SARS-CoV-2: Characterisation and Mitigation of Risks Associated with Aerosol Generating Procedures (AGPs) in Dental Practices

SARS-CoV-2: Characterisation and Mitigation of Risks Associated with Aerosol Generating Procedures (AGPs) in Dental Practices | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article SARS-CoV-2: Characterisation and Mitigation of Risks Associated with Aerosol Generating Procedures (AGPs) in Dental Practices Touraj Ehtezazi, David G. Evans, Ian D. Jenkinson, Philip Evans, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-105294/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The objectives of this study were to characterise the particle size distribution of aerosols generated by standard dental aerosol generating procedures (AGPs) and to assess the impact of aerosol management interventions on ‘fallow time’. Aerosol management interventions included combinations of high-volume intra-oral suction (HVS(IO)), high volume extra-oral suction (HVS(EO)) and an air cleaning system (ACS). A sequence of six AGPs were performed in succession on a phantom head. Real-time aerosol measurements (size range 0.0062 – 9.6 µm) were taken using a high-resolution particle sizer acquiring air samples from six locations within a typical dental treatment room (35 m3). The majority (>99%) of AGP particles were < 0.3 µm diameter and remained at significant levels around the dental team during the AGPs. This emphasises the importance of personal protection equipment, particularly, the use of properly fitted respiratory protection to the appropriate (FFP3) standard. In the absence of active aerosol management interventions, AGP particles were estimated to remain above the baseline range for around 25-31 minutes from the end of the sequence of procedures. It was found that HVS(IO), either alone or in combination with the ACS, reduced particle concentrations to baseline levels on completion of AGPs. These data indicated that there is scope to reduce fallow time to 0 minutes. Dentistry dental aerosol AGPs management particle size fallow time Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Key Points The particle size distribution of aerosols generated by dental procedures are predominantly < 0.3 µm in diameter. This encompasses the reported size range of the SARS-CoV-2 virus (0.05 – 0.15 µm). Even in the presence of interventions such as high volume inter-oral suction HVS(IO) combined with an air cleaning system (ACS), aerosol particles < 0.3 µm were substantially elevated above the baseline range during the dental aerosol generating procedures (AGP) used in this study (these included the use of air-turbine and electric handpieces operating at over 60,000 rpm). Levels of aerosol were especially elevated within the working micro-environment (50 cm radius from the mouth) of the dentist and assistant. This emphasises the importance of properly fitted personal protective equipment such as FFP3 masks. Intra-oral high-volume suction, either alone or in combination with an air cleaning system (in this case operating at 24 room air changes per hour in a typical 35 m 3 surgery) was effective in rapidly reducing AGP-related particle concentrations to within background range in some cases, during or immediately, on cessation of AGPs negating the need for fallow time. These data indicate that a reduction in fallow time may be achieved below the current guidance of 10 minutes through judicious use of aerosol management interventions. Introduction Potentially infectious agents (e.g. bacteria, fungi and viruses) can be transmitted when droplets containing microorganisms generated from an infected person (example by breathing, talking or coughing) are propelled through the air and are directly inhaled, deposited on the skin or mucosal surfaces, or contaminate infrastructure. 1 High-speed dental instruments require effective cooling of the work area in order to avoid damage of the pulp dentine system. These instruments generate a dental aerosol, as cooling water and air are sprayed around the instruments and the oral cavity. Dental aerosols are distributions of particle sizes from 0.001 to >10 µm in diameter. 2,3 Traditionally, dental airborne aerosols were defined as being small particles 50 -100 µm) being described as “splatter”. 4 The WHO definition 5 of aerosols has been adopted in the dental field, which defines large projectile particles as being > 5µm, with smaller (< 5 µm) “droplet nuclei” particles forming through the evaporation of larger particles generating an airborne solid residue. Infectious droplets from saliva or blood may enter the aerosol and expose the dental team to an increased risk of infection though direct inhalation, contact with eyes, and contact with contaminated work surfaces. 6,7 Dental aerosols therefore have the potential to provide a path for the transmission of COVID-19 8,9 which may remain infectious for between 2 hours to 9 days in a humid environment. 7 Research on the influenza virus has also demonstrated that the total viral copies were 8.8 times more numerous in particles <5 µm than in particles ≥5 µm. 10 Previous studies have demonstrated the dispersion of bioaerosols to all areas of the treatment room 11 which remain airborne for 30 minutes following the procedure. 12 Therefore, there is a clear need for the effective removal of aerosols in dental practices. 13 Protocols exist to minimise the risk of infection to clinical staff during dental procedures. 12,14-17 These include: low volume suction (LVS) to remove saliva and excess coolant, coolant disinfectant, high-volume intra-oral suction (HVS (IO)), personal protective equipment (PPE) and improved ergonomics and techniques (e.g. dental dams). A range of additional aerosol removal treatments have been proposed for use in dental procedures including extra-oral high volume suction (HVS (EO)), air cleaning systems (ACS), designed to filter, purify and recirculate room air) and ventilation systems. 7,14,18,19 However, their effectiveness within a diverse range of dental practice environments is difficult to predict. 13 A wide range of ACS with different air flow rates and cleaning technology are commercially available or being marketed for dental use. However, dental practices have no clear standards or specifications to refer to before making an investment. HVS(EO) and ACS 20,21 that contain high efficiency particulate air (HEPA) filters are effective in removing airborne particles with sizes greater than 0.3 µm: viruses, such as coronaviruses, are in the size range of 0.05 – 0.15µm 22 and thus may evade filtration. Hence, ACS have evolved to include the addition of technology such as UV-C lamps (99.97% killing of H3N2 influenza virus), negative ion generators, and high pressure/voltage electrostatic plasma, which eliminate particles greater than 0.0146 µm. The efficiency of these air purifiers has not been evaluated for the removal aerosol particles in the presence of high volume intra-oral or extra-oral suction. Whilst researchers have studied aerosol removal treatments, few studies have examined their effectiveness across the full dental aerosol particle size distribution. For example, the use of HVS(IO) at air flow rates of 250 – 300 L min -1 is an established means of controlling dental aerosols but its effectiveness is based on a qualitative assessment of visible particles or particles greater than 0.65 µm. 19,23 Viruses are smaller than 0.65 µm and therefore the efficacy of HVS(IO) studies are not relevant to COVID 19. The objectives of this current study were to characterise the aerosols generated by standard dental procedures and to investigate the effectiveness of different combinations aerosol management interventions across the particle distribution range from 0.0062 to 10 µm diameter to provide evidence for establishing a revised fallow time. A sequence of six standard dental procedures were performed in series to assess the effectiveness of four combinations of interventions based on HVS (IO), HVS (EO) and an ACS. The effectiveness of each intervention group was measured using a high-resolution particle size analyser, with air samples taken over a 36-minute period from six locations within a standard dental surgery. Method The study was performed within a dental surgery (dimensions 4.4 x 3.1 x 2.6 m: Figure 1). Real-time aerosol analysis was performed with a high-resolution Electric Low-Pressure Impactor particle sizer (HR-ELPI: “ELPI+”, Dekati, Kangasala, Finland). The instrument recorded the concentration of particles detected within 100 pre-set ‘bins’ of particle size, ranging from 0.0062 to 9.6 µm, at a sampling frequency of 1 Hz. Air samples were acquired at six locations (Figure 1, Table 1). Each position was measured relative to the phantom head on which the dental AGPs were performed. Air samples were directed to the ELPI+ via 2 m lengths of silicone tubing (Tygon®”; internal diameter 12.7 mm, external diameter 17.5 mm; Cole-Parmer Instrument Co, Illinois, USA: Figure S1). Each tube was individually connected to the particle sizer for a period of 30 seconds before being replaced with a tube from the next sampling location to enable a serial analysis of all six air sample locations within a 3 min cycle. A pilot study demonstrated that the tubing had no discernible effect on particle size measurements (see supplementary data: Annex A, Figures S1-S3). All non-experimental air-conditioning equipment was turned off during the experimental work, and the average room temperature and relative humidity were recorded at 27 C and 67% respectively. Each experiment comprised a three-minute baseline period, followed by a series of six aerosol generating procedures (AGPs) carried out over 18 minutes with a post-procedural duration of 18 minutes to monitor aerosol decay (Figure 2). Each experiment was performed using one of four treatments (Table 2). The technical specifications of each aerosol removal system are described in Table 3. Each treatment was performed in triplicate. The AGPs incorporated the serial use of six commonly used dental preparation instruments each of which were operated for three minutes within the phantom head, in the upper and lower anterior sextants, in the following order: (I) Air turbine hand-piece, (II) Electric contra-angle hand-piece, (III) Air turbine hand-piece, (IV) Three in one syringe, (V) Ultrasonic scaler and (VI) Ultrasonic scaler (Table 4). Total particle concentration (calculated as the sum of particle concentrations over the 0.0062 to 9.6 µm bin range) did not consistently exhibit