Table of Contents
Disclaimer: “The information contained herein is intended to be informative in nature and is not intended to be a substitute for professional advice. The information was obtained from sources we believe to be reliable but is not guaranteed. This situation is dynamic and continuing to change daily. Henry Schein does not undertake any obligation to update or revise any statements contained herein, or correct inaccuracies whether because of new information, future events, or otherwise. Dental and medical professionals must make their own business decisions and may wish to seek professional advice before acting with regard to the subjects mentioned herein. Nothing contained herein should be treated as legal, business, accounting, insurance, tax, financial or other professional advice.”
Infection control has never been more critical to the health of a dental office in keeping both patients and dental team members safe. The dental profession ranked as the #1 most unhealthy profession by a U.S. Department of Labor study due to exposure to disease contaminants, disease, infections, and radiation.
The dental professional is especially vulnerable to exposures to contaminants, disease and infections; most noticeably, fine and ultra-fine particulate matter. This matter includes harmful bio-aerosol particles that are capable of reaching the deepest part of human lungs; and absorbed into the blood stream with significant impact to overall health.
Dental Office Air Quality
The air quality of a dental office is not visible yet contains unhealthy and often infectious airborne particulate which results from practicing dentistry. The high traffic public access of dental offices can introduce bacterial, viral and fungal infections into the air. In addition, the furniture, dental equipment, and flooring can produce harmful airborne volatile organic compounds (VOCs). Bio-aerosols from the use of ultrasonic instruments along with cleaning and disinfection of contact surfaces adds to increasing the unhealthiness of indoor air of dental offices.
Poor indoor air quality can lead to headaches, dryness and irritation of the eyes, nose and throat; coughing and sneezing; shortness of breath; dizziness and nausea. Dental office HVAC systems redistribute and recirculate harmful airborne contaminants worsen the poor indoor air quality conditions. In addition, HVAC can lower indoor humidity which allows the micro droplets of contaminants to stay airborne longer.
The Next Level of Dental Protection
The dental profession is mandated to sterilize instruments, disinfect surface contaminants, and use precaution protocols, but indoor air quality and aerosol management has not been addressed. The importance of managing indoor air quality and aerosols to prevent the spread of aerobiological viral and bacterial infections is of tantamount importance.
Infection control professionals describe the chain of infection as a process in which a pathogen (a microbe that causes disease) is carried in an initial host or reservoir, gains access to a route of ongoing transmission, and with sufficient virulence finds a secondary susceptible host. Ventilation, filtration, and air distribution systems and disinfection technologies have the potential to limit airborne pathogen transmission through the air and thus break the chain of infection. 
Dental Professionals – Very High COVID-19 Exposure Risk per OSHA
OSHA in its Guidance on Preparing Workplaces for COVID-19 has placed dental professionals in the Very High Exposure Risk, the top of the Occupational Risk Pyramid for COVID-19. They’ve also listed engineering controls that focus on isolating employees from work related hazards. “In workplaces where they are appropriate, these types of controls reduce exposure to hazards without relying on worker behavior and can be the most cost-effective solution to implement.”
Engineering infection controls for COVID-19 prevention include:
- Installing high-efficiency air filters.
- Increasing ventilation rates in the work environment.
- Installing physical barriers, such as clear plastic sneeze guards.
- Specialized negative pressure ventilation in some settings, such as for aerosol generating procedures
- Installing a drive-through window for customer service
Aerosols in Dentistry
Dentistry is a profession that creates aerosols during routine procedures through the use of ultrasonics; high speed handpieces, air/water syringes, etc. The use of rubber dams (product mentions) and high-volume intraoral evacuation devices, often referred to aerosol extraction or extraoral suction (products) effectively limits or captures the majority (90-95%) of the aerosol within the mouth is recommended. Providing your patient with preprocedural antimicrobial rinse (e.g., chlorhexidine gluconate, essential oils, or povidone-iodine) (product) while not necessarily reducing aerosols can reduce the level of oral microorganisms in those aerosols and spatter.
Best Practices for Aerosol Management Process
Steps to control dental office pollutants, as identified by the Environmental Protection Agency (EPA):
- Source Control
- Air Cleaning
The dental team should not rely on a single precautionary strategy. A single step will reduce the risk of infection by a certain percentage. However, infection control is additive, so adding or layering each step will reduce the remaining risk.
In view of the broader understanding of flexible pathogen transmission modes, healthcare facilities are now using multiple modalities simultaneously (measures that are referred to as infection control bundles or layering of protective procedures) A more comprehensive approach is needed to control pathogens, which can use both contact and airborne transmission pathways.
