Since the SMPS tends to overestimate particle counts at high diameters when particle counts at lower diameters are significantly higher (an artifact associated with particle residence time within the system), it is conceivable that, in the absence of such an artifact, better agreement between the SMPS and APS would be seen. A cylindrical grinding wheel, composed of sintered aluminum oxide, was selected for these experiments (diameter 1.6 cm, length 1.0 cm). Furthermore, under high magnification (400), as shown in Fig. Although these data raise some ambiguity over the source of the ultrafine particles, they also raise the question of whether the process leading to mechanical aerosol generation should be considered a source of particles in its own right. Fine grinding reduced the particle sizes to a different extent for each dust type. 2ag and Table 1). government site. Effect of microporosity on scaffolds for bone tissue engineering. 3a). Triplicate, randomized samples were obtained for each grinding substrate. and K.Z. Additionally, it appears that the count median particle diameters varied markedly from substrate to substrate, with no discernable pattern. ANTHONY T. ZIMMER, ANDREW D. MAYNARD, Investigation of the Aerosols Produced by a High-speed, Hand-held Grinder Using Various Substrates, The Annals of Occupational Hygiene, Volume 46, Issue 8, September 2002, Pages 663672, https://doi.org/10.1093/annhyg/mef089. The high density particles produced from the steel substrate ( 7.9 kg/m3), together with uncertainty over their morphology, are probably responsible for the poor transformation between aerodynamic diameter and equivalent-sphere projected area diameter with the APS data. Effect of attachment type on implant strain in maxillary implant overdentures: comparison of ball, Locator, and magnet attachments. Therefore, the occupational protection of the clinician should be increased to reduce the damage of the dust to the doctor. dust particle weight To ensure that the aerosols measured representative products of grinding, background aerosol measurements were also taken with the grinding tool freely spinning within the chamber at 20000 r.p.m. Upadhyay et al. The https:// ensures that you are connecting to the The most effective method of protecting on-site workers and the surrounding community is with dust control systems. The size of the particle has various effects on the organisms exposed to them. These phagosomes mature and bind to lysosomes which digest the particles with enzymes such as hydrolase and oxidase29. Twelve, twenty-four and forty-eight hours after dust treatment, cell viability was significantly reduced. Most of dust is very tiny, so tiny that it's not even visible to the human eye. 5 and and66 The data were subjected to multiple linear regression and showed that the order of influence of the factors on LDH and ROS was the time of exposure to the dust, the dust concentration, and the dust type. method of generation) (ACGIH, 1990; OSHA, 1997). Fig. About Annals of Work Exposures and Health, About the British Occupational Hygiene Society, Receive exclusive offers and updates from Oxford Academic, Comparison of Nanoparticle Filtration Performance of NIOSH-approved and CE-Marked Particulate Filtering Facepiece Respirators, A New Approach to Sampling for Particle Size and Chemical Species Fingerprinting of Workplace Aerosols, Assessment of Particle Size Distributions of Health-relevant Aerosol Exposures of Primary Lead Smelter Workers. The average fluorescence intensities were calculated for the various concentrations of each grinding dust. Cytotoxic and genotoxic potential of respirable fraction of composite dust on human bronchial cells. The amounts of LDH and ROS released were increased with time and concentration, and the differences were statistically significant (P<0.05). The middle form of dust is classified with an approximate 10 micron wide diameter. 81970980 and 31771042), Fok Ying Tung Education Foundation (No. However, with the further increases in concentration, the ROS content levels showed an increasing trend, which may indicate that the cells could not repair the damage caused by exposure to high concentrations of dust37. Finally, Fig. This is the smallest and most common form of dust, sizing up at less than or equal to 5 microns. Previous animal experiments showed that the relatively smaller particle sizes of porcelain and Vitallium dust particles may be more toxic than larger particles15. http://creativecommons.org/licenses/by/4.0/. Critical role of MARCO in crystalline silica-induced pulmonary inflammation. 2ag, with electron micrographs of representative particles shown in Fig. In this study, the morphologies, particle size distributions, and compositions of the three types of dental prosthesis grinding dust were measured. 2). There was no significant difference between the PMMA group and the Vitallium group, and the porcelain group was significantly different from both other groups (P<0.05). Experimental study on pulmonary fibrosis caused by oral denture grinding with mixed dust. Torbica N, et al. Simultaneous aerosol sampling (i.e. The aerosol produced when grinding on a steel substrate is shown in Fig.
