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Inside Dentistry
January 2021
Volume 17, Issue 1

Dawn of a New Day

Jennifer Vishnevsky

The COVID-19 pandemic has brought infection control to the forefront for the entire world; however, preventing the spread of infectious disease has been a point of emphasis in the dental office long before the current crisis. Although SARS-CoV-2 is a new virus, the profession of dentistry had previously established stringent protocols to mitigate the spread of infection in response to other diseases, such as hepatitis B, hepatitis C, tuberculosis, and HIV. "The basic principles of infection control haven't changed in 100 years," says John Molinari, PhD, professor emeritus, University of Detroit Mercy School of Dentistry. "The Occupational Safety and Health Administration (OSHA) placed dentists, hygienists, and assistants in the high- to very high-risk categories for COVID-19 because of their frequent use of aerosol-generating procedures when treating patients. Before COVID-19, dental infection control recommendations included contact- and droplet-based transmission precautions as important second-tier preventive measures to augment our standard precautions. Then the pandemic hit, and we now have a respiratory infection that can be transmitted by both droplets and smaller airborne particles called aerosols. Dental offices were closed down because we still didn't know much about the virus. It required a reevaluation of what measures needed to be added to control both the droplets and aerosols generated during dental procedures. I think this has been done, and dentistry continues to work to respond appropriately."

Comprehensive Surface Disinfection

The highly contagious nature of COVID-19 has highlighted the importance of sterilizing the entire office-from the surfaces to the air-rather than focusing only on the sterilization of instruments that directly contact patients.

According to the American Dental Association (ADA) and the US Centers for Disease Control and Prevention (CDC), protocols and procedures for infection control in the dental industry are well-established and documented. "What we do works," says Ken Tilashalski, DMD, associate dean at the University of Alabama at Birmingham School of Dentistry. "Early on during this pandemic, there was a lot of discussion not just about aerosols, but about fomite transmission from surfaces. That seems to have been downplayed some. What we've been doing in the office works as long as we're doing it properly and training staff to make sure that they're doing it properly. You've got to read the instructions for use from each product's manufacturer because kill times vary."

However, as with other national health emergencies, the research on COVID-19 is ever changing. In dentistry, conventional cleaning and disinfection have always been used, but their effectiveness can be limited by several factors, particularly the choice of products and the cleaning procedures adopted.1 Regarding the types of disinfectant products to use and for how long, the research is solid. The products listed by CDC and ADA have proven to be effective. "There are still emerging pathogens," says Mary A. Bartlett, president of SafeLink Consulting Inc. "We'll be seeing more testing by the US Environmental Protection Agency of the products that are making specific claims on their labels."

Ethanol was shown to be one of the first-choice surface disinfectants when used in concentrations ranging from 62% to 71%.2 The coronavirus is reduced to below recording levels in a variable lapse of time between 30 and 60 seconds.2 A concentration of 70% ethanol is also recommended by the World Health Organization (WHO) for the disinfection of small surfaces.2 However, going forward, alternative procedures, such as ozone disinfectant technologies, could be considered to improve disinfection because they combine an antiseptic ability similar to a liquid sanitizer with the ability to be better distributed on surfaces.3

At the present time, studies show that various human coronaviruses can remain infectious on inanimate surfaces at room temperature for up to 9 days.2 According to the results of one study, when compared with other surfaces, SARS-CoV-2 can survive longer on stainless steel and plastic with average half-lives of approximately 5.6 hours and 6.8 hours, respectively, and the viable virus was detected up to 72 hours after it was applied to these surfaces.4 For the dental industry, this means that sanitizing surfaces is paramount, especially in the area of the cuspidor, but sanitization procedures should be extended to all surfaces, even the dentist's and assistant's stools. Because SARS-CoV-2 is able to remain active for several hours on surfaces, it is obligatory to regularly disinfect everything that has been touched by patients or staff, including door handles, waiting room seats, computer keyboards, drawers, filing cabinets, and more. Sanitizing the floors and other surfaces can be accomplished at the end of the working day with a 1% hypochlorite solution.5