a Gaussian (normal) or log-normal distribution and so excluded the use of parametric statistical tests. The low sample number (n=3) precluded non-parametric analyses. Therefore, descriptive statistics were used and all particle concentration data are expressed as median values. Area under curve (AUC) calculations were performed using GraphPad Prism (v7.0e for Mac OS, GraphPad Software, La Jolla California USA). The AUC calculations reflect the total “dose” of aerosol (units of mL cm -3 min). The AUC calculations were used to assess the overall efficiency of each treatment and were expressed as the median value ± minimum/maximum. Estimation of fallow time in the control treatment group was performed by linear regression of particle concentrations at each sample location following cessation of AGPs and was calculated as the time at which the extrapolated particle concentration decreased below the upper baseline particle concentration. Results The majority (>99.9%) of particles generated by the sequence of dental procedures (Figure 2) were < 0.3 µm diameter when sampled at the proximal position (Location 1: 8 cm). Instruments I, II and III (Table 4) in the sequence generated the highest aerosol levels. Peak concentrations occurred between particle diameters 0.013 to 0.022 µm (Figure 3, t= 3-6, 6-9, and 9-12 min). Aerosol generated under the control conditions (Table 2, intervention group A (LVS only)) was observed at all locations within the surgery and remained detectable at 15 min (Figure 3, t=36 min) from the end of the last procedure (instrument VI at t=21 min). The most persistent particles were in the range 0.012 to 0.025 µm. Particle concentrations decreased with increasing distance from the phantom head, with a notable, time-related decrease of particles in the range 0.054 to 0.236 µm diameter. Particles > 0.05 µm persisted at low concentrations (~25 x 10 3 cm -3 ) for the duration of the study. The particle size distributions generated during the use of all instruments and applying interventions B to E (Table 2) were like those in the control but with markedly reduced concentrations (Figure 3). Compared with control conditions all interventions produced a remarkable decrease in the number and distribution of particles detected in the extra-oral space (Location 2: 20 cm) and more distal locations. Following the end of the sequence of procedures (t=21 min) there was infrequent detection of low concentrations of aerosol particles from beyond the extra-oral space, and particles > 0.05 µm were generally at the baseline level (Figure 3). In the control group, total particle counts remained elevated above the baseline range for the duration of the experiment at all locations (Figure 4, and Figure S4). Therefore, for the control group linear regression was used to calculate the time needed for the total particle concentration at each location to return to baseline levels (Figure 10). This produced an estimated median time of 26 min (range 25 – 31 min) from the end of the sequence of procedures (t=21 min). In the case of experiments using either the HVS(IO), or the HVS(IO) combined with the ACS (Table 2, intervention groups B and C) the concentration of particles returned to within the baseline range at the end of the procedures (t=21 min) (Figures 5, and 6 respectively). However, the total number of aerosol particles remained marginally above the baseline for interventions which included the HVS(EO) (Figures 7 and 8). When the aerosol concentrations are expressed as dose (mL cm -3 min) all interventions reduced total aerosol exposure (Figure 9). Intervention group B (Table 2, HVS(IO) with LVS) reduced the median dose by 80%, while intervention group E (HVS(IO)+HVS(EO)+ACS with LVS) reduced the median dose by 90%. However, HVS(IO) was noticeably less effective than intervention groups C, D and E in controlling the range of (maximum-minimum) of the dose. Discussion The results of this study demonstrate that all the aerosol management interventions evaluated were relatively effective in controlling aerosols generated by dental handpieces. Most particles produced by our sequence of AGPs were < 0.3 µm. The use of either the HVS(IO), or the HVS(IO) combined with the ACS was enough to reduce the fallow time to 0-min. During AGPs the concentration of particles in the range 0.05 to 0.15 µm diameter range is increased substantially. This size range corresponds to the reported size range of the SARS-CoV2 virus (0.05 to 0.15 µm). 22 Within the working micro-environment (Locations 3-4, <50 cm) the presence of active aerosol management interventions substantially reduces the concentration of airborne particles in this range but does not eliminate them. Thus it is important for dental workers to utilise both appropriate and properly fitted respiratory protective equipment such as FFP3 masks in combination with aerosol management interventions. 24 In the absence of aerosol management interventions, particles in the range 0.05 – 0.236 µm, remained at elevated concentrations within the macro-environment (Locations 5-6, >50 cm) for longer than the experimental period. Our control study estimated that it may take at least 28 to 34 minutes after cessation of AGPs for the total particle concentration to return to baseline levels. Intervention groups B and C, which included the addition of HVS(IO), or HVS(IO) with ACS, both had the effect of returning particle concentrations to within the baseline range by the end of the sequence of procedures i.e. no additional fallow-time was required before particle concentrations returned to baseline levels. In the case of interventions D and E, which included HVS(EO), particle concentrations remained marginally above the baseline which is in agreement with previous work. 19 Interventions B and C reduced particle concentrations in the macro-environment (Locations -5-6, >50 cm) to within the baseline range during AGPs. Intervention C, (HVS(IO) in combination with an ACS) was effective in controlling both the median and the range (max-min) of the aerosol dose at all locations. In a dental surgery of the size used in this study (35 m 3 ), and in the context of SARS-CoV-2, it provides further evidence to support a reduction in fallow time below the current recommend period of 10 minutes 24 in agreement with other recent studies. 25 The use of a phantom head is a clear limitation of this study: the presence of saliva and other biological materials within the oral cavity may conceivably affect the particle size distribution of AGPs and so further, confirmatory research should be performed using patients. Such work should incorporate different size surgeries to validate the scalability of aerosol mitigation interventions. It should also be noted that a locally moist and warm atmosphere within a “turbulent gas cloud” allows the contained continuum of droplet sizes to evade evaporation for much longer time periods than occurs with isolated droplets, from a fraction of a second to minutes. 26 This may explain why the most persistent particles measured in our study were within the smaller, 0.012-0.025 µm range. Therefore, a patient-orientated study is needed to confirm the nature of the fine particle aerosols containing mixtures of saliva, coolant, and pathogens. This may provide further evidence to support the use of antiviral disinfectants in coolant solutions. Conclusions Dental AGPs produce aerosols characterised by particles < 0.3 µm in diameter. Although, aerosol suppression treatments such as HVS(IO) alone or in combination with an ACS may rapidly reduce particle concentrations to within background range, they do not eliminate exposure during AGPs and so the use of appropriate respiratory protective equipment by dental practitioners is essential. HVS(IO) combined with the ACS was enough to reduce the fallow time to 0 minute, and to control the median and range of the aerosol particle dose at all areas in the surgery. The ACS used in these experiments was set to deliver 24 air changes per hour in an 35m 3 surgery which was close to maximum and further experimental work is needed to optimise the location and setting of equipment of this type. In the absence of ventilation within a modest sized (35 m 3 ) surgery, particles associated with dental AGPs may persist for approximately half an hour. There appears to be scope for a reduction in fallow time from the current guideline of 10 minutes when effective aerosol management system(s) are used. Declarations Acknowledgements This work was supported by the LJMU Corona Virus Rapid response grant. The authors wish to thank Tayyebeh Rafiei, Rhiannon Powell & Ben Wilkinson for their efforts in assisting the data analysis. The authors would also like to express their gratitude to Louie Chen (Scielutions Ltd) & Dekati Ltd Finland for the loan of the ELPI+ unit and their invaluable technical support. Declaration of Interests The authors have not declared any conflict of interest. Techceram Ltd is a commercial entity in the dental field, but has no interest in any of the equipment used in the present study, only in contributing its network of contacts towards the present study, in order to better understand dental AGPs, so that dental hospitals, practices, labs and associated dental supply chain smaller businesses can remain open and operate safely through any future viral pandemics. References 1 Jayaweera, M., Perera, H., Gunawardana, B. & Manatunge, J. Transmission of COVID-19 virus by droplets and aerosols: A critical review on the unresolved dichotomy. Environmental research 188 , 109819, doi:10.1016/j.envres.2020.109819 (2020). 2 Bogdan, A., Buckett, M. I. & Japuntich, D. A. Nano-sized aerosol classification, collection and analysis--method development using dental composite materials. Journal of occupational and environmental hygiene 11 , 415-426, doi:10.1080/15459624.2013.875183 (2014). 3 Day, C. J., Price, R., Sandy, J. R. & Ireland, A. J. Inhalation of aerosols produced during the removal of fixed orthodontic appliances: a comparison of 4 enamel cleanup methods. American journal of orthodontics and dentofacial orthopedics : official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 133 , 11-17, doi:10.1016/j.ajodo.2006.01.049 (2008). 4 Micik, R. E., Miller, R. L., Mazzarella, M. A. & Ryge, G. Studies on dental aerobiology. I. Bacterial aerosols generated during dental procedures. J Dent Res 48 , 49-56, doi:10.1177/00220345690480012401 (1969). 5 Organisation, W. H. Infection prevention and control of epidemic and pandemic prone respiratory infections in health care . (WHO Library Cataloguing-in-Publication Data 2014). 