As in the case of steel, it is likely that uncertainty over the density of the wood-related aerosol and the particle morphology were responsible for a poor transformation between particle aerodynamic diameter and equivalent-sphere projected area diameter. Yan HP, et al. The aerosol that resulted from grinding a PTFE substrate is shown in Fig. 2c). However, the experimental results showed that Vitallium abrasive dust caused slightly greater damage to the RAW264.7 cells, but the difference was not statistically significant and may be related to the dust particle structures, element compositions or way of entering the body.
At 24h and 48h, culture supernatants were sampled from each well and analysed for LDH level using a lactate dehydrogenase kit. An overview of peroxidation reactions using liposomes as model systems and analytical methods as monitoring tools. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. Sato T, et al. World at work: dental laboratory technicians. The results demonstrate that ultrafine particles do have the potential to form a significant component of a grinding aerosol for a number of substrates. A number of aerosol instruments were used to evaluate the aerosol behavior and the resultant particle size distribution during a grinding operation. 
Larger, nanometer scale particles (60.4 nm < dp < 777 nm) were characterized using a SMPS configured with a long DMA (DMA model 3934 and a condensation particle counter model 3022A; TSI Inc.). Copyright 2022 British Occupational Hygiene Society. The extent of the toxicity and pathogenicity of exposure to PMMA dust, Vitallium dust, and dentin porcelain dust differs. However, for the aluminum, ceramic and granite substrates the source(s) of the nanometer size particles could not be discerned. Dust particles>10m enter through the nasal cavity and are deposited mainly in the back of the pharynx24. In addition, the APS response begins to drop off markedly below 0.7 m aerodynamic diameter, corresponding to a physical diameter of 2 m with a particle density of 7.9 kg/m3. Compared with the control group at different time points, the cell survival rate of the exposed cells gradually decreased. Bethesda, MD 20894, Web Policies During a typical experimental sample run, the grinding substrate was attached to a holder. It gets trapped in the nose, throat and upper respiratory tract.
HEPA-filtered, particle-free air was pulled upward through a stainless steel chamber (0.914 m long, 0.813 m wide, 1.19 m tall) using a commercially available, industrial air cleaner (model 73-800G; ACE Corp., St Louis, MO) (Fig. Indeed, much of the current discussion surrounding the toxicity of low-solubility particles traditionally considered to be chemically inert has focused on particles <100 nm in diameter; commonly termed ultrafine particles. 2b). 5.
Zhang ZQ, et al. The particle size distributions tended to be bimodal, with many substrates showing distinct ultrafine and coarse modes. Lucky for us there are ways toreduce the risk of dust harming those near it. reported that the toxicity of hydrogen peroxide (H2O2) was evaluated by detecting the levels of ROS and LDH in RAW264.7 cells21. RAW264.7 cells are mouse mononuclear macrophage leukaemia cells that play key roles in inflammation, immunity and phagocytosis. Grinding was accomplished such that the cylindrical wheel was placed normal to the substrate with a constant applied force of 3.96 N. A wide variety of grinding substrates were selected for evaluation to represent the broad spectrum of materials available. Grinding of clay ceramic led to a distinct bimodal particle size distribution (Fig. Examining the electron micrographs from each substrate gave little indication of whether particles in the ultrafine mode were primarily associated with the substrate or the carbon brush motor within the grinding tool. Everything is made much larger so you can visually see the comparison. When viewing all of the substrates together for particle diameters corresponding to the ultrafine mode, it can be seen that, with the exception of wood, the size distributions generated by grinding were qualitatively similar to that produced using the grinding tool alone (Fig.
Chen SJ, Chen F. Learning and summary of lactate dehydrogenase. However, apart from these studies there is little in the literature to indicate the likely contribution of mechanical processes to ultrafine aerosols in the workplace. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. The rotational speed of the grinding wheel was determined using a tachometer (Dynapar model HT50; Danaher Controls, Gurnee, IL). 2019-ZD-0749), Shenyang Major Scientific and Technological Innovation Research and Development Plan (No. Rao J, et al. 