1. Source Control of Pathogen Transmission
Of the three steps, source control is the most effective. This involves minimizing the use of products, techniques and materials that cause aerosols, employing good hygiene practices to minimize biological contaminants, and using good housekeeping practices to control particles.
Another source control is considering prioritization of minimally invasive/atraumatic restorative techniques by using only hand instruments. Another option is technologies that reduce the aerosol production while providing effective techniques. One example is an all-tissue laser for the preparation of direct and indirect partial coverage restorations (e.g. Solea). All-tissue lasers use reduced water and air pressure compared to a drill, thus reduced spray and spatter. In addition, a CO2 laser delivers energy that serves as a sterilizing agent by destroying bacteria and viruses. The reduced aerosolization of water spray and increased viral and bacterial decontamination over that of mechanical drills can make a CO2 all-tissue laser another option.
The use of digital impression systems can limit the possible aerosol production vs. handling conventional impressions out of the mouth and using an air water syringe to aid in visual inspection (products). Sending an image (file) via the internet vs. sending a physical impression minimizes saliva traveling out of the mouth and around the office and to a dental laboratory through the mail. Other technologies like chairside milling units and printers can minimize infection control turnover of operatories and PPE by maximizing production during a single visit. At the same time employing Chairside CAD/CAM dentistry reduces the number of provisionals in place, should any situation occur where visits are limited or prohibited. (products).
2. Ventilation of the Dental Office
The second step - Ventilation in the dental office can include placing a high-speed extraoral evacuation system close to the source of contaminants (patient’s mouth) and additionally increasing air flows in mechanical ventilation systems (e.g. hoods, HVAC systems).
Air conditioning of a building or a room controls the purity, humidity and temperature of the indoor air, and it is essential in those buildings with clean zones and clean rooms. Cleaning indoor air of fine particulate matter by filtration requires either a fan or a blower to direct air flow through the selected filter which is often preceded by a prefilter to trap coarse particles and miscellaneous debris, and to act also as a diffuser producing more even distribution of air flow across the filter.
3. Air Purification Systems (APS) – Air Cleaning
The third approach, air cleaning is not generally regarded as sufficient by itself, but is sometimes used to supplement source control and ventilation (bundling/layering). Air filters, electronic particle air cleaners and ionizers are often used to remove airborne particles and volatile organic compounds.
Studies have proven that purified indoor air leads to higher worker productivity. Importantly, it results in lower absences due to health issues, specifically respiratory illnesses. Studies have proven that purified indoor air leads to higher worker productivity. Importantly, it results in lower absences due to health issues, specifically respiratory illnesses. Current building ventilation standards are based on acceptable minimums. Three decades of research demonstrates the human health benefits of increased ventilation above these minimums. Recent research also shows the benefits on human decision-making performance in office workers, which translates to increased productivity. Benefits include:
- Overall well-being and health of staff and dentists due to daily exposure
- Patient health
- Positive patient impression of the dental practice
Dental offices can greatly benefit from purifying their indoor air with an Air Purification System (APS) by reducing the transmittable contaminants. Air purification and filtration systems clean by constantly drawing out polluted indoor air and exhausting clean filtered air into each room. In addition, some units have a Negative Ion generator that refreshes the indoor air to making the air healthy and has been shown to combat afternoon fatigue.
Most of the products offered either clean/purify the air through a combination of the following:
- An air flow filtering process (HEPA, MERV, Carbon)
- Use of shielded UV light (UV Germicidal irradiation (UVGI), Photocatalytic Oxidation (PCO)
- Ionization of the air (Negative Ion Purification)
Filters for Air Purification and Cleaning
Most of the extraoral suction devices and air purifiers combine a variety of filters to ensure high efficiency and extend the life of the filters.
High Efficiency Particulate Air (HEPA)
HEPA air filters are made from very tiny glass fibers that are made into a tightly woven paper. This filter consists of a multitude of very small sieves that can capture extremely small particles, including some biological agents. This type of air filter can remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm). The diameter specification of 0.3 microns is the most penetrating particle size (MPPS). Particles that are larger or smaller are trapped with even higher efficiency. A pre-filter is sometimes used in air purifiers to prolong the life of the HEPA filter.
Minimum Efficiency Reporting Value (MERV)
MERV is a rating system primarily for HVAC air filters created by the American Society of Heating, Refrigerating, and Air Conditioning Engineers or (ASHRAE). A MERV rating reports a filter's ability to capture larger particles between 0.3 and 1.0, 1.0 to 3.0 and 3.0 to 10 microns categories. The higher the MERV rating (1-20) the better the filter is at trapping specific types of particles. A filter with a MERV of 17 and above filter trap 99.97% of particles of the smallest size .03 to 1.0 microns measured.
