Graphic Simulation of SARS-CoV-2 Droplets: Why Respirators should be used in Dental Healthcare Settings?

Introduction: Knowledge about the morphological characteristics of facial masks/respirators and their relationship with the possibility of interaction with respiratory droplets in the COVID19 pandemic is fundamental in dental healthcare settings. Aim: This study evaluated interfibrillar gaps of cloth mask, surgical mask and Filtering Face Piece 2 respirator through Scanning Electron Microscopy (SEM) in order to perform a graphic simulation of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) respiratory droplets in the gaps among mask fibres. Materials and Methods: A fragment (1 cm(2)) of the cloth mask were used to perform a SEM analysis. The distance among fibres was determined by Energy Dispersive Spectrometry (EDS). Graphic simulation of droplets with different sizes (0.5 mu m; 5.7 mu m; 12 mu m) was performed by an image editing program (Adobe Illustrator). Results: The image analysis showed that average distance among the fibres was 67.91 mu m (cloth mask), 11.72 mu m (surgical mask), 11.97 mu m (respirator FFP2). Superimposition of masks layers resulted in no gaps between FFP2 fibres. Surgical mask exhibited openings between fibres in 1.43% of the studied total area. The cloth mask showed large gaps, in which it would be possible to transpose more than 680 million droplets (5.75 mu m). Conclusion: FFP2 respirator showed no spaces among fibres after superimposition of structural layers, which would promote the blockage of the graphic simulation of SARS-CoV-2 droplets.