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 Table of Contents  
Year : 2020  |  Volume : 7  |  Issue : 2  |  Page : 86-90

Combating respiratory hazards in dentistry: A comprehensive review

Department of Conservative Dentistry and Endodontics, Terna Dental College, Navi Mumbai, Maharashtra, India

Date of Submission05-Apr-2020
Date of Decision11-May-2020
Date of Acceptance19-May-2020
Date of Web Publication20-Jun-2020

Correspondence Address:
Sagar J Shah
Department of Conservative Dentistry and Endodontics, Terna Dental College, Navi Mumbai, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jdrr.jdrr_21_20

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Oral healthcare settings are known to produce aerosols during dental procedures. With the outbreak of novel coronavirus, which has a definite droplet and possible aerosol transmission, a review of reducing bioburden due to aerosol generation in oral healthcare settings is warranted. Literature reporting characterization of aerosols in dental and medical settings, and potential for cross-infection in oral healthcare settings, was thoroughly reviewed. This was followed by reviewing studies and guidelines issued by various health organizations on methods of reducing the burden of aerosols in dental setting. Oral healthcare settings can serve as a potential site for cross-infection of diseases such as tuberculosis and severe acute respiratory syndrome. COVID-19 spreads principally by respiratory droplets and may spread through aerosols. Many dental procedures are associated with the generation of a high number of aerosols. Airborne contamination can be kept to a minimum by following the hierarchy of controls which includes triage, engineering, and workplace controls followed by personal protection equipment. The use of high-volume suction is highly recommended to reduce aerosols in the dental office. Preprocedural rinse with 0.2% povidone iodine is effective in reducing viral load against COVID-19.

Keywords: Aerosols, COVID-2019, personal protective equipment, prevention, respiratory protective devices

How to cite this article:
Singh S, Shah SJ, Podar R, Shetty R. Combating respiratory hazards in dentistry: A comprehensive review. J Dent Res Rev 2020;7:86-90

How to cite this URL:
Singh S, Shah SJ, Podar R, Shetty R. Combating respiratory hazards in dentistry: A comprehensive review. J Dent Res Rev [serial online] 2020 [cited 2021 Jan 15];7:86-90. Available from: https://www.jdrr.org/text.asp?2020/7/2/86/287335

  Introduction Top

Human lungs serve as a natural filter to all the particles inhaled in day-to-day life. Larger particles are sequentially cleared in the respiratory tract followed by mucociliary clearance. Smaller particles, i.e., >2.5 μm, poses a significant challenge. These particles can be deposited in nonciliated and terminal bronchioles of the lung. The clearance of these particles is principally taken up by macrophages over a period ranging from weeks to months.[1] Dentistry uses a lot of rotary and ultrasonic instruments that act by coming in direct contact with hard tissues. The majority of these instruments operate in conjunction with air, water, or both leading to the generation of aerosols, fine particles, and splatter. This may contain microbes, particles from dental abrasives and hard tissues, and splatter from patient's saliva and blood exposing oral healthcare workers at a significant risk of respiratory diseases.[2]

The Centers for Disease Control and Prevention (CDC) was reported with a cluster of cases among dentists in Virginia affected by idiopathic pulmonary fibrosis (IPF), which is characterized by progressive lung damage. It takes years to show symptoms and has a median survival rate of 3–5 years from diagnosis. IPF saw significantly higher in dentists who worked without or minimum respiratory protection. Through their investigation, the CDC found that the mortality ratio of dentists suffering from IPF was higher than the general population.[3],[4]

With the discovery of new pathogens such as severe acute respiratory syndrome (SARS) and COVID-19, the risk of respiratory diseases for oral healthcare workers has exponentially increased.[5] The latest epidemic of COVID-19 has become a global healthcare challenge, and infection control has become of paramount importance. Owing to the nature of healthcare and oral healthcare settings, the risk of cross-infections cannot be overstated among patients and doctors.[6],[7] SARS and COVID-19 are transmitted by respiratory droplets and aerosols from infected individuals, and hence, all aerosol-generating practices in oral healthcare settings must be limited and proper personal barrier protocols are to be followed.[8] This review aims to characterize the aerosols in an oral healthcare setting and focus on ways to significantly reduce the burden of respiratory hazards for oral healthcare professionals.

