Abstract
Aerosol generating procedures (AGPs) are defined as any procedure releasing airborne particles <5 μm in size from the respiratory tract. There remains uncertainty about which dental procedures constitute AGPs. We quantified the aerosol number concentration generated during a range of periodontal, oral surgery and orthodontic procedures using an aerodynamic particle sizer, which measures aerosol number concentrations and size distribution across the 0.5–20 μm diameter size range. Measurements were conducted in an environment with a sufficiently low background to detect a patient’s cough, enabling confident identification of aerosol. Phantom head control experiments for each procedure were performed under the same conditions as a comparison. Where aerosol was detected during a patient procedure, we assessed whether the size distribution could be explained by the non-salivary contaminated instrument source in the respective phantom head control procedure using a two-sided unpaired t-test (comparing the mode widths (log(σ)) and peak positions (DP,C)). The aerosol size distribution provided a robust fingerprint of aerosol emission from a source. 41 patients underwent fifteen different dental procedures. For nine procedures, no aerosol was detected above background. Where aerosol was detected, the percentage of procedure time that aerosol was observed above background ranged from 12.7% for ultrasonic scaling, to 42.9% for 3-in-1 air + water syringe. For ultrasonic scaling, 3-in-1 syringe use and surgical drilling, the aerosol size distribution matched the non-salivary contaminated instrument source, with no unexplained aerosol. High and slow speed drilling produced aerosol from patient procedures with different size distributions to those measured from the phantom head controls (mode widths log(σ)) and peaks (DP,C, p< 0.002) and, therefore, may pose a greater risk of salivary contamination. This study provides evidence for sources of aerosol generation during common dental procedures, enabling more informed evaluation of risk and appropriate mitigation strategies.
Highlights
Transmission of respiratory diseases, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative virus for the coronavirus disease 2019 (COVID-19), can occur through direct or indirect physical contact, droplet inhalation or airborne transmission [1]
Our background particle concentration was very low (0.18 cm-3) and of similar magnitude to that generated by a person speaking but less than that generated by a person coughing, enabling confident detection of aerosol produced during dental procedures
Of the six procedures that generated detectable aerosol, the size distributions observed in patients closely matched those observed in phantom head controls for four of them: ultrasonic scaling, 3-in-1 air/ air + water and surgical drilling
Summary
Transmission of respiratory diseases, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative virus for the coronavirus disease 2019 (COVID-19), can occur through direct or indirect physical contact, droplet inhalation or airborne transmission [1]. Aerosol generating procedures (AGPs) may result in respiratory disease transmission and are defined as any procedure that can result in the release of airborne particles
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