6 Miller, R. Air Pollution in the Dental Office. Medical Clinics of North America 22 , 453-476 (1978). 7 Peng, X. et al. Transmission routes of 2019-nCoV and controls in dental practice. International Journal of Oral Science 12 , 9, doi:10.1038/s41368-020-0075-9 (2020). 8 Epstein, J. B., Chow, K. & Mathias, R. Dental procedure aerosols and COVID-19. The Lancet Infectious Diseases , doi: https://doi.org/10.1016/S1473-3099(20)30636-8 (2020). 9 Ge, Z. Y., Yang, L. M., Xia, J. J., Fu, X. H. & Zhang, Y. Z. Possible aerosol transmission of COVID-19 and special precautions in dentistry. Journal of Zhejiang University. Science. B 21 , 361-368, doi:10.1631/jzus.B2010010 (2020). 10 Milton, D. K., Fabian, M. P., Cowling, B. J., Grantham, M. L. & McDevitt, J. J. Influenza virus aerosols in human exhaled breath: particle size, culturability, and effect of surgical masks. PLoS pathogens 9 , e1003205, doi:10.1371/journal.ppat.1003205 (2013). 11 Rautemaa, R., Nordberg, A., Wuolijoki-Saaristo, K. & Meurman, J. H. Bacterial aerosols in dental practice - a potential hospital infection problem? J. Hosp. Infect. 64 , 76-81, doi:10.1016/j.jhin.2006.04.011 (2006). 12 Veena, H. R., Mahantesha, S., Joseph, P. A., Patil, S. R. & Patil, S. H. Dissemination of aerosol and splatter during ultrasonic scaling: A pilot study. Journal of Infection and Public Health 8 , 260-265, doi: https://doi.org/10.1016/j.jiph.2014.11.004 (2015). 13 Sachdev, R., Garg, K., Singh, G. & Mehrotra, V. Is safeguard compromised? Surgical mouth mask harboring hazardous microorganisms in dental practice. J Family Med Prim Care 9 , 759-763, doi:10.4103/jfmpc.jfmpc_1039_19 (2020). 14 Hallier, C., Williams, D. W., Potts, A. J. & Lewis, M. A. A pilot study of bioaerosol reduction using an air cleaning system during dental procedures. Br Dent J 209 , E14, doi:10.1038/sj.bdj.2010.975 (2010). 15 Mupparapu, M. & Kothari, K. R. M. Review of surface disinfection protocols in dentistry: a 2019 update. Quintessence Int 50 , 58-65, doi:10.3290/j.qi.a41337 (2019). 16 Sawhney, A. et al. Aerosols how dangerous they are in clinical practice. J Clin Diagn Res 9 , Zc52-57, doi:10.7860/jcdr/2015/12038.5835 (2015). 17 Joshi, A. A., Padhye, A. M. & Gupta, H. S. Efficacy of Two Pre-Procedural Rinses at Two Different Temperatures in Reducing Aerosol Contamination Produced During Ultrasonic Scaling in a Dental Set-up - A Microbiological Study. J Int Acad Periodontol 19 , 138-144 (2017). 18 Teanpaisan, R., Taeporamaysamai, M., Rattanachone, P., Poldoung, N. & Srisintorn, S. The usefulness of the modified extra-oral vacuum aspirator (EOVA) from household vacuum cleaner in reducing bacteria in dental aerosols. Int. Dent. J. 51 , 413-416, doi:10.1002/j.1875-595X.2001.tb00853.x (2001). 19 Noro, A. et al. A study on prevention of hospital infection control caused by tooth preparation dust in the dental clinic. Part 1. Preventive measures against environmental pollution in the dental clinic caused by microbial particles. Bull. Tokyo Dent. Coll. 36 , 201-206 (1995). 20 Zhao, B., An, N. & Chen, C. Using air purifier as a supplementary protective measure in dental clinics during the COVID-19 pandemic. Infect. Control Hosp. Epidemiol. , 1-4, doi:10.1017/ice.2020.292 (2020). 21 Hubar, J. S., Pelon, W., Strother, E. A. & Sicard, F. S. Reducing Staphylococcus aureus bacterial counts in a dental clinic using an Ionic Breeze air purifier: a preliminary study. Gen Dent 57 , 226-229 (2009). 22 Lin, Y. et al. Probing the structure of the SARS coronavirus using scanning electron microscopy. Antivir Ther 9 , 287-289 (2004). 23 Davies, M. H., Rosen, M., Eccles, J. D. & Marshal, R. J. Criteria of air flow and negative pressure for high volume dental suction. Br. Dent. J. 130 , 483-487, doi:10.1038/sj.bdj.4802680 (1971). 24 Programme, S. D. C. E. Mitigation of AGPs in Dentistry, A rapid review . Vol. 1.0.25 (2020). 25 R Holliday, J. A., CC Currie, DC Edwards, C Bowes, K & Pickering , S. R., J Durham, N Rostami, J Coulter, N Jakubovics. Evaluating dental aerosol and splatter in an open plan clinic environment: implications for the COVID-19 pandemic. https://doi.org/10.31219/osf.io/md49f (2020). 26 Bourouiba, L. Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID-19. JAMA 323 , 1837-1838, doi:10.1001/jama.2020.4756 (2020). Tables Table 1 : Air sampling location coordinates, expressed relative to the phantom head (nominal coordinates x=0, y=0, z=0). Sample Location No. Name Co-ordinates relative to phantom head (mm) Linear Distance from source (mm) x y z 1 Phantom head (source) 0 80 0 80 2 HVS (EO) in-take 135 -110 100 200 3 Dentist -262 145 265 400 4 Assistant 354 160 300 500 5 Wall 0 900 1045 1480 6 Light 726 383 1495 1700 Table 2: Summary of aerosol removal treatments used in each experiment. Note that intra-oral low volume suction (LVS) was used in all treatment groups (including control) to represent standard practice and to prevent excess fluid accumulation within the phantom head. Interventions LVS Low volume suction HVS(IO) High Volume Suction (Intra-oral) with air filtration system. HVS(EO) High Volume Suction (extra-oral). ACS Air Cleaning System. Intervention group A X B X X C X X X D X X X E X X X X Table 3: Aerosol suppressing equipment and corresponding air/water flow rates. Low volume suction (LVS) was used in all treatment groups. In this study, the air cleaning system (ACS) flow rate was equivalent to ~ 20 air changes per hour. Treatment Equipment Water Flow (L min -1 ) Air Flow (L min -1 ) Air changes per hour (in a 35 m 3 surgery) LVS Plastcare USA, 4 mm slow speed salivary ejector. 2.4 79 HVS(IO) Dürr Universal Cannula III 16 mm, connected to Dürr Dental VSA 300S Dürr Dental UK, Kettering, UK. - 297 HVS(EO) Eighteeth VacStation, Sifary Medical Technology, Jiangsu, China. - 3700 6 ACS Woodpecker Q7 Plasma Air Purifier, Guilin Woodpecker Medical Instrument Co, Guilin, China. - 14167 24 Table 4 : Procedural equipment and corresponding coolant flow rates. Procedure Description Coolant Flow Rate (mL min -1 ) I W&H Synea Vision TK94 hand-piece (Air Turbine) with long tapered bur 55 II NSK Ti Max Z95L hand piece (Electric) with long tapered bur 67 III Sirona T1 Control hand-piece (Air turbine) with long tapered bur 56 IV 3 in1 syringe from Belmont Cleo II chair 82 V Cavitron Jet Plus Ultrasonic with 30K FSI-SLI tip 25 VI NSK Vario Lux 2 (Piezo) with G8 tip 78 Supplementary Files SupplementarydataAnnexAFinalEdit2.pdf Annex A Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-105294","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":4530224,"identity":"de6a0729-18b2-4abd-9a41-aa108bc4e8b4","order_by":0,"name":"Touraj Ehtezazi","email":"","orcid":"","institution":"Liverpool John Moores University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Touraj","middleName":"","lastName":"Ehtezazi","suffix":""},{"id":4531689,"identity":"3cdaed5c-342a-4257-844c-480569c96adb","order_by":1,"name":"David G. Evans","email":"","orcid":"","institution":"Liverpool John Moores University ","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"David","middleName":"G.","lastName":"Evans","suffix":""},{"id":4531690,"identity":"a732651b-c20d-44c1-b2b5-9e3da7498b7f","order_by":2,"name":"Ian D. Jenkinson","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/ElEQVRIiWNgGAWjYBACNgYGAwYJIMEG5lZYMMNkDIjUckaCsBaYHEQBY5sEqjA2wMfAvIHBouKOMZ90+8PHhfMk2HVnJDB++MFw2Bi3w9gKGCTOPDNjkzljbDxzmwSz2Y0EZskehsNmuLXwGDBIth22YZPIYZPmhWhhkGZgOGyDX8s/kJb0Z9K8cyC2/CaspeGwGZtEgpk0bwNYCxvIFtwOY2YrOCBx7LAx0GHGxjzHgFrOPGyz7DFIx+l9+fbmjY8lag4bzp+R/vAxT41Nstnx5MM3flRYGzbg0gOMusMSSPxkYOw04I9IIGD8gMSxw692FIyCUTAKRiIAAH81RKAmt+C9AAAAAElFTkSuQmCC","orcid":"","institution":"Liverpool John Moores University ","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Ian","middleName":"D.","lastName":"Jenkinson","suffix":""},{"id":4531691,"identity":"25fae5bd-732f-48f2-bc21-6b6f7f682805","order_by":3,"name":"Philip Evans","email":"","orcid":"","institution":"Techceram Limited","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Philip","middleName":"","lastName":"Evans","suffix":""},{"id":4531692,"identity":"4795bc29-0686-4b60-91bd-d7e126ef25bf","order_by":4,"name":"VJ Vadgama","email":"","orcid":"","institution":"Woodbury Dental \u0026 Laser Clinic","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"VJ","middleName":"","lastName":"Vadgama","suffix":""},{"id":4531693,"identity":"458084d2-a8d2-451f-8fa9-9d5b865f641f","order_by":5,"name":"Jaimini Vadgama","email":"","orcid":"","institution":"Woodbury Dental \u0026 Laser Clinic","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jaimini","middleName":"","lastName":"Vadgama","suffix":""},{"id":4531694,"identity":"5a640765-c52d-42fa-8094-1240c518b7ca","order_by":6,"name":"Fadi Jarad","email":"","orcid":"","institution":"University of Liverpool School of Dentistry","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Fadi","middleName":"","lastName":"Jarad","suffix":""},{"id":4531695,"identity":"0d7ff6fe-0bff-4118-921f-922e20e561c2","order_by":7,"name":"Nicholas Grey","email":"","orcid":"","institution":"University of Manchester School of Dentistry","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Nicholas","middleName":"","lastName":"Grey","suffix":""},{"id":4531696,"identity":"5792214d-86b7-40ab-a9e3-eaf824f3f0ce","order_by":8,"name":"Robert P. Chilcott","email":"","orcid":"","institution":"University of Hertfordshire","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Robert","middleName":"P.","lastName":"Chilcott","suffix":""}],"badges":[],"createdAt":"2020-11-09 17:37:46","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":true,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false,"coiExplicitlySet":false},"doi":"10.21203/rs.3.rs-105294/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-105294/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":3567991,"identity":"4f19f626-e89d-47d6-9a16-bf8316586ce3","added_by":"auto","created_at":"2020-11-13 16:29:56","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":280261,"visible":true,"origin":"","legend":"Layout and sampling positions of the dental treatment room. Note that tube location 6 was moved from the ceiling light fitting to be visible in the photograph.","description":"","filename":"Figure1Layout.jpg","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/4a8a2cc8cb0b131df96b283e.jpg"},{"id":3567992,"identity":"7b0d578e-86ce-48de-b9a4-02c740c4b6b2","added_by":"auto","created_at":"2020-11-13 