  Terminologies and Definitions Top

Micik et al. first introduced the terms “aerosol” and “splatter” in dentistry.[9] Aerosols are defined as “liquid or solid particles suspended in the air by humans, animals, instruments, or machines. Bio-aerosols are aerosols consisting of particles of any kind of organism.”[10] Micik et al. defined aerosol “as particles <50 μm in diameter.” Particles from 0.5 to 10 μm possess the largest potential for transmitting infections.

Particles larger than 50 μm in diameter are defined as splatter.[9] They are believed to behave in a ballistic manner, i.e., ejected forcibly, and follow a trajectory until they hit a surface. These particles are too heavy to stay airborne. Aerosols pose the greatest threat in dentistry as they stay airborne and may enter respiratory passages. Splatter droplets may dry and eventually reduce to the size that allows them to remain airborne such as dust particles. Aerosols or droplet nuclei may be suspended in the operatory for about 30 min after completion of the procedure.

  Characterization of Aerosol and Fine Particles in Dentistry Top

All procedures carried out by engine-driven or ultrasonic devices generate aerosols. These aerosols contain body fluids such as blood and saliva, as well as organisms such as bacteria, fungi, and viruses. The understanding of the composition of aerosols and splatter is thus of paramount importance to safeguard the health of oral healthcare professionals. The characterization of aerosols and fine particles in the oral healthcare setting is given in [Table 1].
Table 1: Characterization of aerosols and fine particles in oral healthcare setting

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Qualitative and quantitate analysis of aerosols is demanding, and the composition of aerosol differs with location and patient. Cultivation of any bacteria that require special conditions for its growth and development is difficult. Furthermore, the cultivation of viruses is difficult, and hence, quantification of atypical bacterial and viral load in aerosols is not possible.[10] Other pathogens that require droplet precautions include Mycoplasma pneumonia, Mumps virus, Pertussis virus, viral hemorrhagic fever Lassa, Ebola, and Marburg.[5]

  Methods to Reduce Airborne Contamination Top

As discussed above, aerosols pose a definite work hazard to oral healthcare professionals. Specific measures are needed to reduce its burden in a healthcare setting. Occupational Safety and Health Administration and health and safety professionals recommend using the “hierarchy of controls”, i.e., begin from the most effective controls to least effective controls.

Elimination/isolation of hazards

Usage of ultrasonic and sonic handpieces generates maximum aerosols in the dental operatory. Following scalers, air polishing is known to cause equal airborne contamination as ultrasonic and sonic devices. Studies have shown that the usage of high-volume evacuator (HVE) reduces the airborne contamination by 78%.[14],[18] Studies have shown that bacterial contamination while using air/electric turbines or air–water syringes can be kept minimum using a rubber dam. It is recommended to treat patients with active infectious diseases, and also, perform laboratory procedures involving dust and aerosol generation in a separate room using mask/respirator. Patients with active or suspected infections such as SARS and COVID-19 should be triaged and screened all elective treatment to be postponed. Emergency dental treatment should not be performed in routine dental settings instead these patients to be treated in negative pressure rooms or airborne infection isolation rooms.[6]

Engineering controls

Dental ventilation guidelines given by Indian health service[19] has laid down specific ventilation requirements in dental facilities. Air change per hour (ACH) corresponds to air volume added to or removed from a space divided by the volume of the space. Open operatories have a large room of operatories divided by modular fashion. Closed operatories have separate rooms per operatory. Minimum ACH for enclosed operatories should be 12 and for open dental operatories should be 6. If proper air change ratio is maintained, 63% of aerosols are removed from the environment.[20]

From a practical standpoint, it is most desirable to remove aerial contamination from a site as soon as it is developed. A HVE system in dental offices is designed to eliminate air volume of 100 cubic feet per minute. HVE alone has shown to reduce contamination in operatory by 90%.[14]

