scholarly journals Spray mist reduction by means of a high-volume evacuation system—Results of an experimental study

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257137
Author(s):  
Martin Koch ◽  
Christian Graetz
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
High Speed ◽  
Statistical Tests ◽  
Mouth Opening ◽  
High Volume ◽  
Worst Case ◽  
Significant Difference ◽  
Tooth Preparation ◽  
Evacuation System

Objectives High-speed tooth preparation requires effective cooling to avoid thermal damage, which generates spray mist, which is a mixture of an aerosol, droplets and particles of different sizes. The aim of this experimental study was to analyze the efficacy of spray mist reduction with an intraoral high-volume evacuation system (HVE) during simulated high-speed tooth preparation for suboptimal versus optimal suction positions of 16 mm sized cannulas and different flow rates of the HVE. Material and methods In a manikin head, the upper first premolar was prepared with a dental turbine, and generated particles of 5–50 microns were analyzed fifty millimeters above the mouth opening with the shadow imaging technique (frame: 6.6×5.3×1.1 mm). This setup was chosen to generate a reproducible spray mist in a vertical direction towards an imaginary operator head (worst case scenario). The flow rate (FR) of the HVE was categorized into five levels (≤120 l/min up to 330 l/min). The number of particles per second (NP; p/s) was counted, and the mass volume flow of particles per second (MVF; μg/s*cm3) was calculated for 10 sec. Statistical tests were nonparametric and two-sided (p≤0.05). Results With increasing flow rate, the NP/MVF values decreased significantly (eta: 0.671/0.678; p≤0.001). Using a suboptimally positioned cannula with an FR≤160 l/min, significantly higher NP values (mean±SD) of 731.67±54.24 p/s (p≤0.019) and an MVF of 3.72±0.42 μg/s*cm3 (p≤0.010) were measured compared to those of the optimal cannula position and FR≥300 l/min (NP/MVF: 0/0). No significant difference in NP and MVF was measurable between FR≥250 l/min and FR>300 l/min (p = 0.652, p = 0.664). Conclusion Within the limitations of the current experimental study, intraoral high-flow rate suction with ≥300 l/min with an HVE effectively reduced 5–50 μm sized particles of the spray mist induced by high-speed tooth preparation with a dental turbine.

scholarly journals Understanding the Characteristics of Pedestrians when Passing Obstacles of Different Sizes: An Experimental Study

2021 ◽  
Vol 6 ◽  
Author(s):  
Abdullah N Alhawsawi ◽  
Majid Sarvi ◽  
Emad Felemban ◽  
Abbas Rajabifard ◽  
Jianyu Wang
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
High Speed ◽  
The Body ◽  
Agent Based ◽  
Significant Difference ◽  
Speed Level ◽  
Collective Movements ◽  
The Right ◽  
Insight Into

The aim of this study is to understand the collective movements of individuals and to observe how individuals interact within a physical environment in a crowd dynamic, which has drawn the attention of many researchers. We conducted an experimental study to observe interactions in the collective motions of people and to identify characteristics of pedestrians when passing obstacles of different sizes (bar-shaped, 1.2 m, 2.4 m, 3.6 m and 4.8 m), going through one narrow exit and employing three different flow rates in walking and running conditions. According to the results of our study, there were no differences in collision-avoidance behaviour of pedestrians when walking or running. The pedestrians reacted early to the obstacles and changed the direction in which they were walking by quickly turning to the left or to the right. In terms of the speed of the pedestrians, the average velocity was significantly affected while performing these tasks, decreasing as the size of the obstacle increased; therefore, the size of obstacles will affect flow and speed levels. Travel time was shorter when participants were in the medium-flow rate experiments. In terms of the distance of each individual’s travel, our data showed that there was no significant difference in all the flow rate experiments for both speed levels. Our results also show that when the pedestrians crossed an obstacle, the lateral distance averaged from 0.3 m to 0.7 m, depending on the flow rate and speed level. We then explored how the body sways behaved while avoiding obstacles. It is observed that the average sway of the body was less in the high-speed conditions compared to the low-speed conditions – except for the HF & 4.8 m experiment. These results are expected to provide an insight into the characteristics of the behaviour of pedestrians when avoiding objects, and this could help enhance agent-based models.

