LAUSR

BACKGROUND Wearing masks has become an essential safety measure during the coronavirus 2019 (COVID-19) pandemic. Especially clinicians in dental clinics should focus on infection control. However, there is currently no data regarding the frequency of replacement of the masks used in hospitals. Hence, it is necessary for dental clinic staff, who deal with many patients in an aerosol-producing environment, to have precise mask-wearing guidelines. OBJECTIVES The aim of this study was to evaluate the contamination on the inner surface of the masks used by clinicians in dental clinics and provide basic data to describe hospital infection control guidelines in greater detail. MATERIAL AND METHODS For Study I,12 participants were recruited. The experiment was conducted indoors. After wearing the mask, the temperature and the humidity inside the mask were measured at the set time points (immediately after wearing the mask, and 10 min, 30 min, 1 h, 2 h, and 4 h after wearing the mask). During the experiment, talking was not allowed. For Study II, 23 clinicians from dental clinics were recruited. After wearing the mask, the temperature, the humidity and the number of colony-forming units (CFU) inside the mask were measured at the set time points. Finally, 15 samples were selected for the study based on a survey. Bacterial identification was conducted using the 16S rDNA sequencing. RESULTS The temperature and the humidity inside the mask increased significantly relative to room temperature and room humidity, respectively. Bacteria were found in all the masks worn for more than 10 min and the CFU values increased with the mask-wearing time. Bacteria belonging to the genera Staphylococcus, Bacillus and Roseomonas were detected in the used mask. CONCLUSIONS A mask should not be worn for more than 2 h; however, the frequency of mask replacement can vary, depending on the number of patients encountered and the working environment.