IADR Abstract Archives
Handpiece Design and Coolant Delivery Affect Aerosol and Droplet Production
Objectives: High-speed dental instruments produce aerosol and droplets which may potentially disperse pathogens. The objective of this study was to evaluate aerosol and droplet production from a novel electric micromotor handpiece (without compressed air irrigation) in real world clinical settings.
Methods: 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 which allows irrigation without compressed air (Ti-Max Z95L, NSK) was used at three speeds: 60,000 (60K), 120,000 (120K), and 200,000 (200K) revolutions per minute. Irrigation solutions contained fluorescein sodium tracer (2.65 mmol L−1). High-speed air-turbine positive control, and negative control conditions were conducted. Aerosol production was evaluated using: (1) an optical particle counter (OPC; 3016-IAQ, Lighthouse) to detect all aerosol; (2) a liquid cyclone air sampler (BioSampler, SKC Ltd.) to detect aerosolised fluorescein, which was quantified by spectrofluorometric analysis. Settled large droplets were detected by spectrofluorometric analysis of filter papers placed onto a rig across the open-plan clinic.
Results: Local (within treatment bay) settled large droplet contamination was elevated above negative control for all conditions, with no difference between conditions. Large droplet contamination was not detected above negative controls outside the treatment bay for any condition. Aerosol detection by OPC at 0.5 m was highly elevated for the air-turbine, moderate aerosol was detected when the micromotor handpiece was used at 200K and 120K, and no elevated aerosol was seen at 60K. At 1.5 m, increased aerosol levels were detected by OPC only for the air-turbine condition. Aerosolised fluorescein tracer was detected using the BioSampler only for the air-turbine condition.
Conclusions: Electric micromotor handpieces which use water-jet irrigation alone without compressed air produce localised (within treatment bay) large droplet contamination but do not produce detectable aerosol beyond the immediate treatment area (1.5 m).
Methods: 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 which allows irrigation without compressed air (Ti-Max Z95L, NSK) was used at three speeds: 60,000 (60K), 120,000 (120K), and 200,000 (200K) revolutions per minute. Irrigation solutions contained fluorescein sodium tracer (2.65 mmol L−1). High-speed air-turbine positive control, and negative control conditions were conducted. Aerosol production was evaluated using: (1) an optical particle counter (OPC; 3016-IAQ, Lighthouse) to detect all aerosol; (2) a liquid cyclone air sampler (BioSampler, SKC Ltd.) to detect aerosolised fluorescein, which was quantified by spectrofluorometric analysis. Settled large droplets were detected by spectrofluorometric analysis of filter papers placed onto a rig across the open-plan clinic.
Results: Local (within treatment bay) settled large droplet contamination was elevated above negative control for all conditions, with no difference between conditions. Large droplet contamination was not detected above negative controls outside the treatment bay for any condition. Aerosol detection by OPC at 0.5 m was highly elevated for the air-turbine, moderate aerosol was detected when the micromotor handpiece was used at 200K and 120K, and no elevated aerosol was seen at 60K. At 1.5 m, increased aerosol levels were detected by OPC only for the air-turbine condition. Aerosolised fluorescein tracer was detected using the BioSampler only for the air-turbine condition.
Conclusions: Electric micromotor handpieces which use water-jet irrigation alone without compressed air produce localised (within treatment bay) large droplet contamination but do not produce detectable aerosol beyond the immediate treatment area (1.5 m).