Dentistry in the time of COVID-19: The role of aerosols

27 Jan 2021

Woman wearing red shirt and mask sitting in scientific laboratory — Linsey Marr spoke to a worldwide audience of dental professionals earlier this month. “Where there are droplets, there are almost always aerosols that you did not detect,” she said.

Dental professionals worldwide tuned in to a recent presentation by Linsey Marr, aerosol scientist and Charles P. Lunsford Professor in Engineering at Virginia Tech, to hear her summary of studies on the role of aerosols as they relate to dentistry. Marr’s lecture was hosted by the Virginia Tech Carilion School of Medicine through a grant from Delta Dental of Virginia.

Marr’s research group applies interdisciplinary approaches to study pollutants in indoor and outdoor air. She is especially interested in emerging or nontraditional aerosols, such as influenza virus and other microorganisms, and how they are physically and chemically transformed in the environment.

Marr said while updated studies on the presence and transmission of aerosols during dental procedures are needed, many studies have found settled bacteria in droplets in dental offices, which is relevant.

“Airborne viruses are not naked,” Marr said. “Where there are droplets, there are almost always aerosols that you did not detect.”

Droplets are larger particles that are sprayed onto surfaces and then transmitted by touch. Aerosols, which are much smaller, are transmitted by inhalation. The size of the aerosol or droplet defines important measures such as how long it stays in the air, how far it can travel, how quickly it falls onto surfaces, where it deposits in the respiratory system (aerosols), and how efficiently it is removed by masks and filters.

Where do aerosols come from in dental offices? Marr cited mainly producing coolant water, saliva, and blood. She outlined some known aerosol-generating procedures in dentistry from studies dating back several years, which included use of wet and dry drills, air/water syringe, air polisher and air-driven high-speed handpiece. A study from last year showed many dental procedures produce aerosols, but the research was limited in the fact that it did not study the sources of the aerosols.

“More studies on the generation and transmission of aerosols during dental procedures are needed,” Marr said. “Updated studies can help us determine the best interventions for reducing the risk of transmission.”

Until then, Marr reviewed measures that should be used as standard practice at dental offices during the COVID-19 pandemic, which included:

Mask requirement for patients.
Mask and shield requirement for staff.
HEPA air filter in every exam room.
Stringent ventilation. A carbon dioxide sensor reading should be less than 800 parts per million. Dental offices can use one sensor and carry it around to different rooms. Marr carries her own sensor for indoor spaces. They can be found for sale on the internet with good ones starting at about $100.

“Try to get the first appointment of the day when the office has been empty, and there hasn’t been time for aerosols to build up in the air,” Marr said. “Also, there should be as little talking as possible during the appointment. Talking produces 10 times as many aerosols compared to just breathing.”

Since the COVID-19 pandemic, Marr’s research has been cited in The New York Times, The Washington Post, CNN, The Today Show, and hundreds of other media outlets worldwide.

If you missed the presentation, you can find a recording of it here.