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Objective Glass ionomers are preferred in many different treatment procedures in dentistry due to their positive features. The aim of this study is to evaluate the color difference and microhardness values of various glass ionomer cement after storing them in different solutions. Material and Method A total of 120 samples were prepared, including 40 of each of the Equia Forte, AHfil Silver, and Ionofil glass ionomers. Each glass ionomer sample was stored in distilled water, cola, tea, and coffee solutions. Color and microhardness measurements of the specimens were performed before and after a week before it was immersed in solutions. The color measurements of the samples were evaluated with a spectrophotometer and microhardness values were evaluated with Vickers microhardness device. For color analysis, color changes (ΔE) were calculated by obtaining the values of L*, a*, and b* of the samples before and after a week after being immersed in solutions. The data obtained were evaluated by variance analysis (ANOVA) and Tukey's test. Results Except for specimens stored in cola for AHfil Silver, microhardness values were increased for all materials immersed in test solutions. The highest color change was obtained in coffee for Equia Forte, in the samples immersed in cola for AHfil Silver and Ionophil (p<0.05). The lowest color change was detected in samples stored in distilled water, and for Equia Forte and Ionofil, the color change was below the acceptable threshold value. Conclusion All the materials tested differ in microhardness and color change values after being immersed in the test environment. The increase in microhardness value can be attributed to the increasing maturation of glass ionomer cement over time, and color change can be attributed to the amount of yellow dyestuff contained in the solutions. [ABSTRACT FROM AUTHOR]

In this study, the surfaces of AISI 1050 Medium Carbon Steel and D2 Cold Work Tool Steel, which are commonly used in the machine manufacturing industry, were processed using the burnishing method. In the burnishing experiments, cylindrical materials with dimensions of Ø50x30mm and a Ø20mm hole drilled in the center were used. For the turning process, the cutting speed was selected as 60 m/min and the feed rate as 0.25 mm/rev. The burnishing process was applied in a single pass. The properties such as microhardness, surface morphology, circularity, cylindricality and surface roughness of the materials by the burnishing process were examined in detail. After burnishing, the hardness of AISI 1050 and D2 cold work tool steel materials was measured to be 292 HV and 302 HV, respectively. The results obtained showed that the burnishing process increased the hardness value of AISI 1050 steel proportionally more than the hardness value of D2 steel. It was determined that the circularity and cylindrical properties of the hole surfaces were improved. The obtained results show that the burnishing process will increase the efficiency of the machine elements working in contact and the damage that may occur during the operation of these machine elements can be minimized by burnishing process. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to compare the microhardness of high viscosity glass ionomer, glass carbomer (GC) and bioactive restorative material (BRM) exposed to different polymerization times, and the intrapulpal thermal changes they caused on teeth. Methods: Sixty human molar teeth were used in this study. During Class I cavity preparation,1 mm dentine thickness was left between the pulp chamber and occlusal cavity floor.Teeth were randomly divided into six groups. Group 1: restored with high viscosity glass ionomer cement (HV-GIC), cured for 20 sec., Group 2: restored with HV-GIC, cured for 40sec., Group 3: restored with conventional glass ionomer cement, cured for 60 sec., Group 4: restored with GC and cured for 90 sec., Group 5: restored with BRMs, cured for 20 sec., Group 6: restored with BRM, cured for 40 sec. All glass ionomer cements were polymerized with a LED light curing unit except GC groups. GC groups were cured with a special thermocure lamp. As soon as the materials were placed in the cavities, temperature increase on the tooth during setting/ polymerization reactions were measured with a thermocouple wire connected to a data logger. All of the specimens were polished with discs.Then, microhardness values were evaluated from three different points. Data were analyzed using one-way ANOVA, Tukey test and paired t-tests (p<0.05). Results: Group 2 showed statistically significantly higher increase in temperature when compared to Group 1. Group 4 showed statistically significantly higher temperature than Group 3. There was no significant difference between Groups 5 and 6 in terms of temperature changes. The highest microhardness values were obtained in GC groups, when the groups were compared to each other. Group 2 showed significantly higher microhardness value than Group 1. Group 6 showed significantly higher microhardness values than Group 5. Conclusion: Fourty sec polymerization of the BRM positively affected the microhardness without causing an intrapulpal temperature increase. While high microhardness values were obtained in 90 sec polymerization of GC, it also caused an increase in temperature that would damage the pulp. [ABSTRACT FROM AUTHOR]

