Best methods for dental aerosol evacuation
Dental aerosol evacuation or reduction is a major issue with the COVID-19 virus and dentists are buying up all kinds of filtration devices without any testing or knowledge of effectiveness.
Why is dental aerosol dangerous?
Dental aerosols are small droplets which remain suspended in air and consist of blood, saliva, tooth debris, dental plaque, calculus and restorative materials. An infected person will cover anyone working on them with dental aerosols that have the potential to infect those individuals. Although this is not likely to be the main method in which dental professionals can contract diseases from patients, it very possible. Prior to COVID, dental aerosol was not seen as a major risk to our profession and that may continue but right now, no one knows.
Differences between true large droplet transmission and airborne transmission
True aerosol transmission or airborne transmission require the disease agent to be transmissible in the 10 μm and under particles. 10 μm and under is the definition of aerosol. 20 μm and over are large droplets and have different properties, they only need surgical masks for PPE. This typically means that those droplets fall to the floor quickly but airflow issues make that complicated. The 10-20 μm particles are the gray area. Tellier 2019 BMC Infectious Diseases 50 μm particles are considered splatter in dentistry and are definitely not of a concern in regards to aerosols. Harrel JADA 2004
How long do aerosols stick around?
Complicated question because it depends. However, a true aerosol may be present in the air of the operatory for up to 30 minutes after a procedure. Hinds 1999
When do we produce aerosols in dentistry?
Dental handpieces, ultrasonic scalers and piezo units, air polishers and air abrasion units produce the most visible aerosols.
Are HEPA filters the answer right?
Yes, they are. Some will say that since the HEPA filter is rated for .3μm and viruses are around .1μm that means they will not work on viruses. Well that’s not true. The hardest particle size to capture is .3μm but both larger AND smaller are actually easier to catch. The rational is counter-intuitive but is easily understood once you read the attached article.
The problem with N95 masks
N95 filter more particles in the lab but when it comes to real life studies they repeatedly perform no better than surgical masks. Smith 2016 and Long 2020 Sometimes the N95 even perform worse! Loeb JAMA 2009 One can find lab studies that show surgical masks by themselves could prevent corona virus and influenza. Leung 2020 It is my opinion that the PPE is not the weak link and making it better isn’t helping. Stopping people from touching their face and increasing hand washing will help. The biggest thing we can do IMHO is to reduce the creation of aerosol or eliminate it quickly.
What are dental professionals using today to reduce our risk from aerosol?
Dentists currently use pre-procedural rinses, standard and cone modified high evacuation suction, rubber dams, and things such the Isolite to reduce aerosol. The rubber dam reduces nearly all the infectious aerosol. Additionally, simply using a high-volume evacuator reduces the contamination by more than 90%. JADA 2004Harrel However, none of these are 100% effective and we are unlikely to ever hit that number. We can lower the amount and lower our risks but there will never be a perfect solution. We are currently doing a very good job but there is always room for improvement, the question is at what cost. Fox 2010
What methods are there to reduced dental aerosol?
Will mainly discuss the new aerosol units that are popping up everywhere. There is a nice dt thread on the issue. It is my opinion a central exhaust or chair-side external exhaust unit would be best to eliminate the contaminated aerosol outside instead of trying to filter and kill the viruses and bacteria. Theoretically these units could actually make us more sick. These units increase the airflow which prevents droplets from falling to the floor. Furthermore, they can not filter out all of the virus and could possibly end up spreading the virus even further. Overall, I feel they significantly reduce the viral load in the air but that is not known.
Office HEPA units
Surgically clean air is the unit we have in our office. It does not get the aerosol directly and is more like a high level stand-alone HEPA filtration system you buy at the store.
Chair side dental aerosol evacuation units.
The VacStation looks similar to many “generic” units available. Another similar generic unit. The Vaniman looks very similar to the two units before this but you will be able to get more data and talk to someone from this company. It should be more trustworthy. Another unit that was not meant for dental but should work well.