## 4 Discussion  
Our study demonstrates that the location of the tip of the high-volume evacuator, facing the aerosol-generating procedure side, and combined with rubber dam isolation, significantly reduce the volume fraction of the ultrafine particles (PM\({}_{0.1}\) or nanoparticles). In addition, the total concentration of aerosol particles produced during the drilling of resin-made teeth under controlled conditions was also significantly reduced in both vestibular and palatal sides using RDI + HVE. The ultrafine particles  
Figure 3: Rubber dam isolation and high-volume suction reduce dental aerosol particles. The distribution by volume (Dv) parameters for percentiles 10, 50 and 90 are shown for the vestibular side in plot (**a**) and the palatal side in plot (**b**). For these three percentiles, there is an increase in the average size of the particles based on the volume percent when the RDI is implemented. A significant increase in the d\({}_{3,2}\) (the average size of particles below 10 \(\upmu\)m) is observed with the use of the RDI, but no effect is detected in the RDI + HVE group, when compared with the SS group. (**c**) The RDI and the RDI + HVE strategies reduce the concentration of aerosol-generating procedures (AGPs) in the vestibular side when compared with the SS group. In contrast, the RDI + HVE reduce this parameter when compared with both the SS group and the RDI group, in the palatal side. Results are shown as mean \(\pm\) SEM; \(n=3\); *: \(p<0.05\). Abbreviations: SS, standard suction; RDI, rubber dam isolation; HVE, high-volume evacuator. The Y axis of (**a**), (**b**) and (**c**) is Log\({}_{10}\) scaled. here detected corresponded to the highest proportion among aerosol dental particles in the hazardous range (aerodynamic diameter below 10 \(\upmu\)m) [21; 26; 28] when standard suction is implemented. Also, the use of rubber dam isolation combined with standard suction (RDI group) increased the average size of the dental aerosol particles, when compared with standard suction alone (SS). Moreover, the rubber dam isolation combined with high-volume suction effectively reduced the volume fraction of ultrafine particles in both vestibular side and palatal side. However, a significant reduction of total dental aerosol particles was only obtained in the palatal side using RDI + HVE when compared with SS and RDI conditions. This result suggests that the location of the high-volume evacuator based on the drilling side should be considered in aerosol mitigation strategies. Simulation training is an effective method to test under safe conditions the response and the performance of health care personnel during AGPs in highly infectious disease context [29]. This dental simulator unit is a fast-response strategy to study AGPs in a dental office under controlled and patient-free conditions. Although this experimental setting is accurate for the study, it cannot replace real crown preparations, plus the use of artificial teeth for gridding might be different to that with natural teeth. Other clear limitation is the equipment use which require to be fixed, secure, and close to the mouth for proper measurement. In this context, the laser beam is not flexible due to the limited spatial range for aerosol quantitation. Therefore, this result should be used for comparisons with experiments carried out under similar controlled conditions, considering limitations such as the lack of microbial biofilms that bind to natural teeth, caries, oral and periodontal mucosa, quantity and quality of saliva and blood presence (which may affect the particle size of the dental aerosol particles) and other physiological confounding factors that may affect the behaviour of AGPs such as breathing and previous oral hygiene or previous rinse use within a real patient [30; 31; 32]. This study demonstrated that AGPs after teeth drilling are polydisperse by using a laser diffraction technique, with the highest proportion of ultrafine particles (PM\({}_{0.1}\)) in the hazardous particle size range (PM\({}_{10}\)).