Data Mining and Social Media for promotion and marketing in the Aerospace Industry

Data mining and social media is an innovative platform for the aerospace industry to focus, promote and market the industry in the upcoming economy. Data mining techniques allow the industry to build a comprehensive system that helps to make intelligent management decisions in a formal system. On the other hand Social Media is used as a tool to ensure maximum return by entering a hybrid media landscape, one where the rapid growth of Social Media complements and enhances the efficiency of the industry. By using trend analysis this research would showcase benefits that the industry will achieve by increasing their profit margins and market competiveness. This research mainly focuses on supporting the aerospace industry to build trust among customers and meeting demand specifications by using data mining techniques and social media platform

Preliminary Study on the Optimization of Femtosecond Laser Treatment on the Surface Morphology of Lithium Disilicate Glass-Ceramics and Highly Translucent Zirconia Ceramics

All-ceramic restorations have become increasingly popular in dentistry. Toward ensuring that these restorations adhere to the tooth structure, this study determines the optimal femtosecond laser (FL) treatment parameters for lithium disilicate glass-ceramics and highly translucent zirconia ceramics with respect to surface morphology. For both the ceramics, the following surface conditions were investigated: (1) as-sintered; (2) Al2O3 sandblasted; (3) FL treatment (dot pattern with line distances of 14, 20, and 40 µm); (4) FL treatment (crossed-line pattern with a line distance of 20 and 40 µm). Surface roughness parameters were estimated using a 3D confocal laser microscope; microstructures were analyzed using a scanning electron microscope. Peak fluence (Fpeak) values of 4 and 8 J/cm2 and irradiation numbers (N) of 20 and 10 shots were selected to create dot patterns in highly translucent zirconia and lithium disilicate glass-ceramics, respectively. Furthermore, Fpeak = 8 J/cm2 and N = 20 shots were chosen to obtain crossed-line patterns in both ceramics. Our results show that lithium disilicate glass-ceramics and highly translucent zirconia exhibit a similar surface morphology under each of the surface treatment conditions. Therefore, FL irradiation of dot or crossed-line patterns (at a distance of 20 and 40 µm) are potential candidates for future investigations

AGEING-RESISTANT ZIRCONIA CERAMICS FOR DENTAL RESTORATIONS

Today, zirconia-based restorations have become popular in dentistry. Thanks to their superb biocompatibility and favourable mechanical properties, yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics are used not only as an alternative for conventional porcelain-fused-to-metal restorations, but also as implant abutments or even implants.The overall objectives of this work were (1) to assess the low-temperature degradation behavior and the mechanical properties of dental zirconia, (2) to characterize the zirconia-veneering ceramic interface, and (3) to improve the bonding receptiveness of zirconia.The first part of this doctoral dissertation focused on the low-temperature degradation (LTD) and mechanical properties of dental zirconia. Our aim was to assess the influence of the sintering conditions (paper 1) and the influence of different surface treatments (papers 2 & 3) on the LTD behavior and mechanical properties of zirconia.We have found that the kind of sintering conditions affect the ZrO2-grain size and -phase composition. In general, an increased sintering temperature and prolonged sintering time resulted in a higher sensitivity of Y-TZP zirconia to LTD. Moreover, a significant decrease in Vickers hardness and only a moderate increase in fracture toughness resulted from an increase in sintering temperature and time. The best sintering condition, we found to combine excellent mechanical properties with a satisfactory LTD resistance, was sintering at 1450°C for 1 h.The LTD behavior of the surface-treated zirconia depended on the kind of zirconia grade. We have assessed four different surface treatments ( as sintered (untreated), rough polishing, Al2O3 sandblasting, and tribochemical silica sandblasting) on three kinds of zirconia grades (Y-TZP zirconia, Ce-TZP/Al2O3 zirconia, and Y-TZP/Al2O3 zirconia). For Y-TZP zirconia, the three surface treatments induced a ferroelastic domain switch and produced residual compressive stress at the surface. Both effects improved the aging resistance of Y-TZP zirconia. The surface treatments did not affect the aging resistance of Ce-TZP/Al2O3 zirconia. Although the as sintered (untreated) Y-TZP/Al2O3 zirconia showed a quite strong aging resistance, this zirconia grade slightly degraded after surface treatment. In particular the c-ZrO2 phase contributed to the aging resistance of the Y-TZP/Al2O3 zirconia. As the surface treatment reduced the amount of the c-ZrO2, the Y-TZP/Al2O3 zirconia became more sensitive to LTD.Surface treatment also affected the mechanical properties of zirconia. We have investigated the influence of surface treatment on the four-point bending strength of a Y-TZP and a Y-TZP/Al2O3 zirconia grade. Grinding, Al2O3 sandblasting and tribochemical silica sandblasting induced residual compressive stress at the zirconia surface. This increased the bending strength of the two zirconia grades. On the other hand, grinding made the bending strength less consistent. Surface grinding Y-TZP/Al2O3 zirconia with or without additional Al2O3 or tribochemical silica sandblasting resulted in a deeper compressive stress zone than when Y-TZP zirconia was exposed to the same surface treatment. This on its turn resulted in an more consistent bending strength and concomitantly improved the consistency of the zirconia s mechanical properties in general. Thermal treatment after grinding however eliminated the residual compressive stress layer, and significantly decreased the bending strength.In the second part of this thesis, we morphologically and chemically characterized the interface between the veneering ceramic and zirconia at a high resolution (paper 4), this because the chipping of the veneering ceramic from the zirconia framework is today still a major clinical concern.Some indication of chemical interaction between the veneering ceramic and zirconia was found by EDS analysis. Micro-Raman analysis revealed a partially t-ZrO2 to m-ZrO2 phase transformation immediately beneath the zirconia-veneering ceramic interface and the presence of residual tensile stresses within this transformed zirconia zone. Although the zirconia-veneering ceramic interface was found to be tight, no indications suggesting chemical interaction between both substrates were detected. The veneering procedure introduced tensile stress and phase transformation in the zirconia area immediately underneath the interface. This may explain in part the chipping clinically observed rather frequently.The third part of this thesis focused on the bonding effectiveness to dental zirconia. We systematically analyzed the literature to disclose general trends in bonding effectiveness to zirconia (paper 5) and we measured the micro-tensile bond strength (µTBS) of different bonding/luting protocols to zirconia (papers 6, 7 & 8). Furthermore, we investigated the influence of light irradiation delivered by two light-curing units through zirconia restorations on the degree of monomer conversion of composite cements (paper 9).The systematic review revealed that a combination of mechanical and chemical pre-treatment is essential to obtain durable bonding to zirconia. Interestingly, the cement choice was not revealed as determining factor after aging as long as composite cement was employed. Regarding the test protocol, a tensile test appeared more discriminative, in particular when it was combined with water-storage aging.The µTBS test demonstrated that combined mechanical/chemical pre-treatment, using tribochemical silica sandblasting followed by a combined 10-MDP/silane ceramic primer resulted in the most durable bond to zirconia. Although Al2O3 sandblasting is the mechanical pre-treatment mostly applied, it resulted in a less durable bond as compared to when the zirconia surface is tribochemical silica sandblasted. In case of a chemical pre-treatment with a primer containing the functional monomer 10-MDP, the purity of the latter functional monomer may affect the bond durability of the composite cement to zirconia.We have finally also measured the degree of conversion of composite cements cured through zirconia. Although zirconia reduced the light energy delivered by light-curing units, composite cements under Y-TZP zirconia-based restorations could be light-cured. The amount of light transmitted through Ce-TZP/Al2O3 zirconia was however too low to be measured. Such opaque/ dark zirconia should definitely be luted using a dual-cure composite cement with an effective self-cure potential.status: publishe

