Objective
The present study determined the mechanical properties and the wear behavior, as results of the micro(nano)structure, of the enamel, transition, and dentine layers, which comprise the ...polychromic multilayer zirconia materials of hybrid composition fabricated by milling technology.
Materials and Methods
Prismatic blocks were fabricated from two commercial pre‐sintered dental polychromic multilayer zirconia materials of hybrid composition, IPS e.max ZirCAD Prime (medium and high translucency, from the dentine to the incisal layer) and 3D Pro ML (translucency gradient, from the dentine to the incisal layer) by milling technique, and then, cut into 3 distinct parts to separate the enamel, transition, and dentine layers. The samples were sintered, thermally treated (similarly to the glazing procedure), and polished for characterization. Their microstructure, mechanical properties (determined by nanoindentation and microhardness), and wear behavior (evaluated by scratch test), were examined.
Results
The produced materials had a homogeneous and dense nanostructure, where the grain size decreased from the enamel to dentine layer. The mechanical properties decreased from the dentine to enamel layer. However, the three layers manifested similar dynamic friction coefficient.
Conclusion
The differences in the above properties in the three layers negligibly influenced the wear behavior of the entire multilayer zirconia material.
Clinical Significance
The properties of dental restorations produced from polychromic multilayer zirconia of hybrid composition by milling technology (i.e., strong, non‐fragile, and esthetic materials), anticipate good performance in oral cavity.
Three Co-Cr alloy types (Co-Cr-Mo, Co-Cr-W, and Co-Cr-Mo-W) have been commonly used in the fabrication of dental prostheses. These alloys can be manufactured using either conventional casting or ...selective laser melting (SLM) techniques. Nevertheless, research that directly compares these materials and/or manufacturing processes in terms of their microstructural and mechanical characteristics is sparse.
The purpose of this in vitro study was to conduct microstructural and mechanical analysis via X-ray interpretation, optical microscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), image analysis, X-ray diffraction (XRD), instrumented indentation testing (IIT), and 3-point bending testing to characterize Co-Cr-Mo, Co-Cr-W, and Co-Cr-Mo-W alloys produced through conventional casting and SLM.
Six Co-Cr-based alloys were analyzed and divided into 3 types based on their elemental composition (Co-Cr-Mo, Co-Cr-W, and Co-Cr-Mo-W). Additionally, each group was categorized based on the manufacturing process used (casting or SLM). X-ray scans were used to assess porosity. The microstructures of the specimens were assessed through SEM/EDS examination and XRD analysis. IIT was used to determine the Martens hardness (HM) and elastic index (ηIT), while the elastic modulus (E) was estimated through the 3-point bending test. The mechanical properties were statistically analyzed using 2-way analysis of variance (ANOVA) and the Tukey multiple comparison post hoc test, with alloy type and manufacturing process as discriminating variables (α=.05).
All cast groups exhibited gross porosity, while no pores or other flaws were found in the SLM groups. Based on the XRD results, the crystalline structure of all Co-Cr specimens consisted of the face-centered cubic γ phase (γ-fcc), along with the hexagonal close-packed ε phase (ε-hcp) and Cr23C6 carbide. Different microstructures were identified between the cast and SLM alloys. Significant differences were identified for the mean standard deviation HM (ranging from 2601 ±94 N/mm2 to 3633 ±61 N/mm2) and mean ±standard deviation ηIT (ranging from 16.8 ±0.3% to 20.9 ±0.3%) among alloys prepared by the same manufacturing process, while all SLM alloys had statistically higher HM and ηIT results than their cast counterparts (P<.05). No statistically significant differences were identified for the mean ±standard deviation Eb (ranging from 170 ±25 GPa to 244 ±36 GPa) among the groups prepared with the same manufacturing process (P>.05), but the SLM alloys had significantly higher results (P<.05) than the cast alloys.
In general, the manufacturing procedure significantly affected the porosity, microstructure, and mechanical properties of the tested Co–Cr alloys. SLM decreased the internal porosity, provided a uniform microstructure, and improved the mechanical properties for all the tested alloy types.
The present study aimed to compare the microstructure, physical, and mechanical properties of three commercially available dental polychromatic multilayer zirconia materials of uniform composition: ...Dima Mill Zirconia ML, VITA YZ/ST Multicolor, and VITA YZ/XT Multicolor (with 3, 4, and 5 mol% Y2O3, respectively); thus, the influence of Y2O3 content on the above properties of the produced materials was experimentally studied. Homogeneous zirconia ceramics with a dense micro‐ and nanostructure, without pores or defects, were produced after milling the blocks and sintering, which resulted in yttrium‐stabilized tetragonal and cubic zirconia. Statistical analysis of the results of measurable magnitudes was performed by the one‐way ANOVA test. The increase of Y2O3 content (from 3 to 5 mol%) favored larger grain and crystallite sizes and a decrease of the values of the mechanical properties; yet, the differences were statistically insignificant. Clinically, these differences are expected to have no impact on their function in the oral cavity, both in terms of their fracture propensity and the damage that can be caused to the opposing teeth. Accordingly, the experimental results qualify the polychromic multilayer zirconia ceramics of uniform composition fabricated by milling technology for use in dental restorations.