Many practitioners are struggling with the increased time that it's taking to disinfect different surfaces. "The issue of maintaining a certain volume of patients while adhering to all of these infection control practices can be very challenging," says Michelle E. Doll, MD, MPH, assistant professor of internal medicine at Virginia Commonwealth University in Richmond, Virginia. "It's not just a question of economics and the pressure to see a certain number of patients; there are patients who really need care that cannot be put off indefinitely. I think we are waiting to see what happens with the pandemic in early 2021 to see whether we can resume some more of the usual volume that we had previously." Teledentistry, which can be used for education, consultation, and triage, allows providers to advise patients remotely about issues such as whether their dental concerns constitute the need for urgent or emergency care, whether a condition could be temporarily alleviated at home, or whether treatment could be postponed.6

"Regarding instruments, in general, the high-level disinfection and sterilization procedures are going to take care of COVID-19 like other viruses," says Doll. "For efficiency's sake, instruments should be readily available by the patient. As you're digging through a drawer, you risk contaminating the package of an instrument. Be really sure you're separating your instruments in use so that you're not accidentally touching the outside of a package." One recommendation for minimizing the overall time required for surface disinfection is to adopt the use of single-use disposable instruments, as long as they are used and then disposed of properly.7

Materials can be approached similarly. "Unit dose what you need," says Eve Cuny, MS, executive associate dean at the University of the Pacific Arthur A. Dugoni School of Dentistry. "Don't have containers of materials out that are going to be used for subsequent patients. Make sure that anything that's out is really something that's going to be removed and discarded or sterilized. If not, it should be easy to clean, and the contents should not be accessed during patient care."

This stringent level of cleaning and disinfecting must also be maintained for products that are coming into the office, such as those from dental laboratories. "This is where hand hygiene comes into play in a big way," says Doll. "When we approach the patient care encounter, I think that is when providers are the most vigilant in making sure that their hands are washed and that they have personal protective equipment (PPE). Within the rest of the office, it is easier to become more lax about infection control. The circulation of regular office items and mail delivery throughout a busy practice necessitates frequent hand hygiene."

Bartlett works with numerous dental laboratories around the country. "To me, it is the dentist's responsibility to protect the patient," she says. "You can't see how outside laboratories are disinfecting. What chemical did they use? Did they leave it on for the recommended time or did they just spray and rinse? I believe that it is the dentist's responsibility to ensure that everything for intraoral use is disinfected or sterilized. Now with COVID-19, the dental practice should be concerned not only about devices, but also about the people and other packages coming into the practice."

Improving Air Flow and Quality

At this time, there haven't been any clusters of COVID-19 outbreaks associated with dental practices. However, there are still documented occupational risks for dentists, hygienists, and assistants. To help reduce these risks, dentists have been asked to improve air quality. "The first thing that most have done is to check their HVAC systems," says Molinari. "This was an important issue for air quality even before COVID-19. Sick building syndrome is real. There are buildings used for many workplaces where, for example, the ductwork has not been routinely cleaned. One approach to improving air quality uses ultraviolet germicidal irradiation (UVGI). These units can be portable or installed in HVAC systems."

In addition to UVGI, Molinari notes that HEPA filters can also be very efficient in removing airborne material. "Now, they have increased efficiency," he says. "There are also units that actually have a HEPA component and a UVGI system in the same standalone product so that air quality in the operatory can be improved by reducing treatment-generated airborne microbial contaminants. Hospitals have been using these technologies for years in their ‘clean' areas."

HEPA filters are used in various fields when contamination control is required, such as in pharmaceutical production and in hospitals. These filtration systems are designed to trap much smaller particles and pollutants, which remain staked thanks to different mechanisms such as diffusion, interception, inertial impaction, and electrostatic attraction. It is possible for microorganisms to grow in bioaerosols in operating rooms even after cleaning, disinfection, and sterilization due to factors such as high humidity, poor ventilation, insufficient disinfection, and floor sweeping; however, the use of a HEPA filtration system could help reduce the bioaerosol levels in such environments, including dental environments.1

One of the main steps being taken during the pandemic is to improve existing filtration systems and potentially add new technology. "Right now, you have multiple levels of filters, like ones that can kill viruses in a single pass," explains David A. Reznik, DDS, president of the HIV Dental Alliance. "There has been some remarkable technology in existence for some time. HEPA filters, carbon filters, and UVGI can all kill almost 100% of the viruses and bacteria in the air."

