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Researchers from the University of Illinois at Chicago College of Dentistry have recently discovered a novel means of mitigating aerosol generation in order to lower the risk of SARS-CoV-2 transmission among patients and staff in dental clinics. (Image: Alexander Limbach/Shutterstock)

SARS-CoV-2 as invisible threat: Mitigating aerosols in dental clinics

By Dental Tribune International
September 17, 2020

CHICAGO, U.S.: In the face of the COVID-19 pandemic, dentists have been provided with strict infection prevention and control guidelines. These include ensuring the appropriate amount of personal protective equipment, reviewing sterilization and disinfection protocols, and allowing a fallow period between dental visits. However, since the aforementioned measures do not completely protect staff and patients from the inhalation of aerosols in dental settings, researchers from the University of Illinois at Chicago College of Dentistry (UIC Dentistry) have engineered a novel method for aerosol mitigation that could be implemented in dental clinics worldwide.

“For years, we have been vigilant about infection control, and the COVID pandemic has focused a lens on the issues,” Dr. Clark Stanford, dean of UIC Dentistry and UIC distinguished professor of restorative dentistry told UIC Today.

“COVID is a wake-up call, and there could be something else down the road”
— Dr. Clark Stanford, UIC Dentistry

“With billions of viruses in the world, we have been pretty lucky. COVID is a wake-up call, and there could be something else down the road,” he continued.

Owing to the vast size of UIC Dentistry, the risk of infection poses an even greater risk to its staff and patients compared with other, smaller dental settings. Dr. Lyndon F. Cooper, associate dean for research and head of oral biology at UIC Dentistry, explained that, since patients may present as asymptomatic or pre-symptomatic and aerosols are not visible to the naked eye, dental staff often become less vigilant. “In an open dental setting, such as a dental school or a dental practice with multiple chairs, you’re confronted with an invisible threat that has to be contained. And that really puts this in the sphere of the unknown,” he commented.

To increase safety and minimize recirculation of air in the dental school, facility managers and consultants at the school reviewed the heating, ventilation and air conditioning system and air quality and added HEPA filtration and bipolar ionization technology. Additionally, the school turned to various experts from the UIC College of Engineering for advice on how to reduce airborne transmission and to minimize droplet spread.

The Cavitron scaler adjacent to a dental mannequin. (Image: Plog et al., Physics of Fluids, Vol. 32, Issue 8, 10.1063/5.0021476, 2020)

The engineering team is currently studying how aerosols are dispersed from dental instruments, such as a vibrating tool called a Cavitron. “There is potential for spreading of COVID-19 in dental offices and clinics when the spray generated by this device strikes a tooth or other tissue in the mouth, picks up some saliva, and is released out of the mouth cavity with the breath. My lab is using high-speed imaging and optical tools to observe the shedding of droplets from the Cavitron tip in terms of their size and concentration in space,” said Dr. Constantine M. Megaridis, a UIC distinguished professor in the Department of Mechanical and Industrial Engineering (MIE).

Reducing viral load in dental clinics by suppressing droplet formation

The research team employed some state-of-the-art experimental techniques to track, measure and examine droplet velocities and the distance they are spread. With the help of shadowgraph techniques, they were able to easily define the distribution of both the coarse and fine droplets that emanated from various dental instruments, which helped to predict the viral load in the clinic. Since increasing evidence suggests that SARS-CoV-2 is airborne, some researchers also examined particles that are below 1 µm in size, the so-called ultrafine aerosols, since their diminutive size makes them a major source of transmission in the dental setting.

“Our work bridges the engineering data generated by the simulations and the published data on viral load in order to create a heat map for the room, thus enabling the dentists to evaluate the risk in different locations inside the clinic,” said MIE department Head Prof. Farzad Mashayek. He added that the approach could also be used to create heat maps in other school areas as well as in different dental clinics.

“You can completely suppress the formation of sprays using a diluted aqueous polymer solution”

— Dr. Alexander L. Yarin, UIC

Besides aiming at gaining a better understanding of droplet formation and spread, the researchers were seeking ways to mitigate the risk of aerosol generation. Dental Tribune International has previously reported on a study that proposed adding povidone-iodine to the water bottle that is attached to the dental unit to minimize the spread of the virus.

Similarly, after identifying several polymer solutions approved by the U.S. Food and Drug Administration that could replace the water in the Cavitron and dental drill, the researchers in the present study discovered that these fluids inhibited the formation and detachment of spray droplets in both devices.

“What I proposed and demonstrated is that you can completely suppress the formation of sprays using a diluted aqueous polymer solution,” said Dr. Alexander L. Yarin, a UIC distinguished professor in MIE. “Essentially, I can take over-the-counter materials and use them in this operation without any droplets being formed,” he explained.

Yarin noted that the method is unique in that no one has ever used polymer for mitigating the spread of droplets and aerosol before. Additionally, he explained that the approach can be quickly implemented, is cost-effective and does not require any changes to the devices.

The UIC is currently filing a patent for the novel technology and working with various companies to fully implement the process in the dental school.

The study, titled “Reopening dentistry after COVID-19: Complete suppression of aerosolization in dental procedures by viscoelastic Medusa Gorgo,” was published online on Aug. 25, 2020, in Physics of Fluids.

Editorial note: This news is based on an article by David Staudacher, which was published on Aug. 10, 2020 on the UIC today website.

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