Effect of Additives on Mineral Trioxide Aggregate Setting Reaction Product Formation

Introduction Mineral trioxide aggregate (MTA) sets via hydration of calcium silicates to yield calcium silicate hydrates and calcium hydroxide (Ca[OH]2). However, a drawback of MTA is its long setting time. Therefore, many additives have been suggested to reduce the setting time. The effect those additives have on setting reaction product formation has been ignored. The objective was to examine the effect additives have on MTA\u27s setting time and setting reaction using differential scanning calorimetry (DSC). Methods MTA powder was prepared with distilled water (control), phosphate buffered saline, 5% calcium chloride (CaCl2), 3% sodium hypochlorite (NaOCl), or lidocaine in a 3:1 mixture and placed in crucibles for DSC evaluation. The setting exothermic reactions were evaluated at 37°C for 8 hours to determine the setting time. Separate samples were stored and evaluated using dynamic DSC scans (37°C→640°C at10°C/min) at 1 day, 1 week, 1 month, and 3 months (n = 9/group/time). Dynamic DSC quantifies the reaction product formed from the amount of heat required to decompose it. Thermographic peaks were integrated to determine enthalpy, which was analyzed with analysis of variance/Tukey test (α = 0.05). Results Isothermal DSC identified 2 main exothermal peaks occurring at 44 ± 12 and 343 ± 57 minutes for the control. Only the CaCl2 additive was an accelerant, which was observed by a greater exothermic peak at 101 ± 11 minutes, indicating a decreased setting time. The dynamic DSC scans produced an endothermic peak around 450°C–550°C attributed to Ca(OH)2 decomposition. The use of a few additives (NaOCl and lidocaine) resulted in significantly less Ca(OH)2 product formation. Conclusions DSC was used to discriminate calcium hydroxide formation in MTA mixed with various additives and showed NaOCl and lidocaine are detrimental to MTA reaction product formation, whereas CaCl2 accelerated the reaction

Feasibility Study of Gas Engine Driven Air Compressors

The objective of this research is to conduct a feasibility study of Gas Engine Driven Air Compressors versus Electric Motor Driven Air Compressors. The methodology adopted in achieving this objective was to develop a linear equation, which was used to develop payback graphs. These graphs were used for the feasibility study. It was concluded that investing in engine driven air compressors is feasible only for a limited combinations of rate schedules and operating hours.Industrial Engineering and Managemen

Analysis of MTA\u27s Setting Reaction: A Differential Scaning Calorimetry Study

Mineral Trioxide Aggregate, a common root-end filling material, was investigated using differential scanning calorimetry (DSC) to identify and characterize the formation of hydration products when the powder is mixed with water. Portland cement was used as a comparative material as it is the active component of MTA. Unmixed powders of both cements and individual components such as bismuth oxide, gypsum, and calcium hydroxide powders were also studied using DSC. The mixed pastes of MTA and Portland cement were studied at- immediate (0 hr), 2 hr, 4 hr, 12 hr, 24 hr, I week, 1 month, 3 months, and 1 year intervals after preparation. Except for the immediate sample, all samples were stored at 37°C and a relative humidity of 100%. The change in weight due to storage conditions and after DSC analysis was also studied. DSC thermogram peaks were identified and integrated to yield enthalpy to serve as an indicator of reaction products formed over time. The results showed water, calcium silicate hydrate, gypsum, and calcium hydroxide endothermic peaks in the thermograms obtained from the DSC analysis of MTA at various time intervals. Peaks at 90-110°C, 110-130°C, and 450-550°C were attributed to water, gypsum, and calcium hydroxide decomposition/dehydration, respectively. The size and the location of these peaks changed depending on the amount of phase present at that point of time. Mapping of the calcium hydroxide hydration product helped to study the hydration behavior and the progression of the reaction over time. Overall, similar endothermic peaks were seen in Portland cement pastes, but the size of the calcium hydroxide peak was generally smaller compared to MTA, although a large ettringite peak and small additional peaks were observed. The endothermic peaks from the various powders were helpful in corroborating the peaks formed in mixed pastes and also in differentiating the peaks formed due to hydration. There was initial loss of weight due to evaporation of loosely bound water in storage, followed by weight gain due to uptake of water by the cement paste in both MTA and Portland cement. The weight loss resulting from DSC due to water evaporation decreased as the water became more chemically bound as the time advanced. While the Portland cement samples showed a gradual decrease in weight loss, MTA showed an initial sharp decline in the first few hours followed by a small gain at three months. Based on the findings of this study, the formation of calcium hydroxide in mixed MTA increased till one month after which a decrease was seen, which may be due to a carbonation reaction. MTA\u27s hydration reaction yielded greater amounts of calcium hydroxide when compared to Portland cement

Data_Sheet_1_A dynamic approach for visualizing and exploring concept hierarchies from textbooks.pdf

In this study, we propose a visualization technique to explore and visualize concept hierarchies generated from a textbook in the legal domain. Through a human-centered design process, we developed a tool that allows users to effectively navigate through and explore complex hierarchical concepts in three kinds of traversal techniques: top-down, middle-out, and bottom-up. Our concept hierarchies offer an overview over a given domain, with increasing level of detail toward the bottom of the hierarchy which is consisting of entities. In the legal use case we considered, the concepts were adapted from section headings in a legal textbook, whereas references to law or legal cases inside the textbook became entities. The design of this tool is refined following various steps such as gathering user needs, pain points of an existing visualization, prototyping, testing, and refining. The resulting interface offers users several key features such as dynamic search and filter, explorable concept nodes, and a preview of leaf nodes at every stage. A high-fidelity prototype was created to test our theory and design. To test our concept, we used the System Usability Scale as a way to measure the prototype's usability, a task-based survey to asses the tool's ability in assisting users in gathering information and interacting with the prototype, and finally mouse tracking to understand user interaction patterns. Along with this, we gathered audio and video footage of users when participating in the study. This footage also helped us in getting feedback when the survey responses required further information. The data collected provided valuable insights to set the directions for extending this study. As a result, we have accounted for varying hierarchy depths, longer text spans than only one to two words in the elements of the hierarchy, searchability, and exploration of the hierarchies. At the same time, we aimed for minimizing visual clutter and cognitive overload. We show that existing approaches are not suitable to visualize the type of data which we support with our visualization.</p