Photocatalytic oxidation is another technology in the HVAC sector. The main function of typical HVAC systems is to control the temperature and relative humidity of the ambient air, and thanks to the presence of mechanical or electrostatic filters, it is also possible to remove polluting air particles. However, when the temperature or humidity increases, trapped organic compounds can be desorbed, contaminating the air. Instead of absorbing organic compounds, the photocatalytic process oxidizes them. Further research is necessary to establish whether this type of system is valid as a control of biological contamination in the field of dentistry.1

COVID-19 has forced hospitals to build negative pressure rooms, a practice that Reznik is also implementing. "We need to look at air flow and work with our HVAC partners to engineer everything in the right direction," says Reznik. "Some of the portable equipment is wonderful, particularly the units that have multiple different kinds of filters, as opposed to those that just vacuum through a HEPA filter."

A specific area of focus for air flow is in the dental operatories themselves. "The good news with an open operatory is that air flow patterns can in some ways be easier than in a closed operatory," says Tilashalski. "The downside is that you're potentially around people. Is 6 feet enough? Maybe not. Closed operatory air flow can also present issues, especially in established offices. But with new design, if you can establish positive air flow where the air is flowing away from the operator and up into a vent, that is ideal."

For dental facilities with open floor plans, CDC's guidelines for dental settings during COVID-19 recommend that operatories be oriented parallel to the direction of airflow, if possible, and employ floor to ceiling barriers between patient chairs to help prevent the spread of pathogens.8 However, there is some research indicating that open clinics are no worse than those with closed operatories when it comes to the risk of contamination associated with conducting aerosol-generating procedures.9

Regarding the future of airborne infection control, one area worth investigating is the use of air ionizers. These devices generate negative ions by passing high voltage through metal plates. The ions attach to airborne particles that are then electrostatically attracted to a charged collector plate. Some of these devices, which are referred to as electron wind generators, are filtration systems capable of purifying the ambient air of dangerous bioaerosols in locations such as operatories.1

Another way that dentists can minimize airborne exposure in their practices is by redesigning waiting rooms and the entire patient check-in experience. "This is tricky because of space constraints," says Doll. "If you could design a waiting room to be as large as you wanted, everyone could have their own space. But risk mediation is currently in place to the extent possible. The recommendations are to use signage indicating that masks are required, provide handwashing stations, remove any communal reading material, space out appointments, and control volume. You can also have patients call from the parking lot when they've arrived and remain in their vehicles until the room is ready."

Emphasis on Aerosol Reduction

Aerosol generation is the area of dentistry that seems to be getting the most attention during the COVID-19 pandemic, leaving many industry professionals wondering how they can adapt their practices to minimize aerosols and improve infection control. The instrumentation being used is a key factor in the question of whether or not aerosols can be reduced or eliminated and whether or not the levels of PPE, surface disinfection, and air filtration are sufficient.

It is difficult to imagine that aerosols could be completely eliminated, but they can be reduced. "Technology will be developed that will reduce the aerosols that we generate," says Reznik. "Currently, there are some high-end laser technologies that you can use for restorative procedures that actually somewhat kill the virus, but they are remarkably expensive. The key is to figure out how to accommodate our aerosol-generating procedures now. People are going to need endodontics. There's only so much hand scaling we can do. We need the science to catch up."

