SRM Journal of Research in Dental Sciences

REVIEW ARTICLE
Year
: 2021  |  Volume : 12  |  Issue : 4  |  Page : 216--221

Dental aerosol: An insight


B Srishti Raj, Kharidhi Laxman Vandana 
 Department of Periodontics, College of Dental Sciences, Davangere, Karnataka, India

Correspondence Address:
Kharidhi Laxman Vandana
Department of Periodontics, College of Dental Sciences, Davangere - 577 004, Karnataka
India

Abstract

Aerosols are produced during dental procedures. An airborne route has long been said to be involved in transmission of infections. The recent COVID-19 has also been considered to spread by respiratory droplets or by the contact of contaminated surfaces. The nature of the dental practice hence poses threat to dentists, dental team, and patients owing to the accompanied aerosol-generating procedures. A thorough knowledge about the dental aerosol originated from various dental procedure needs to be present for suitable prevention of infectious hazards like the COVID-19. Hence, this review aims to throw light on literature related to mechanism and source of production, composition, microbial load, and potential diseases transmitted by dental aerosol.



How to cite this article:
Raj B S, Vandana KL. Dental aerosol: An insight.SRM J Res Dent Sci 2021;12:216-221


How to cite this URL:
Raj B S, Vandana KL. Dental aerosol: An insight. SRM J Res Dent Sci [serial online] 2021 [cited 2023 Feb 1 ];12:216-221
Available from: https://www.srmjrds.in/text.asp?2021/12/4/216/332895


Full Text



 Introduction



Microorganism such as bacteria, viruses, fungi is found in the aerosol produced during procedures done using dental handpieces, air water syringe, ultrasonic scaler, air abrasion, and polishing.[1] Right before the advent of infectious agents such as bacteria and viruses, the role of airborne route as a potential infection source was recognized significantly.[2] In the recent times of the COVID-19 pandemic, a detailed information of dental aerosol is very significant owing to its mode of transmission.

Bioaerosols have been implicated in contributing to indoor air pollution and gained notoriety in association with various conditions, such as Legionnaires' disease and sick building syndrome. For dental staff and patients around dental units, bioaerosols become the source of infection transmission via dental aerosol.[3]

It is of surprise that although aerosols are omnipresent in a dental setting, these are the ones, least studied.[2] The transmission of various diseases occurs through aerosols even without the knowledge of the dentist/patient. This is all due to the lack of awareness and incomplete information on the formation and dissemination of these infected particles in the dental clinic. For transmission in diseases such as severe acute respiratory syndrome (SARS), tuberculosis (TB), herpes virus, measles, the splatter, and droplet nuclei are implicated.[2] The recent coronavirus disease is known to be predominantly transmitted by droplet transmission. Coronavirus disease can become aerosolized by “aerosol-generating procedures” and then airborne transmission is possible.[4] The clinical implication of invisible aerosol found its importance during this pandemic and the spread of infection is being little understood.

There are few clinical studies pertinent to dental aerosol in dental clinic[5] and are not dealt commonly. There is a scarcity of literature related to dental aerosols under one roof. Hence, this current paper was planned to present definition, composition, mechanism of production, various diseases transmitted, potential diseases transmitted by dental aerosol.

 Terminologies and Definition



The terms aerosol and splatter have been used in literature interchangeably often. The difference between the two is represented in [Table 1]. Although both are potentially dangerous, aerosols can penetrate deep whereas the splatter, liquid evaporates, leaving the droplet nuclei which are the cause of many diseases.[2] The clinician should, however, know the distinction between the two and the procedures producing each so that appropriate precautions can be taken.{Table 1}

 Sources of Dental Aerosol Production in a Dental Clinic



Dental aerosols produced during any dental procedure are known to originate from the following sources.

Dental unit water lines

The water flowing from the dental unit waterlines (DUWLs) is known to be involved in the process of aerosol production significantly. The DUWL tubing has adherent bacterial biofilm which becomes the source of spread of infectious disease due to inadequate sterilization of DUWL and allows the shedding of bacterial following their usage at the time of dental procedures.[6]

Instruments

Instruments which aid in production of dental aerosols are dental burs along with handpieces, sonic and ultrasonic scalers, and polishing agents.[6] The high-speed handpieces and ultrasonic scaler tips are known to produce splatter and intensive aerosol emission.[3],[7]

Patients

Patient factors such as dental plaque, saliva, periodontal infection, blood, throat infection, and other dental infection are known to contribute toward aerosol production.[8] Depending on the type and site of dental procedure employed, aerosol composition differs from patient to patient.[1]

 Composition of Dental Aerosol



Dental aerosol is believed to be an ubiquitous aerosolized cloud comprising of debris arising from the treatment sites and DUWLs.[2] The varied composition of dental aerosol probably includes the following

Salivary componentsSecretions from nasopharynxDental PlaqueBlood componentsComponents of toothComponents of dental materials used during polishing such as abrasives.[2]