The Al-13.6Cu-6Si (wt.%) ternary alloy was solidified upward unidirectional directionally in a Bridgman-type directional solidification furnace at a constant solidification rate (V=17.4 μm/s), different temperature gradients (1.6-6.12 K/mm), and different solidification rates (8.3-166.0 μm/s) at a constant temperature gradient (G=4.64 K/mm). After completion of the solidification process, the alloy samples were subjected to metallographic treatments to reveal their microstructures. The effect of solidification parameters (V and G) on microstructure parameters (λ1 and λ2) was examined. In addition, the dependence of microhardness on solidification rate, temperature gradient, and microstructure parameters was investigated. The results were also compared with similar experimental results reported in the literature. [ABSTRACT FROM AUTHOR]

Since gamma radiation is a type of radiation that can change the structural properties of materials, CuAlBe shape memory alloy with two different weight percentages was used in this study. CuAlBe shape memory alloys were irradiated with a constant gamma radiation dose of 40 kGy, and the resulting thermal and structural changes in the alloys were investigated. Changes in enthalpy and in the transformation temperature of the alloys were determined by differential scanning calorimetry (DSC), and thermodynamic parameters of alloy samples were calculated. Microstructural changes were determined by X-ray analysis. Microstructural changes were verified by metallographic observations, and microhardness measurements were taken. The study investigated to what extent the physical parameters of CuAlBe shape memory alloys changed depending on the alloying elements when subjected to a constant irradiation dose. [ABSTRACT FROM AUTHOR]

In this study, Al50Si25B25 alloy was produced as ingot by arc melting method. The microstructure of the Al50Si25B25 alloy was investigated by X-ray diffraction (XRD), the morphological properties were investigated by scanning electron microscopy (SEM), and its thermal properties were investigated by differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The mechanical properties of the alloy were investigated by Vickers microhardness (HV) test. The XRD result showed that B and Si atoms dissolved in the Al lattice to form the intermetallic phase of the a-Al (B, Si) solid solution. XRD and SEM results showed that the microstructure of the alloys consisted of a-Al(B,Si) solid solution, Si and AlB2 intermetallic phases. SEM results showed that the morphological structure of the alloys formed as dendritic and eutectic structures. DSC and DTA results showed an endothermic peak indicating the melting of the a-Al(B,Si) phase. The microhardness value of the alloy was measured as 108±15 HV at room temperature. This value increased as a result of the heat treatment and increased to 232±9 HV at 300 °C. It was observed that the microhardness value of the alloy decreased at temperatures higher than 300 °C. [ABSTRACT FROM AUTHOR]

The aim of this study is to compare the microhardness of five different bulk fill composites (SDR, TEC, XTF, SF, FBF). A total of 25 cylindrical molds were prepared. Composite resin was placed in each mold in sequence, at one time, by condensing it thoroughly. Then, the polymerization of the composites was achieved with the LED light device which was applied for 20 seconds. Microhardness measurements of the samples were made with the classical Vicker's test. The data of our study were evaluated by using the Kruskal Wallis H test with the SPSS 20.0 package program. When the measured surface microhardness values were compared between the groups; microhardness values SDR and FBF groups were found to be significantly lower than TEC, XTF and KSF groups (p<0.05). When the sub-surface microhardness values were compared between the groups; the microhardness value of the SDR group was found to be significantly higher than the FBF group, and significantly lower than the TEC, XTF and KSF groups (p<0.05). When both the lower and upper surface microhardness values were compared between the groups, XTF was found to be the bulk fill composite group with the best microhardness. [ABSTRACT FROM AUTHOR]

In this study, the effect of different electrode tip types on weld nugget diameter, tensile shear strength and microhardness properties of advanced high strength steel combined with resistance spot welding method was investigated. For this purpose, resistance spot welded joints were performed using conical round, flat R3, flat R6 and flat conical electrode tips, which are preferred especially in the automotive industry. Test samples were subjected to weld nugget geometry macro-micro examination, mechanical and metallurgical investigations. Experimental results showed that there is a linear relationship between weld nugget diameter value, microhardness results and tensile shear strength values. The highest tensile shear strength values were obtained with flat 3 mm radius tip electrodes, and the lowest tensile shear strength values with flat conical tip electrodes. [ABSTRACT FROM AUTHOR]

