## 1 Introduction  
The ongoing Coronavirus Disease 2019 (COVID-19) pandemic has triggered several forms of collateral damage but one obvious effect is the paralysis of dental services caused by the potential spread of severe acute respiratory syndrome (SARS)-CoV-2 [1]. In dentistry, approaches such as preventive, restorative and surgical use water-cooled rotary devices (i.e., high-speed handpieces) to perform interventions that are considered aerosol-generating procedures (AGPs) [2; 3; 4]. Taking into account that the SARS-CoV-2 viral load is high at saliva, nose and oropharyngeal secretions in COVID-19 patients [5; 6], other patients and dental personnel are considered at high risk for cross-infection spreading [7]. Recommendations have been released oriented to reopen dental practice and mitigate the risk of AGPs [3; 4; 8; 9] that include the use of rubber dam isolation (RDI) and high-volume evacators (HVE) for dental procedures [3; 7; 10; 11; 12]. However, there is a lack of evidence that supports the effectiveness of RDI and HVE, either alone or combined, to control dental aerosols during dental restorative procedures [4; 13; 14; 15].  
Dental aerosols contain potentially hazardous particulate matter of submicron size. Restorative dental procedures such as tooth grinding produce particulate matter (PM) that exhibit a high proportion of particles with an aerodynamic diameter smaller than 10 \(\upmu\)m (PM\({}_{10}\)) [16; 17]. Aerosolized particles, based on the size below each name, are defined as coarse (PM\({}_{10}\)) and fine (PM\({}_{2.5}\)) particles [18]. After reaching the lower respiratory airways, the PM\({}_{2.5}\) are associated with systemic inflammation and increased respiratory mortality risk [19; 20; 21]. A significant correlation was found between new COVID-19 cases and the average amount of outdoor coarse particles in cities from China and Italy [22; 23]. Viral RNA was detected in samples taken after coughing in influenza positives from particles with an aerodynamic diameter smaller than one micron (PM\({}_{1}\)), which correspond to a fraction of the PM\({}_{2.5}\), [24]. In a similar fashion, the SARS-CoV-2 RNA was also detected in PM\({}_{2.5}\) from aerosol-coated areas of two hospitals from Wuhan [25]. Ultrafine particles (PM\({}_{0.1}\)), another fraction of PM\({}_{2.5}\), also known as nanoparticles, are also associated with health risks, including also systemic inflammation and cancer [26]. However, there is a lack of published evidence regarding the control of fine and ultrafine particles using mitigation strategies in dentistry. Inasmuch as PM includes fine and ultrafine particles that are associated with AGPs in dental settings, it is relevant to understand its behaviour and determine the potential risk of airborne infections during dental practice [7; 16; 27]. In this first study, the authors test the effectiveness of two mitigation strategies, the RDI and the HVE, and their effectiveness on coarse (PM\({}_{10}\)), fine (PM\({}_{2.5}\)) and ultrafine (PM\({}_{0.1}\)) dental aerosol particles distribution during a full-crown preparation of anterior teeth (teeth grinding), under controlled conditions in a simulated patient.