The use of
standard precautions (
including hand hygiene, PPE, safe use and disposal of sharps, routine environmental cleaning, reprocessing of instruments and equipment, respiratory hygiene and cough etiquette, aseptic technique, and waste management) is the
principal way we minimise the transmission of infections in any healthcare setting, including dental practice, and are applied to everyone, regardless of their perceived or confirmed infectious status. They ensure a
basic level of infection prevention and control. Standard precautions are used when undertaking treatments or procedures where there is handling of blood, body fluids (e.g. saliva), non-intact skin, and mucous membranes.
Transmission based precautions (contact, droplet or airborne) are used in addition to standard precautions when there is suspected or confirmed presence of infectious agents
that are not effectively contained by standard precautions alone. The type of transmission based precaution required is dependent on the route of transmission of the infectious agent:
- Contact precautions
- are used when there is a risk of direct/indirect transmission of infectious agents e.g. highly contagious skin infections/infestations such as methicillin-resistant staphylococcus aureus (MRSA) and vancomycin resistant enterococcus (VRE)
- Direct transmission occurs when infectious agents are transferred from one person to another, without a contaminated intermediate object or person.
- Indirect transmission involves the transfer of an infectious agent through a contaminated intermediate object (fomite) or person.
- Droplet precautions
- are used when there is a risk of transmission through large respiratory droplets (>5 microns) or mucous membrane contact with respiratory secretions, generated by a patient who is coughing, sneezing, or talking. e.g. influenza, norovirus, pertussis, meningococcus.
- Transmission via large droplets requires close contact as the droplets do not remain suspended in the air and generally only travel short distances. As the droplets do not travel over long distances, special air handling and ventilation are not required.
- The droplets can contaminate horizontal surfaces close to the patient, and the hands of healthcare workers can become contaminated through contact with these surfaces.
- Airborne precautions
- are used when there is risk of transmission through small respiratory droplets (<5 microns) that remain infective over time and distance when suspended in air. e.g. measles, chickenpox, tuberculosis
- Transmission via small droplets can result due to inhalation by susceptible individuals who have not had face-to-face contact with (or been in the same room as) the infected individual.
The WHO has confirmed that coronavirus responsible for SARSCoV2 or COVID-19 is spread primarily through droplets generated when an infected person coughs, sneezes or speaks, however transmission can also occur by touching a contaminated surface and then touching the eyes, nose or mouth before washing your hands. While this would suggest that droplet precautions are required for patients identified as positive to COVID-19, most dental treatments are identified as aerosol generating procedures, and therefore the Australian Guidelines for the Prevention and Control of Infection in Healthcare (2019)
[1], states that
“if a patient requires care under droplet precautions but an aerosol generating procedure is undertaken, then droplet precautions should be increased to airborne precautions for at least the duration of the procedure.”
The Center for Disease Control and Prevention advice for Dental Settings[2] states that there is currently no data available to assess the risk of SARS-CoV-2 transmission during dental treatments, or to determine whether dental healthcare professionals are adequately protected when providing dental treatment when using
Standard Precautions, however they have referenced the Occupational Safety and Health Administration’s Guidance on Preparing Workplaces for COVID-19
[3] which places dental practitioners in the
very high exposure risk category, as their jobs are those with high potential for exposure to known or suspected sources of the virus that causes COVID-19.
The CDC concluded that when practicing dentistry in the absence of Airborne Precautions, the risk of SARS-CoV-2 transmission during aerosol generating dental procedures cannot be eliminated, and provided the following recommendation:
- Avoid aerosol generating procedures whenever possible. Avoid the use of dental handpieces and the air-water syringe. Use of ultrasonic scalers is not recommended during this time. Prioritize minimally invasive/atraumatic restorative techniques (with hand instruments only).
- If aerosol generating procedures are necessary for emergency care, use four-handed dentistry, high evacuation suction and dental dams to minimize droplet spatter and aerosols.
This is not the first coronavirus pandemic this century. In 2003 we had Sudden Acute Respiratory Syndrome caused by SARSCoV1. A retrospective review
[4], outlined measures to reduce the risk of cross infection with coronavirus in the dental setting, including the identification of patients with SARS through targeted screening questions, pre-procedural rinsing, hand hygiene, PPE, rubber dam isolation and recommended that
“aerosol-generating procedures should be avoided as much as possible if rubber dam isolation is not feasible. Some of these procedures include ultrasonic scaling, root-surface debridement, and high- or low-speed drilling with water spray.” These measures were adopted in both the ADA Managing COVID-19 Guidelines and ADA Dental Service Restrictions documents. A conclusion of this article was that while no dental healthcare worker was affected in either a nosocomial or dental setting, this was thought to be due to the use of universal infection control measures and/or the low degree of viral shedding in the prodromal phase of SARSCoV1.
While both SARSCoV2 and SARSCoV1 demonstrate high viral loads in posterior oropharyngeal saliva samples, SARSCoV1 viral load was found to peak at 10 days after symptom onset. In comparison, SARS CoV2 has the highest viral load on presentation, suggesting that SARS-CoV-2 can be transmitted easily, even when symptoms are relatively mild. This finding could account for the fast spreading nature of this pandemic, with efficient person-to-person transmission noted in community and health-care settings.
[5]
[4] Samaranayake L, Peiris M
Severe acute respiratory syndrome and dentistry. A retrospective review
JADA 2004; 135: 1929-1302.
[5] To KK-W, Tsang O T-K et al
Temporal profiles of viral load in posterior oropharyngeal saliva samples and serum antibody responses during infection by SARSCoV2: an observational cohort study
The Lancet Infec Dis 2020; 20: 565-74