Although it has a lot of usage area in the industry because the Al-Cu alloy is defined among the base alloys, the uncontrolled solidified casting of this alloy does not always have the desired properties and performance. For the production of Al-Cu alloys with superior properties, the solidification parameters known as the solidification rate, temperature gradient and composition ratio are changed and the results of this change are evaluated. It is known that changing the properties of the microstructure by growth rate affects the mechanical, electrical and thermal properties of the materials. For this reason, Al-%33 wt. Cu eutectic composition to carrying out correctly microstructure evaluation was prepared, then controlled solidification experiments were carried out by a Bridgman type furnace at a constant temperature gradient (G = 8.50 K/mm) and at five different growth ratios (V = 8.25˗164.80 μm/s). Thus, the effect of the growth rate on the microstructure was investigated and values of microhardness, tensile strength and electrical resistivity were investigated with the effect of change in the microstructure. Both linear regression analysis and Hall-Petch type correlations were used to determine the relationship between microstructure, microhardness, tensile strength and electrical resistivity values. The results obtained in this work were compared with the previous similar experimental results. [ABSTRACT FROM AUTHOR]

Current caries removal methods are classified in various categories including rotating instruments (burs) or excavator, mechanical methods performed by air abrasion, ultrasonic and sono-abrasion, chemomechanical and photoablation (lasers) methods. While conventional caries removal methods are effective, chemomechanical methods were developed to avoid from some possible disadvantages. The action mechanism of chemomechanical caries removal method is based on use of an solution to chemically alter caries tooth tissue to further soften it thus its easier removal. The altered dentine tissue is then mechanicallly removed with hand instruments. Chemomechanical method is claimed to remove caries tissue by only removing the infected dentine layer selectively without causing pain and intact hard tooth tissue loss. Furthermore, the bactericidal and bacteriostatic effects of the method and absence of potential deleterious effects to dental pulp due to heat and pressure make it to be considered as an alternative caries removal method. The aim of this study is to provide information about sodium hypochlorite and enzyme based chemomechanical caries removal agents. Advantages and disadvantages of the method as well as the caries removal efficacy will be examined together with the findings obtained from laboratory and clinical studies on the presence of residual caries and bacteria, micro-hardness and chemical structure of the dentine. [ABSTRACT FROM AUTHOR]

In this study, test specimens were produced by using DMLS device is one of the additive manufacturing methods. Test specimens were produced by using Ti6Al4V powders with some different process parameters such as laser power, laser velosity, hatch distance and these parameters related to energy density and applied to X hatching strategy. It was investigated that microhardnes, manufacturing density and microstructure by applying to different laser energy density. While microhardness was 1.36 J/mm2 energy 345 HV, microhardness was increased 414 HVapplied to energy density 3 J/mm2. While production (sintering) density was 1.36 J/mm2 energy 4.40 g/cm3, produced (sintering) was increased 4.44 g/cm3 applied to energy density 3 J/mm2.It is observationed that microstructure was occured equiaxed grains in the cross section of the sample. [ABSTRACT FROM AUTHOR]

In the present study, 21NiCrMo2 steel were plasma paste boronized by using 100 wt.% B2O3, 70 wt.% B2O3 + 30 wt. % SiC, 70 wt.% B2O3 + 30 wt.% B4C, 30 wt. % B2O3 + 70 wt.% SiC, 30 wt.% B2O3 + 70 wt.% B4C pastes. This steel ispopular bearing steel and have a widespread use in engineering applications. Plasma paste boronizing process was carried out in a dc plasma system at temperature of 700, 750 and 800 °C for 2, 5 and 7 h in a gas mixture of 70%H2 - 30%Ar under a constant pressure of 10 mbar. Pack boronizing of same steel was also carried out at 700, 750 and 800 °C for 2, 5 and 7 h. The properties of boride layer were evaluated by SEM, EDX, X-ray diffraction, Vickers micro-hardness testing. X-ray diffraction analysis of boride layers on the surface of the boronized steel revealed FeB and Fe2B. Plasma paste boronizing process showed that since the plasma activated the chemical reaction more, a thicker boride layer was formed than conventional boronizing methods at same temperatures. It was possible to form boride layer with the same thickness at lower temperatures in plasma environment by using B2O3 paste mixture. [ABSTRACT FROM AUTHOR]