This review article summarizes important findings on the interfaces between the coronavirus disease 2019 (COVID-19) pandemic and neurology with an emphasis of the implications for neurointensive care ...medicine. More specifically, the prevalence, pathomechanisms and impact of neurological manifestations are reported. The most common neurological manifestations of critically ill COVID-19 patients are cerebrovascular complications, encephalopathies and intensive care unit-acquired weakness (ICUAW). A relevant direct pathophysiological effect by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) itself has not yet been established with certainty. In fact, indirect systemic inflammatory processes triggered by the viral infection and side effects of intensive care treatment are much more likely to cause the reported sequelae. The impact of the pandemic on patients with neurological disorders and neurointensive care medicine is far-reaching but not yet sufficiently studied.
A variety of liver disorders are associated with characteristic histopathological findings that help in their diagnosis and treatment. However, percutaneous liver biopsy (PLB) is prone to limitations ...and complications. We evaluated all PLBs done in our hospital in a 13-year period, aiming to assess PLB's utility and complications.
All PLBs conducted in an internal medicine department of a tertiary university hospital in Athens, Greece, during a 13-year period were reviewed. Recorded data included demographic characteristics, laboratory results acquired on biopsy day, indication for liver biopsy, and occurrence of side effects. All patients were followed for 1 month post-hospital discharge for possible PLB-related complications.
A total of 261 patients underwent PLB during the study period. The commonest indication of PLB was investigation of liver mass, followed by transaminasemia. PLB assisted in setting a diagnosis in 218 patients and was unhelpful in only 43, in 14 of them due to inadequate or inappropriate biopsy specimen. Complications attributable to PLB were rare, with 10 patients exhibiting pain, either at biopsy site or in the right shoulder, and 3 having bleeding episodes; no deaths were noted.
Our study shows that PLB is still a powerful diagnostic tool in everyday practice, provided it is used when indicated.
•Modern stroke Treatments (endovascular thrombectomy and intravenous thrombolysis) are cost-effective.•Moving from more traditional to modern stroke treatments can reduce mortality and disability at ...affordable cost.•Results of this study could be leveraged by including effects of preventive policies and rehabilitation.
Stroke is the most common cause of disability in high-income countries. Several countries offer a limited range of advanced treatments with implications for outcomes, disability and costs. This study estimates the burden of disability that could have been avoided through the transition from traditional (no intravenous thrombolytic therapy (IVT), or endovascular thrombectomy (EVT)) to modern stroke treatments (treatment in stroke units, IVT and EVT). We perform a cost-effectiveness analysis comparing best practice with traditional stroke care, using Greece as a case study.
A Markov model was used to calculate costs and Quality Adjusted Life Years (QALYs) for each treatment strategy, using a lifetime horizon. Data for model inputs were derived from meta-analyses of trials, and national and international cost databases. Sensitivity analyses were also performed to address potential uncertainty and test the robustness of the findings.
Incremental effectiveness comprised 0.22 QALYs per patient and year. Best practice was cost-effective for more than 90% of all iterations (ICER for the baseline scenario: €2,109.25/QALY). Sensitivity analysis demonstrated that the findings remain robust. Considering the stroke incidence in Greece, the annual additional cost to implement best practice was calculated to be between 0.07%-0.15% of the total health expenditure.
Best practice stroke treatment was cost-effective and affordable in a case study based on Greece. The results could be leveraged by including effects of preventive policies and rehabilitation. They also highlight the importance of adopting modern treatment strategies from a cost-effectiveness perspective, apart from the improved clinical outcomes.
Colonoscopy is the gold standard for colorectal cancer prevention; however, it is still an imperfect modality. Precancerous lesions can be lost during screening examinations, thus increasing the risk ...of interval cancer. A variety of factors either patient-, or endoscopist dependent or even the procedure itself may contribute to loss of lesions. Sophisticated modalities including advanced technology endoscopes and add-on devices have been developed in an effort to eliminate colonoscopy’s drawbacks and maximize its ability to detect potentially culprit polyps. Novel colonoscopes aim to widen the field of view. They incorporate more than one cameras enabling simultaneous image transmission. In that way the field of view can expand up to 330°. On the other hand a plethora of add-on devices attachable on the standard colonoscope promise to detect lesions in the proximal aspect of colonic folds either by offering a retrograde view of the lumen or by straightening the haustral folds during withdrawal. In this minireview we discuss how these recent advances affect colonoscopy performance by improving its quality indicators(cecal intubation rate, adenoma detection rate) and other metrics(polyp detection rate, adenomas per colonoscopy, polyp/adenoma miss rate) associated with examination’s outcomes.
Abstract
This paper reports on development of novel alumina‐containing glass‐ceramics (GCs) with a high content of Al
2
O
3
(12.5 wt.%) in the CaO–MgO–Al
2
O
3
–SiO
2
system aimed for dental ...restorations. The thermal properties of the parent glasses, the microstructure and the mechanical properties of the produced sintered and crystallized GCs along with bio‐inertia performance were experimentally studied. Dense, white, and bio‐inert GCs, comprised of melilite, either as a single‐phase or with diopside, were produced. The values of flexural strength ranged between 120 and 171 MPa, the modulus of elasticity varied between 28 and 42 GPa, while the values of the hardness and the fracture toughness (measured by the indentation–Niihara equation) ranged from 6.3 to 7.0 GPa, and from 2.6 to 2.8 MPa m
0.5
, respectively. The mechanical properties of the produced GCs, after being meticulously compared with the mechanical properties of GCs of various compositions reported in literature, including commercial ones, are a good match to the properties of dental hard tissues, and satisfy the requirements of the ISO 6872 “Dentistry‐Ceramic Materials”.
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