Dentistry and COVID-19 – how risky is it?
The dental profession has been considered at increased risk of acquiring SARS-CoV-2 from patients given most dental procedures generate aerosols.
When the SARS-CoV-2 pandemic first surfaced in 2020, there was a lot of speculation about the increased risk for dental practitioners, both from onward transmission of the virus from patient to dental staff, but also from patient to patient. This was predicated on the fact that many dental procedures generate aerosols, and the aerosols and droplets produced during treatment would remain airborne for extended periods before settling onto surfaces or infecting other people who shared or entered the room. There was a further challenge in that the viral load was known to peak around the time of symptom onset, making it difficult to screen patients who may have been infectious but asymptomatic.
Of course, this sparked a great deal of panic across the dental profession, particularly when images such as this, from the New York Times in March 2020 attempted to quantify that risk and placed dentists in the highest risk category.
As a result, routine dental care was suspended or restricted in many countries through concerns of virus transmission, and professional bodies and governments grappled with the most appropriate way to deliver care in a safe way. Of course, the impact on the provision of dental care was significant, and there is no doubt that many people saw their oral health deteriorate as a consequence.
Dentists (and their patients) in Victoria experienced more than 200 days of lockdown where they were mandated by the Victoria government mandated to only provide dental care for urgent and emergency cases. The rationale for restricting access to care was the perceived increased risk of transmission in the dental setting and the need to limit movement of people in the community to minimise the risk of transmission. Routine dental care to be non-essential and therefore able to be deferred, which points to a lack of understanding of the importance of oral health in the broader context of overall health.
From an infection control perspective, the dental profession developed guidelines to assist practitioners, based on the best available international evidence as it emerged. This included a layered protection approach to including patient screening, enhanced personnel protective equipment (PPE), preprocedural mouthwash, rubber dam, high volume suction, and a triage and management framework that proposed various levels of restriction on dental services based on the risk of community transmission to provide the dental profession with staged guidance in the event of an escalation of SARS-CoV-2 infections in the community.
Despite concerns about the perceived risk of transmission in the dental practice setting, there is little evidence of this in the literature, with very few documented cases of transmission in the dental setting in reported.
Risk of transmission of SARS-CoV-2 in the dental practice setting
Despite the perception that the dental profession is at increased risk of workplace acquired SARS-COV-2, the evidence does not appear to support this, with very few reported cases of transmission in the dental setting in Australia or in the international literature.
The Victorian Department of Health collected routine surveillance data on healthcare worker infections. There were 262 documented cases of staff working in dental settings contracting SARS-COV-2 between March 2020 and December 2021. This included 62 cases of a dentist test positive for SARS-CoV-2 whilst working in a dental setting during their acquisition phase. Four were likely to have been patient acquired based on contact tracing, with the vast majority of cases involving dental staff likely to have been acquired at home or in the community, and not during the provision of dental treatment.
A self-reported study of 2195 dentists in the USA found that twenty dentists had either confirmed or probable SARS-COV-2 cases - an estimated prevalence of 0.9% weighted to age and location of dentists nationally, and for those investigated by contact tracing, none identified the dental practice as the source of transmission. A follow up study found 57 dentists with confirmed or probable SARS-COV-2 infection, representing a cumulative prevalence of 2.6% over a 6-month period from June to November 2020 in the USA, with no confirmed cases of transmission related to patients receiving oral health care.
A seroprevalence cohort study of dental care providers in the United Kingdom found a higher baseline seroprevalence of SARS-COV-2 infection of 16.3% than the general population in May 2020, which was seen as evidence of the higher occupational risk that the dental profession faces. When enhanced PPE and other measures were introduced, the seroprevalence of previously seronegative dental care providers decreased to 11.7%, suggesting these risk mitigations measures reduced the occupational exposure risk to that of the background population level. A number of other studies in Argentina, Canada, Israel and Germany all found similar or lower levels of SARS-CoV-2 infection in dental practitioners than the general population. The low level of cases reported in Victoria, notwithstanding the reduced dental activity during lockdowns, is consistent with this international data that suggests that the practice of dentistry was not inherently higher risk for transmission.
Aerosol generating procedures
The perception of high risk in the dental environment was linked to droplet and aerosol transmission with the generation of dental aerosols mixed with patient saliva. Several recent studies have called into question the risk posed by aerosol generating procedures in dentistry. Although dental aerosols are known to cause significant contamination of the operator and assistant and have the potential to travel several metres in the absence of other mitigating measures, most of this contamination is the water from the dental handpiece, with the irrigant used to cool the dental handpieces diluting the saliva by 10-200 fold. This irrigant is the major source of bioload in dental aerosols. This suggests the risk for transmission of SARS-CovV-2 from aerosolised saliva in dental operatories is moderately low, with little evidence to definitively implicate saliva as the primary source of contamination of aerosols.
High volume evacuation
High volume evacuation used for routine dental procedures is effective in reducing both localised spatter and aerosols generated during dental treatment. Although it has only a moderate impact within the local area – likely due to local contamination being due to large droplets or high velocity small droplets not removed by dental suction, it has a marked effect on aerosol contamination at further distance because it removes smaller lighter droplets and aerosol more easily, and it is these that likely cause distant contamination.
Implications for dentistry
The initial decision to restrict the provision of dental care was based on uncertain and unknown risk, and appeared reasonable at the outset of the pandemic. However, dentistry had a strong track record with respect to infection control, with significant enhancements following on from HIV in the 1990s.
Restricting access to essential dental care meant that many patients had to defer care, increasing the risk of dental disease remaining undiagnosed and becoming progressively worse, or planned treatment being compromised. There are also quality-of-life impacts when necessary dental care is restricted.
Decision makers and health planners often do not include oral health care when defining or designing essential health care services and dental care is usually viewed as separate, and often a private responsibility. This is despite the significant burden of oral diseases worldwide and the impact of poor oral health on general health, well-being and the broader economy. This lack of understanding from government officials about the importance of oral health and the impact of restricting access to dental care has likely created a tsunami of oral health problems. It is therefore critical that dental experts are more involved in future pandemic preparedness planning, to ensure that we have learnt from these mistakes.
There should not be a requirement in the future to restrict access to dental services or defer any necessary dental care on the basis that it involves the generation of aerosols. This is critically important in ensuring that patients can access necessary dental care to prevent adverse outcomes that result from delayed or deferred care.