 Microbial Content of Dental Aerosol



Bacterial content

For the determination of the bacterial content, most of the studies measured the number of bacteria which settle over the period of time on culture plate media following which the colony-forming units (CFUs) were counted.[8] Most common disease-causing bacteria present in aerosol were found to be Staphylococci and Streptococci species, Mycobacterium tuberculosis, Legionella, Anthrax bacilli, and the by product of Gram-negative bacteria such as endotoxins.[3] Kobza et al. reported presence of Gram-negative, Gram-positive rod-shaped bacteria, endospore generating bacteria, and nonporous type bacteria in the aerosol of oral surgical; operating rooms.[9],[10]

Fungi in dental aerosols

Various fungi present in aerosol which are reported to be causative agent for allergic and respiratory infections comprise acremonium, penicillium, paecilomyces, aspergillus, cladosporium, and mucor. The aspergillosis fungal infection is found to be common in immunocompromised host and also present us secondary infection following inhalation of fungal toxins or spores produced by them.[11] The fungi isolated from dental unit waterlines are Phoma spp, Penicillium spp, Cladosporium spp, Alternaria spp, Scopulariopsis spp.[6]

Viruses in dental aerosols

The SARS coronavirus 2 (CoV 2) in the saliva of infected persons can be transmitted through droplets, and hence, COVID-19 transmission is possible during dental procedures.[12] The stability of SARS-CoV 2 in aerosols was evaluated by Neeltje Van Doremalen, who reported that there is a possibility of SARS- CoV 2 aerosol transmission due to viability of infectious virus in the aerosol for few hours. The mean half-life of SARS-CoV-2 was estimated to be 1.1 to 1.2 h.[11] The airborne transmission of COVID-19 has been reported to occur by two distinct modes with and without any physical contact between infected and susceptible individuals. At the instance of a sneeze or a cough, “droplet sprays” of virus-laden respiratory tract fluid, typically >5 mm in diameter, impact directly on a susceptible individual. Alternatively, the aerosol particles consisting of the residual solid components of evaporated respiratory droplets can also be inhaled by a susceptible person. These are reported to be tiny enough (<5 mm) to remain airborne for hours.[13]

It was reported that during speech, aerosol particles likely derive in part from a “fluid film burst” mechanism in the alveoli in the lungs as well as by means of the vibration of the vocal cords. Hence, if the mucus in the respiratory tracts would contain the virions, they would be expelled through the breath and speech.[14]

van Doremalen et al. conducted an experiment to evaluate the stability of the virus in aerosols and also estimated their decay rates using a Bayesian regression model. The results showed that SARS-CoV-2 remained viable in aerosols throughout the duration of the experiment (3 h), with a reduction in infectious titer from 103.5 to 102.7 TCID50 (50% tissue-culture infectious dose) per liter of air. It was thereby concluded that, the transmission of SARS-CoV-2 by the means of aerosol is plausible since the virus is bound to remain viable and infectious in aerosols for hours.[11]

However, neither the viral load in the aerosol nor the minimum infectious dose for COVID-19 has been definitively established, although it is believed that a single virus can serve its purpose to initiate infection.[15]

 Diseases Transmitted by the Dental Aerosols



Historically, the potential infection spread by airborne route was recognized much before the specific bacterial and viral infectious agents were discovered. A variety of diseases are known to spread by aerosols such as pneumonic plague, TB, and influenza. [Table 2] represents the list of occupational hazards to the dentist that can be transmitted through aerosol.[16] The risk assessment of infectious hazards during dental treatment showed that the M. tuberculosis exposure is a small risk while compared to close transmission by infectious patients.[17] It has been shown that the microorganisms in the DUWL and oral cavity gets mixed with environmental microflora as the air-water stream gets ejected from high-speed handpieces which are health hazard for the dental team and patient. Thus, it should be considered that dental team is immunized through specific (vaccines) or nonspecific (e.g., gamma globulin) immunization against biological hazards in their workplace.[1]{Table 2}

 Dental Procedures Producing Aerosols



The dental procedures requiring the mechanical instrumentation are the major source of production of airborne particles.[2] The airborne contamination produced by dental devices and procedures is given in [Table 3].{Table 3}

 Role of Saliva



The dental procedures which are known to aerosolize will allow the bacteria and viruses present in the saliva to cause airborne contamination.[2] This COVID-19 outbreak is a reminder that dental professionals should be responsible in the prevention of spread of infection and be diligent in utilization of noninvasive saliva, diagnostic for COVID-19 virus detection to prevent the spread.[18] The salivary diagnostic platforms can be utilized[19] for the diagnosis of COVID-19 as few of the virus strains are found in saliva for nearly 29 days after infection.[20],[21]

 Interpersonal Distance to Prevent Contamination



It has been demonstrated that exhalations, sneezes, and coughs not only consist of mucosalivary droplets following short range semiballistic emission trajectories but also actually are primarily made of a multiphase turbulent gas (a puff) cloud that entrains ambient air and are known to carry within it clusters of droplets with a continuum of droplet sizes.[22]

