The risks of transmission by aerosols in the dental and medical practice

In a working day of eight hours, the average number of breaths amounts to 7,680. Are you protected from the risk of inhalation of bioaerosols during patient care and infection control-related activities?

An article published by Leann Keefer in RDH Magazine, a leading online magazine dedicated to dental hygiene professionals, opens with this question. It is a legitimate question, especially at this time of global emergency, and the answer highlights on the one hand the invisible risks associated with working in the dental profession, and on the other hand the importance of the choice and correct use of PPE in the dental practice, in particular masks.

Covid-19 is a respiratory infectious disease caused by the virus known as SARS-CoV-2 belonging to the coronavirus family. Its spread in the dental field occurs mainly via respiratory droplets: saliva secretions emitted from an infected subject by coughing or sneezing, or even just talking, that are inhaled by a second individual who is nearby.

The droplets can cover a distance of up to 2 metres, remain suspended in the air for a short time and also remain on surfaces, with a variable duration depending on the porosity of the material.

Future medical procedures will be strongly influenced by the current epidemic will lead to greater use of gowns, shoe covers, caps, visors and especially surgical masks and respirators, such as FFP2 masks. It is therefore important to know the risks and the types of surgical masks on the market.

The average of 7,680 breaths each working day is a figure that makes us realise just how high the exposure and the likelihood of contamination are for dentists and operators who are in close contact with patients on a daily basis and for much of their working lives. One should not overlook the fact that the instruments used in the dental environment (scalers, ultrasonic scalers, handpieces) are able to release particles into the environment, forming what is called “bioaerosol”, a mix of invisible airborne particles that can be a vehicle for viruses, bacteria and spores.

As Leann Keefer reminds us in her article: “The composition of bioaerosol is heterogeneous: it may contain blood, micro-organisms, mucous cells, restorative materials, tooth particles and large quantities of saliva. […] aerosols in the dental environment can travel up to 1.2 metres from the workstation and also remain airborne for up to 30 minutes, putting the dental team at risk of infection.”

In addition to inhalation, there may be multiple means of transmission (contact, inoculation, ingestion) and also relate to very small particles which, in the case of transmission by aerosol, are carried by air currents even at a great distance. In this case we speak of transmission by infected micro-droplets released into the environment, which may come into contact with eyes, nose and mouth.

While not explicitly mentioning the concept of “indoor pollution”, i.e. the contamination factors in enclosed environments, Leann Keefer’s article goes on to identify the water supplied by the hydraulic circuit of the dental chairs as another possible threat.

Each change of water, or aerosols generated by the equipment, constitutes a potential source of exposure to opportunistic micro-organisms present in the water, including Legionella, Pseudomonas and Mycobacterium, that can survive and proliferate in the intricate pipes of the dental chair.

In fact, we should not forget that the surgery is an enclosed environment and using air conditioning and water are further sources of pollution and spreading of aerosols. 

 It is well documented that the most likely mode of dental disease transmission is through the inhalation of aerosols or bacterial spray. 95% of the aerosol in the dental environment has a diameter of 5.0 µm or less and is not visible. Microorganisms isolated from these particles include staphylococci, pneumococci, tubercle bacilli, influenza and hepatitis viruses, rhinoviruses and herpes viruses.

In order to prevent and deal with pollution from aerosols and the spread of the coronavirus in the dental practice, the use of barrier products becomes a key element for both the patient and the operators involved.

Read the article “How to Protect Yourself from Inhaling Aerosols” and find out about the differences between surgical masks and respirators and their use according to the dental procedure to be performed (procedures that do not generate aerosols vs. procedures that generate aerosols).