Venom flow in rattlesnakes: mechanics and metering

2001 ◽  
Vol 204 (24) ◽  
pp. 4345-4351
Author(s):  
Bruce A. Young ◽  
Krista Zahn
Keyword(s):  
Functional Morphology ◽  
Delivery System ◽  
Flow Rate ◽  
High Speed ◽  
Distal Portion ◽  
Retrograde Flow ◽  
Crotalus Atrox ◽  
Direct Recording ◽  
Significant Difference ◽  
Digital Videography

SUMMARY The functional morphology of venom injection in Crotalus atrox was explored using high-speed digital videography combined with direct recording of venom flow using perivascular flow probes. Although venom flow was variable, in most strikes the onset of venom flow was coincidental with fang penetration, and retrograde flow (venom suction) was observed prior to fang withdrawal. The duration of venom flow was consistently less than the duration of fang penetration. The occurrence of retrograde flow, ‘dry bites’ (which accounted for 35 % of the strikes) and unilateral strikes all support a hypothesis for venom pooling in the distal portion of the venom-delivery system. No significant difference in temporal or volumetric aspects of venom flow were found between defensive strikes directed at small and large rodents. With the species and size of target held constant, the duration of venom flow, maximum venom flow rate and total venom volume were all significantly lower in predatory than in defensive strikes.

scholarly journals The Efficacy of High-Volume Evacuators and Extraoral Vacuum Aspirators in Reducing Aerosol and Droplet in Ultrasonic Scaling Procedures during the COVID-19 Pandemic

2022 ◽  
Author(s):  
Trijani Suwandi ◽  
Vidya Nursolihati ◽  
Mikha Sundjojo ◽  
Armelia Sari Widyarman
Keyword(s):  
Statistical Analysis ◽  
High Speed ◽  
High Volume ◽  
Limited Data ◽  
Dental Procedures ◽  
Significant Difference ◽  
Kolmogorov Smirnov ◽  
Airborne Disease ◽  
Better Than ◽  
Smirnov Test

Abstract Objective SARS-CoV-2 can be carried by aerosols and droplets produced during dental procedures, particularly by the use of high-speed handpieces, air-water syringes, and ultrasonic scalers. High-volume evacuators (HVEs) and extraoral vacuum aspirators (EOVAs) reduce such particles. However, there is limited data on their efficacy. This study aimed to determine the efficacy of HVE and EOVA in reducing aerosols and droplets during ultrasonic scaling procedures. Materials and Methods Three ultrasonic scaling simulations were conducted on mannequins: 1. saliva ejector (SE) was used alone (control); 2. SE was used in combination with HVE; and 3. SE was used in combination with HVE and EOVA. Paper filters were placed on the operator's and assistant's face shields and bodies, and the contamination of aerosols and droplets was measured by counting blue spots on the paper filters. Statistical Analysis All data were analyzed for normality using the Kolmogorov–Smirnov test. The differences between each method were analyzed using a two-way ANOVA, followed by a posthoc test. The differences were considered statistically significant when p < 0.05 Result Using HVE and EOVA reduced aerosols and droplets better than using SE alone or SE and HVE: the posthoc test for contamination revealed a significant difference (p < 0.01). The assistant was subjected to greater contamination than the operator during all three ultrasonic scaling procedures. Conclusion The usage of HVE and EOVA significantly reduced aerosols and droplets compared with using SE solely. Using these techniques together could prevent the transmission of airborne disease during dental cleanings, especially COVID-19. Further studies of aerosol-reducing devices are still needed to ensure the safety of dental workers and patients.

scholarly journals Effect of Passageway Width on Pedestrians Flow Characteristics in Intercity Railway Stations

2019 ◽  
Vol 20 (4) ◽  
pp. 357-364
Author(s):  
Eswar Sala ◽  
K.V.R. Ravishankar
Keyword(s):  
Flow Rate ◽  
Walking Speed ◽  
Statistical Tests ◽  
Flow Characteristics ◽  
Pedestrian Flow ◽  
Affecting Factors ◽  
Road Transportation ◽  
Railway Stations ◽  
Significant Difference ◽  
Intercity Railway

Abstract Rail transportation is most economical means of the mode in comparison to road transportation. Intercity railway stations are nodal points of the rail network. With the growing demand and land use constraints, these are to be well planned, managed and designed. In intercity railways station infrastructure, passageways are confined and elevated elements for pedestrian movements to access among platforms to alight and board trains. Provision of appropriate width for passageway is of greater importance regarding comfort, convenient, evacuation, efficient, aesthetic, cost-effective, environment-friendly and well integrated with other elements of infrastructure. A proper understanding of pedestrian flow characteristics and affecting factors on passageway aids in design implications. In the present work, pedestrian flow characteristics variation on passageway and its width effect is studied. Results showed that, under normal conditions, flow rate (ped/m/min) and mean walking speed (m/min) reduces with increase in width (m). For a given flow rate, volume (ped/min) of pedestrians served on passageway increases with increase in width. Statistical tests revealed that there exists a significant difference in mean walking speed of pedestrians on passageways with different widths.

scholarly journals Dental Mitigation Strategies to Reduce Aerosolization of SARS-CoV-2

