Dental high-speed handpiece and ultrasonic scaler aerosol generation levels and the effect of suction and air supply

Abstract

Objective: Exposure to aerosol spray generated by high-speed handpieces (HSHs) and ultrasonic scalers poses a significant health risk to oral health practitioners from airborne pathogens. Aerosol generation varies with different HSH designs, but to date, no study has measured this.

Materials and methods: We measured and compared aerosol generation by (1) dental HSHs with 3 different coolant port designs and (2) ultrasonic scalers with no suction, low-volume evacuation (LVE) or high-volume evacuation (HVE). Measurements used a particle counter placed near the operator's face in a single-chair, mechanically ventilated dental surgery. Volume concentrations of aerosol, totaled across a 0.3-25-µm size range, were compared for each test condition.

Results: HSH drilling and scaling produced significantly high aerosol levels (P < .001) with total volume concentrations 4.73×10⁸µm³/m³ and 4.18×10⁷µm³/m³, respectively. For scaling, mean volume of aerosol was highest with no suction followed by LVE and HVE (P < .001). We detected a negative correlation with both LVE and HVE, indicating that scaling with suction improved operator safety. For drilling, simulated cavity preparation with a 1-port HSH generated the most aerosol (P < .01), followed by a 4-port HSH. Independent of the number of cooling ports, lack of suction caused higher aerosol volume (1.98×10⁷ µm³/m³) whereas HVE significantly reduced volume to -4.47×10⁵ µm³/m³.

Conclusions: High concentrations of dental aerosol found during HSH cavity preparation or ultrasonic scaling present a risk of infection, confirming the advice to use respiratory PPE. HVE and LVE both effectively reduced aerosol generation during scaling, whereas the new aerosol-reducing 'no air' function was highly effective and can be recommended for HSH drilling.

Fig. 1.

Dental test room layout.

Fig. 2.

Diagrams showing the sequence of ultrasonic scaling for each quadrant (left) and drilling for Class II and III preparations (right). Q1: quadrant 1, patient’s upper right; Q2: quadrant 2, patient’s upper left; Q3: quadrant 3, patient’s lower left; Q4: quadrant 4, patient’s lower right. Dots in the first figure (left) indicate the starting point of ultrasonic scaler and the arrow indicates the direction and the finishing point. Gray areas highlighted on the teeth in the second figure (right) indicate the location of cavity preparations.

Fig. 3.

The total volume of aerosol (µm/m) created by (a) different activities; (b) during scaling and drilling with different types of suction; and (c) during scaling and drilling with different types of suction [the volume mean diameters for each size range are 0.42 µm (channel 1), 0.83 µm (channel 2), 2.4 µm (channel 3), 4.2 µm (channel 4), 8.3 µm (channel 5), and 20 µm (channel 6)]; and (d) during drilling in different locations; 1 incisor and 1 posterior tooth per maxillary and mandibular arch, with and without HVE.