Jayson Cook explains how you can reduce the Covid-19 aerosol transmission risk and cut fallow time.
As new data that informs infection control measures around coronavirus emerges, industry leaders are looking for safe ways to decrease fallow time after high risk aerosol generating procedures (AGPs).
Although our knowledge of the infectivity of aerosols generated through dental treatment is still evolving, accumulating data shows the virus that causes Covid-19 is transmitted by both small and large particle aerosols.
The World Health Organisation publicly recognised airborne transmission in July, and the U.S. Centers for Disease Control and Prevention updated its guidelines in early October to say that coronavirus can spread from airborne transmission over a distance greater than six feet via aerosols that can remain in the air for minutes – or even hours.
So, what can be done to prevent the airborne transmission of coronavirus in healthcare environments, and justifiably reduce fallow periods after high risk AGPs? One answer lies in an as yet largely unregulated industry: air purification.
Recommended ventilation methods
You’ll be familiar with the CGDent/FGDP Covid-19 guidelines for the safe management of general dental practice, last revised on October 2, 2020 (at the time of writing), which state that procedural and environmental mitigation is key in reducing the fallow time, with air ventilation seen as a critical element in reducing risk.
These mitigations can either act to reduce the production of the aerosol or work to remove or dilute the bioaerosol. Procedural mitigation includes use of rubber dam and high-volume aspiration, while environmental mitigation may include air ventilation or air cleaners, according to the guidelines.
The October version states, “Until very recently, air ventilation within dental surgeries has perhaps not had the focus which it deserved, but this is likely to change with the impending publication of a revised version of HTM 03-01 in late 2020.”
Air cleaning systems using HEPA filtration are now recommended in the guidelines but concerns over their efficiency are mentioned. Such hesitation in officially recommending air purifiers is, in our view, justified.
A HEPA filter is a type of mechanical air filter that traps harmful particles but, unfortunately, it is not a standardised term and even low quality air purifiers can use it, despite the fact that they may not even be able to achieve a 50 per cent removal efficiency of fine airborne particles in real-life situations.
Proper regulation of the air filtration market is long overdue and is now urgent.
Those currently researching the market are generally advised to look for high-quality air filtration units that are individually tested, certified, and have a guaranteed filtration efficiency of 99.95 per cent at a particle size of 0.3 microns, the HEPA test standard. But 90 per cent of airborne particles (including coronavirus) are smaller than this.
The very best air filtration products can also trap what is called ‘most penetrating particle size’ (MPPS) of less than 0.01 microns and are classified according to the world’s most stringent HEPA filter test – EN1822 – to prove it. So, especially in healthcare settings, it’s advisable to look for that European classification.
While the quality of air filtration products varies considerably, one unit’s effectiveness in removing viruses from the air has just been officially confirmed by the European accredited research and testing institute Airmid Healthgroup in Ireland.
The study, carried out in June 2020 on the IQAir Cleanroom 250 in a test chamber of nearly 30 cubic metres, found it reduced airborne viruses by more than 99.9 per cent in less than 10 minutes on the highest speed setting. The virus used in the test was Influenza A (H1N1) which is in the same size range as SARS-Cov-2.
This study is potentially game-changing for dental practices. It follows that the use of high-performance air purifiers is adopted to minimise viral pollution and protect both medical personnel and patients from exposure, when used alongside other effective infection control measures.
Case study
Implant and restorative dental surgeon Jason Burns is the clinical director of Whitehouse Dental Clinic in Richmond, Surrey. The practice reopened to patients in early June, having followed guidelines issued by Public Health England, the CQC and the chief dental officer.
But, determined to make their workplace as safe as possible for patients and staff, Jason and his colleagues also looked to countries that appeared to be “ahead of the curve”. It was when they researched how South Korea had dealt with past pandemics that the idea of using air filtration first cropped up.
He said, “It seemed logical that if you could actually change the air in the room frequently enough then it would be incredibly helpful alongside the standard protocols in keeping cross-infection to an absolute minimum.”
Jason was also concerned that the initial response – not just in dentistry but nationwide – was so heavily focused on contact transmission: wash your hands and sanitise surfaces. He adds, “That has changed as now we know airborne transmission is as important as contact, but there has still been too little thought given to how we deal with it.”
Jason and his colleagues set about researching the air filtration market, taking apart machines to examine their HEPA filters, which trap fine particles in the air, and using a device that samples air going in and out of the machines.
He recalled, “We found a large number of players who were trying to muscle in on the market, but their technology just didn’t work. Eventually we picked the IQAir Cleanroom 250 because it was the only one we found that returned zero particles in the air after passing through the unit. The rest were leaking.” He also bought an IQAir FlexVac which allows dentists to position a suction duct close to the patient’s mouth.
Jason said, “It’s all been pretty easy to set up. It doesn’t produce any heat or cool air, just a box with a small footprint that you plug in at the foot of the chair. We went for the FlexVac as well, so instead of the room being hoovered up and changed, that really directs the source of the air intake where we work which makes sure we get maximum withdrawal of air around the patient.”
He added, “It puts me at ease, knowing that I am safe, and my staff are safe. Irrespective of the virus, I wish I had got one of these years ago.”
References available upon request.