Dental aerosols might not be on the top of everyone's mind during a dental visit, but their impact is far-reaching. From bacteria and viruses to dental materials, these aerosols created during dental treatments can compromise the health of both patients and dental professionals. During the height of the COVID-19 pandemic, the widespread suspension of elective dental procedures highlighted the critical role these aerosols play in disease transmission. Recognizing the importance of managing dental aerosols is key to maintaining a safe and hygienic dental practice.
Dental procedures produce aerosols (small liquid and solid particles suspended in air or gas) and splatter (a mixture of air with water and/or solid substance). Splatter typically refers to large droplets (>50 μm) or debris heavy enough to settle quickly and not spread far. In contrast, aerosols are smaller droplets (< 50 μm) that can further reduce in size through evaporation, creating residual aerosols (≤ 10 μm).
Heavier particles (>50 μm) within the aerosols tend to remain suspended in the air briefly and settle quickly onto surfaces. However, lighter particles can stay suspended for longer periods, particularly in indoor environments. This is due to their minimal size allowing them to resist gravitational settling. These lighter particles also travel farther from the source.
Many dental procedures, such as caries removal, periodontal supragingival scaling, and prosthodontic tooth preparation are associated with the formation of aerosols and splatter. Dental aerosols are composed of saliva and blood, tooth and dental materials, food debris, dental plaque, and microbial content. The potential sources of airborne contamination in a dental setting are listed below.
1. Dental instrumentation
Contamination from dental instrumentation can arise from the microorganisms on instruments and in dental unit water lines (DUWL).
2. Saliva and respiratory sources
The saliva in the oral environment constantly replenishes fluids in the mouth, which are heavily populated with bacteria and viruses. The mouth being a part of the oronasal pharynx, harbors bacteria, and viruses from the nose, throat, and respiratory tract. Pathogenic viruses and bacteria present in saliva and oral fluids can be aerosolized during dental procedures, leading to airborne contamination from these sources. Dental plaque is another significant source of these microorganisms.
3. Dental operative site
Most dental procedures use mechanical instruments which generate airborne particles from the site of use. Dental handpieces, ultrasonic scalers, three-way air/water spray, air polishers, and air abrasion units are among the primary sources of visible aerosols. Clinical procedures like dental cleaning and polishing, periodontal treatment using ultrasonic instrumentation, any dental preparation, direct and indirect restoration and polishing, definitive cementation of crown or bridge, mechanical endodontic treatment, surgical tooth extraction, and implant placement are called Aerosol Generating Procedures (AGPs) in oral healthcare.
These instruments remove material from the operative site, which becomes aerosolized through rotary action, ultrasonic vibrations, or the combined effect of water sprays and compressed air. The water spray is usually the most visible component of the aerosol, noticeable to both patients and dental personnel. Aerosols and splatter from these procedures can originate from both the coolant water source and directly from the patient.
4. Dental laboratories
Dental prosthetic technicians in dental laboratories are exposed to dust and vapor of various materials including silica, and metals like beryllium, cobalt, chromium, nickel, and acrylates. These substances are encountered in liquid or powder form during processes such as grinding, polishing, and sandblasting of metal alloys, resins, and ceramics.
There are various problems we as dentists face with dental aerosols: i) Infection transmission: Dental aerosols can carry bacteria, viruses, and other pathogens, potentially transmitting infections between patients and dental staff. ii) Occupational exposure: Dental professionals are at risk of inhaling aerosolized particles, leading to respiratory infections or exposure to bloodborne pathogens. iii) Environmental contamination: Aerosols can settle on surfaces in the dental operatory, leading to contamination of equipment, instruments, and surrounding areas.Dr. Yung-Chung Chen, DDS., MDsc., PhD., Associate Professor, School of Dentistry & Institute of Oral Medicine, National Cheng Kung University (NCKU), and Chief, Division of Prosthodontics, Department of Stomatology, NCKU Hospital, Tainan, Taiwan.
The size of the aerosol is crucial in determining its potential for transmitting infectious diseases. Smaller aerosols when inhaled, can deposit in the lungs. Aerosols are classified based on where they deposit in the respiratory tract:
1. Respirable Aerosol (≤ 5 µm): These droplets penetrate and lodge into the smaller passages of the lungs, reaching the respiratory bronchioles and alveoli.
2. Thoracic Aerosol (up to 10–15 µm): These droplets penetrate the trachea and large intrathoracic airways.
3. Inhalable Aerosol (100–200 µm): These can be aspirated into the nose.
4. Droplets (> 200 μm): These may splash into mucus membranes. These particles are visible to the naked eye, are too large to be inhaled, and are embedded deep within the lungs.
Dental aerosols can pose risks to clinicians, staff, and other patients. The bioaerosols provide a pathway for infectious disease transmission. Diseases known to be spread by droplets or aerosols include pneumonic plague, tuberculosis, influenza, Legionnaires' disease, and severe acute respiratory syndrome (SARS).
In dental technicians, the airborne particles released from dental materials can cause chronic inflammation of the lungs, epithelial damage and eventually lead to fibrosis of lung tissues causing respiratory disorders like idiopathic pulmonary fibrosis (IPF), silicosis, pneumoconiosis and greatly reducing the efficiency of gaseous exchange.
1. Intra-oral High-Volume Evacuator (HVE):
High-volume evacuators (HVEs) have been shown to reduce contamination by more than 90%. The dental HVE removes a large volume of air quickly, typically up to 100 cubic feet per minute, and has a large opening (usually 8 millimeters or greater). HVEs are often used by an assistant who can aim the vacuum to minimize visible water spray. When an assistant is not available, operators can use the HVE with one hand while operating the instrument with the other, use HVE devices that attach to the operating instrument or employ "dry field" devices that connect to an HVE. Devices for air polishing and air abrasion that combine a barrier and a vacuum are also available to contain and remove airborne abrasive material particles.