2021 ◽  
pp. 002203452110328
Author(s):  
J.J. Vernon ◽  
E.V.I. Black ◽  
T. Dennis ◽  
D.A. Devine ◽  
L. Fletcher ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
High Speed ◽  
Artificial Saliva ◽  
High Volume ◽  
Mitigation Strategies ◽  
Particle Analysis ◽  
Worst Case ◽  
Dental Surgery ◽  
Rubber Dam ◽  
Air Turbine

Limiting infection transmission is central to the safety of all in dentistry, particularly during the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Aerosol-generating procedures (AGPs) are crucial to the practice of dentistry; it is imperative to understand the inherent risks of viral dispersion associated with AGPs and the efficacy of available mitigation strategies. In a dental surgery setting, crown preparation and root canal access procedures were performed with an air turbine or high-speed contra-angle handpiece (HSCAH), with mitigation via rubber dam or high-volume aspiration and a no-mitigation control. A phantom head was used with a 1.5-mL min−1 flow of artificial saliva infected with Φ6-bacteriophage (a surrogate virus for SARS-CoV-2) at ~108 plaque-forming units mL−1, reflecting the upper limits of reported salivary SARS-CoV-2 levels. Bioaerosol dispersal was measured using agar settle plates lawned with the Φ6-bacteriophage host, Pseudomonas syringae. Viral air concentrations were assessed using MicroBio MB2 air sampling and particle quantities using Kanomax 3889 GEOα counters. Compared to an air turbine, the HSCAH reduced settled bioaerosols by 99.72%, 100.00%, and 100.00% for no mitigation, aspiration, and rubber dam, respectively. Bacteriophage concentrations in the air were reduced by 99.98%, 100.00%, and 100.00% with the same mitigations. Use of the HSCAH with high-volume aspiration resulted in no detectable bacteriophage, both on nonsplatter settle plates and in air samples taken 6 to 10 min postprocedure. To our knowledge, this study is the first to report the aerosolization in a dental clinic of active virus as a marker for risk determination. While this model represents a worst-case scenario for possible SARS-CoV-2 dispersal, these data showed that the use of HSCAHs can vastly reduce the risk of viral aerosolization and therefore remove the need for clinic fallow time. Furthermore, our findings indicate that the use of particle analysis alone cannot provide sufficient insight to understand bioaerosol infection risk.

Control of Liquid Impingement With Electrical Field

2005 ◽  
Author(s):  
Xin Feng ◽  
James E. Bryan
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Flow Rate ◽  
High Speed ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Geometrical Parameters ◽  
Mode Transition ◽  
Electrical Field ◽  
Spray Impingement

An initial experimental study was performed to better understand the effect of various operating and geometrical parameters on mode transition in EHD spray impingement. Detailed experimental data is provided for the different modes observed with ethanol. Previous research has focused on the effects of applied voltage and volume flow rate with limited experimental data. Using high-speed digital video imaging, details of eight different spray modes are presented.

scholarly journals The Spread of Droplets and Aerosols of Surgical Motor Handpiece Irrigation Using Different Suction Systems

2021 ◽  
Vol 2 ◽  
Author(s):  
James K. H. Tsoi ◽  
Hao Ding ◽  
Ki Hon ◽  
Yiu Yan Leung
Keyword(s):  
High Speed ◽  
Learning Algorithm ◽  
Irrigation System ◽  
Mouth Opening ◽  
High Volume ◽  
Dental Clinic ◽  
Single Operator ◽  
Droplet Sizes ◽  
Low Volume ◽  
Phantom Head

Objective: This study aimed to compare the effectiveness of various combinations of dental suction devices in reducing the amount and distance of spread of aerosols and droplets using an electrical surgical motor model with a self-irrigation system.Materials and Methods: In a standard single-chaired air-conditioned ventilated dental clinic, an electrical dental surgical motor with a high-speed handpiece (Implantmed) cooled with 0.2% fluorescein containing normal saline was used to drill a gypsum block mounted on a phantom head in a supine position. A single operator performed thrice each of the following suction settings: (a) no suction, (b) low-volume suction, (c) low-volume + high-volume suctions, and (d) low-volume + external oral suctions. Aerosols (0.1–5 μm) were measured with a particle counter at the mouth opening of the phantom head, and droplet sizes and distances were analyzed via a machine learning algorithm by identifying fluorescence droplets on pre-loaded pieces of paper on the floor for each group.Results: The different suction systems have different performances in terms of droplet distance (p = 0.007), whereas using (c) high volume suctions (41.1 ± 22.9 cm) and (d) external oral suction unit (39 ± 18.2 cm) had significantly reduced the spread of droplets when compared with (a) without suction (58.9 ± 17.1 cm). Using (d) external oral suction or (c) high volume suction could reduce the number for all droplet sizes. The use of (c) high volume suction was most effective in reducing aerosol count of 0.3–1 μm, while (d) external oral suction was most effective in reducing aerosol count of 3–5 μm.Conclusions: Both external oral suction and high-volume suction were effective in reducing aerosols and droplets generated by the irrigation of a surgical high-speed motor handpiece. External oral suction could be an effective alternative to high volume suction in dental surgical procedures to reduce the spread of aerosols and droplets.Clinical Relevance: External oral suction or high-volume suction should be used in conjunction with low-volume suction in surgical procedure to reduce the spread of aerosols and droplets in a dental clinic environment.

