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Thanks to COVID-19, we are discussing the hierarchy of hazard controls for dentistry

Oct. 1, 2020
As types of infections and risks evolve, so do the methods of containment and control. But one thing will stay the same—the hierarchy of hazard controls. Michelle Strange, MSDH, RDH, explains how to implement these infection controls in your practice.

COVID-19, like many other infectious diseases, will be contained someday. When that happens, the way we approach patient care will be different, and infection control practices may need to be more rigorous. But what will stay the same is the time-tested hierarchy of hazard controls.1 

Since its establishment during the 1990 fight against tuberculosis, the hierarchy of hazard controls has been updated by the National Institute for Occupational Safety and Health, the Occupational Safety and Health Administration, and the Centers for Disease Control and Prevention.2,3 The hierarchy of controls has since seen the country through severe acute respiratory syndrome (SARS), Middle East respiratory syndrome-related coronavirus (MERS), Ebola, and Zika outbreaks,4 proving its effectiveness. However, it only works if dental health-care settings understand and follow the recommendations and regulations. 

Regrettably, the dental profession has not been fully implementing these safety precautions. A 2017 systematic scoping review of the use of bioaerosols in dentistry and health care found that even in the absence of infectious disease outbreaks, dental environments put workers at higher risks of acquiring infectious diseases.5 To keep ourselves, our patients, and even our loved ones safe, here are some simple ways to put the hierarchy of hazard controls into practice.

The hierarchy of infection controls begins with the elimination or removal of risk and substitution, which swaps out potential risk factors for practices or processes less likely to cause infection. These are the most effective ways of controlling the environment. The next step is to engineer the removal of the hazard, followed by administration controls that attempt to protect when it is not possible to remove the risk. Personal protective equipment (PPE) is the last defense in the hierarchy, and it requires the previous steps to be in place to be most effective. 

As the types of infections and risks evolve, so do the methods of containment and control. It is essential to stay up to date with changes in regulations and requirements to provide the best possible protection in your environment. Let’s now look at the steps of the hierarchy of controls in more detail.

No. 1: Elimination

The best way to prevent hazards from harming anyone is to physically remove them from the space. Coming to work sick has been normalized6 in our workaholic7 culture. Just last October, a survey conducted by the human resources firm Robert Half of more than 2,800 employees in 28 US cities,8 found that 90% of employees have gone to work when ill. Dental professionals know more than anyone else the importance of maintaining oral health and consistently scheduling dental visits—they are essential. However, with global infectious disease outbreaks per year more than tripling since 1980, we cannot continue with our usual ways anymore.9

Instead, we need to set up a screening process to check both employees and patients before they arrive at the office. This may be as simple as having a strict protocol: if individuals or anyone in their households are unwell or recovering, especially from acute upper respiratory infections, they should stay home. Our work and oral health are vital, but even these can take a temporary back seat when individuals are possibly contagious. The CDC has clear recommendations on staying home when we are sick, including remaining at home for at least 24 hours after being free of fever in the case of influenza-like illnesses.10 

No. 2: Substitution

For vital dental procedures, elimination is not always an option. Instead, consider controlling the situation via substitution—i.e., replacement with a safer alternative.11 During times when someone is contagious or potentially contagious but requires care, some substitutions can reduce the risk of exposure while still helping the patient. For instance, instead of using a high-speed handpiece to prep and repair a decayed tooth, utilize the silver modified atraumatic restorative technique (SMART) or atraumatic restorative treatment (ART) protocols until the patient can return for a more long-term solution.12 Using minimally invasive protocols to reduce spatter, spray, and aerosol production would be great options, considering the alternatives are letting the patient suffer without treatment and possibly producing bioaerosols from a contagious person. 

Substitution can be a forgotten rung on the ladder of controls to reduce potential exposure risks. Before attempting to treat a possibly contagious patient, it is always a good first step to ask if there is a better substitution for the procedure. Find the least involved procedure to deal with the emergency elements, such as antibiotics for an infection and treatments that will see the patient through until he or she is well enough for full treatment.

Another example is hand scaling to remove calculus. If a possibly contagious patient presents with a periodontal abscess, instead of using an ultrasonic scaler, consider a hand scaler to remove the irritant in addition to starting the patient on proper at-home biofilm management. Then, when well, the patient can return to the practice for proper biofilm management in the area of acute concern. If there is no option other than treatment for a patient who is possibly contagious, don a respirator and ensure that you, your team, and the environment are as protected as possible. 

No. 3: Engineering controls

The third preferred approach to deal with hazards is engineering controls—i.e., using mechanical tools or barriers to isolate the hazard from people.13 Most essential dental procedures will likely produce contaminated aerosols, spatters, or sprays,14 so controlling and containing these fluids before they reach practitioners or begin traveling through the air is crucial. 

Engineering controls are essential, as they help us perform the work we need to and promote safety. Dentistry has embraced many engineering devices, such as sharps containers, devices that eliminate the possibility of needlestick, and ultrasonic units to disrupt the bioburden on instruments versus hand scrubbing sharp instruments. All of these devices were developed to reduce the chance of exposure to pathogens in the industry.