16:29:56","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":72801,"visible":true,"origin":"","legend":"Outline study design. After an initial baseline period (3 min), six aerosol generating procedures (I to VI) were performed in series (18 min) followed by a period to quantify aerosol decay kinetics (15 min). Air samples from each location (1 – 6) were acquired over a 30 second period. The total duration of each experiment was 36 minutes.","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/2b41745e19145d4bd892ab7b.png"},{"id":3567993,"identity":"d84b2f26-9850-4e56-8b38-4e9bf73203a9","added_by":"auto","created_at":"2020-11-13 16:29:56","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":575901,"visible":true,"origin":"","legend":" Temporal, spatial and size characterisation of particles generated during AGPs (measured by HR-ELPI) for each location (1 – 6; Table 1) and treatment group (A – E; Table 2). Acquisition of air samples were performed during the baseline period (0 – 3 min), during the six procedures (3 – 18 min) and following cessation of procedures (18 – 36 min). Each data point represents the median particle concentration per size bin (# cm-3) derived from n=3 replicates. The dotted lines indicate the lower reported size for a SARS-CoV-2 virus particle (50 nm diameter).","description":"","filename":"Figure3TimeSpaceSizeCharacteristics.jpg","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/888adb1427ccbba99a35d880.jpg"},{"id":3567994,"identity":"5d2e054f-b164-4945-bbb0-bc6c50e307c9","added_by":"auto","created_at":"2020-11-13 16:29:56","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":127065,"visible":true,"origin":"","legend":"Total particle concentration generated during AGPs in the absence of interventions (group A; Table 2) at each air sampling location (1 – 6; Table 1). Acquisition of air samples were performed during the baseline period (0 – 3 min), during the six procedures (3 – 18 min) and following cessation of procedures (18 – 36 min). Dotted lines indicate the upper and lower boundaries of the baseline data. Each data point represents the sum of particles measured by HR-ELPI over 1 second during each replicate (n=3).\n\n","description":"","filename":"Figure4TotalConcGenAGPs.jpg","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/6bd29a42292e8836ba3504c3.jpg"},{"id":3567995,"identity":"faebc3aa-1ba1-49e4-bfc4-7f960f9154c9","added_by":"auto","created_at":"2020-11-13 16:29:57","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":128012,"visible":true,"origin":"","legend":"Total particle concentration generated during AGPs in the presence of HVS(IO) (group B; Table 2) at each air sampling location (1 – 6; Table 1). Acquisition of air samples were performed during the baseline period (0 – 3 min), during the six procedures (3 – 18 min) and following cessation of procedures (18 – 36 min). Dotted lines indicate the upper and lower boundaries of the baseline data. Each data point represents the sum of particles measured by HR-ELPI over 1 second during each replicate (n=3).","description":"","filename":"Figure5TotalConcHVSio.jpg","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/676de6059da6d0ae05caf6f6.jpg"},{"id":3567996,"identity":"f240fcd0-b91a-49e1-b515-cd596d9b3238","added_by":"auto","created_at":"2020-11-13 16:29:57","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":115818,"visible":true,"origin":"","legend":" Total particle concentration generated during AGPs in the presence of HVS(IO) and ACS (group C; Table 2) at each air sampling location (1 – 6; Table 1). Acquisition of air samples were performed during the baseline period (0 – 3 min), during the six procedures (3 – 18 min) and following cessation of procedures (18 – 36 min). Dotted lines indicate the upper and lower boundaries of the baseline data. Each data point represents the sum of particles measured by HR-ELPI over 1 second during each replicate (n=3).\n\n","description":"","filename":"Figure6TotalConcHVSioACS.jpg","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/9cee1ac4c9a76f66fb7dfe7b.jpg"},{"id":3567997,"identity":"d701eb73-10dd-411f-8aa3-b0aa1b4a79c9","added_by":"auto","created_at":"2020-11-13 16:29:57","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":126835,"visible":true,"origin":"","legend":"Total particle concentration generated during AGPs in the presence of HVS(IO) and HVS(EO) (group D; Table 2) at each air sampling location (1 – 6; Table 1). Acquisition of air samples were performed during the baseline period (0 – 3 min), during the six procedures (3 – 18 min) and following cessation of procedures (18 – 36 min). Dotted lines indicate the upper and lower boundaries of the baseline data. Each data point represents the sum of particles measured by HR-ELPI over 1 second during each replicate (n=3).","description":"","filename":"Figure7TotalConcHVSioHVSeo.jpg","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/4ad5798cf8dbb69ce838a48c.jpg"},{"id":3567998,"identity":"6b4fcd1b-a4b5-44f4-a31b-6d1605a857c6","added_by":"auto","created_at":"2020-11-13 16:29:57","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":126835,"visible":true,"origin":"","legend":" Total particle concentration generated during AGPs in the presence of HVS(IO), HVS(EO) and ACS (group E; Table 2) at each air sampling location (1 – 6; Table 1). Acquisition of air samples were performed during the baseline period (0 – 3 min), during the six procedures (3 – 18 min) and following cessation of procedures (18 – 36 min). Dotted lines indicate the upper and lower boundaries of the baseline data. Each data point represents the sum of particles measured by HR-ELPI over 1 second during each replicate (n=3).","description":"","filename":"Figure8TotalConcHVSioHVSeoACS.jpg","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/197f82a5fa1377537fc2d9ba.jpg"},{"id":3567999,"identity":"49682044-5c3b-403d-ad2c-7b085856b873","added_by":"auto","created_at":"2020-11-13 16:29:57","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":94722,"visible":true,"origin":"","legend":" Total dose of particles measured over the 36-minute experimental period (expressed as area under curve) for each location (1 – 6; Table 1) and treatment group (A – E; Table 2). Each data point represents the median ± minimum/maximum of n=3 replicates.","description":"","filename":"Figure9TotalDose36min.jpg","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/e9ecf267e89fe54f0f8a7e37.jpg"},{"id":3568000,"identity":"397f41af-8292-452b-b49a-6dcf86c01487","added_by":"auto","created_at":"2020-11-13 16:29:57","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":172376,"visible":true,"origin":"","legend":"Linear regression (with 95% confidence intervals) of decay-phase particle concentration data. Each data point represents the median sum particle concentration measured by HR-ELPI per second during each replicate (n=3). Horizontal dotted red lines indicate baseline particle range.\n\n","description":"","filename":"Figure10LinRegression.jpg","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/7112b055f8a69efcdc4588f2.jpg"},{"id":13613974,"identity":"c657c0a0-7d95-470b-908b-dfe9f2361df3","added_by":"auto","created_at":"2021-09-17 06:39:16","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1377415,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/c52014b2-f466-4318-98cb-30a58437009c.pdf"},{"id":3567990,"identity":"07ae1aec-79e4-41d2-a4a5-cb998fab5042","added_by":"auto","created_at":"2020-11-13 16:29:56","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":549190,"visible":true,"origin":"","legend":"Annex A","description":"","filename":"SupplementarydataAnnexAFinalEdit2.pdf","url":"https://assets-eu.researchsquare.com/files/rs-105294/v1/af4eef75134ed7b043dabe3e.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eSARS-CoV-2: Characterisation and Mitigation of Risks Associated with Aerosol Generating Procedures (AGPs) in Dental Practices\u003c/p\u003e","fulltext":[{"header":"Key Points","content":"\u003col\u003e\n\u003cli\u003eThe particle size distribution of aerosols generated by dental procedures are predominantly \u0026lt; 0.3 \u0026micro;m in diameter. This encompasses the reported size range of the SARS-CoV-2 virus (0.05 \u0026ndash; 0.15 \u0026micro;m).\u003c/li\u003e\n\u003c/ol\u003e\n\u003col start=\"2\"\u003e\n\u003cli\u003eEven in the presence of interventions such as high volume inter-oral suction HVS(IO) combined with an air cleaning system (ACS), aerosol particles \u0026lt; 0.3 \u0026micro;m were substantially elevated above the baseline range during the dental aerosol generating procedures (AGP) used in this study (these included the use of air-turbine and electric handpieces operating at over 60,000 rpm). Levels of aerosol were especially elevated within the working micro-environment (50 cm radius from the mouth) of the dentist and assistant. This emphasises the importance of properly fitted personal protective equipment such as FFP3 masks.\u003c/li\u003e\n\u003c/ol\u003e\n\u003col start=\"3\"\u003e\n\u003cli\u003eIntra-oral high-volume suction, either alone or in combination with an air cleaning system (in this case operating at 24 room air changes per hour in a typical 35 m\u003csup\u003e3\u003c/sup\u003e surgery) was effective in rapidly reducing AGP-related particle concentrations to within background range in some cases, during or immediately, on cessation of AGPs negating the need for fallow time. These data indicate that a reduction in fallow time may be achieved below the current guidance of 10 minutes through judicious use of aerosol management interventions.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Introduction","content":"\u003cp\u003ePotentially infectious agents (e.g. bacteria, fungi and viruses) can be transmitted when droplets containing microorganisms generated from an infected person (example by breathing, talking or coughing) are propelled through the air and are directly inhaled, deposited on the skin or mucosal surfaces, or contaminate infrastructure.\u003csup\u003e1\u003c/sup\u003e High-speed dental instruments require effective cooling of the work area in order to avoid damage of the pulp dentine system. These instruments generate a dental aerosol, as cooling water and air are sprayed around the instruments and the oral cavity. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eDental aerosols are distributions of particle sizes from 0.001 to \u0026gt;10 \u0026micro;m in diameter.\u003csup\u003e2,3\u003c/sup\u003e\u003csup\u003e\u0026nbsp;\u003c/sup\u003e Traditionally, dental airborne aerosols were defined as being small particles \u0026lt;50 \u0026micro;m, with larger ballistic/projectile particles (\u0026gt;50 -100 \u0026micro;m) being described as \u0026ldquo;splatter\u0026rdquo;.