The Effect of Preparation Design on the Fracture Resistance of Zirconia Crown Copings (Computer Associated Design/Computer Associated Machine, CAD/CAM System)

Objective: One of the major problems of all ceramic restorations is their probable fracture against the occlusal force. The aim of the present in-vitro study is was to compare the effect of two marginal designs (chamfer & shoulder) on the fracture resistance of zirconia copings, CERCON (CAD/CAM).MATERIALS AND METHODS: This in vitro study was done with single blind experimental technique. One stainless steel dye with 50’ chamfer finish line design (0.8 mm depth) was prepared using milling machine. Ten epoxy resin dyes were made, The same dye was retrieved and 50' chamfer was converted into shoulder (1 mm).again ten epoxy resin dyes were made from shoulder dyes. Zirconia cores with 0.4 mm thickness and 35 µm cement Space fabricated on the20 epoxy resin dyes (10 samples chamfer and 10 samples shoulder) in a dental laboratory. Then the zirconia cores were cemented on the epoxy resin dyes and underwent a fracture test with a universal testing machine (GOTECH AI-700LAC, Arson, USA) and samples were investigated from the point of view of the origin of the failure.RESULT: The mean value of fracture resistance for shoulder margins were 788.90±99.56 N and for the chamfer margins were 991.75±112.00 N. The student’s T-test revealed a statistically significant difference between groups (P=0.001).CONCLUSION: The result of this study indicates that marginal design of the zirconia cores effects on their fracture resistance. A chamfer margin could improve the biomechanical performance of posterior single zirconia crown restorations. This may be because of strong unity and round internal angle in chamfer margin

Electrospinning piezoelectric fibers for biocompatible devices

The field of nanotechnology has been gaining great success due to its potential in developing new generations of nanoscale materials with unprecedented properties and enhanced biological responses. This is particularly exciting using nanofibers, as their mechanical and topographic characteristics can approach those found in naturally occurring biological materials. Electrospinning is a key technique to manufacture ultrafine fibers and fiber meshes with multifunctional features, such as piezoelectricity, to be available on a smaller length scale, thus comparable to subcellular scale, which makes their use increasingly appealing for biomedical applications. These include biocompatible fiber-based devices as smart scaffolds, biosensors, energy harvesters, and nanogenerators for the human body. This paper provides a comprehensive review of current studies focused on the fabrication of ultrafine polymeric and ceramic piezoelectric fibers specifically designed for, or with the potential to be translated toward, biomedical applications. It provides an applicative and technical overview of the biocompatible piezoelectric fibers, with actual and potential applications, an understanding of the electrospinning process, and the properties of nanostructured fibrous materials, including the available modeling approaches. Ultimately, this review aims at enabling a future vision on the impact of these nanomaterials as stimuli-responsive devices in the human body

Academic misconduct, misrepresentation and gaming: a reassessment

The motivation for this Special Issue is increasing concern not only with academic misconduct but also with less easily defined forms of misrepresentation and gaming. In an era of intense emphasis on measuring academic performance, there has been a proliferation of scandals, questionable behaviors and devious stratagems involving not just individuals but also organizations, including universities, editors and reviewers, journal publishers, and conference organizers. This introduction first reviews the literature on the prevalence of academic misconduct, misrepresentation and gaming (MMG). The core of the article is organized around a life-cycle model of the production and dissemination of research results. We synthesize the findings in the MMG literature at the level of the investigator or research team, emphasizing that misbehavior extends well beyond fabrication and falsification to include behaviors designed to exaggerate or to mislead readers as to the significance of research findings. MMG is next explored in the post-research review, publication, and post-publication realms. Moving from the individual researcher to the organizational level, we examine how MMG can be engaged in by either journals or organizations employing or funding the researchers. The changing institutional environment including the growth of research assessment exercises, increased quantitative output measurement and greater pressure to publish may all encourage MMG. In the final section, we summarize the main conclusions and offer suggestions both on how we might best address the problems and on topics for future research

Solid-state synthesis of NASICON (Na3Zr2Si2PO12) using nanoparticle precursors for optimisation of ionic conductivity

In this work, the effect of varying the size of the precursor raw materials SiO2 and ZrO2 in the solid-state synthesis of NASICON in the form Na3Zr2Si2PO12 was studied. Nanoscale and macro-scale precursor materials were selected for comparison purposes, and a range of sintering times were examined (10, 24 and 40 h) at a temperature of 1230 °C. Na3Zr2Si2PO12 pellets produced from nanopowder precursors were found to produce substantially higher ionic conductivities, with improved morphology and higher density than those produced from larger micron-scaled precursors. The nanoparticle precursors were shown to give a maximum ionic conductivity of 1.16 × 10−3 S cm−1 when sintered at 1230 °C for 40 h, in the higher range of published solid-state Na3Zr2Si2PO12 conductivities. The macro-precursors gave lower ionic conductivity of 0.62 × 10−3 S cm−1 under the same processing conditions. Most current authors do not quote or consider the precursor particle size for solid-state synthesis of Na3Zr2Si2PO12. This study shows the importance of precursor powder particle size in the microstructure and performance of Na3Zr2Si2PO12 during solid-state synthesis and offers a route to improved predictability and consistency of the manufacturing process

Evaluation of input indicators related to human resource productivity in a military hospital in Iran

Introduction: Productivity is usually the main and ultimate goal for most organizations. At the present time, healthcare organizations must study and assess the productivity of their employees to a greater extent than ever before. This issue can be an important concern for healthcare managers who are striving to improve quality and contain costs. The goal of this study is to determine and measure productivity indicators for employees of an Iranian military hospital. Methods: The study was conducted in a crosssectional design. The target group included 150 administrative employees of the military hospital, and a questionnaire was utilized for collecting data. Results: The group that was studied ranked high in terms of ability, job clarity, motivation, feedback, and environmental causes and condition indicators, with scores of 3.66, 3.34, 3.38, 3.25, and 3.29 in a 1-5 score Likert scale, respectively. However, the group's score in the organizational support category was 3.00, which is considered to be an intermediate score. The group's score for decision credibility was even lower, at 2.96. Discussion: In the study group, most of the employees' productivity indicator scores were better than the intermediate score of 3.00, but they were still considerably lower than the ultimate level. The most important problems in this regard consisted of failing to adequately consider the staff's views, the staff's jobs frequently were unrelated to their educational backgrounds, the lack of written duties for each job, poor matches between workloads and salaries, lower salaries than other comparable departments, and deficiencies in the workplace. In summary, the key factors identified for increasing the employees' productivity were suitable organizational structure, participative management, and periodic rotation of staff between jobs, job enrichment, and equal pay for equal work

Left Atrial Appendage Aneurysm

Left atrial appendage aneurysms (LAAA) are extremely rare. This condition is usually diagnosed incidentally or after the occurrence of thrombotic events or cardiac tachyarrhythmias in the second to fourth decades of life. It can predispose to hazardous adverse events, including atrial fibrillation, myocardial infarction, and systemic thromboembolism. We report a case of LAAA in a 68-year-old woman presenting with atypical chest pain, exertional dyspnea, and episodes of sudden-onset palpitation. Aneurysmectomy with the patient under cardiac arrest with cardiopulmonary bypass was performed. In addition, we explore the diagnosis, management, and prognosis of this entity through a meticulous literature review. © 2016 The Society of Thoracic Surgeon