scholarly journals In Vivo Study of Aerosol, Droplets and Splatter Reduction in Dentistry

Viruses ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1928
Author(s):  
Naeemah Noordien ◽  
Suné Mulder-van Staden ◽  
Riaan Mulder
Keyword(s):  
Health Care Workers ◽  
High Speed ◽  
High Volume ◽  
In Vivo Study ◽  
Aerosol Droplet ◽  
Care Workers ◽  
Air Turbine ◽  
Significant Difference ◽  
Post Hoc

Oral health care workers (OHCW) are exposed to pathogenic microorganisms during dental aerosol-generating procedures. Technologies aimed at the reduction of aerosol, droplets and splatter are essential. This in vivo study assessed aerosol, droplet and splatter contamination in a simulated clinical scenario. The coolant of the high-speed air turbine was colored with red concentrate. The red aerosol, droplets and splatter contamination on the wrists of the OHCW and chests of the OHCW/volunteer protective gowns, were assessed and quantified in cm2. The efficacy of various evacuation strategies was assessed: low-volume saliva ejector (LV) alone, high-volume evacuator (HV) plus LV and an extra-oral dental aerosol suction device (DASD) plus LV. The Kruskal–Wallis rank-sum test for multiple independent samples with a post-hoc test was used. No significant difference between the LV alone compared to the HV plus LV was demonstrated (p = 0.372059). The DASD combined with LV resulted in a 62% reduction of contamination of the OHCW. The HV plus LV reduced contamination by 53% compared to LV alone (p = 0.019945). The DASD demonstrated a 50% reduction in the contamination of the OHCWs wrists and a 30% reduction in chest contamination compared to HV plus LV. The DASD in conjunction with LV was more effective in reducing aerosol, droplets and splatter than HV plus LV.

Maximum Temperature Through a Yttrium Stabilized Zirconia Ceramic After Er,Cr:YSGG Laser Irradiation

2020 ◽  
Vol 02 ◽  
Author(s):  
Laurel Stringer ◽  
Sarah Malley ◽  
Darrell M. Hutto ◽  
Jason A. Griggs ◽  
Susana M. Salazar Marocho
Keyword(s):  
High Speed ◽  
Potential Method ◽  
Maximum Temperature ◽  
Zirconia Ceramic ◽  
Tooth Pulp ◽  
Control Group ◽  
Stabilized Zirconia ◽  
Significant Difference ◽  
Power Setting ◽  
Group A

Background: The most common approach to remove yttria stabilized zirconia (YSZ) fixed-dental prostheses (FDPs) is by means of diamond burs attached to a high-speed handpiece. This process is time-consuming and destructive. The use of lasers over mechanical instrumentation for removal of FDPs can lead to efficient and predictable restoration retrievability. However, the heat produced might damage the tooth pulp (>42˚C). Objective: The purpose of this study was to determine the maximum temperature (T) reached during the use of different settings of the erbium, chromium:yttrium-scandium-gallium-garnet Er,Cr:YSGG laser through a YSZ ceramic. Methods: YSZ slices (1 mm thick) were assigned into 7 groups. For the control group, a diamond bur was used to cut a 1 mm groove into the YSZ slices. For the 6 experimental groups, the laser was operated at a constant combination of 33% water and 66% air during 30 s with two different power settings (W) at three frequencies (PPS), as follows (W/PPS): 2.5/20, 2.5/30, 2.5/45, 4.5/20, 4.5/30, 4.5/45. The T through the YSZ slice was recorded in degrees Celsius by using a digital thermometer with a K thermocouple. Results: The median T of the control group was 26.5˚C. The use of 4.5 W resulted in the median T (˚C) of 44.2 at 20 PPS, 53.3 at 30 PPS, and 58.9 at 45 PPS, while 2.5 W showed 34.6, 31.6, and 25.0 at 20, 30, and 45 PPS, respectively. KruskalWallis one-way ANOVA showed that within each power setting, the T was similar. The high power and lowest frequency (4.5/20) showed no significant difference from the 2.5 W settings and the control group. Conclusion: The lower power setting (2.5 W) is a potential method for the use of the Er,Cr:YSGG laser to debond YSZ structures. The higher power (4.5 W) with high frequencies (30 and 45 PPS) is unsuitable.

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