Mechanisms of Atomization from Rotary Dental Instruments and Its Mitigation.

Area of Science:

• Dental research
• Aerosol science
• Infectious disease transmission

Background:

• Dental procedures generate sprays (aerosols and splatters) posing a risk for severe acute respiratory syndrome coronavirus 2 transmission.
• Existing studies on dental sprays lack generalizability, necessitating a deeper understanding of production mechanisms.

Purpose of the Study:

• To elucidate fundamental mechanisms of spray production from rotary dental instruments.
• To identify controllable parameters influencing high-risk spray characteristics, such as suspended droplets and high-velocity splatter.

Main Methods:

• Parametric study of procedural sprays using variables like rotation speed, burr-to-tooth contact, and coolant premixing.
• High-speed imaging and laser light-sheet illumination for visualization and droplet velocity estimation.
• Spatial probability distribution mapping to identify atomization thresholds.

Main Results:

• Rotary instruments produce complex sprays, with air turbines projecting droplets over 12 m/s and generating millions of suspended droplets.
• Eliminating coolant premixing significantly reduced small droplet formation.
• Radial atomization threshold identified between 80,000 and 100,000 rpm, with reduced cutting efficiency but maintained coolant effectiveness.

Conclusions:

• Multiple mechanisms contribute to fluid atomization in rotary dental instrumentation.
• Controlling parameters like coolant premixing and rotation speed can modify spray characteristics to mitigate infectious disease transmission risks.
• Findings offer practical strategies for enhancing operatory safety during the COVID-19 pandemic.