Last Updated: 7 June, 2020
An aerosol is defined as a suspension of solid or liquid particles in a gas, containing bacteria or viruses. The particle size of an aerosol is less than 50µm whereas spatter is the airborne particle larger than 50 µm. Spatter being the largest particle will fall until it contacts other objects (floor, countertop, sinks, table, computer, patient, operators, etc.).
The current scientific consensus is that the transmission of COVID-19 virus occurs via respiratory secretions, in the form of large respiratory droplets rather than small aerosols. Droplets being heavy enough do not travel far; falling from the air after traveling up to a maximum six feet distance. The problem occurs when viral particles are aerosolized by a cough, sneeze, or dental care procedures. According to a study, ultrasonic and sonic transmission during nonsurgical treatments has the highest incidence of particle transmission, followed by air polishing, air/water syringe, and high-speed handpiece aerosolization.  In these instances, particles can potentially travel greater distances, estimating up to 20 feet, from an infected person and can spur secondary infections elsewhere in the milieu. These aerosolized droplet nuclei can remain in an area, suspended in the air, even after the person who emitted them has left, which can contaminate surfaces and be the source of infection for health-care worker. The virus is viable in suspended aerosols up to three hours.
The nose can typically filter air particles above 10 µm. If a particle is less than 10 µm, it can enter the respiratory system and can enter the alveoli if its size is less than 2.5 µm. A particle which is less than 0.1 µm, or an ultrafine particle like the COVID-19 virus, can enter the bloodstream and target vital organs such as the heart and brain.
Therefore, to effectively minimize aerosol contamination, American Dental Association (ADA) and the Center of Disease Control and Prevention (CDC) have recommended preprocedural mouth rinse AS AN IMPORTANT PROTOCOL TO BE FOLLOWED BY EVERY DENTIST.
Following are the list of chemicals that can be used as a preprocedural mouthwash:
Chlorhexidine is considered as the most potent anti-plaque agent. It possesses an excellent property of substantivity which means that it has an intrinsic ability to be retained by oral surfaces, and is gradually released into oral fluids over many hours. Studies indicate that it can result in a prolonged suppression (up to five hours) of oral microorganisms. The oral rinse can be gargled in back of the throat and q-tips can be moistened with chlorhexidine to swab the inside of the nostrils.
Although, some studies concluded that chlorhexidine is NOT effective against the novel corona virus (Kamph G et al 2020)  and that it has poor viricidal property (Farzan and Firoozi, 2019) . But these studies have analyzed the effect of Chlorhexidine as a surface disinfectant at a very low concentration of 0.02%. According to a recent study published in The Lancet chlorhexidine (0.05%) is as effective as povidone-iodine against the corona virus . Chlorhexidine mouthwashes are typically available in 0.12% and 0.2% concentrations, both of which are 2 to 4 times more concentrated than the 0.05% chlorhexidine solution. (Dr. Rajeev Chitguppi) . A latest study published on 25th May concluded that chlorhexidine (0.12%, 15 mL for 30 seconds) mouthwash was effective in viral suppression for 2 hours after using the mouthwash once. Moreover, it is a low risk, cheap and readily available mouthwash in medical stores. It is not recommended for people under the age of 18 and during pregnancy.
Dose for the pre-procedural mouth rinse: 15ml of 0.12% chlorhexidine for 1 minute or 10 ml of 0.2% for 1 minute.
It exhibits considerably greater viricidal activity than chlorhexidine against respiratory viruses by a factor of 8000 times. It is also more clinically accepted by the patient in terms of taste. However, it exhibits poor substantivity allowing the oral microflora to reestablish within several minutes. If the patient were to have Covid-19 the virus could potentially be replaced quite rapidly via the saliva (Khurshid et al., 2020) 
Availability: Hydroxyl by Sandika Pharmaceutical is available in India. Peroxyl by Colgate is another brand with same composition.