Arnoldussen YJ, et al. Fig. A phase-displaced microscope was used to observe the morphological changes of the RAW264.7 cells after 24h and 48h of exposure at a concentration of 300gml1. The large amount of ROS can produce cell lipid peroxidation, which damages normal cells and tissues18. In addition, the multiple comparison analysis based on LSD showed that the effect of the porcelain dust group was higher than the PMMA group and the Vitallium group, and the difference was statistically significant (P<0.05). High-speed grinding has been used as the basis for testing the hypothesis that ultrafine particles do not form a substantial component of mechanically generated aerosols.
Wen ZS, et al. After 6h of exposure, numerous cells had extended pseudopods, indicating active removal of particles26. The information is extracted from Fig. Composite of the coarse mode experimental results for the Dremel tool and various grinding substrates. contributed to the analysis of the experiments.
It showed evidence of charring at the grinding interface, supporting the hypothesis that frictional heating during grinding can lead to the formation of ultrafine particles. Liu SJ, et al. A2, B2, and C2 were finely ground by an agate mortar for 2h, and their morphologies, sizes, chemical compositions, and cytotoxicity were examined. 
Respiratory morbidity in a population of French dental technicians.
TEM images were characterized by large numbers of compact particles >1m, with some evidence for abraded particles <<1m (Fig. Transmission electron microscope samples of the various grinding substrates were also collected. (, Oxford University Press is a department of the University of Oxford. Cardiovascular and inflammatory effects of intratracheally instilled ambient dust from Augsburg, Germany, in spontaneously hypertensive rats (SHRs). In the case of PTFE and steel, the ultrafine particle morphology indicates formation through nucleation, suggesting that temperatures were sufficiently high at the grinding interface to lead to vaporization or combustion of the substrate. This result was subtracted from measured size distributions for each grinding substrate.
Particles engulfed by macrophages are transported in vesicles. Therefore, clinicians who regularly work with these materials should wear the appropriate personal protection equipment to minimize exposure and reduce the health risks caused by these particulates. Grinding was accomplished using a Multipro (model 395; Dremel, Racine, WI), a variable speed tool with rotational speeds that can be varied from 5000 to 30000 r.p.m. Fig. The new PMC design is here! After fine milling, only the particle sizes were reduced, but their shapes did not significantly change. formId: "e7fc0871-5cca-47e3-95b8-26eb8d9c3013", National Institute for Occupational Safety and Health, Division of Applied Research and Technology, 4676 Columbia Parkway, Cincinnati, OH 45226, USA. For example, Sato et al. Coverslips were autoclaved, placed in a six-well plate (1105 cells/well), and exposed to 2mL of 300gmll grinding dust suspension in 5% CO2 at 37C for 24h and 48h. The coverslips were then removed and placed onto clean glass slides.
The aerosol produced solely by the grinding tool and the background corrected measurements for each of the substrates are presented in Fig. In this study, high-speed grinding was used to test the hypothesis that ultrafine particles do not form a substantial component of mechanically generated aerosols. showed that the release of ROS from astrocytes increased with increasing concentration, but these cells did not produce ROS when exposed to a low concentration level (0.0009g/cm2) for 72 h38. Calculations indicated sampling train losses to each SMPS to be negligible. A wide variety of grinding substrates were selected for evaluation to represent the broad spectrum of materials available. using a rheostat (model 3PN751; Matheson Scientific) and a tachometer. 5). Variation in particle number concentration [dN/d log(dp)] as a function of equivalent-sphere projected surface area diameter for (a) the Dremel tool without a grinding substrate, (b) a granite substrate, (c) a clay ceramic substrate, (d) a steel substrate, (e) an aluminum substrate, (f) a PTFE substrate and (g) a hardwood substrate using the SMPS/NDMA (solid circles), SMPS/LDMA (hollow circles) and APS (solid triangles). Pulmonary toxicity and extrapulmonary tissue distribution of metals after repeated exposure to different welding fumes.
