An experimental approach to analyze aerosol and splatter formations due to a dental procedure

Abstract

Graphical abstract Throughout 2020 and beyond, the entire world has observed a continuous increase in the infectious spread of the novel coronavirus (SARS-CoV-2) otherwise known as COVID-19. The high transmission of this airborne virus has raised countless concerns regarding safety measures employed in the working conditions for medical professionals. Specifically, those who perform treatment procedures on patients which intrinsically create mists of fine airborne droplets, i.e., perfect vectors for this and other viruses to spread. The present study focuses on understanding the splatter produced due to a common dentistry technique to remove plaque buildup on teeth. This technique uses a high-speed dentistry instrument, e.g., a Cavitron ultrasonic scaler, to scrape along the surface of a patient’s teeth. This detailed understanding of the velocity and the trajectory of the droplets generated by the splatter will aid in the development of hygiene mechanisms to guarantee the safety of those performing these procedures and people in clinics or hospitals. Optical flow tracking velocimetry (OFTV) method was employed to obtain droplet velocity and trajectory in a two-dimensional plane. Multiple data collection planes were taken in different orientations around a model of adult mandibular teeth. This technique provided pseudo-three-dimensional velocity information for the droplets within the splatter developed from this high-speed dental instrument. These results indicated that within the three-dimensional splatter produced there were high velocities (1–2 m/s) observed directly below the intersection point between the front teeth and the scaler. The splatter formed a cone-shape structure that propagated 10–15 mm away from the location of the scaler tip. From the droplet trajectories, it was observed that high velocity isolated droplets propagate away from the bulk of the splatter. It is these droplets which are concerning for health safety to those performing the medical procedures. Using a shadowgraphy technique, we further characterize the individual droplets’ size and their individual velocity. We then compare these results to previously published distributions. The obtained data can be used as a first step to further examine flow and transport of droplets in clinics/dental offices.

Precise control of digital dental unit to reduce aerosol and splatter production: new challenges for future epidemics

“…The latest research utilized state-of-the-art experimental fluid mechanics tools to detect the number and the transmission speed of aerosol droplets through the advanced high-speed imaging techniques and optical flow tracking velocimetry. The initial velocity of these droplets can be quite significant, typically ranging between 1 m/s and 2.6 m/s [ 14 , 26 , 27 ].…”

“…Those studies concentrated on analyzing the properties of aerosol generation at a constant rotational speed, noting that the transmission path of aerosols varied with the turbine’s direction. In contrast, the purpose of our research is to find the best combination of generating less aerosol by precisely adjusting the rotation speed of the dental handpiece and the air-water ratio, so as to explore the methods of protecting oral hygiene professionals [ 14 , 26 , 27 ]. In this study, a simulated clinical working environment was established, and the transmission of aerosols and droplets was observed from various directions and angles on patients and medical staff.…”

“…In addition to the commonly used capturing fluorescein dye with filter papers, we innovatively replaced the filter paper with petri dish to collect splattered liquid drops containing S6P-encoding plasmid to quantify viral load. However, in previous aerosol research methods, S6P plasmids were not introduced into the experiments [ 14 , 19 , 26 , 27 ]. We then analyzed the copy number of the S6P plasmid through quantitative PCR, enabling the assessment of viral concentration and transmission.…”

Novel use of riboflavin as a fluorescent tracer in the dissemination of aerosol and splatter in an open operatory dental clinic

“…Droplets and aerosols can be generated from high‐ and low‐speed handpieces, air–water syringes, polishers, and ultrasonic devices (Innes et al, 2021 ). In the present study, we focused on the dissemination of droplets and aerosol from an ultrasonic scaler, which has been reported to be the main sources of aerosol and splatter generation in a dental practice (Haffner et al, 2021 ). While other studies commonly used fluorescein, adenosine triphosphate, citric acid, or bacteria as tracers for measuring dispersal, our study is novel in that we are the first to use riboflavin in live patient volunteers (Holliday et al, 2021 ; Lloro et al, 2021 ; Puljich et al, 2022 ; Shahdad et al, 2020 ; Watanabe et al, 2018 ).…”

Quantifying strategies to minimize aerosol dispersion in dental clinics

“…Particles were released with an initial velocity of 7 m/s perpendicular to a circular surface at the center of the patient's mouth. The velocity of 7 m/s is a median of the particle velocity range of 2-12 m/s reported for dental instrumentation (dental drilling, ultrasonic scaler, and 3-in-1 air water syringe) (Eames et al, 2021;Haffner et al, 2021;Li et al, 2021;Sergis et al, 2021;Ohya et al, 2022). An inlet-velocity boundary condition with air velocity of 7 m/s was imposed at this circular release surface to approximate the momentum transfer from particles to the surrounding air.…”