2. Extraoral suction unit (ESU):
Using the extraoral suction unit (ESU) during dental procedures reduces droplet spatter and aerosols thus reducing the risk of infection in dentists, dental assistants, and patients. In operatory sites, there was a reduction in the frequency and mean intensity of splatter contamination, but it did not eradicate the aerosols. In practical applications, a combination of HVE and ESU was found to be more effective in aerosol control.
3. Dust collector box:
For extra-oral trimming and polishing of dental prostheses, protective devices like dust collector boxes are used in dental laboratories. Dental chair-side acrylic cabinets can also be used for reducing acrylic particle debris.
To manage dental aerosols effectively, dentists employ various strategies: i) High-volume evacuation systems: These systems use powerful suction to capture aerosols directly at the source, such as the patient's mouth, reducing the dispersion of particles into the air. ii) Preprocedural mouth rinses: Using antimicrobial mouth rinses, such as chlorhexidine or povidone-iodine, before dental procedures can help reduce the microbial load in the oral cavity and minimize aerosol contamination. iii) Personal protective equipment (PPE): Dental staff wear appropriate PPE, including masks, face shields, goggles, and protective clothing, to minimize exposure to aerosols. iv) Air filtration and ventilation: Installing HEPA filters and improving ventilation systems in the dental office can help remove aerosols from the air and reduce their concentration.Dr. Yung-Chung Chen, DDS., MDsc., PhD., Associate Professor, School of Dentistry & Institute of Oral Medicine, National Cheng Kung University (NCKU), and Chief, Division of Prosthodontics, Department of Stomatology, NCKU Hospital, Tainan, Taiwan.
4. Rubber dam and saliva ejector:
A rubber dam is a latex or nitrile square sheet used in to isolate the operative site (one or more teeth) from the rest of the mouth. During AGPs, it can prevent patient saliva from being mixed with the water spray generated from the dental instruments. Saliva ejectors which are low-volume evacuators or aspirators remove excess saliva and other fluids from the mouth and also reduce the aerosols escaping the mouth.
5. Heating, ventilating, and air-conditioning (HVAC) system
HVAC system is a forced-air system often designated to an entire office space which provides air exchange continuously. They play a crucial role in reducing the airborne concentration of bioaerosols, thereby lowering the risk of transmission through the air. These systems improve air circulation and filtration, removing contaminated air and replacing it with fresh, clean air.
6. High-efficiency particulate air (HEPA) filters:
Portable air cleaners with HEPA filters can be used to reduce aerosol contamination that escapes the operating area. They aim to reduce the overall contamination of the dental operating room.
7. Personal barrier protection:
Masks, gloves, face shields, surgical gowns, and eye goggles can eliminate much of the danger from splatter droplets and aerosols.
8. Preprocedural rinse:
0.01% chlorhexidine, povidone‐iodine, hydrogen peroxide or essential oil–containing mouthwash can be used for one minute before a dental procedure to significantly reduce bacterial count in the air.
9. Sterilization of instruments and treatment of dental unit water lines (DUWLs):
Routine cleaning and sterilization procedures can eliminate contamination of all dental instruments. DUWLs should be treated according to the ADA-recommended methods to minimize or eliminate airborne contamination from them.
10. Scheduling high-aerosol procedures
Well-ventilated individual operatories are preferred for dental procedures. In case of an open floor plan, it should be confirmed that there is at least 6 feet of space between patient chairs with physical barriers between them. Operatories should be oriented parallel to the direction of airflow if possible. Additional time between high-aerosol generating procedures should be allowed to ensure thorough disinfection and adequate air exchange. These procedures should be carried out in designated rooms with enhanced ventilation and air purification systems.
11. Patient screening and triaging
Pre-appointment screening for symptoms of respiratory infections can be done using temperature checks, taking a medical history and continuously monitoring symptoms. Appointments can be rescheduled if any signs of infection are present, except in emergency cases where extra precautions can be taken to mitigate risk. Patients can be triaged based on their risk of infection and high-risk patients should be scheduled at specific times or provided with additional protective measures.
A layered approach to infection control is recommended to reduce the risk of infection incrementally with personal protection barriers as the first layer, antiseptic preprocedural rinse with a mouthwash as the second layer routine us of a suction system as the third layer, and the use of HEPA filters as an additional layer of protection.
The recent advancements in aerosol control technologies include advanced suction systems and aerosol containment devices. Engineers have been working on developing more efficient and ergonomic high-volume evacuation (HVE) systems that can effectively capture aerosols and reduce their spread in the dental operatory. These systems may incorporate innovations such as adjustable nozzles, improved suction power, and quieter operation to enhance usability and effectiveness. Collaborations between dentists and engineers have led to the design and development of aerosol containment devices that can be placed around the patient's mouth during procedures to minimize the dispersion of aerosols into the surrounding air. These devices often feature transparent barriers and integrated suction systems to capture aerosols at the source.Dr. Yung-Chung Chen, DDS., MDsc., PhD., Associate Professor, School of Dentistry & Institute of Oral Medicine, National Cheng Kung University (NCKU), and Chief, Division of Prosthodontics, Department of Stomatology, NCKU Hospital, Tainan, Taiwan.
In conclusion, dental aerosols present a significant yet often overlooked risk in dental practices. It is essential that dentists and their staff adopt and consistently implement safe dental practices, including the use of personal protective equipment and effective aerosol mitigation strategies. Continued education and awareness will be key to fostering safety and preparedness in dental practices. By prioritizing these measures, the dental community can protect both patients and practitioners, ensuring a safer environment and promoting overall public health.
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