Air Quality in a Dental Skills Lab during the SARS-CoV-2 Pandemic: Results of an Experimental Study

Objectives. The study aimed to analyze different ways to control air quality during/after aerosol-generating procedures (AGPs) in a small skills lab with restricted natural air ventilation in preclinical dental training (worst-case scenario for aerogen infection control). Different phases were investigated (AGP1: intraoral high-volume evacuation (HVE); AGP2: HVE plus an extraoral mobile scavenger (EOS)) and afterward (non-AGP1: air conditioning system (AC), non-AGP2: AC plus opened door). Methods. Continuous data collection was performed for PM1, PM2.5, and PM10 (mu g/m(3)), CO2 concentration (ppm), temperature (K), and humidity (h(-1)) during two summer days (AGP: n = 30; non-AGP: n = 30). While simulating our teaching routine, no base level for air parameters was defined. Therefore, the change in each parameter (delta = [post]-[pre] per hour) was calculated. Results. We found significant differences in delta PM2.5 and delta PM1 values (median (25/75th percentiles)) comparing AGP2 versus AGP1 (delta PM2.5: 1.6(0/4.9)/-3.5(-10.0/-1.1), p=0.003; delta PM1: 1.6(0.6/2.2)/-2.2(-9.3/-0.5), p=0.001). Between both non-AGPs, there were no significant differences in all the parameters that were measured. delta CO2 increased in all AGP phases (AGP1/AGP2: 979.0(625.7/1126.9)/549.9(4.0/788.8)), while during non-AGP phases, values decreased (non-AGP1/non-AGP2: -447.3(-1122.3/641.2)/-896.6(-1307.3/-510.8)). delta Temperature findings were similar (AGP1/AGP2: 12.5(7.8/17.0)/9.3(1.8/15.3) versus non-AGP1/non-AGP2: -13.1(-18.7/0)/-14.7(-16.8/-6.8); p <= 0.003)), while for delta humidity, no significant difference (p > 0.05) was found. Conclusions. Within the limitations of the study, the combination of HVE and EOS was similarly effective in controlling aerosol emissions of particles between one and ten micrometers in skill labs during AGPs versus that during non-AGPs. After AGPs, air exchange with the AC should be complemented by open doors for better air quality if natural ventilation through open windows is restricted.