Abstract
The global outbreak of coronavirus disease 2019 (COVID-19) has raised concerns about the risk of airborne infection during dental treatment. Aerosol-generating dental procedures (AGDP) produce droplets and aerosols, but the details of the risks of COVID-19 transmission in AGDP are not well-understood. By discriminating between droplets and aerosols, we devised a method to measure particle size using laser diffraction analysis and evaluated aerosols generated from dental devices for providing a basis for proper infection control procedures. The droplets and aerosols generated from dental devices were characterized by multimodal properties and a wide range of droplet sizes, with the majority of droplets larger than 50 μm. AGDP emitted few aerosols smaller than 5 μm, which are of concern for pulmonary infections due to airborne transmission. In addition, the use of extraoral suction was found to prevent the spread of aerosols from high-speed dental engines. This study suggests that the risk of aerosol infections is considerably limited in regular dental practice and that current standard precautions, such as mainly focusing on protection against droplet and contact infections, are sufficient. While several cases of airborne transmission of COVID-19 in general clinics and emergency hospitals have been reported, cluster outbreaks in dental clinics have not yet been reported, which may indicate that AGDP does not pose a significant threat in contributing to the spread of SARS-CoV-2.
Highlights
The Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has occasioned a serious pandemic, radically changing the life of people
We found that droplets and aerosols from dental devices varied widely in size
In order to accurately and broadly measure the size of particles from dental devices regardless of the size of water droplet particles, we assembled an airborne aerosol measurement device that combines an acrylic cylinder with a laser diffraction particle size analyzer, by separating small aerosols from large droplet particles (Figure 1)
Summary
The Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has occasioned a serious pandemic, radically changing the life of people. According to a WHO report, the main transmission routes of SARS-CoV-2 are contact and droplet transmission, but the airborne transmission of virus particles can occur during aerosol-producing medical procedures in the hospital, especially in poorly ventilated indoor environments [3]. Droplet and airborne transmissions in dentistry were previously recognized in the 2003 outbreak which was a viral respiratory disease caused by a SARS-associated coronavirus [10], but the COVID-19 outbreak has reawakened the threat of aerosols [11, 12]. Droplet and aerosol size are significant in assessing the risk of droplet and airborne infections, and more studies on how and to what extent aerosols are produced from aerosol-generating dental procedures (AGDPs) are required to verify infectivity in confined areas [16]. The technique has been successfully used in studies to quantify the size of aerosols generated from coughs [20] and nasal sprays [21]
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