Studies have shown that commercial air filters containing high-efficiency particulate arrestor (HEPA) can arrest contaminants measuring 0.3 μ and larger with 99.97% efficacy with laminar airflow.[21] HEPA filters have effectively demonstrated a reduction in the concentration of airborne particles and a reduction in disease transmission. Also, air Purifiers with HEPA and Carbon filters limit allergens and reduce mercury vapor in dental operatory.[22]

Administrative controls and work practices

Reduction in contact time with patients significantly reduces the biological burden in the dental operatory. Rubber dam practically eliminates all the bacterial and viral contamination arising from the saliva and blood, except for the tooth to be working upon.[18]

Aerosols remain airborne for up to 30 min and hence may pose a hazard even after the operator has completed his/her treatment and communication with the patient. A simple yet extremely effective way to reduce the generation bacterial burden during dental procedures is the usage of preprocedural rinse. Usage of 0.1% chlorhexidine (CHX) for 1 min is shown to significantly decrease the count of floating bacteria in the mouth.[23] Certain viruses such as influenza virus and SARS-coronavirus are resistant to CHX, and hence, 1% hydrogen peroxide or 0.2% povidone-iodine mouthwash is recommended in patients with high viral load.[24]

Dental unit waterline (DUWL) can harbor numerous bacteria, thus affecting the workplace. As per thee CDC guidelines for the management of DULVs, the output water to be used for the dental procedures should contain <500 CFU/mL of aerobic heterotrophic bacteria. Agents such as 3-ppm sodium hypochlorite, 0.12 CHX, 1:10 dilution of listerine mouthwash, and 1% hydrogen peroxide may be used in cleaning DUWL. Care must be taken while using specific agents against their possible adverse effects.[15],[25]

Personal protective equipment

Personal protective equipment is reported as the last line of defense from airborne contamination when all the aforementioned measures fail to reduce contamination to an acceptable level. Of clinical importance, surgical masks and surgical respirators hold strategic importance. Surgical masks are defined as “a loose-fitting, disposable type of facemask that creates a physical barrier between the mouth and nose of the wearer and potential contaminants in the immediate environment.” Masks offer some degree of fluid resistance and protect the wearer from splashes, sprays, and splatter.[5],[26]

It is of paramount importance to understand that surgical mask fails to provide a tight seal against wearers face and do not provide the wearer with complete protection against airborne contamination. Hence, they fail to qualify as respiratory protection.[27],[28]

Masks should be changed:

  • For each patient
  • After 1 h of prolonged treatment
  • Every 20 min in the highly aerosolized environment.[5],[28]

Food and Drug Administration has adopted a classification system by The American Society of Testing Materials Standard specification F2100–11 for the performance of materials in the face mask.[29] Specifications for surgical masks are given in [Table 2].
Table 2: American Society of Testing Materials classification of surgical masks

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Surgical respirators are a filtering facepiece respirator designed to filter particles as small as 0.3 μ. They are reinforced with fluid-resistant material on the exterior to protect the wearer against splash and splatter. Respirators must be individually selected to wearer's face and should provide a tight seal. The CDC recommends a respirator mask in the dental healthcare setting only for very few organisms which are truly transmissible through the airborne route. The masks should be used for patients with active infections with methicillin-resistant Staphylococcus aureus, multidrug-resistant-tubercluosis, and varicella-Zoster, etc. The usage of surgical respirators in the dental office is recommended only for patients requiring dental treatment when suffering from these conditions.[5],[28],[30]

Respirators used should be manufactured and certified by the National Institute for Occupational Safety and Health.[5]

Filter class abbreviation:

  • N95= Nonresistant to oil. Filters at least 95% of airborne particles
  • R99= Resistant to oil. Filters at least 99% of airborne particles
  • P100=Oil Proof. Filters least 99.73% of airborne particles.

  Conclusion Top

The generation of aerosols and splatter has the potential to spread infection in oral healthcare settings. The generation of aerosols and splatter can be reduced to a substantial level but cannot be completely avoided. Following the hierarchy of controls best helps to minimize the risk of respiratory healthcare hazards. Healthcare operators must identify patients with active infectious diseases with airborne transmission such as SARS and COVID-19, and triage, initial screening, and special precautions should be taken while treating them.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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  [Table 1], [Table 2]


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