Carbon filters consist of a vast system of pores of molecular size. These pores are highly adsorbent, forming a strong chemical bond/attraction to odorous, gaseous, and liquid contaminates, especially organic chemicals/compounds. Research has not yet shown that other technologies such as plasma, photocatalytic oxidation, or ultraviolet (UV) light can remove gases effectively in portable air cleaners. Other studies have shown that APS with activated carbon filters reduced airborne ozone compared to those without activated carbon
UV (Ultraviolet) Light
Ultraviolet germicidal irradiation (UVGI) is a method of disinfection that uses short wavelength ultraviolet light (UV-C <290nm) to inactivate or kill microorganisms and pathogens by damaging their RNA and DNA. UVGI is the use of UV light with sufficiently short wavelengths to disinfect surfaces, air, and water. The UV-C wavelength of 253.7 nanometers has been proven to be effective at neutralizing (inactivating) microorganisms. The challenge is that this wavelength can cause skin and eye irritation/damage and needs to be shielded when used in occupied spaces.
Filters and UV Light Combinations
Some Air Purification Systems (APS) and Extraoral suction devices are combining filtration (MERC or HEPA filters) with UVGI as an added insurance. In some cases, the APS purposely uses a lower CFM air flow (cubic feet minute), low level filters (to allow particles to reach the UV-C light) and a parallel airflow to the light in order allow a longer exposure time to the UVGI. (e.g. VidaShield)
Air Purification Technologies
An ionizer is a device that disperses negatively (and/or positively) charged ions into the air. Virtually all particles in the air have either a positive or negative charge. Negative ions magnetically attach to particles in the air giving them a negative (or positive) charge so that the particles may attach to nearby surfaces such as walls or furniture, or attach to one another and settle out of the air  , preventing it from being inhaled into the respiratory tract. This can result in reductions in airborne microbials, neutralization of odors, fine particulates and specific volatile organic compounds (VOCs).
Photocatalytic Oxidation is an effective way to neutralize many types of airborne bacteria, chemical contaminates and odors. Photocatalytic oxidation is achieved when UV rays are combined with a TiO2-coated filter. This process creates hydroxyl radicals and super-oxide ions, which are highly reactive electrons. These highly reactive electrons aggressively combine with other elements in the air, such as bacteria and volatile organic compounds, (e.g. formaldehyde, ammonia). Once bound together, the chemical reaction takes place between the super-charged ion and the pollutant, effectively "oxidizing" (or burning) the pollutant. This breaks the pollutant down into harmless carbon dioxide and water molecules, making the air more purified.
Most of the Air Purification Systems (APS) and extraoral aerosol suction combine one or more of these methods to remove contaminants and purify the air. It is important to consider a layering of these protective technologies in order to disrupt the transmission pathways of infectious aerosols for the dental team and patients.
Negative Pressure Rooms
Negative pressure rooms, which are engineered to control infection are used in hospitals and medical clinics to prevent the spread of contagious illnesses from one area to another. Air is pumped out of the treatment area, creating a negatively pressured space so, for example, when a door is opened into that space from, say, the lobby, the air rushes in, instead of out. The air that is pumped out of the affected space passes through a series of three filters, ending with a HEPA (high-efficiency particular air) filter, which gives the same degree of filtration as an N95 mask.
Studies suggest directing airflow through a negative pressure isolation room is a preferred model for protecting healthcare workers during patient care. For a negative pressure room, the sum of the mechanically exhausted air must exceed the sum of the mechanically supplied air. In a negative pressure room, air should flow from hallways and corridors (cleaner areas) into the isolation rooms (less clean areas). While a negative pressure isolation is considered the best method of infection control, installation of a negative pressure room can be cost prohibitive to private dental practices.
Important Selection Criteria of APS
Crucial to effectively and efficiently remove all the air pollutants created in the dental office. An effective system must be capable of removing, dust, volatile organic compounds (VOCs), mold, bacteria, odors, as well as killing germs and viruses using UV-C light.
Air Flow Capacity – cubic feet per minute (CFM)
CFM is the most common way to measure airflow. Areas are measured in square units (like square feet) while volumes (like a room full of air) are measured in cubic units. CFM determines how much cubic feet can be moved or exchanged each minute. A room measuring 1,000 ft³ would need a 1,000 CFM system to replace all the air each minute. As most blueprints show only length and width of rooms, an 8’ ceiling is often assumed when suggesting a square foot treatment area. It is important to understand the cubic feet per minute (CFM) that the system can handle; and how often it can turn-over dental office air.