\u003csup\u003e4\u003c/sup\u003e The WHO definition\u003csup\u003e5\u003c/sup\u003e of aerosols has been adopted in the dental field, which defines large projectile particles as being \u0026gt; 5\u0026micro;m, with smaller (\u0026lt; 5 \u0026micro;m) \u0026ldquo;droplet nuclei\u0026rdquo; particles forming through the evaporation \u0026nbsp;of larger particles generating an airborne solid residue.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eInfectious droplets from saliva or blood may enter the aerosol and expose the dental team to an increased risk of infection though direct inhalation, contact with eyes, and contact with contaminated work surfaces.\u003csup\u003e6,7\u003c/sup\u003e Dental aerosols therefore have the potential to provide a path for the transmission of COVID-19 \u003csup\u003e8,9\u003c/sup\u003e which may remain infectious for between 2 hours to 9 days in a humid environment.\u003csup\u003e7\u003c/sup\u003e Research on the influenza virus has also demonstrated that the total viral copies were 8.8 times more numerous in particles \u0026lt;5 \u0026micro;m than in particles \u0026ge;5 \u0026micro;m.\u003csup\u003e10\u003c/sup\u003e\u0026nbsp; Previous studies have demonstrated the dispersion of bioaerosols to all areas of the treatment room\u003csup\u003e11\u003c/sup\u003e which remain airborne for 30 minutes following the procedure.\u003csup\u003e12\u003c/sup\u003e Therefore, there is a clear need for the effective removal of aerosols in dental practices.\u003csup\u003e13\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eProtocols exist to minimise the risk of infection to clinical staff during dental procedures.\u003csup\u003e12,14-17\u003c/sup\u003e These include: low volume suction (LVS) to remove saliva and excess coolant, coolant disinfectant, high-volume intra-oral suction (HVS (IO)), personal protective equipment (PPE) and improved ergonomics and techniques (e.g. dental dams). A range of additional aerosol removal treatments have been proposed for use in dental procedures including extra-oral high volume suction (HVS (EO)), air cleaning systems (ACS), designed to filter, purify and recirculate room air) and ventilation systems.\u003csup\u003e7,14,18,19\u003c/sup\u003e However, their effectiveness within a diverse range of dental practice environments is difficult to predict.\u003csup\u003e13\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA wide range of ACS with different air flow rates and cleaning technology are commercially available or being marketed for dental use. However, dental practices have no clear standards or specifications to refer to before making an investment. HVS(EO) and ACS\u003csup\u003e20,21\u003c/sup\u003e that contain high efficiency particulate air (HEPA) filters are effective in removing airborne particles with sizes greater than 0.3 \u0026micro;m: viruses, such as coronaviruses, are in the size range of 0.05 \u0026ndash; 0.15\u0026micro;m\u003csup\u003e22\u003c/sup\u003e and thus may evade filtration. Hence, ACS have evolved to include the addition of technology such as UV-C lamps (99.97% killing of H3N2 influenza virus), negative ion generators, and high pressure/voltage electrostatic plasma, which eliminate particles greater than 0.0146 \u0026micro;m. The efficiency of these air purifiers has not been evaluated for the removal aerosol particles in the presence of high volume intra-oral or extra-oral suction.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWhilst researchers have studied aerosol removal treatments, few studies have examined their effectiveness across the full dental aerosol particle size distribution. For example, the use of HVS(IO) at air flow rates of 250 \u0026ndash; 300 L min\u003csup\u003e-1\u003c/sup\u003e is an established means of controlling dental aerosols but its effectiveness is based on a qualitative assessment of visible particles or particles greater than 0.65 \u0026micro;m.\u003csup\u003e19,23\u003c/sup\u003e Viruses are smaller than 0.65 \u0026micro;m and therefore the efficacy of HVS(IO) studies are not relevant to COVID 19.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe objectives of this current study were to characterise the aerosols generated by standard dental procedures and to investigate the effectiveness of different combinations aerosol management interventions across the particle distribution range from 0.0062 to 10 \u0026micro;m diameter to provide evidence for establishing a revised fallow time. A sequence of six standard dental procedures were performed in series to assess the effectiveness of four combinations of interventions based on HVS (IO), HVS (EO) and an ACS. The effectiveness of each intervention group was measured using a high-resolution particle size analyser, with air samples taken over a 36-minute period from six locations within a standard dental surgery. \u0026nbsp;\u003c/p\u003e"},{"header":"Method","content":"\u003cp\u003eThe study was performed within a dental surgery (dimensions 4.4 x 3.1 x 2.6 m: Figure 1). Real-time aerosol analysis was performed with a high-resolution Electric Low-Pressure Impactor particle sizer (HR-ELPI: \u0026ldquo;ELPI+\u0026rdquo;, Dekati, Kangasala, Finland). The instrument recorded the concentration of particles detected within 100 pre-set \u0026lsquo;bins\u0026rsquo; of particle size, ranging from 0.0062 to 9.6 \u0026micro;m, at a sampling frequency of 1 Hz. Air samples were acquired at six locations (Figure 1, Table 1). Each position was measured relative to the phantom head on which the dental AGPs were performed. Air samples were directed to the ELPI+ via 2 m lengths of silicone tubing (Tygon\u0026reg;\u0026rdquo;; internal diameter 12.7 mm, external diameter 17.5 mm; Cole-Parmer Instrument Co, Illinois, USA: Figure S1). Each tube was individually connected to the particle sizer for a period of 30 seconds before being replaced with a tube from the next sampling location to enable a serial analysis of all six air sample locations within a 3 min cycle. A pilot study demonstrated that the tubing had no discernible effect on particle size measurements (see supplementary data: Annex A, Figures S1-S3). All non-experimental air-conditioning equipment was turned off during the experimental work, and the average room temperature and relative humidity were recorded at 27 C and 67% respectively.\u003c/p\u003e\n\u003cp\u003eEach experiment comprised a three-minute baseline period, followed by a series of six aerosol generating procedures (AGPs) carried out over 18 minutes with a post-procedural duration of 18 minutes to monitor aerosol decay (Figure 2). \u0026nbsp;Each experiment was performed using one of four treatments (Table 2). The technical specifications of each aerosol removal system are described in Table 3. Each treatment was performed in triplicate. The AGPs incorporated the serial use of six commonly used dental preparation instruments each of which were operated for three minutes within the phantom head, in the upper and lower anterior sextants, in the following order: (I) Air turbine hand-piece, (II) Electric contra-angle hand-piece, (III) Air turbine hand-piece, (IV) Three in one syringe, (V) Ultrasonic scaler and (VI) Ultrasonic scaler (Table 4).\u003c/p\u003e\n\u003cp\u003eTotal particle concentration (calculated as the sum of particle concentrations over the 0.0062 to 9.6 \u0026micro;m bin range) did not consistently exhibit a Gaussian (normal) or log-normal distribution and so excluded the use of parametric statistical tests. The low sample number (n=3) precluded non-parametric analyses. Therefore, descriptive statistics were used and all particle concentration data are expressed as median values. Area under curve (AUC) calculations were performed using GraphPad Prism (v7.0e for Mac OS, GraphPad Software, La Jolla California USA). The AUC calculations reflect the total \u0026ldquo;dose\u0026rdquo; of aerosol (units of mL cm\u003csup\u003e-3\u003c/sup\u003e min). The AUC calculations were used to assess the overall efficiency of each treatment and were expressed as the median value \u0026plusmn; minimum/maximum. Estimation of fallow time in the control treatment group was performed by linear regression of particle concentrations at each sample location following cessation of AGPs and was calculated as the time at which the extrapolated particle concentration decreased below the upper baseline particle concentration.\u0026nbsp;\u003c/p\u003e\n"},{"header":"Results","content":"\u003cp\u003eThe majority (\u0026gt;99.9%) of particles generated by the sequence of dental procedures (Figure 2) were \u0026lt; 0.3 \u0026micro;m diameter when sampled at the proximal position (Location 1: 8 cm). Instruments I, II and III (Table 4) in the sequence generated the highest aerosol levels. Peak concentrations occurred between particle diameters 0.013 to 0.022 \u0026micro;m (Figure 3, t= 3-6, 6-9, and 9-12 min).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAerosol generated under the control conditions (Table 2, intervention group A (LVS only)) was observed at all locations within the surgery and remained detectable at 15 min (Figure 3, t=36 min) from the end of the last procedure (instrument VI at t=21 min). The most persistent particles were in the range 0.012 to 0.025 \u0026micro;m. Particle concentrations decreased with increasing distance from the phantom head, with a notable, time-related decrease of particles in the range 0.054 to 0.236 \u0026micro;m diameter. Particles \u0026gt; 0.05 \u0026micro;m persisted at low concentrations (~25 x 10\u003csup\u003e3\u0026nbsp;\u003c/sup\u003ecm\u003csup\u003e-3\u003c/sup\u003e) for the duration of the study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe particle size distributions generated during the use of all instruments and applying interventions B to E (Table 2) were like those in the control but with markedly reduced concentrations (Figure 3). Compared with control conditions all interventions produced a remarkable decrease in the number and distribution of particles detected in the extra-oral space (Location 2: 20 cm) and more distal locations. Following the end of the sequence of procedures (t=21 min) there was infrequent detection of low concentrations of aerosol particles from beyond the extra-oral space, and particles \u0026gt; 0.05 \u0026micro;m were generally at the baseline level (Figure 3).