Microscopic characterization of level 3 surgical masks in a simulation model of dental care: a preliminary study

This study evaluated the morphology of level 3 surgical masks before and after aerosols' passage using a simulation model of dental care with human breathing system to evaluate the aerosol filtering efficacy, as close as possible to the reality of a dental clinical setting.

Eight groups of level 3 surgical masks were selected. The model used for analysis consisted of a human head prototype, a respirator system (artificial trachea, pneumatic plunger, and spirometry syringe), and a dummy head with artificial dental arch. Masks were exposed to 5 min of aerosol generation and the number of specimens with aerosol passage and total areas of aerosol pigmentation were evaluated. The microscopic analysis of masks using optical microscopy, helium ion microscopy and scanning electron microscope were performed before and after aerosols' passage.

All groups presented aerosols passage (55-88%). The areas of aerosol passage revealed differences between groups (p < 0.05). In microscopy analysis, the inner and outer layers of masks showed a spunbond processing technique; the middle layer differed among groups of masks showing spunbond or meltblown processes, confirming what was reported by manufactures.

The inner and outer layers of masks are morphologically similar, different to the middle layer. All level 3 surgical masks presented high levels of aerosols passage.

This study highlights the need for more effective surgical masks in dental care settings. Understanding the morphological differences between mask layers can inform improvements in mask design for better protection for healthcare professionals.