Air Change Rate or Air Changes per Hour is a measure of the air volume added to or removed from a space divided by the volume of the space. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced. In a situation like this it can be calculated by ACH=(60xCFM)/Volume of the room. The CDC also defines a minimum of six air changes per hour (ACH) as criteria for an efficient ventilation system (12 ACH for new construction or renovation areas).
Air Cleaner Calculation for Adequate Room Size Efficacy
Multiply the length and width of the area in which you intend to operate the air cleaner. The result will provide you with the size of the room or area in square feet. Compare this to the maximum recommended room size on the product packaging. However, this is based on 8’ ceilings in a closed room. If you have an open floor plan and/or ceilings above 8’ you should consider the entire space (cubic feet) that the air cleaner would serve. You should consider using an air cleaner that is sized for a larger area. Also, if you have an area that is larger than any available product will serve, you could consider using multiple air cleaners and/or incorporating purification within the HVAC system. 
Sound Level – decibel level (dB)
The movement of air generates sound, yet it should not be so loud as to infringe on the working dental environment. The unit for measuring the relative intensities of sound on a logarithmic scale is called a decibel. Typically, on air purification systems that have multiple air flow settings, the greater the airflow the greater the sound level. If an APS is too loud and needs to be turned down to a lower level; the air flow capacity (CFM) and efficacy will both be reduced. A sound level of 50 dB or lower is desired – the average sound of a quiet dishwasher. Normal conversation is usually around 60 decibels, and use of high-speed handpieces and ultrasonic scalers create sound in the range of 60-99 decibels
Operational Cost – Consider replacement consumables
Long term operational costs must be considered and not just the purchase price. All Air Management systems have different components of various prices that need replacing with varying frequency and usage over time such as filters and UV light bulbs. It is important to understand the frequency of needing to replace parts and the associated cost. An inexpensive unit to purchase may soon become quite expensive to own and use over time.
Intraoral Dental Evacuation
Dental evacuation is a vital part of dental procedures. A popular method for reducing the risk of aerosol contaminants is through high-volume suction and/or isolation. High-volume suction removes a large volume of air up to 100 cubic feet per minute. Continuous suction, along with isolation, provides increased control and reduced aerosols. Properly cleaning, disinfecting and removing dental evacuation lines are crucial to avoid cross contamination.
Many specialized suction devices can assist with evacuation by helping to maintain a dry field during various dental and hygiene procedures. Most quickly connect to HVE (High Volume Evacuator) units and easily meld into current workflows. These systems can provide hands-free isolation while also providing a clear and unobstructed view. Hands-free solutions can be critical for clinicians and assistants so they can focus on the procedure at hand rather than concentrating on managing water flow. Not only are these systems safe, but they can also minimize fluid build-up, aerosol contaminants, and risk of backflow. Most systems contain mouthpieces or pieces for the oral cavity that are soft and flexible allowing for comfort for the patient.
Aerosol Extraction – Extraoral Suction
Dentists and especially hygienists (single operators) are now considering these extraoral high speed evacuation systems that claim to capture up to 99% of the aerosol generated that leaves the patient’s mouth when properly placed. These units typically have high speed suction (approximately 100 CFM) that captures the aerosol through a funnel and tube and then through either HEPA filters, chemical filters, UV light or a combination.
Reducing the risk of Aerosol contamination
Several options are available for the control of aerosol in the dental practices. Equipment producing less aerosols such as all-tissue lasers, and additional barriers such as respirator masks or face shields can be used to reduce aerosol contamination. Another way to reduce the contamination risk is extraction of the aerosols at or close to the source since most of the aerosols have been found to radiate toward the patient's chest and the operator, as well the dental assistant's face. While it is difficult to completely eliminate the risk posed by dental aerosols, it is possible to minimize the risk with relatively simple precautions.
A well-fitting surgical facemask is preferable to the paper type which rapidly can becomes permeable and inefficient.
Protect eyes against splatter and aerosols which may arise during operative dentistry.
Wear protective clothing which covers areas that can be contaminated.
Surface cleaning and decontamination
The area around the dental unit becomes contaminated for example by direct splatter and by touching surfaces with gloved hands. Cleaning the surface prevents transmission of infection by direct contact with hands and equipment.
Extraction and ventilation
Good ventilation and source extraction which exhaust the aerosol reduce the risk of cross-infection and cross-contamination.