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LONDON, UK: One of the greatest challenges for the dental profession in returning to normal business is the inherent risk of SARS-CoV-2 transmission via emitted sprays, associated with commonly performed dental procedures. A recent study by researchers at Imperial College London, King’s College London, and Guy’s and St Thomas’ NHS Foundation Trust found that controlling certain parameters could help during the current crisis to alter the key properties of sprays.
The use of high-velocity air and water streams in dentistry is essential for cooling rotary instrumentation or high-frequency instrumentation. Even though several safety measures have been installed in dental clinics, the likely contamination of practice spaces by sprays has led to the need to introduce periods of fallow time between appointments, in order to protect staff and patients. This limitation can be financially challenging for practice owners and, in addition, restricts patient access to dental care and the nature of care that can be provided.
While the study of dental sprays is not new, key information on the potential transmission of SARS-CoV-2 is insufficiently documented. This includes information on ranges of droplet size, emission trajectories, and droplet lifetimes.
Dental Tribune International contacted Dr Nicholas Jakubovics, editor-in-chief of the Journal of Dental Research, to ask how the study findings may support dental practices during the pandemic. He responded: “It is well known that dental instruments lead to aerosols and splatter, which pose major problems for infection control. This study provides important new information on how droplets of liquid are dispersed from rotary dental instruments.”
“In addition, the authors assessed approaches to mitigating the distribution of sprays. Potentially, this will help dental practices to identify the optimal approaches for conducting aerosol-generating procedures safely,” he added.
Using high-speed imaging, the researchers studied the characteristics of dental sprays produced using high-speed rotary instrumentation to identify the mechanisms leading to atomisation and ejection of high-velocity droplets. Variables examined included rotation speed, bur-to-tooth contact and coolant pre-misting. The research team highlighted that, by understanding these fundamental mechanisms, it may be possible to make generalisable findings to improve spray mitigation, independent of the operatory setting.
The research team found the elimination of pre-misting—mixing of coolant water and air prior to bur contact—to be highly beneficial for reducing sprays. However, radial atomisation may still occur and is modified by bur-to-tooth contact. In addition, reduced rotation speeds of 80,000–100,000 rpm were shown to control aerosol formation. Although this resulted in reduced cutting efficiency, the machining of enamel, dentine and some restorative materials was achievable with sufficient cooling to avoid pulp injuries.
“We will hopefully be able to manage the infection control risks even more effectively and to keep the profession working safely and efficiently not just in this pandemic, but also in more ‘normal’ times in future”
The study authors concluded that these measures may allow many routine dental procedures to be performed in the short term and may be realised without major changes to surgery environments. However, they also emphasised that individual risk assessment, for example taking into account local infection rates, must always guide the decision-making process.
According to Jakubovics, more research on the impact of mitigation procedures on aerosols and splatter is needed, as the research experiments were performed under controlled conditions only. The study authors found it difficult to model natural sprays from dental procedures because the positioning of the dental instrument by the individual clinician greatly affects the distribution of aerosols, he said.
While the SARS-CoV-2 pandemic has highlighted an urgent need for a better understanding of infection control in dentistry, it appears that steps such as enhanced personal protective equipment, fallow times and prescreening of patients have worked very well in keeping dental healthcare professionals and patients safe while maintaining the ability to deliver urgent dental care, Jakubovics noted.
He concluded: “With new information from studies like this one, we will hopefully be able to manage the infection control risks even more effectively and to keep the profession working safely and efficiently not just in this pandemic, but also in more ‘normal’ times in future.”
The study, titled “Mechanisms of atomization from rotary dental instruments and its mitigation”, was published online on 16 December 2020 in the Journal of Dental Research, ahead of inclusion in an issue.