Li Xiujie, Mak Cheuk Ming, Ma Kuen Wai, Wong Hai Ming
Department of Building Services Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China.
Faculty of Dentistry, The University of Hong Kong, Pok Fu Lam, Hong Kong Island, Hong Kong, China.
Phys Fluids (1994). 2021 Apr;33(4):047111. doi: 10.1063/5.0048848. Epub 2021 Apr 21.
In the setting of widespread severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) community transmission, reducing the exposure risk on dental professionals and the next patients is the key to reopening dental services in this pandemic environment. The study is motivated by the lack of understanding of the flow-field characteristics and droplet distribution during aerosol-generating procedures. The particle image velocimetry measurements with high temporal and spatial resolutions were performed under ultrasonic scaling in the mockup experimental dental clinic. Compared with other methods focusing on the settled droplet particles, the study focused on the visualization of suspended droplets. From the results of the velocity vector and trajectory map, the high-level contaminated area will be within 1 m from the oral cavity. The vortex structures were identified by the vorticity index. In the surface near the patient's head, a counterclockwise vortex would carry some droplets and contaminate this region. The small droplets circulated in the turbulence cloud and the droplet nuclei generated by dehydration are the two primary sources of suspended particles, which may cause airborne transmission in the dental clinic. About 65%-74% of the droplets in ultrasonic scaling were in the range of 50-180 . The research will provide references to the development of the precaution measures to reduce the SARS-CoV-2 exposure risk of dental professionals.
在严重急性呼吸综合征冠状病毒2（SARS-CoV-2）广泛社区传播的背景下，降低牙科专业人员及后续患者的暴露风险是在这种大流行环境中重新开放牙科服务的关键。该研究的动机是缺乏对气溶胶产生过程中流场特征和飞沫分布的了解。在模拟实验牙科诊所中，于超声洁牙操作下进行了具有高时空分辨率的粒子图像测速测量。与其他关注沉降飞沫颗粒的方法不同，该研究着重于悬浮飞沫的可视化。从速度矢量和轨迹图的结果来看，高污染区域将在距口腔1米范围内。通过涡度指数识别出了涡旋结构。在患者头部附近的表面，逆时针涡旋会携带一些飞沫并污染该区域。在湍流云中循环的小飞沫以及脱水产生的飞沫核是悬浮颗粒的两个主要来源，这可能导致牙科诊所内的空气传播。超声洁牙中约65%-74%的飞沫粒径在50-180 范围内。该研究将为制定降低牙科专业人员SARS-CoV-2暴露风险的预防措施提供参考。