To minimize droplet splatter and aerosol generation, the Agency for Healthcare Research and Quality recommends using a dental handpiece with an anti-retraction function, four-handed dentistry, high-volume evacuation suction, and rubber dam isolation.10 High-speed rotary instruments, such as the turbine and the contra-angle, should be equipped with an anti-retraction system to prevent the release of debris and fluids that can accidentally be inhaled by healthcare professionals during clinical procedures.11 The use of these devices should be avoided; if this is not possible, the last appointment of the day should be reserved for patients who need dental treatments that require the use of high-speed rotary instruments.12 Employing rubber dam isolation also reduces the amount of aerosol generated. According to the results of one study, the use of a rubber dam can reduce the number of airborne particles within an approximately 3-foot diameter of the operational field by 70%. When a rubber dam is applied, in addition to regular suction, extra high-volume evacuation suction for aerosol and spatter should also be used during the procedure.13

Cuny believes that although we can't eliminate the use of aerosol-generating devices, there are better ways to control aerosols, and she emphasizes the need for research. "We have to understand whether aerosol is implicated in transmission," she explains. "There are some good studies being done on how aerosols are generated. By the end of 2021, we'll have a whole body of evidence that will help us understand what types of infection control precautions we might need to take. We know how long it takes for room air to completely turn around, but we don't know how long it takes for aerosol particles to settle."

Helping Patients Return

With patient care being top of mind for dental professionals, many feel that their patients need reassuring. One way to accomplish this is with pre-appointment patient education. It's important to recognize that some patients have will have fears about dental treatment during the pandemic, especially if they see coverage in the news about aerosols. It's natural for patients to feel a certain level of trepidation knowing that they have to remove their mask and have a dental provider in their mouth, the area that is susceptible to COVID-19 transmission.

"This is where prescreening phone calls come into play," says Tilashalski. "We want to keep everyone safe, so we ask about symptoms ahead of time. The messaging starts early and should continue. Patients will walk in and see that things are being done a little differently. That should be seen as a positive thing."

Doll believes that having signage around the practice is especially important as well as providing written documentation about the policies and procedures. These steps go a long way toward making patients feel more comfortable.

What the Future Holds

The COVID-19 pandemic presents several opportunities for dental researchers to focus on key infection control issues, such as estimating the costs and benefits of expanded PPE use (and other changes in dental practice workflows), developing and testing innovative approaches to minimize aerosol generation during dental procedures, testing and validating teledentistry models, and evaluating alternative dental workforce models, such as dental therapists.10

It's also as important as ever for practitioners to stay on top of emerging research in the field. Many practitioners have been using a preprocedural mouth rinse, such as one containing 1.5% hydrogen peroxide, 0.2% povidone iodine, or 0.12% chlorhexidine gluconate, to reduce the bacterial burden in the mouth. In addition, preprocedural mouth rinses with 100 ppm molecular iodine could play a vital role in combating the COVID-19 pandemic by preventing the spread of infection. Research has shown that it can effectively inactivate COVID-19 after 30 seconds of exposure.14

Regardless of what the studies show, Cuny believes that aerosols are the main concern for the future. "It's not just about COVID-19," she says. "It's about any respiratory illness for which you don't want to be aerosolizing a patient's respiratory fluids. I think there will be a number of devices developed that aren't so cumbersome. There may be smaller, more optimally designed products that will come out over the next 6 months, but we don't know yet how effective they will be."

Tilashalski believes that many, if not all, of the current protocols are going to become the standard of care going forward. "COVID-19 is not going to be the last aerosol-transmittable virus that comes around," he says. "You look at what other industries have done with aerosol cleaning. Are we going to have filtration systems, air flow mandates, and UV light disinfection systems? There's a lot on the horizon."

One area in which Doll would like to see more specific data is the risk of transmission from aerosol depending on the type of procedure being performed. "The list of potentially aerosolizing procedures is extensive," she says. "We are using a lot of N95 masks in fear of aerosols, but it's not entirely clear when this level is required. That's one area that many of us in infection control are looking at with interest. Can we better model our transmission risks?"

Molinari recognizes that although effective infection prevention procedures and practices are already engrained in clinical practice, dentistry has also looked for added insight from the practices used by hospitals. "Hospitals have experience dealing with patients who have airborne infections," he says. "The majority of dental facilities would not be able duplicate all of the engineering precautions that hospitals have in place. However, we can improve where needed by continuing to follow established healthcare infection prevention science as well as emerging science that is aimed at developing technologies to control COVID-19 and other diseases that will come."


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