Adhesively luted zirconia restorations: why and how?

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Meta-analysis of Bonding Effectiveness to Zirconia Ceramics

Dental zirconia can no longer be considered un-bondable to tooth tissue. In literature, an increasing number of papers indeed report on the bonding effectiveness of different luting techniques to zirconia. We aimed to disclose general trends in bonding to zirconia by systematically collecting zirconia bond-strength data. A search in PubMed and EMBASE revealed 1,371 bond-strength tests reported on in 144 papers. A macro-shear bond-strength protocol was most frequently used; it revealed significantly lower bond strengths and was less discriminative than the other test methods. Regarding luting technique, the combination of mechanical and chemical pre-treatment appeared particularly crucial to obtain durable bonding to zirconia ceramics. The cement choice was not revealed as a determining factor after aging conditions, as long as composite cement was used. Regarding test protocol, a tensile test appeared more discriminative, particularly when combined with 'water storage' aging.status: publishe

Bonding effectiveness to different chemically pre-treated dental zirconia

The objective of this study was to evaluate the effect of different chemical pre-treatments on the bond durability to dental zirconia.status: publishe

Lifetime estimation of zirconia ceramics by linear ageing kinetics

Up to now, the ageing kinetics of zirconia ceramics were mainly derived from the sigmoidal evolution of the surface phase transformation as a function of time, as quantified by means of X-ray diffraction (XRD). However, the transformation propagation into the material should be better to monitor the ageing kinetics. In this work, µ-Raman spectroscopy was used to quantitatively measure the transformation profiles in depth as a function of ageing time at 160 °C, 140 °C, 134 °C and 110 °C. A linear relationship between the transformed depth and the ageing time was observed for all investigated yttria stabilized tetragonal zirconia polycrystals (3Y-TZP). Furthermore, the µ-Raman investigation of residual stresses in the subsurface of aged 3Y-TZPs showed that the highest tensile stress was located just ahead of the transformation front, indicating the key responsibility of stress accumulation for transformation front propagating into the material. Moreover, the linear kinetics of the transformation propagation were more accurate to calculate the apparent activation energy of the ageing process and allowed a more straightforward estimation of the lifetime of 3Y-TZP at body temperature, as compared to the conventional ageing kinetic parameters obtained from the surface transformation analysis by XRD.publisher: Elsevier articletitle: Lifetime estimation of zirconia ceramics by linear ageing kinetics journaltitle: Acta Materialia articlelink: http://dx.doi.org/10.1016/j.actamat.2015.04.001 content_type: article copyright: Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.status: publishe

Influence of alumina addition on low temperature degradation of Y2O3-coated powder based Y-TZP ceramics

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Influence of sintering conditions on the low-temperature degradation of dental zirconia

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Strength, toughness and aging stability of highly-translucent Y-TZP ceramics for dental restorations

The aim was to evaluate the optical properties, mechanical properties and aging stability of yttria-stabilized zirconia with different compositions, highlighting the influence of the alumina addition, Y2O3 content and La2O3 doping on the translucency.publisher: Elsevier articletitle: Strength, toughness and aging stability of highly-translucent Y-TZP ceramics for dental restorations journaltitle: Dental Materials articlelink: http://dx.doi.org/10.1016/j.dental.2016.09.025 content_type: article copyright: © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.status: publishe