Volume 7 • 2020 • Issue 4

Another challenge is cost. At the moment, a single point-of-care rapid test costs about $100 per test to conduct. I believe they will become more reliable and less expensive, but it will take more time. Q Which of our dental instruments will we be able to use? What about saliva ejectors, lasers, air water syringes? AB: There are two main things that you're trying to control with COVID-19: splatter (the big droplets) and aerosols (the very small droplets). Recommendations often say, “judicious use of slow speed with high volume evacuator (HVE) suction.” What they really mean is, “Let’s not go full gas.” Going slow greatly reduces the risk of splatter or aeorsol to negible levels. A saliva ejector does not control splatter or aerosols. Most of the new protocols call for the use of HVE. I think that as more research comes out, we will find that HVE is dentistry’s new best friend. In my work as a public health dentist, I’ve been wearing face shields since the 1990s. Once you start using a face shield, you're going to see splatter in a whole new light. In this new context, we are going to need to reimagine how we do almost everything to prevent splatter from getting on us and on surfaces in the operatory. It’s a lot of change, and on Day One it is going to be hard. But as we move forward, we will get better at it. Q Will electric handpieces be permitted at lower RPMs? AB: I think this question arises because at slow speeds, electric handpieces technically produce very small amount of aerosols. They do have the potential to generate a lot of splatter. Again, we are trying to minimize both aerosol and splatter. In a public health environment, we go slow on the electric handpiece by using a reduction gear, try not to generate splatter, use water or saline streams, and use high volume suction. This helps to reduce the risk. I don’t see us using prophy angles in the short term because they spin at much higher RPM and generate a whole lot of splatter. Q What is the settling time for aerosol droplets? And, what will the operatory turnover time be after aerosol generating procedures? AB: Unfortunately, this is a simple question with a very complicated answer. This is an area where, for dentistry in particular, we do not have definitive scientific knowledge or experience. The Centers for Disease Control and Prevention (CDC) looked at aerosols in the hospital setting, and has produced tables with recommended settling times based on ventilation. How long does it take for aerosol particles to settle in a room? The answer is a complicated equation based on ventilation, size of room, and many other factors. The Canadian military is doing preliminary testing related to aerosol generating procedures and what is required to manage them in the dental settings. They are considering the impact of high volume suction and other elements to control aerosols. Both the military and other researchers have been surprised by the results. Sometimes aerosols were much higher than expected. In other conditions, much lower. So what does that mean for settling time? Generally, the dental regulators consider worst case scenarios and therefore take a precautionary approach. Dalhousie University arrived at 207 minutes as part of it guidance for room resting. The Royal College of Dental Surgeons of Ontario (RCDSO) says dentists should consider 180 minutes, or three hours, for particles to settle in a room. What factors can be modified to shrink those numbers? In the room where I practise, we know our air changes per hour rate. With a greater number of air changes per hour, settling time is lower. But figuring out something like air changes per hour and how it affects aerosols in a specific space requires an HVAC expert. Recently, I was reminded of an important concept by a military dentist. To use good judgment, we need two things: experience and knowledge. And most of us are not ventilation experts. There will be a lot more information about this over time. As the military finishes its research, the government will fast-track the findings to be evaluated by external experts so that we can start using the data to inform how we practise dentistry. There are two main things that you're trying to control with COVID-19: splatter (the big droplets) and aerosols (the very small droplets). The views expressed are those of the author and do not necessarily reflect the opinions or official policies of the Canadian Dental Association. 15 Issue 4 | 2020 | CDA at W ork