SARS-CoV-2: characterisation and mitigation of risks associated with aerosol generating procedures in dental practices

Abstract

Introduction The objectives were to characterise the particle size distribution of aerosols generated by standard dental aerosol generating procedures (AGPs) and to assess the impact of aerosol-management interventions on 'fallow time'. Interventions included combinations of high-volume intraoral suction (HVS[IO]), high-volume extraoral suction (HVS[EO]) and an air cleaning system (ACS).Method A sequence of six AGPs were performed on a phantom head. Real-time aerosol measurements (particle size range 0.0062-9.6 μm) were acquired from six locations within a typical dental treatment room (35 m³).Results The majority (>99%) of AGP particles were <0.3 μm diameter and remained at elevated levels around the dental team during the AGPs. With no active aerosol-management interventions, AGP particles were estimated to remain above the baseline range for up to 30 minutes from the end of the sequence of procedures.Conclusions The results emphasise the importance of personal protection equipment, particularly respiratory protection. Use of HVS(IO), either alone or in combination with the ACS, reduced particle concentrations to baseline levels on completion of AGPs. These data indicate potential to eliminate fallow time. The study was performed using a phantom head so confirmatory studies with patients are required.

Fig. 1

Layout and sampling positions within the dental treatment room. Note that the tube at location 6 was moved from the ceiling light fitting to be visible in the photograph. X axis (room width) Y axis (room length) Z axis (room height)

Fig. 2

Outline study design. After an initial baseline period (three minutes), six AGPs (I to VI) were performed in series (18 minutes) followed by a period to quantify aerosol decay kinetics (15 minutes). Air samples from each location (1-6) were acquired over a 30-second period. The total duration of each experiment was 36 minutes

Fig. 3

Temporal, spatial and size characterisation of particles generated during AGPs (measured by HR-ELPI) for each location (1-6; Table 1) and intervention group (A-E; Table 2). Acquisition of air samples were performed during the baseline period (0-3 minutes), during the six procedures (3-21 minutes) and following cessation of procedures (21-36 minutes). Each data point represents the median particle concentration per size bin (# cm^-3) derived from n = 3 replicates. The dotted lines indicate the lower reported size for a SARS-CoV-2 virus particle (50 nm diameter)

Fig. 4

Total particle concentration generated during AGPs in the absence of interventions (group A; Table 2) at each air sampling location (1-6; Table 1). Acquisition of air samples were performed during the baseline period (0-3 minutes), during the six procedures (3-21 minutes) and following cessation of procedures (21-36 minutes). Dotted lines indicate the upper and lower boundaries of the baseline data. Each data point represents the sum of particles measured by HR-ELPI over one second during each replicate (n = 3)

Fig. 5

Total particle concentration generated during AGPs in the presence of HVS(IO), HVS(EO) and ACS (group E; Table 2) at each air sampling location (1-6; Table 1). Acquisition of air samples were performed during the baseline period (0-3 minutes), during the six procedures (3-21 minutes) and following cessation of procedures (21-36 minutes). Dotted lines indicate the upper and lower boundaries of the baseline data. Each data point represents the sum of particles measured by HR-ELPI over one second during each replicate (n = 3)

Fig. 6

Total dose of particles measured over the 36-minute experimental period (expressed as area under curve) for each location (1-6; Table 1) and intervention group (A-E; Table 2). Each data point represents the median ± minimum/maximum of n = 3 replicates