SARS-CoV-2: characterisation and mitigation of risks associated with aerosol generating procedures in dental practices. Br Dent J 2021; 230: https://doi.org/10.1038/s41415-020-2504-8.
Of all the new phrases that were adopted into the COVID-19 lexicon during 2020, 'fallow time' does characterise the unproductive frustration felt by many. Therefore, further research that can inform an evidence base to safely reduce fallow time and maximise productivity would be a welcome good news story.
To assess the best strategies to reduce potentially pathogen-carrying droplets that are aerosolised during dental procedures requires a degree of ingenuity and some fancy technology. The methodology in this paper involves some flexible tubes sucking air from around the dental surgery during a 'representative' aerosol generating procedure (AGP) and, in turn, funnelling the air into a 'high resolution electrical low-pressure impactor particle sizer'. It is made in Finland and is the type of technology used in car exhaust testing; it gives real-time measurements of particle number, size and concentration. The authors then compared various interventions against a control group of low-volume intraoral suction alone.
Using the proxy of the known diameter of an infectious coronavirus particle (0.05-0.15μm) as one of a range of measurements, the experiment assesses the effectiveness of various combinations of suction and an air cleaning system (ACS). The study showed that aerosol-management interventions substantially reduce, but do not eliminate, these particles during the AGP. The authors make it clear that none of these interventions are attempting to replace strict PPE protocols for practitioners during the procedure.
The ACS in this case was a high-pressure air purifier that increases in-surgery air changes per hour to 24. The key being not just the increased filtration, but an electrostatic plasma function that can eliminate smaller particles that evade a filter, such as virus particles.
After some number crunching, the combination of intraoral low-volume and high-volume suction, and an ACS are suggested to reduce fallow time below ten minutes, even eliminate it altogether. Interestingly, that addition of high-volume extraoral suction might not be helpful.
Limitations, as set out by the authors of the study, are the use of a phantom head which may not be an exact replacement for a living, salivating, spluttering patient. The specifics of the environment need to be considered as well; in this case an average-sized dental surgery is probably comparable to most clinical environments, with the exception of open-plan clinics in a dental hospital.
All of this hints at an end to fallow time, which would be a breath of fresh air.
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McCarthy, S. A breath of fresh air. Br Dent J 230, 305 (2021). https://doi.org/10.1038/s41415-021-2813-6