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The novel coronavirus pandemic has resulted in an urgent need to study the risk of infection from aerosols generated during dental care and to conduct a review of infection controls. However, existing studies on aerosol particles related to dental treatment have mainly evaluated only the scattering range. Few studies have been conducted on the specifics of the generation of aerosol particles in clinical settings, their mechanisms and patterns of distribution throughout open or enclosed spaces, the duration that they remain suspended in air, and the amount and size of particles present. To minimize the influence of background particles, laser lights, a high-sensitivity camera, and particle counters were used in a large super clean laboratory to investigate the dynamics of aerosols generated during the operation of dental micromotors. The results indicate that aerosols tend to scatter upward immediately after generation and then gradually disperse into the surroundings. Most of the particles are less than 5 µm in size (only a few are larger), and all particles are widely distributed over the long term. Our research clearly elucidates that aerosols produced in dental care are distributed over a wide area and remain suspended for a considerable time in dental clinics before settling.

RationaleAerosol dispersion under various oxygen delivery modalities, including high flow nasal cannula, is a critical concern for healthcare workers who treat acute hypoxemic respiratory failure during the coronavirus disease 2019 pandemic. Effects of surgical masks on droplet and aerosol dispersion under oxygen delivery modalities are not yet clarified.ObjectivesTo visualize and quantify dispersion particles under various oxygen delivery modalities and examine the protective effect of surgical masks on particle dispersion.MethodsThree and five healthy men were enrolled for video recording and quantification of particles, respectively. Various oxygen delivery modalities including high flow nasal cannula were used in this study. Particle dispersions during rest breathing, speaking, and coughing were recorded and automatically counted in each condition and were evaluated with or without surgical masks.Measurements and Main ResultsCoughing led to the maximum amount and distance of particle dispersion, regardless of modalities. Droplet dispersion was not visually increased by oxygen delivery modalities compared to breathing at room air. With surgical masks over the nasal cannula or high-flow nasal cannula, droplet dispersion was barely visible. Oxygen modalities did not increase the particle dispersion counts regardless of breathing pattens. Wearing surgical masks significantly decreased particle dispersion in all modalities while speaking and coughing, regardless of particle sizes, and reduction rates were approximately 95 and 80-90 % for larger (> 5 μm) and smaller (> 0.5 μm) particles, respectively.ConclusionsSurgical mask over high flow nasal canula may be safely used for acute hypoxemic respiratory failure including coronavirus disease 2019 patients.Subject Category List4.13 Ventilation: Non-Invasive/Long-Term/Weaning*This article has an online data supplement, which is accessible from this issue’s table of content online at www.atsjournals.org.

This study aimed to assess the efficacy of a novel aerosol-exposure protection (AP) mask in preventing coronavirus disease in healthcare professionals during upper gastrointestinal endoscopy and to evaluate its clinical feasibility. Methods: In Study 1, three healthy volunteers volitionally coughed with and without the AP mask in a cleanroom. Microparticles were visualized and counted with a specific measurement system and compared with and without the AP mask. In Study 2, 30 patients underwent endoscopic resection with the AP mask covering the face, and the SpO2 was measured throughout the procedure. Results:In Study 1, the median number of microparticles in volunteers 1, 2, and 3 with and without the AP mask was 8.5 and 110.0, 7.0 and 51.5, and 8.0 and 95.0, respectively (p<0.01). Using the AP mask, microparticles were reduced by approximately 92%. The median distances of microparticle scattering without the AP mask were 60, 0, and 68 in volunteers 1, 2, and 3, respectively. In Study 2, the mean SpO2 was 96.3%, and desaturation occurred in three patients. Conclusion:The AP mask could provide protection from aerosol exposure and can be safely used for endoscopy in clinical practice.

There is an urgent need to examine the risk of infection from aerosols generated during dental treatment and to review infection control. However, existing research on aerosol particles associated with dental treatment is by no means sufficient, and little research has been done on the details of aerosol particle generation in the clinical environment, the mechanisms, and patterns of distribution in open and closed spaces, the time they are suspended in the air, the amount and size of particles present. Therefore, to minimize the influence of background particles, laser beams, a high-sensitivity camera, and a particle counter were used in a large super-clean laboratory (SCL) to investigate the dynamics of aerosols generated during dental micromotor operation. The large number of aerosol particles generated by the use of the micro-engine rose rapidly within 30 seconds and were suspended in the room atmosphere. Within a 100 cm radius of the user, the scattering