The effect of high-speed dental handpiece coolant delivery and design on aerosol and droplet production

High-speed dental instruments produce aerosol and droplets. The objective of this study was to evaluate 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 triplicate an open-plan clinic with mechanical ventilation providing 3.45 changes per hour. A 1:5 ratio which allows water coolant without (Ti-Max Z95L, NSK) used at three speeds: 60,000 (60 K), 120,000 (120 200,000 (200 K) revolutions minute. Coolant solutions contained fluorescein sodium as tracer (2.65 mmol L ? 1). air-turbine positive control, negative control conditions conducted. Aerosol evaluated 3 locations (0.5 m, 1.5 1.7 m) using: (1) optical particle counter (OPC; 3016-IAQ, Lighthouse) detect all aerosol; (2) liquid cyclone sampler (BioSampler, SKC Ltd.) aerosolised fluorescein, quantified by spectrofluorometric analysis. Settled droplets detected analysis filter papers placed onto rig across the clinic. Local (within treatment bay) settled contamination elevated above for conditions, no difference between conditions. not controls outside bay any condition. detection m only increased At 0.5 levels highly air-turbine, minimally 200 K 120 K, 60 K. Electric handpieces use water-jet alone localised contamination, but are unlikely beyond immediate area (1.5 m), allowing them be safely most