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn the control group, total particle counts remained elevated above the baseline range for the duration of the experiment at all locations (Figure 4, and Figure S4). Therefore, for the control group linear regression was used to calculate the time needed for the total particle concentration at each location to return to baseline levels (Figure 10). This produced an estimated median time of 26 min (range 25 \u0026ndash; 31 min) from the end of the sequence of procedures (t=21 min). In the case of experiments using either the HVS(IO), or the HVS(IO) combined with the ACS (Table 2, intervention groups B and C) the concentration of particles returned to within the baseline range at the end of the procedures (t=21 min) (Figures 5, and 6 respectively). However, the total number of aerosol particles remained marginally above the baseline for interventions which included the HVS(EO) (Figures 7 and 8).\u003c/p\u003e\n\u003cp\u003eWhen the aerosol concentrations are expressed as dose (mL cm\u003csup\u003e-3\u003c/sup\u003e min) all interventions reduced total aerosol exposure (Figure 9). Intervention group B (Table 2, HVS(IO) with LVS) reduced the median dose by 80%, while intervention group E (HVS(IO)+HVS(EO)+ACS with LVS) reduced the median dose by 90%. However, HVS(IO) was noticeably less effective than intervention groups C, D and E in controlling the range of (maximum-minimum) of the dose.\u0026nbsp;\u003c/p\u003e\n"},{"header":"Discussion","content":"\u003cp\u003eThe results of this study demonstrate that all the aerosol management interventions evaluated were relatively effective in controlling aerosols generated by dental handpieces. Most particles produced by our sequence of AGPs were \u0026lt; 0.3 \u0026micro;m. The use of either the HVS(IO), or the HVS(IO) combined with the ACS was enough to reduce the fallow time to \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;0-min.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eDuring AGPs the concentration of particles in the range 0.05 to 0.15 \u0026micro;m diameter range is increased substantially. This size range corresponds to the reported size range of the SARS-CoV2 virus\u0026nbsp;(0.05 to 0.15 \u0026micro;m).\u003csup\u003e22\u003c/sup\u003e\u0026nbsp; Within the working micro-environment (Locations 3-4, \u0026lt;50 cm) the presence of active aerosol management interventions substantially reduces the concentration of airborne particles in this range but does not eliminate them. Thus it is important for dental workers to utilise both appropriate and properly fitted respiratory protective equipment such as FFP3 masks in combination with aerosol management interventions.\u003csup\u003e24\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn the absence of aerosol management interventions, particles in the range 0.05 \u0026ndash; 0.236 \u0026micro;m, remained at elevated concentrations within the macro-environment (Locations 5-6, \u0026gt;50 cm) for longer than the experimental period.\u0026nbsp;Our control study estimated that it may take at least 28 to 34 minutes after cessation of AGPs for the total particle concentration to return to baseline levels.\u0026nbsp;Intervention groups B and C, which included the addition of HVS(IO), or HVS(IO) with ACS, both had the effect of returning particle concentrations to within the baseline range by the end of the sequence of procedures i.e. no additional fallow-time was required before particle concentrations returned to baseline levels. In the case of interventions D and E, which included HVS(EO), particle concentrations remained marginally above the baseline which is in agreement with previous work.\u003csup\u003e19\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eInterventions B and C reduced particle concentrations in the macro-environment\u0026nbsp;(Locations -5-6, \u0026gt;50 cm)\u0026nbsp;to within the baseline range during AGPs. Intervention C, (HVS(IO) in combination with an ACS) was effective in controlling both the median and the range (max-min) of the aerosol dose at all locations. In\u0026nbsp;a dental surgery of the size used in this study (35 m\u003csup\u003e3\u003c/sup\u003e), and in the context of SARS-CoV-2, it provides\u0026nbsp;further evidence to support a reduction in fallow time below the current recommend period of 10 minutes\u003csup\u003e24\u003c/sup\u003e in agreement with other recent studies.\u003csup\u003e25\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe use of a phantom head is a clear limitation of this study: the presence of saliva and other biological materials within the oral cavity may conceivably affect the particle size distribution of AGPs and so further, confirmatory research should be performed using patients. Such work should incorporate different size surgeries to validate the scalability of aerosol mitigation interventions. It should also be noted that a locally moist and warm atmosphere within a \u0026ldquo;turbulent gas cloud\u0026rdquo; allows the contained continuum of droplet sizes to evade evaporation for much longer time periods than occurs with isolated droplets, from a fraction of a second to minutes.\u003csup\u003e26\u003c/sup\u003e This may explain why the most persistent particles measured in our study were within the smaller, 0.012-0.025 \u0026micro;m range. Therefore, a patient-orientated study is needed to confirm the nature of the fine particle aerosols containing mixtures of saliva, coolant, and pathogens. This may provide further evidence to support the use of antiviral disinfectants in coolant solutions.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eDental AGPs produce aerosols characterised by particles \u0026lt; 0.3 \u0026micro;m in diameter. Although, aerosol suppression treatments such as HVS(IO) alone or in combination with an ACS may rapidly reduce particle concentrations to within background range, they do not eliminate exposure during AGPs and so the use of appropriate respiratory protective equipment by dental practitioners is essential.\u003c/p\u003e\n\u003cp\u003eHVS(IO) combined with the ACS was enough to reduce the fallow time to 0 minute, and to control the median and range of the aerosol particle dose at all areas in the surgery. The ACS used in these experiments was set to deliver 24 air changes per hour in an 35m\u003csup\u003e3\u003c/sup\u003e surgery which was close to maximum and further experimental work is needed to optimise the location and setting of equipment of this type.\u003c/p\u003e\n\u003cp\u003eIn the absence of ventilation within a modest sized (35 m\u003csup\u003e3\u003c/sup\u003e) surgery, particles associated with dental AGPs may persist for approximately half an hour. There appears to be scope for a reduction in fallow time from the current guideline of 10 minutes when effective aerosol management system(s) are used.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch1\u003eAcknowledgements\u003c/h1\u003e\n\u003cp\u003eThis work was supported by the LJMU Corona Virus Rapid response grant. The authors wish to thank Tayyebeh Rafiei, Rhiannon Powell \u0026amp; Ben Wilkinson for their efforts in assisting the data analysis. The authors would also like to express their gratitude to Louie Chen (Scielutions Ltd) \u0026amp; Dekati Ltd Finland for the loan of the ELPI+ unit and their invaluable technical support.\u003c/p\u003e\n\u003ch1\u003eDeclaration of Interests\u003c/h1\u003e\n\u003cp\u003eThe authors have not declared any conflict of interest. Techceram Ltd is a commercial entity in the dental field, but has no interest in any of the equipment used in the present study, only in contributing its network of contacts towards the present study, in order to better understand dental AGPs, so that dental hospitals, practices, labs and associated dental supply chain smaller businesses can remain open and operate safely through any future viral pandemics.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003cp\u003e1\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Jayaweera, M., Perera, H., Gunawardana, B. \u0026amp; Manatunge, J. 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Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID-19. \u003cem\u003eJAMA\u003c/em\u003e \u003cstrong\u003e323\u003c/strong\u003e, 1837-1838, doi:10.1001/jama.2020.4756 (2020).\u003c/p\u003e"},{"header":"Tables","content":"\u003cp style='margin-top:0in;margin-right:0in;margin-bottom:10.0pt;margin-left:0in;text-align:justify;font-size:13px;font-family:\"Calibri\",sans-serif;'\u003e\u003cstrong\u003e\u003cspan style=\"font-size:16px;\"\u003eTable\u0026nbsp;\u003c/span\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cspan style=\"font-size:16px;\"\u003e1\u003c/span\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cspan style=\"font-size:16px;\"\u003e:\u003c/span\u003e\u003c/strong\u003e\u003cspan style=\"font-size:16px;\"\u003e\u0026nbsp;Air sampling location coordinates, expressed relative to the phantom head (nominal coordinates x=0, y=0, z=0).\u003c/span\u003e\u003c/p\u003e\n\u003ctable style=\"border-collapse: collapse;border:none;\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width:56.5pt;border:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.95pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e\u003cstrong\u003eSample Location No.