Which Mask and When

Last updated: 15 July 2021

In July 2020 the World Health Organisation recognised officially that COVID-19 could be spread by the aerosol route. By that time there had been numerous studies published showing airborne transmission of the virus. This mode of transmission is particularly important when people are in close proximity for longer periods of time, as is the case when dental treatment is being provided. The emergence of variants of the virus, particular the Delta strain, increases the need to address airborne transmission.
 
It is necessary to not only use appropriate respiratory protection, but also to use layered infection control measures such as preprocedural mouth rinsing and high volume evacuation to limit the spread of aerosolised material from the patient's mouth.
 
Moreover the respiratory protection that is being used needs to have the ability to filter the virus. For clarity, when a surgical mask is being worn, consider the performance of the mask and only use a mask that has a high value for particle filtration efficiency (PFE) which relates to particles of the size range of 0.1-0.2 microns.  A surgical mask does not provide an airtight seal against the face so cannot be relied upon to remove viruses. The information below provides further elaboration around issues of selecting masks and respirators. The choice of suitable respiratory protection equipment is addressed in the ADA decision trees.

Regulatory obligations

Public health regulators or local authorities may stipulate the people in the community in certain regions should wear masks in public, while some health services may stipulate that, depending on the stage of the pandemic, all staff in a health care workplace (whether working chairside or not) should wear a mask whilst in the clinical environment. Implementation of such measures may occur in public sector clinics as a directive of the health minister, jurisdictional chief medical officer or director general of health. This can create a situation where the application of such measures differ between public sector and private practice dental clinics, so staff working across both need to keep abreast of the changing requirements for their workplace.  

The use of masks whilst in the clinical workplace  coincide with changes in the advice that have come through the literature and from the WHO on the possibility of airborne spread of SARS-CoV-2 and the  benefits of wearing masks to reduce this spread, particularly when there may be a large number of asymptomatic infected persons in the community.

Dental staff need to comply with public health directives and local policies.

Masks

The ADA Infection Control Guidelines states:

Dental procedures can generate large quantities of aerosols of three microns or less in size and a number of diseases may be transmitted via the airborne (inhalational) route. In the dental surgery environment, the most common causes of airborne aerosols are the high-speed air rotor handpiece, the ultrasonic scaler and the triplex syringe. The aerosols produced may be contaminated with bacteria and fungi from the oral cavity (from saliva and dental biofilms), as well as viruses from the patient’s blood. Therefore, dental practitioners and clinical support staff must wear suitable fluid-resistant surgical masks that block particles of three microns or less in size.

Masks protect the mucous membranes of the nose and mouth and must be worn wherever there is a potential for splashing, splattering or spraying of blood, saliva or body substances, or where there is a probability of the inhalation of aerosols with a potential for transmission of airborne pathogens. However, it is suggested that masks be worn at all times when treating patients to prevent contamination of the working area with the operator’s respiratory or nasal secretions/organisms.

Surgical masks for dental use are fluid-repellent paper filter masks and are suitable for both surgical and non-surgical dental procedures that generate aerosols. The filtration abilities of a mask begin to decline with moisture on the inner and outer surfaces of the mask after approximately 20 minutes. It is difficult to change masks during long procedures (such as surgical procedures) and is not necessary unless the mask becomes completely wet from within or without. For more information please see ADA guidelines for Infection Control Page 8

Surgical Masks

Masks supplied for use in dental practice are required to conform to AS/NZS 4381.

LEVEL 1
  • Level 1 masks are not generally or widely used in dental practice, however, should a practice need to be judicious with their supplies during this shortage of level 2 masks, practitioners may wish to consider their use where there is no risk of blood or body fluid splash. This may be the case in some areas of practice (e.g. when conducting post-insertion reviews for removable prosthodontics, mouthguards or removable orthodontic appliances, or performing orthodontic adjustments which exclude the use of the triplex syringe).
LEVEL 2
  • Most commonly used in dental practices
  • Restorative, endodontic and periodontal procedures using powered devices such as air turbine high speed drills, ultrasonic scalers and triplex syringes generate large quantities of aerosols of three microns or less in size.
  • When undertaking such procedures, Standard AS/NZS 4381, NHMRC and ADA guidelines all require clinical staff to wear suitable surgical masks that block particles of three microns or less in size, with level 2 splash resistance, so that splashes of fluid do not compromise the filtration performance of the mask.
LEVEL 3
  • For surgical or other procedures or tasks where large amounts of fluid splashing are expected, level 3 splash resistance may be appropriate. This is specified in AS/NZS 4381.
Overuse:
  • It is important that we all be prudent in our use of masks as a consumable item as overuse will contribute to a greater supply issue.
  • A practical example of overuse would be that it is NOT necessary for a dental assistant to change their mask at the end of a patient appointment just to undertake the normal change-over environmental cleaning stage. They would remove these masks prior seeing the next patient.

Unacceptable practices:

  • Using one mask for more than one patient.
  • Using one mask for more than 2 hours.
  • Resterilising masks. Steam sterilising would alter the charge on the microfibers that are responsible for particle filtration, cause degradation of the mask straps, render the splash protection useless, and actually cause parts of the mask to disintegrate or melt, and release some toxic vapours.
  • Using a cloth (e.g. cotton or gauze) mask.  These have poor filtration (no bacterial filtration or particle filtration), no splash protection and no resistance to fluids from the user coming through.
  • Using a face-shield with no mask.
 
Alternative solutions to surgical masks:
  • Respirators
  • The ADA is looking at ensuring a supply of suitable level 2 masks for dental practices and will provide further advice once alternate sources have been identified.  This may include N95/P2 respirators which are beyond the protection of level 2 masks.

 
If you require any further information about the use of masks, please call your local Branch of the ADA or [email protected]

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