The effect of high-speed dental handpiece coolant delivery a
High-speed dental instruments produce aerosol and droplets. The objective of this study was to evaluate aerosol and droplet production from a novel electric micromotor handpiece (without compressed air coolant) in real-world clinical settings.

10-minute upper incisor crown preparations were performed in triplicate in an open-plan clinic with mechanical ventilation providing 3.45 air changes per hour. A 1:5 ratio electric micromotor handpiece that allows water coolant without compressed air was used at three speeds: 60,000, 120,000, and 200,000 revolutions per minute. Coolant solutions contained fluorescein sodium as a tracer. High-speed air-turbine positive control and negative control conditions were conducted.

Aerosol production was evaluated at 3 locations using: (1) an optical particle counter to detect all aerosol; and (2) a liquid cyclone air sampler to detect aerosolized fluorescein, which was quantified by spectrofluorometric analysis. Settled droplets were detected by spectrofluorometric analysis of filter papers placed onto a rig across the open-plan clinic.

- Local settled droplet contamination was elevated above negative control for all conditions, with no difference between conditions.

- Settled droplet contamination was not detected above negative controls outside the treatment bay for any condition.

- Aerosol detection at 1.5 m and 1.7 m, was only increased for the air-turbine positive control condition. At 0.5 m, aerosol levels were highly elevated for the air-turbine, minimally elevated for 200 K and 120 K, and not elevated for 60 K.

Electric micromotor handpieces that use water-jet coolant alone without compressed air produce localized droplet contamination but are unlikely to produce aerosol contamination beyond the immediate treatment area, allowing them to be used safely in most open-plan clinic settings.

Journal of Dentistry