Additional examples of engineering controls are rubber dams, cassettes that hold instruments in place, and even the plastic guard on model trimmers—all of which prevent the exposure to flying material. Another important engineering control is the high-volume evacuator (HVE), which, when correctly used, can reduce 90% of aerosol production.15 However, as most of these instruments are handheld,16 dental professionals may be drawn to using hands-free high-volume suction or fishhooking the saliva ejector on the side of the patient’s mouth should assistants be unavailable.

Unfortunately, saliva ejectors, or low-volume evacuation, are immensely inadequate for containing aerosols.17 Dental practices need to ensure that HVEs connected to other instruments or dry-field devices are available for use too.18 More research is needed to understand the levels of spatter and aerosols that are eliminated with the use of these devices. Using HVE tools in conjunction with low-volume saliva ejectors has the potential to cause backflow, and therefore they are not recommended for use together.19

When combatting aerosols that linger after procedures, one possible engineering control is the use of ventilation systems.20 They purify outdoor air by filtering out microbes and discharge used air through a separate exhaust duct, especially in high-contamination areas such as the operatory or around toilets.21 In this way, the ventilation systems prevent contaminated air from traveling to the rest of the office. Portable units may also be helpful, as they can be placed where required to enhance effectiveness.22

When we start seeing patients again, engineering controls like these will play a significant role in our practices. They have always been recommended, but now we must step up our efforts to implement these tools and embrace new technologies to protect our community.

No. 4: Administrative (or work practice) controls

Similar to having seat belts in a car but not clicking them into place before driving, administrative controls, also known as work practice controls, are employer-dictated measures—i.e., policies and procedures that change the way the dental team works so as to lessen or avoid hazard exposure.23 For instance, if you have HVE available and the recommendation is that you utilize it during procedures with spatter or aerosol production, the work practice control would be that you actually use it. Having a sharps container but then tossing a needle into the garbage is another example of having engineering controls but not proper work practice controls. 

Standard operating procedures (SOPs) are useful to make sure work practice controls are implemented. SOPs can help employees quickly visualize and understand the processes for tasks, even in complicated procedures, thus eliminating repetitive questions. Having systems and best practices defined can also encourage accountability among staff, which helps establish behaviors that will ultimately keep everyone safe.

Your SOPs can help guide employees on how to properly use and maintain engineering controls, such as devices used for dental unit waterline maintenance to prevent the growth of biofilm and breeding of bacteria, which could cause pneumonia or Legionnaires’ disease.24

It is vital to have comprehensive training and ongoing evaluations with engineering controls so team members can properly implement the devices. For example, if a dental hygienist has not worked with an HVE during ultrasonic scaling, this can be a challenging device to handle at first. More training may be required until full adoption of the control into patient care without difficulty. 

No. 5: Personal protective equipment

The CDC’s hierarchy of controls4 ranks categories of hazard controls from most to least effective, and PPE is its last-recommended line of defense. Although PPE is a critical protective mechanism (just ask any hospital worker now), we cannot expect it to be our sole defense, a foolproof mechanism, or work beyond its capacity. The FDA reminds us, “a surgical mask is meant to help block large-particle droplets, splashes, sprays, or splatter that may contain germs (viruses and bacteria), keeping it from reaching your mouth and nose. Surgical masks may also help reduce exposure of your saliva and respiratory secretions to others.”25

The next level of PPE, a respirator, may be required to provide complete protection. Similar to how social distancing follows the elimination strategy, we need to double down on the other four levels of hazard control to isolate spatter, spray, and aerosols, so that they do not get a chance to reach our PPE.

During the current COVID-19 crisis, PPE has been a massive concern for health-care workers on the frontlines—and rightly so. Such equipment is designed to protect wearers from hazards. Standard precautions include wearing properly fitting gowns, eyewear, face shields, masks, and gloves.26 After each patient, replace masks and gloves. Furthermore, if any PPE is visibly soiled, wet, or torn, it should be switched out. But not all infectious material is visible. Much of it can land or dry clear—the coronavirus included. Hence, we could be seeing tighter guidelines suggesting complete PPE changes between patients. 

It is vital to understand that not all PPE is created equally. Not all surgical masks undergo the same testing criteria. Surgical masks have different levels of bacterial filtration and fluid resistance. Wearing a surgical mask without knowing the level of fluid resistance for the procedure being performed is not recommended. Some masks do not have a level designated on the outside of the box, which means they did not undergo specific testing or performance requirements by the American Society for Testing and Materials.27 This international organization provides standards for masks used during patient care to ensure they will adequately protect both the clinician and patient. 

Should patients contract diseases from our dental offices, these cases will be considered health-care-associated infections, and there are consequences for practices that do not take infection control seriously, including possible financial penalties.28 The solution could be just this simple: stay updated on the latest regulations and recommendations, and then diligently put into practice all levels of the hierarchy of hazard controls. In this way, we’re taking full advantage of each of their benefits without overly relying on any. Not only will we safeguard our practices, but ultimately our health and the health of our patients and loved ones. 


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Michelle Strange, MSDH, RDH, has been a dental clinician since 2000 and is currently a practicing hygienist, speaker, writer, content developer, consultant, and podcast cohost for A Tale of Two Hygienists. With a belief in lifelong learning, she hopes to continue to grow within the dental profession and one day see the gap bridged between medicine and dentistry.