Dose for the pre-procedural mouth rinse: 10 ml of 1.5% hydrogen peroxide for 1 minute prior to the procedure
Povidone Iodine (PI)
Povidone-iodine is a chemical complex of polyvinylpyrrolidone, hydrogen iodide, and elemental iodine. PI exhibits the highest viricidal activity as compared to chlorhexidine and other commercially available mouth washes. Previous studies have shown that SARS-CoV and MERS-CoV were highly susceptible to povidone mouth rinse. However, it must also be kept in mind that PI also has poor substantivity property. (Addy and Wright, 1978)
Dose for the pre-procedural mouth rinse: 5% PI diluted to 0.2% and after 15 seconds. (To obtain this ratio: Dilute 5 % in 1:25 ratio or 10% in 1:50 ratio)
1% Sodium hypochlorite mouthwash is advised for a pre-procedural rinse in Periodontics. For the mouthwash to be effective, it should be freshly prepared and the recommended dilution is 1:49 ratio of 5% Sodium hypochlorite.
Calculation for dilution: To dilute 5% of Sodium hypoclorite to 1%, 4 times water is to be added to the stock solution.
Eg: To convert 10 ml of 5 % Sodium Hypochlorite to 1 % Sodium hypoclorite, 40 ml of water is to be added.
Just add a line on any role of alcohol-based mouthwashes. Any study done with them?
The simple step of having patients rinse with a preprocedural mouth rinse can lower the concentration of microorganisms found in splatter and aerosols and prevent cross infection among dentists and patients. Studies indicate that Corona Virus is susceptible to oxidation and therefore a pre-procedural mouth rinse with 1% hydrogen peroxide or 0.2% povidone-iodine is a good choice. Some worthy recommendations for pre-procedural rise have been proposed by esteemed Indian dental specialist. Dr. Ajay Kakkar  has suggested using 0.2% poividone-iodine followed 0.2 % chlorhexidine digluconate mouthwash or an essential oil mouthwash like Listerine. This causes suppression of oral micro-organism for a period of 1.5 hours. Similar combination can be done by using hydrogen peroxide followed by Chlorhexidine mouthwash. Studies have shown that adjunctive use of hydrogen peroxide with chlorhexidine is far superior to the usage of chlorhexidine alone in reduction of microorganisms in aerosols ,  Dr. V. Gopikrishna suggested using either 1% hydrogen peroxide or 0.2% povidone-iodine as both these mouthwashes exhibit substantially more virucidal activity than chlorhexidine. Although a latest study published in Journal of Korean Medical Sign reported that chlorhexidine (0.12%, 15 ml used for 30 seconds) is effective in reducing corona virus load from oral cavity for 2 hrs. (25th May, 2020) . More such studies are required to establish the ideal protocol for the preprocedural mouth rinse in the dental surgery environment.
Also, it is very necessary for us clinicians to understand that the COVID-19 pandemic is a rapidly developing situation, and information may quickly become outdated. Therefore, we need to keep ourselves updated with all the latest articles related to COVID -19.
 Harrel SK, Molinari J. Aerosol and splatter in dentistry: a brief review of the literature and infection control implications. J Am Dent Assoc. 2004;135(4):429-437. doi:10.14219/jada.archive.2004.0207
 Kampf G. et al Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents. J Hosp Inf. 2020;104:246-251. https://doi.org/10.1016/j.jhin.2020.01.022
 Farzan A, Firoozi P. Common Mouthwash for Pre-Procedural Rinsing in Dental Practice: Which One is approproiate for Eliminating Coronaviruses? A Mini Literature Review. Regen Reconstr Restor 20202;5(1)
 Chin AWH et al. Stability of SARS-CoV-2 in different environmental conditions. The Lancet. Open Access Published: April 02, 2020. DOI: https://doi.org/10.1016/S2666-5247(20)30003-3
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 Coronavirus Disease 19 (COVID-19): Implications for Clinical Dental Care joe
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 Prevention of cross-contamination in dental clinics: Practical suggestions from Dr Ajay Kakar – By Dental Tribune South East Asia. (Link)
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