells associated with better outcomes for implant patients challenge conventional thinking, said Lei, who also has an appointment at the Rogel Cancer Center.

"Much emphasis has been placed on the immune cell types that are more adept at wound healing and tissue repair," he said. "However, here we show that immune cell types that are central to microbial control are strongly correlated with superior clinical outcomes.

"Surgical management can reduce bacterial burdens across all patients, however, only the patients with more immune cell subtypes for bacterial control can suppress the recolonization of pathogenic bacteria and show better regenerative outcomes."

Dental implant-supported crowns offer esthetic, functional and natural-feeling tooth replacements, and the market is estimated to reach $6.8 billion by 2024. Dental implants have transformed reconstructive options, but the emerging endemic of peri-implantitis has severely compromised the long-term success of implant dentistry, the researchers said.

Peri-implantitis can lead to progressive bone loss, bleeding, pus and eventual loss of the dental implants and associated crowns or dentures that they support. Replacement of a new dental implant at the previously damaged site is often challenging because of poor bone quality and delayed healing. Preventive implant maintenance and long-term management of peri-implantitis becomes part of the routine practice after implant reconstruction.

"Regenerative therapy for peri-implantitis is expensive and treatment outcomes are unpredictable," said first author Jeff Wang, U-M clinical assistant professor and principal investigator for the regenerative treatment of peri-implantitis clinical trial. "It would be very helpful if we could use the information to determine the best course of treatment, or maybe we'd decide that the more sensible option would be to replace an old implant with a new one, despite the challenge to rebuild the bone."

In the future, it may be possible to predict the risk of peri-implantitis before a dental implant is placed, he said. More human clinical trials are required before FARDEEP is ready to be used widely by clinicians.

"However, this proof-of-concept study offers a personalized approach to identify the types of patients that better respond to regenerative therapies," said co-author William Giannobile, a professor of oral medicine, infection and immunity, and dean of the Harvard School of Dental Medicine. Previously, Giannobile was at the U-M School of Dentistry.

Sources of SARS-CoV-2 and other microorganisms in dental aerosols

 

INTERNATIONAL & AMERICAN ASSOCIATIONS FOR DENTAL RESEARCH

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Alexandria, Va., USA -- COVID-19 was declared a global pandemic in March 2020 and given an incomplete understanding of the transmission of SARS-CoV-2 at that time, the American Dental Association recommended that dental offices refrain from providing non-emergency services. As a result, 198,000 dentists in the United States closed their doors to patients. The study "Sources of SARS-CoV-2 and Other Microorganisms in Dental Aerosols," published in the Journal of Dental Research (JDR), sought to inform infection-control science by identifying the source of bacteria and viruses in aerosol generating dental procedures.

Researchers at The Ohio State University College of Dentistry, Division of Periodontology, Columbus, USA, tracked the origins of microbiota in aerosols generated during treatment of 28 patients undergoing ultrasonic scaling, implant osteotomy or restorative procedures by combining reverse transcriptase qPCR, to identify and quantify SARS-CoV-2, and 16S sequencing, to characterize the entire microbiome, with fine-scale enumeration and source-tracking. Thirty minutes following the procedure, condensate was collected from the operator and assistant's face shield, the patient's chest and an area 6-feet distant from the site of operation.

The results show that it is possible to trace the source of contamination through DNA microbiome analysis and that the major source of microbes in aerosols came from the dental irrigant. Saliva did not significantly contribute as infection control measures such as pre-operative mouthrinses and intra-oral high-volume evacuation were used. The authors conclude that the risk for transmission of SARS-CoV-2 and other respiratory pathogens from aerosolized saliva in dental operatories is moderately low and that current infection control practices are adequately robust to protect personnel and patients alike.

"Understanding the sources of microbial load in aerosols is important, not only for infection control in dental operatories during the COVID pandemic, but also to inform best practices in aerosol reduction, mitigation and abatement in the long term." said JDR Editor-in-Chief Nicholas Jakubovics, Newcastle University, England. "While further studies are needed with larger sample sizes, this study sets the stage for future work on risk of microbial transmission in oral health care settings."

Study examines connection between oral and general health in patients with diabetes

AMERICAN ACADEMY OF FAMILY PHYSICIANS

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Individuals with diabetes are at greater risk of developing oral health issues, like gum disease, yet care for these linked health issues are usually disconnected, split between primary care and dental care. A research team from the University of Amsterdam developed an intervention that provided primary care-based oral health information and dental referrals for patients with diabetes. In a cluster randomized controlled trial, 764 patients from 24 primary care practices received either the oral health support or standard primary care. Participants were asked to rate their oral health quality of life, as well as their general health and any oral health complaints, at the start and end of the study. Analysis showed that individuals who received the primary care-based oral health support intervention had a significant increase in their self-reported oral health quality of life when compared with the control group. The authors conclude that, "patients with type 2 diabetes who attend primary diabetes care can benefit from extra attention to oral health." They add, "It also further reflects the concept of oral health and general health being connected."