CATEGORY 62 AUSTRALASIAN DENTIST LINICAL (80%) power setting. Scaling started from the distal side of the last molar in quadrant 1 (Q1, patient’s right), continuously moving toQ2,Q3, andQ4 for 2minutesper quadrant (Fig. 2). Each test was repeated using no suction and 2 different types of suction tip: LVE suction (saliva ejector clear blue tip, Henry Schein, Melville, NY, USA) and HVE suction (206P HVE tubes, Premium Plus, Bournemouth, UK). Following standard clinical protocols, the LVE suction tip was placed at the posterior region of the last molar and remained there throughout the procedure. The saliva ejector is designed to be used by a single operator, which was simulated in the current study. During scaling with HVE suction, the assistant positioned the suction tip to continuously follow ∼1 cm behind the scaler as indicated in Figure 2 and Table 2. For drilling, a class III cavity was prepared for a maxillary left central incisor (FDI notation tooth 21) and a mandibular central incisor (tooth 41). A class II cavity was prepared for the maxillary left first molar (tooth 26) and mandibular right first molar (tooth 46). A Diamond Cylinder bur (841F 314 012 Fine/5, Ivoclar Vivadent, Schaan, Liechtenstein) was used with each HSH, with each set repeated 5 times (Table 1). Also, 10 surfaces in total were drilled per set per test including the mesial or distal part of the tooth (Table 2). Proximal and/or occlusal teeth surfaces are more susceptible to dental caries than smooth (eg, buccal, labial, lingual, or palatal) surfaces. The central incisor was chosen to demonstrate maximum aerosol generation because this tooth has the least soft-tissue barrier. A class II cavity preparation (proximal and occlusal surfaces) on the first molar was chosen because this tooth has a higher caries incidence among adults.19,20 The HSH speed was set at 40,000 revolutions per minute. The 4-port HSH had a minimum water consumption rate of 37 mL per minute and minimum ‘chip air’ rate of 2 mL per minute. The whole test was performed first with HVE and then without suction. Maximum suction was used with the tip kept close to the cavity being prepared. Statistical analyses Dental aerosol levels generated during different operative procedures (section 2.4) were compared using the Kruskal-Wallis and post hoc tests. Dental aerosol particle volume levels were compared using the Mann-Whitney U test. Statistical analyses were conducted using SPSS version 27 software (IBM, Armonk, NY, USA) with statistical significance set at P < .05. The effects of the dental operative procedures and the corresponding variables were also investigated using the Pearson correlation coefficient (R value). Because the signal noise in the measurements is considerable, R values of >0.1 and <−0.1 were interpreted as evidence of correlation. Results Drillingandscalinggenerateda total aerosol volume of 4.73(±0.774)×108 μm3/m3 and 4.18(±1.22)×108 μm3/m3, respectively, which were significantly higher (P < .001) than those generated with other activities, for example, by talking during the patient– clinician consultation, using the triplex airwater syringe, or during rest periods (Table 3 and Fig. 3A). For scaling, the mean aerosol particle volume recorded was significantly higher, with no suction (8.06±1.21×104 μm3/m3), with the least aerosol generated when HVE was used (P < 0.001) (Table 3 and Fig. 3C). For the scaling activities, a negative correlation (reduced risk-associated variables) was found with both low and high-volume suction (Fig. 3C). When each particle size range was compared separately for scaling with the different suction systems, HVE reduced the aerosol level significantly compared to LVE or no suction, and there was no significant difference in the total volume of smaller or bigger particles detected (P = .01) (Fig. 3B). Simulated cavity preparation (drilling) with the 1-port HSH showed the highest aerosol level (P < 0.01), followed by drilling with the 4-port handpiece and 4-port handpiece with no air function (Table 3 and Fig. 3C). Regardless of the number of cooling ports, suctionless drilling resulted in a higher aerosol volume, 1.98(±3.82)×107 μm3/m3, whereas the particle volume was reduced significantly with HVE (−4.47(±1.43)×105 μm3/m3). The mean level of aerosol produced by drilling (with no suction) was also influenced by the location of cavity preparation (Fig. 3D), but we did not detect significant differences either between maxillary and mandibular teeth preparations or between anterior and posterior teeth (P = 1.00) (Fig. 3D). Correlation analysis, however, revealed a negative correlation for posterior teeth, drilling with a 4-port handpiece with ‘chip air’ deactivated or drilling with any number of ports with HVE. A positive correlation (riskier variables) was reported with drilling maxillary incisors, using a 1- or 4-port HSHwith normal spray function and with drilling with any type of high-speed handpiece without suction. Discussion We investigated the effect of suction and air supply on aerosol generation during dental drilling and scaling to stratify risk from different combinations of variables for each procedure and enable guidance for oral health practitioners treating patients during the COVID-19 pandemic or considering other airborne pathogens. The null hypotheses were rejected because Table 1. List of Dental Equipment Used in the Current Study No. of Brand Name Cooling Chip-Air Equipment (NSK, Japan) Ports Function High-speed Ti-Max Z45L 1 Yes handpiece Ti-Max Z95L 4 Yes (electrical) Ultrasonic scaler Varios2 VA2-LUX – – 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.
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