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Background: COVID-19 has spread worldwide and caused severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) led to numerous dead cases. However, with the new COVID-19 outbreaks, there is a shortage of personal protective equipment (PPE) especially N95 masks worldwide including Thailand. This issue had placed the health professional in great need of an alternative mask. Aim: This study aimed to measure the fit factor of 3D printed frames by quantitative fit testing (QNFT) to find an alternative facemask by using a mask fitter together with 2 different kinds of the American Society for Testing and Materials (ASTM) level 1 surgical mask. Materials and Methods: Two commonly used surgical masks (Sultan Com-Fit Super Sensitive Ear Loop Mask or "White Mask Group," not water-resistant, and Sultan Blue Com-Fit Super High Filtration Ear Loop Mask or "Blue Mask Group," water-resistant) with and without 3D printed frame covering. The fit performance was measured by a quantitative fit test (QNFT) device (PortaCount, model 8048, TSI Incorporated, Minnesota, USA) accepted by the Occupational Safety and Health Administration (OSHA). The PortaCount device, which is based on a miniature continuous flow condensation nucleus counter (CNC), assesses the respiratory fit by comparing the concentration of ambient dust particles outside the surgical mask to the concentration that has leaked into the surgical mask. The ratio of these two concentrations (Cout/Cin) is called the fit factor. A fit factor of a 3D printed frame of at least 100 is required and considered as a pass level. Results: We found that the mask fitter improves the overall performance of surgical masks significantly. The improved performance is comparable to that of N95. Conclusion: The mask fitter improves the performance of surgical masks. The authors suggested that further study on frame material, shape, and expanded sample size would be beneficial to society.
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INTRODUCTION: Important limitations of mineral trioxide aggregate for use in clinical procedures are extended setting time and difficult handling characteristics. The removal of gypsum at the end stage of the Portland cement manufacturing process and polycarboxylate superplasticizer admixture may solve these limitations. METHODS: Different concentrations of polycarboxylate superplasticizer (0%, 1.2%, 1.8%, and 2.4% by volume) and liquid-to-powder ratios (0.27, 0.30, and 0.33 by weight) were mixed with white Portland cement without gypsum (AWPC-experimental material). Type 1 ordinary white Portland cement mixed with distilled water at the same ratios as the experimental material was used as controls. All samples were tested for setting time and flowability according to the International Organization for Standardization 6876:2001 guideline. The data were analyzed by two-way analysis of variance. Then, one-way analysis of variance and multiple comparison tests were used to analyze the significance among groups. RESULTS: The data are presented in mean ± standard deviation values. In all experimental groups, the setting times were in the range of 4.2 ± 0.4 to 11.3 ± 0.2 minutes, which were significantly (p < 0.05) lower than the control groups (26.0 ± 2.4 to 54.8 ± 2.5 minutes). The mean flows of AWPC plus 1.8% and 2.4% polycarboxylate superplasticizer groups were significantly increased (p < 0.001) at all liquid-to-powder ratios compared with control groups. CONCLUSIONS: Polycarboxylate superplasticizer at concentrations of 1.8% and 2.4% and the experimental liquid-to-powder ratios reduced setting time and increased flowability of cement, which would be beneficial for clinical use.