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width:119.95pt;border:solid windowtext 1.0pt;border-left:none;padding:0in 5.4pt 0in 5.4pt;height:24.95pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e\u003cstrong\u003eName\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" style=\"width:191.85pt;border:solid windowtext 1.0pt;border-left:none;padding:0in 5.4pt 0in 5.4pt;height:24.95pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e\u003cstrong\u003eCo-ordinates relative to phantom head (mm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width:82.2pt;border:solid windowtext 1.0pt;border-left:none;padding:0in 5.4pt 0in 5.4pt;height:24.95pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e\u003cstrong\u003eLinear Distance from source (mm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:64.3pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e\u003cstrong\u003ex\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.8pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e\u003cstrong\u003ey\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.75pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e\u003cstrong\u003ez\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:56.5pt;border:solid windowtext 1.0pt;border-top: none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:119.95pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003ePhantom head (source)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:64.3pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.8pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.75pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:82.2pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:56.5pt;border:solid windowtext 1.0pt;border-top: none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:119.95pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003eHVS (EO) in-take\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:64.3pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e135\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.8pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e-110\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.75pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:82.2pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e200\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:56.5pt;border:solid windowtext 1.0pt;border-top: none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:119.95pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003eDentist\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:64.3pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e-262\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.8pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e145\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.75pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e265\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:82.2pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e400\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:56.5pt;border:solid windowtext 1.0pt;border-top: none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:119.95pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003eAssistant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:64.3pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e354\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.8pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e160\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.75pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:82.2pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e500\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:56.5pt;border:solid windowtext 1.0pt;border-top: none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:119.95pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003eWall\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:64.3pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.8pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.75pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e1045\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:82.2pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e1480\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:56.5pt;border:solid windowtext 1.0pt;border-top: none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:119.95pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003eLight\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:64.3pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e726\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.8pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e383\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:63.75pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e1495\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:82.2pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;margin-bottom:10.0pt;'\u003e1700\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cstrong\u003eTable 2:\u0026nbsp;\u003c/strong\u003eSummary of aerosol removal treatments used in each experiment. Note that intra-oral low volume suction (LVS) was used in all treatment groups (including control) to represent standard practice and to prevent excess fluid accumulation within the phantom head.\u003c/p\u003e\n\u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n\u003ctable style=\"border-collapse:collapse;border:none;\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 76.2pt;border: 1pt solid windowtext;padding: 0in 5.4pt;vertical-align: bottom;\"\u003e\n \u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"color:black;\"\u003e\u0026nbsp;\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"4\" style=\"width: 341.75pt;border-top: 1pt solid windowtext;border-right: 1pt solid windowtext;border-bottom: 1pt solid windowtext;border-image: initial;border-left: none;padding: 0in 5.4pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cstrong\u003e\u003cspan style=\"color:black;\"\u003eInterventions\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 74.9pt;border-top: none;border-left: none;border-bottom: 1pt solid windowtext;border-right: 1pt solid windowtext;padding: 0in 5.4pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eLVS\u0026nbsp;\u003c/p\u003e\n \u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size:15px;\"\u003eLow volume suction\u0026nbsp;\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 89.65pt;border-top: none;border-left: none;border-bottom: 1pt solid windowtext;border-right: 1pt solid windowtext;padding: 0in 5.4pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"color:black;\"\u003eHVS(IO)\u003c/span\u003e\u003c/p\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size:15px;color:black;\"\u003eHigh Volume Suction (Intra-oral) with air filtration system.\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 85.05pt;border-top: none;border-left: none;border-bottom: 1pt solid windowtext;border-right: 1pt solid windowtext;padding: 0in 5.4pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"color:black;\"\u003eHVS(EO)\u003c/span\u003e\u003c/p\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size:15px;color:black;\"\u003eHigh Volume Suction (extra-oral).\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 92.15pt;border-top: none;border-left: none;border-bottom: 1pt solid windowtext;border-right: 1pt solid windowtext;padding: 0in 5.4pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"color:black;\"\u003eACS\u0026nbsp;\u003c/span\u003e\u003c/p\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size:15px;color:black;\"\u003eAir Cleaning \u0026nbsp;System.\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 76.2pt;border-right: 1pt solid windowtext;border-bottom: 1pt solid windowtext;border-left: 1pt solid windowtext;border-image: initial;border-top: none;padding: 0in 5.4pt;height: 28.35pt;vertical-align: bottom;\"\u003e\n \u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cstrong\u003e\u003cspan style=\"color:black;\"\u003eIntervention group\u0026nbsp;\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:74.9pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:89.65pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:85.05pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.15pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:76.2pt;border:solid windowtext 1.0pt;border-top: none;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cstrong\u003e\u003cspan style=\"color:black;\"\u003eA\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:74.9pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:89.65pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:85.05pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.15pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:76.2pt;border:solid windowtext 1.0pt;border-top: none;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cstrong\u003e\u003cspan style=\"color:black;\"\u003eB\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:74.9pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:89.65pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:85.05pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.15pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:76.2pt;border:solid windowtext 1.0pt;border-top: none;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cstrong\u003e\u003cspan style=\"color:black;\"\u003eC\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:74.9pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:89.65pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:85.05pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.15pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:76.2pt;border:solid windowtext 1.0pt;border-top: none;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cstrong\u003e\u003cspan style=\"color:black;\"\u003eD\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:74.9pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:89.65pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:85.05pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.15pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:76.2pt;border:solid windowtext 1.0pt;border-top: none;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cstrong\u003e\u003cspan style=\"color:black;\"\u003eE\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:74.9pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:89.65pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:85.05pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.15pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cstrong\u003eTable 3:\u003c/strong\u003e Aerosol suppressing equipment and corresponding air/water flow rates. Low volume suction (LVS) was used in all treatment groups. In this study, the air cleaning system (ACS) flow rate was equivalent to ~ 20 air changes per hour.\u003c/p\u003e\n\u003cp style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n\u003cdiv align=\"right\" style='margin:0in;text-align:justify;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\n \u003ctable style=\"width:466.3pt;border-collapse:collapse;border:none;\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:54.75pt;border:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cstrong\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eTreatment\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:197.3pt;border:solid windowtext 1.0pt;border-left: none;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cstrong\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eEquipment\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:73.35pt;border:solid windowtext 1.0pt;border-left: none;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cstrong\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eWater Flow (L min\u003csup\u003e-1\u003c/sup\u003e)\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:50.0pt;border:solid windowtext 1.0pt;border-left: none;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cstrong\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eAir Flow (L min\u003csup\u003e-1\u003c/sup\u003e)\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90.9pt;border-top: 1pt solid windowtext;border-right: 1pt solid windowtext;border-bottom: 1pt solid windowtext;border-image: initial;border-left: none;padding: 0in 5.4pt;height: 8.