Which mask?
Masks supplied for use in dental practice are required to conform to AS/NZS 4381 developed by Standards Australia. This standard specifies types of masks and their use. Below is an explanation of the types of masks that dental practitioners might use.
LEVEL 1
Level 1 masks are not generally or widely used in dental practice, and they would only be appropriate 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
Level 2 masks are most commonly used in dental practices due to their ability to block particle sizes commonly encountered in routine dental practice. 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, National Health and Medical Research Council (NHMRC) and ADA Infection Control Guidelines stipulate that clinical staff are to wear surgical masks which meet Standard AS 4381 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.
A correctly fitted well-adapted Level 2 surgical mask will block 95% of total viral influenza particles, but effectiveness drops to 56% or less if loosely fitted or if the mask is gaping at its sides. Instructions available HERE.
LEVEL 3
Level 3 masks have a higher level of splash protection and are used for procedures where there is a greater risk for potential exposure to blood and body fluids, such as surgical procedures and major trauma. The correct use of Level 3 masks is specified in Australian Standard AS4381:2002.
During the COVID-19 pandemic Level 2 and 3 surgical masks may be used while treating low risk and medium risk cases (where aerosols are avoided).
P2/N95 Respirators
Airborne precautions are required when treating medium risk COVID-19 patients if aerosol generation is likely (there is no reasonable alternative), and for all treatment of high-risk patients. Airborne precautions, such as wearing P2 (N95) surgical respirators, are designed to reduce the likelihood of transmission of microorganisms that remain infectious over time and distance when suspended in the air. In addition to COVD-19, other infectious agents for which airborne precautions are indicated include measles, chickenpox (varicella), and Mycobacterium tuberculosis, as well as novel respiratory pathogens such as H5N1 influenza and avian influenza.
Maintaining safe practice
With respect to the challenges many practices are facing as a consequence of the mask supply issue it is vital that as a profession and individuals maintain safe practices, to protect ourselves, our staff, our patients, family and friends.
Examples of unacceptable practices include:
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 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.
Similarly, 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. For example, 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.
ADA Guidelines for Infection Control
Page 8 of the ADA's Infection Control Guidelines offers further information as outlined below:
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.