The possible mechanism of toxicity may relate to the manner in which the dust entered the cell and its production of lipid peroxidation, which damaged the cell membrane and other structures. The effect of these dust particles at different concentrations on RAW264.7 cells was evaluated. The reason for the ROS increase might be related to short-term and low-dose dust exposure initiating defence measures in the body. dust curtain controlling walls answer longer needs control think than powderbulksolids Transmission electron microscope micrographs of the various grinding substrates including: (a) granite, (b) clay ceramic, (c) steel, (d) aluminum and (e) PTFE. Limited data indicate that it is possible to generate high particle number concentrations from mechanical processes. 2ag. Jordan JA, et al. Very little attention has been given to the possibility of mechanical generation leading to substantial aerosol exposure from ultrafine particles. Particle binding to cell surface receptors such as scavenger and Toll-like receptors may induce polymerization of the actin cytoskeleton and the formation of pseudopods to envelop the dust particles28. It appears that the ultrafine aerosols were formed by the following processes: (i) from within the grinding motor, (ii) from the combustion of amenable grinding substrates and (iii) from volatilization of amenable grinding materials at the grinding wheel/substrate interface. It was proposed that grinding dust induced fibrosis in rat lung tissue14.
Even in cases for which the particles are not clearly observed in the nucleus, in the presence of large vesicles, the shape of the nucleus appears abnormal and compressed27. Tel:+1-513-841-4370; fax: +1-513-841-4545; e-mail:azimmer@cdc.gov. There is evidence that grinding of some substrates produced ultrafine particles through vaporization or combustion of the substrate material. Interpolation between data points below 400 nm and above 800 nm gave a smooth distribution. The importance of reporting house dust mite endotoxin abundance: impact on the lung transcriptome. Barrett TE, et al. Due to the assumption that the aerosols generated from these processes mainly result from mechanical attrition of the substrate, prior research to characterize the particle size distribution has focused upon the micrometer size regime using techniques such as cascade impaction (Lehmann and Frohlich, 1988; Kusaka et al., 1992). The viability of the RAW264.7 cells exposed to the three kinds of dust was lower than that of the blank control group cells (Fig.
For a better understanding of the source of the ultrafine mode arising from grinding on these substrates, the use of alternative sample collection methods or analytical methods such as electron energy loss spectroscopy (EELS) should be considered for future research (Brydson, 2000; Maynard, 2000). In addition, free radicals can lead to lipid peroxidation of the cell membrane35. Large particles (diameter < 10m) can be trapped by the nose and mouth, while smaller particles (diameter < 2.5m, also known as PM2.5) may permeate deep into lungs. 2a). Particles large enough to be sampled by the APS were assumed to arise predominantly through attrition and therefore to have a compact morphology. The information is extracted from Fig.
The assumption was therefore made that the data from each SMPS could be interpreted in terms of particle equivalent-sphere projected area diameter. It was also evaluated with LDH and ROS assays. The macrophage pneumoconiosis model is a currently established model16. In presenting number statistics for the ultrafine mode, the data obtained by the SMPS/NDMA were used for fitting the left-hand side of this mode as this instrument was optimized to sample aerosols in the particle size range 10100 nm. FOIA 
reported that macrophages exposed to silica dust activated classical pathways and therefore generated superoxide anion (O2) and hydroxyl (OH), which caused oxidative damage to the cells34. reported that macrophages produce ROS after engulfing dust particles17. Radi S, et al.
1, PMMA dust (g) contained mainly C and O, Vitallium dust (h) was composed mostly of Cr, Co, and Mo, and porcelain dust (i) consisted principally of Si, Al, and O. Various particles produce similar results. (1993) have shown particle mobility diameter to agree well with equivalent-sphere projected area diameter for fractal-like particles <1 m. Pulmonary disease in dental laboratory technicians. As the particle number or surface area per unit mass increases with decreasing particle size within an aerosol, the presence of sub-micrometer particles becomes increasingly significant as exposure metrics other than mass are considered. Vitallium (h), porcelain (i).
In the overlap regions there was relatively good agreement among the aerosol instruments. 2e). Isolevuglandins as a gauge of lipid peroxidation in human tumors. Using stainless steel and flexible graphite tubing to attenuate charging effects within the sample line, the grinding aerosols were collected from the stainless steel chamber from a position located directly above the grinding operation (height 15 cm). Acrylic resin pneumoconiosis: report of a case in a dental student. Statistical analysis was performed with SPSS 17.0 (IBM Corp., Armonk, NY, USA). Small, nanometer scale particles [4.22 nm < dp (particle diameter) < 100 nm] were characterized using a scanning mobility particle sizer (SMPS) configured with a nano differential mobility analyzer (DMA) (electrostatic classifier model 3080 using a DMA model 3085 and a condensation particle counter model 3022A; TSI Inc., St Paul, MN).