Evaluating splatter and settled aerosol during orthodontic debonding: implications for the COVID-19 pandemic

Llandro, Hayley; Allison, James R.; Currie, Charlotte C; Edwards, D. G.; Bowes, Charlotte; Durham, Justin; Jakubovics, Nicholas S.; Rostami, Nadia; Holliday, Richard

doi:10.1038/s41415-020-2503-9

Cited by 23 publications

(44 citation statements)

References 34 publications

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“…The results were similar for the 3-in-1 air/ air + water and surgical drilling, where patient size distributions again matched the phantom head control data. For orthodontic debonding, during use of both the high and slow speed drills, very high numbers of aerosol particles were detected, supporting recent settling plate (Llandro et al 2021) and optical particle sizer studies (Din et al 2020). In our study, there were additional, unaccounted for modes in these aerosol size distributions, suggesting aerosol was possibly generated from within the oral cavity and not just from the instrument source.…”

Section: Discussionsupporting

confidence: 87%

A clinical observational analysis of aerosol emissions from dental procedures

Dudding

Sheikh

Gregson

et al. 2021

Preprint

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There remains uncertainty as to which dental procedures constitute aerosol generating procedures. We aimed to quantify aerosol concentration produced during different dental procedures. Where aerosol was detected, we assessed whether the aerosol size distribution from patient procedures was explained by the non-salivary contaminated instrument source, using phantom head controls. This study obtained ethical approval within the AERATOR grant. Patients were recruited consecutively, and written consent was obtained. Both an optical and an aerodynamic particle sizer were used to measure aerosol, attached to a 3D-printed polylactide funnel 22cm from the patients face. A range of periodontal, oral surgery and orthodontic procedures were captured using time-stamped protocols. High-fidelity phantom head control experiments for each procedure were performed, under the same conditions. Aerosol was measured for each procedure. Where aerosol was detected, phantom head control and patient procedure aerosol size distributions were compared, with the assumption that if the distributions were the same, aerosol detected from the patient could be explained by the instrument source. 41 patients underwent fifteen different dental procedures. For nine procedures, no aerosol was detected. 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. High and slow speed drilling produced aerosol from patient procedures which appear to have different size distributions from a phantom head control and so may pose a greater risk of (potentially infected) salivary contamination. Ultrasonic scaling does not appear to generate additional aerosol above that of the instrument itself and therefore does not increase the risk to dental teams, relative to the risk from being in close proximity to the patient.

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Section: Discussionsupporting

confidence: 87%

A clinical observational analysis of aerosol emissions from dental procedures

Dudding

Sheikh

Gregson

et al. 2021

Preprint

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“…Various methodologies for determining aerosolization in dental environments have been implemented, including air particle measurement ( Din et al 2020 ; Allison et al 2021 ), biological air sampling ( Bennett et al 2000 ; Dutil et al 2009 ), culture of settle plates ( Timmerman et al 2004 ; Rautemaa et al 2006 ; Holloman et al 2015 ), and detection of fluorescent markers ( Allison et al 2021 ; Holliday et al 2021 ; Llandro et al 2021 ). However, each has limitations.…”

Section: Introductionmentioning

confidence: 99%

Dental Mitigation Strategies to Reduce Aerosolization of SARS-CoV-2

et al. 2021

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Limiting infection transmission is central to the safety of all in dentistry, particularly during the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Aerosol-generating procedures (AGPs) are crucial to the practice of dentistry; it is imperative to understand the inherent risks of viral dispersion associated with AGPs and the efficacy of available mitigation strategies. In a dental surgery setting, crown preparation and root canal access procedures were performed with an air turbine or high-speed contra-angle handpiece (HSCAH), with mitigation via rubber dam or high-volume aspiration and a no-mitigation control. A phantom head was used with a 1.5-mL min−1 flow of artificial saliva infected with Φ6-bacteriophage (a surrogate virus for SARS-CoV-2) at ~108 plaque-forming units mL−1, reflecting the upper limits of reported salivary SARS-CoV-2 levels. Bioaerosol dispersal was measured using agar settle plates lawned with the Φ6-bacteriophage host, Pseudomonas syringae. Viral air concentrations were assessed using MicroBio MB2 air sampling and particle quantities using Kanomax 3889 GEOα counters. Compared to an air turbine, the HSCAH reduced settled bioaerosols by 99.72%, 100.00%, and 100.00% for no mitigation, aspiration, and rubber dam, respectively. Bacteriophage concentrations in the air were reduced by 99.98%, 100.00%, and 100.00% with the same mitigations. Use of the HSCAH with high-volume aspiration resulted in no detectable bacteriophage, both on nonsplatter settle plates and in air samples taken 6 to 10 min postprocedure. To our knowledge, this study is the first to report the aerosolization in a dental clinic of active virus as a marker for risk determination. While this model represents a worst-case scenario for possible SARS-CoV-2 dispersal, these data showed that the use of HSCAHs can vastly reduce the risk of viral aerosolization and therefore remove the need for clinic fallow time. Furthermore, our findings indicate that the use of particle analysis alone cannot provide sufficient insight to understand bioaerosol infection risk.

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“…Besides, the proportion of liquid droplets dehydration depended on the ratio of nonvolatile substances in saliva. Traditionally, the high normal stimulated salivary flow was about

( Llandro et al., 2020 ). The pure saliva contained 99.5% water, and the weight fraction of nonvolatile substances was within the range of 1 to 5% ( Stadnytskyi et al., 2020 ).…”

Section: Results and Analysismentioning

confidence: 99%

Restoration of dental services after COVID-19: The fallow time determination with laser light scattering

Mak

Wai

et al. 2021

Sustainable Cities and Society

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In time, dental health care has slowly expanded beyond emergency treatment to treat oral diseases. How to reduce the cross-transmission risk in dental surgery has raised much more attention. Considering the lack of consistency of fallow time (FT) in its necessity and duration, the highly sensitive laser light scattering method has been proposed to visualize the airborne lifetime and decay rate of suspended particles in the dental surgery environment. The FT is defined as when the number of suspended particles drops to the level that the next patient can safely enter after the aerosol-generating procedures (AGPs). The ultrasonic scaling was performed in the mock-up experimental dental clinic with 6 air changes per hour (ACH), and the instantaneous moments of the droplets were recorded by a high-speed camera. Without any mitigation measures, the estimated FT in the single dental surgery environment with 6 ACH was in the range of 27–35 min, significantly affecting the number of daily dental services. Despite the cooperation of high-volume evacuation (HVE [IO]) cannot eliminate the FT to zero minutes, the equipment could reduce the required FT by 3–11 min for the suspended particles reducing the baseline levels. Owing to the longer airborne lifetime of suspended particles, the relevant protection equipment, especially respiratory protection, is quite essential in dental surgery. The obtained results of this study will provide evidence to establish the revised FT in dental surgery guidelines and protect the health and wellbeing of urban dwellers.

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Evaluating splatter and settled aerosol during orthodontic debonding: implications for the COVID-19 pandemic

Cited by 23 publications

References 34 publications

A clinical observational analysis of aerosol emissions from dental procedures

A clinical observational analysis of aerosol emissions from dental procedures

Dental Mitigation Strategies to Reduce Aerosolization of SARS-CoV-2

Restoration of dental services after COVID-19: The fallow time determination with laser light scattering

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