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cstrong\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eAir changes per hour (in a 35 m\u003csup\u003e3\u003c/sup\u003e surgery)\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:54.75pt;border:solid windowtext 1.0pt;border-top:none;padding:0in 5.4pt 0in 5.4pt;height:29.2pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003eLVS\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:197.3pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:29.2pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003ePlastcare USA, 4 mm slow speed salivary ejector.\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:73.35pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:29.2pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e2.4\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:50.0pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:29.2pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e79\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:90.9pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:29.2pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e\u0026nbsp;\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:54.75pt;border:solid windowtext 1.0pt;border-top:none;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003eHVS(IO)\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:197.3pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003eD\u0026uuml;rr Universal Cannula III 16 mm, connected to D\u0026uuml;rr Dental VSA 300S D\u0026uuml;rr Dental UK, Kettering, UK.\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:73.35pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e-\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:50.0pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e297\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:90.9pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e\u0026nbsp;\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:54.75pt;border:solid windowtext 1.0pt;border-top:none;padding:0in 5.4pt 0in 5.4pt;height:42.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003eHVS(EO)\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:197.3pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:42.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003eEighteeth VacStation, Sifary Medical Technology, Jiangsu, China.\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:73.35pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:42.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e-\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:50.0pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:42.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e3700\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:90.9pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:42.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e6\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:54.75pt;border:solid windowtext 1.0pt;border-top:none;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003eACS\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:197.3pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003eWoodpecker Q7 Plasma Air Purifier, Guilin Woodpecker Medical Instrument Co, Guilin, China.\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:73.35pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e-\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:50.0pt;border-top:none;border-left:none;border-bottom: solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e14167\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:90.9pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:8.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:15px;line-height:106%;color:black;\"\u003e24\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;'\u003e\u003cstrong\u003eTable\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e4\u003c/strong\u003e: Procedural equipment and corresponding coolant flow rates.\u003c/p\u003e\n\u003ctable style=\"border: none;width:6.3in;margin-left:-.25pt;border-collapse:collapse;\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:52.9pt;border:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cstrong\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eProcedure\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:308.6pt;border:solid windowtext 1.0pt;border-left:none;padding: 0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cstrong\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eDescription\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.1pt;border:solid windowtext 1.0pt;border-left:none;padding: 0in 5.4pt 0in 5.4pt;height:28.35pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cstrong\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eCoolant Flow Rate (mL min\u003csup\u003e-1\u003c/sup\u003e)\u003c/span\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:52.9pt;border:solid windowtext 1.0pt;border-top:none;padding: 0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eI\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:308.6pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eW\u0026amp;H Synea Vision TK94 hand-piece \u0026nbsp;(Air Turbine) with long tapered bur\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.1pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003e55\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:52.9pt;border:solid windowtext 1.0pt;border-top:none;padding: 0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eII\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:308.6pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eNSK Ti Max Z95L hand piece (Electric) with long tapered bur\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.1pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003e67\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:52.9pt;border:solid windowtext 1.0pt;border-top:none;padding: 0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eIII\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:308.6pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eSirona T1 Control hand-piece (Air turbine) with long tapered bur\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.1pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003e56\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:52.9pt;border:solid windowtext 1.0pt;border-top:none;padding: 0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eIV\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:308.6pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003e3 in1 syringe from Belmont Cleo II chair\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.1pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003e82\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:52.9pt;border:solid windowtext 1.0pt;border-top:none;padding: 0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eV\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:308.6pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:left;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003eCavitron Jet Plus Ultrasonic with 30K FSI-SLI tip\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:92.1pt;border-top:none;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;height:24.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:16px;font-family:\"Calibri\",sans-serif;line-height:106%;'\u003e\u003cspan style=\"font-size:13px;line-height:106%;color:black;\"\u003e25\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:52.9pt;border:solid windowtext 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dental, aerosol, AGPs, management, particle, size, fallow time,","lastPublishedDoi":"10.21203/rs.3.rs-105294/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-105294/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe objectives of this study were to characterise the particle size distribution of aerosols generated by standard dental aerosol generating procedures (AGPs) and to assess the impact of aerosol management interventions on ‘fallow time’. Aerosol management interventions included combinations of high-volume intra-oral suction (HVS(IO)), high volume extra-oral suction (HVS(EO)) and an air cleaning system (ACS). A sequence of six AGPs were performed in succession on a phantom head. Real-time aerosol measurements (size range 0.0062 – 9.6 µm) were taken using a high-resolution particle sizer acquiring air samples from six locations within a typical dental treatment room (35 m3). The majority (\u0026gt;99%) of AGP particles were \u0026lt; 0.3 µm diameter and remained at significant levels around the dental team during the AGPs. This emphasises the importance of personal protection equipment, particularly, the use of properly fitted respiratory protection to the appropriate (FFP3) standard. In the absence of active aerosol management interventions, AGP particles were estimated to remain above the baseline range for around 25-31 minutes from the end of the sequence of procedures. It was found that HVS(IO), either alone or in combination with the ACS, reduced particle concentrations to baseline levels on completion of AGPs. These data indicated that there is scope to reduce fallow time to 0 minutes.\u0026nbsp;\u003c/p\u003e","manuscriptTitle":"SARS-CoV-2: Characterisation and Mitigation of Risks Associated with Aerosol Generating Procedures (AGPs) in Dental Practices","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2020-11-13 16:29:54","doi":"10.21203/rs.3.rs-105294/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"2b50000d-f5c5-481f-bf25-79924181246e","owner":[],"postedDate":"November 13th, 2020","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":1022455,"name":"Dentistry"}],"tags":[],"updatedAt":"2020-11-13T16:29:54+00:00","versionOfRecord":[],"versionCreatedAt":"2020-11-13 16:29:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-105294","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-105294","identity":"rs-105294","version":["v1"]},"buildId":"ehx78VzkSd0WSzXnipQa-","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}