Droplets settling down along the trajectory course can contaminate surfaces, while the rest of the droplets remain trapped and clustered in the moving cloud. Eventually, the cloud and its droplet payload lose momentum and coherence capacity, and the rest of the droplets within the cloud evaporate, producing residues or droplet nuclei that may stay suspended in the air for hours.[22]

Taking into consideration, various factors such as patient's physiology and environmental conditions, such as humidity and temperature, the gas cloud and its payload of pathogen bearing droplets of all sizes can travel 23 to 27 feet (7–8 m).[23],[24]

However, Morawska and Cao[25] have brought out to notice that small particles with viral content may travel in indoor environments, covering distances up to 10 m starting from the emission sources, thus activating aerosol transmission. Similarly, Paules et al.[26] recently highlighted that the airborne transmission of SARS-COV-2 may also occur besides close distance contacts. Both experimental and computational fluid dynamic approaches have known to be supportive to these assumptions.[27]

Hence, it was on a general note, the inter-personal distance of 2 m can be reasonably considered as an effective protection only if everybody wears face masks.[28]

 Measures to Reduce Aerosol Contamination



The American Dental Association has recommended that potential contaminated aerosols or splatter be controlled during dental procedures. The various methods and devices are preprocedural rinsing with antiseptic mouthwash, barrier protection techniques, etc.[2] The advantages and disadvantages of each of these are presented in [Table 4].{Table 4}

 Measures in Particular for Reducing Aerosol Contamination from Severe Acute Respiratory Syndrome Coronavirus 2



Use of preprocedural mouth rinseRubber dam isolationAdequate ventilation in dental operatoryUse of protective gearEnvironmental Surface Disinfection.

Preprocedural mouth rinse for severe acute respiratory syndrome coronavirus 2

A preoperational antimicrobial mouth rinse is in general reported to reduce the number of oral microbes. However, as instructed by the Guideline for the Diagnosis and Treatment of Novel Coronavirus Pneumonia (the 5th edition) released by the National Health Commission of the People's Republic of China, CHX, routinely utilized as mouth rinse in dental practice, may not be effective to kill 2019-nCoV. The 2019-nCoV is known to be vulnerable to oxidation phenomenon, hence, a preprocedural mouth rinse containing oxidative agents such as 1% hydrogen peroxide or 0.2% povidone is recommended, for the purpose of reducing the salivary load of oral microbes, including potential 2019-nCoV carriage.[28]

Rubber dam isolation

During dental procedures that are known to generate aerosols, application of rubber dam will produce a barrier protection from the primary source and will virtually eliminate all pathogens emerging from respiratory secretion. The application of a rubber dam can significantly reduce airborne particles in an approximately 3-foot diameter of the operational field by 70%.[29] Disadvantage of rubber dam isolation is that it is not feasible in procedures that will require subgingival instrumentation, such as in case of subgingival restoration and subgingival crown margin preparation.[30]

Adequately Ventilated Dental Operatory

Indoor ventilation in a dental clinic is very essential in the time of this pandemic of COVID-19. These reports indicated that, the aerosol transmission of SARS CoV 2 was possible when the following three conditions were met

Closed spaceProlonged exposureHigh concentration of virus in air.[15]

Dilution of the indoor air from virus-laden aerosols can be made possible by continuously introducing fresh air into operating rooms by means of open windows.[31] Other means can be incorporation of the use of indoor air purifiers to improve the air quality and significantly reduce exposure to personnel in the dental clinic.[32] Furthermore, it has been reported that negative pressure rooms are also effective in reducing the risk of transmission for respiratory infections.[33]

Protective gear

Coronavirus disease can become aerosolized by “aerosol-generating procedures” and then airborne transmission is possible. Hence, to aid prevention for this use of personal protective equipment is only one part of a system to protect staff and other patients from COVID-19 transmission and hence has been recommended.[4]

Environmental surface disinfection

During aerosol generating procedures, droplets containing infective pathogens could be deposited on the surrounding surfaces. An analysis of 22 studies revealed that human coronaviruses, such as SARS and Middle East respiratory syndrome, can persist on inanimate surfaces for up to 9 d. However, they can be efficiently inactivated by surface disinfects within one minute. Surfaces are disinfected after each patient visit, especially surfaces in close proximity to the operating areas.[29],[34]

 Conclusion



Dental procedures are bound to produce aerosol and splatter which in turn is potential for the spread of various microbial infections and diseases to the dentists, patients, and other personnel in the dental clinic. Hence, a thorough knowledge of information regarding dental aerosol holds great significance which includes factors such as its source of production, mechanism of production, its microbial content, and the types of diseases transmitted through aerosol.

Furthermore, owing to the fact that, the dental professionals are at the high risk for exposure to infectious bacterial and viral diseases originating from aerosol spread, including the recent COVID-19, suitable strategies for prevention of aerosol production and contamination should be devised and considered.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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