Search

This study presents a comprehensive evaluation of the mechanical, micro-mechanical and physical properties of Reva Medical Fantom Encore Bioresorbable Scaffolds (BRS) subjected to a thermally-accelerated degradation protocol. The Fantom Encore BRS were immersed in phosphate buffered saline solution at 50 °C for 112 days with radial compression testing, nanoindentation, differential scanning calorimetry, gel permeation chromatography and mass loss characterisation performed at consecutive time points. In the initial stages of degradation (Days 0-21), the Fantom Encore BRS showed increases in radial strength and stiffness, despite a substantial reduction in in molecular weight, with a slight increase in the melt temperature also observed. In the second phase (Days 35-54), the radial strength of the BRS samples were maintained despite a continued loss in molecular weight. However, during this phase, the ductility of the stent showed a reduction, with stent fracture occurring earlier in the crimp process and with lower amounts of plastic deformation evident under visual examination post-fracture. In the final phase (Days 63-112), the load-bearing capacity of the Fantom Encore BRS showed continued reduction, with decreases in radial stiffness and strength, and drastic reduction in the work-to-fracture of the devices. Throughout each phase, there was a steady increase in the relative crystallinity, with limited mass loss until day 112 and only minor changes in glass transition and melt temperatures. Limited changes were observed in nano-mechanical properties, with measured local elastic moduli and hardness values remaining largely similar throughout degradation. Given that the thermally-accelerated in vitro conditions represented a four-fold acceleration of physiological conditions, these results suggest that the BRS scaffolds could exhibit substantially brittle behaviour after ∼ one year of implantation., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Recently, researchers focused their attention on the use of polymeric bioresorbable vascular scaffolds (BVSs) as alternative to permanent metallic drug-eluting stents (DESs) for the treatment of atherosclerotic coronary arteries. Due to the different mechanical properties, polymeric stents, if compared to DESs, are characterized by larger strut size and specific design. It implies that during the crimping phase, BVSs undergo higher deformation and the packing of the struts, making this process potentially critical for the onset of damage. In this work, a computational study on the crimping procedure of a PLLA stent, inspired by the Absorb GT1 (Abbott Vascular) design, is performed, with the aim of evaluating how different strategies (loading steps, velocities and temperatures) can influence the results in terms of damage risk and final crimped diameter. For these simulations, an elastic-viscous-plastic model was adopted, based on experimental results, obtained from tensile testing of PLLA specimens loaded according to ad hoc experimental protocols. Furthermore, the results of these simulations were compared with those obtained by neglecting strain rate and temperature dependence in the material model (as often done in the literature), showing how this lead to significant differences in the prediction of the crimped diameter and internal stress state., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The proof of the reliability of a numerical model is becoming of paramount importance in the era of in silico clinical trials. When dealing with a coronary stenting procedure, the virtual scenario should be able to replicate the real device, passing through the different stages of the procedure, which has to maintain the atherosclerotic vessel opened. Nevertheless, most of the published studies adopted commercially resembling geometries and generic material parameters, without a specific validation of the employed numerical models. In this work, a workflow for the generation and validation of the computational model of a coronary stent was proposed. Possible sources of variability in the results, such as the inter-batches variability in the material properties and the choice of proper simulation strategies, were accounted for and discussed. Then, a group of in vitro tests, representative of the device intended use was used as a comparator to validate the model. The free expansion simulation, which is the most used simulation in the literature, was shown to be only partially useful for stent model validation purposes. On the other hand, the choice of proper additional experiments, as the suggested uniaxial tensile tests on the stent and deployment tests into a deformable tube, could provide further suitable information to prove the efficacy of the numerical approach., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

"Rhupus" or "rhupus syndrome" is a poorly described and underdiagnosed disease in which features of both rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) appear in the same patient, most often sequentially. The SLE-related involvement is usually mild, dominated by hematological abnormalities and skin, serosal and renal involvement. The natural history of rhupus arthritis follows an RA-like pattern and can progress towards typical inflammatory erosions, deformations and disability. Despite the lack of consensus on the definition of rhupus and on its place in the spectrum of autoimmunity, a growing number of studies are pointing towards a true overlap between RA and SLE. However, the inclusion criteria employed in the literature during the last 4 decades are heterogeneous, making the already rare cohorts and case reports difficult to analyze. Because of this heterogeneity and due to the rarity of the disease, the prevalence, pathophysiology and natural history as well as the radiological and immunological profiles of rhupus are poorly described. Moreover, since there is no validated therapeutic strategy, treatment is based on clinicians' experience and on the results of a few studies. We herein present a systematic literature review to analyze the clinical and laboratory data of all reported rhupus patients and to provide up-to-date information about recent advances in the understanding of the pathophysiological mechanisms, diagnostic tools and treatment options., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this work pentose sugar (D-xylose, D-ribose and D-arabinose) gas phase dehydration reaction was investigated by means of mass spectrometric techniques and theoretical calculations. The ionic species derived from the dehydration reaction of protonated D-ribose and D-arabinose were structurally characterized by their fragmentation patterns and the relative dehydration energies measured by energy resolved CAD mass spectra. The results were compared with those recently obtained for D-xylose in the same mass spectrometric experimental conditions. Dehydration of C1-OH protonated sugars was theoretically investigated at the CCSD(T)/cc-pVTZ//M11/6-311++G(2d,2p) level of theory. Protonated pentoses are not stable and promptly lose a water molecule giving rise to the dehydrated ions at m/z 133. D-xylose, D-ribose and D-arabinose dehydration follows a common reaction pathway with ionic intermediates and transition states characterized by similar structures. Slightly different dehydration energies were experimentally measured and the relative trend was theoretically confirmed. The overall dehydration activation energy follows the order arabinose < ribose < xylose. Gas-phase pentose sugar dehydration leads to the formation of protonated 2-furaldehyde as final product. Based on the experimental and theoretical evidence a new mechanistic hypothesis starting from C1-OH protonation was proposed., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Introduction: The purpose of this study was to evaluate the changes of the marginal periodontium 1 year after apical surgery., Methods: Clinical and radiographic (cone-beam computed tomographic) examinations of 54 teeth treated with buccal access flaps for apical surgery were performed at baseline and after 1 year. Clinical assessment included measurements of probing pocket depth, the level of gingival margin (GM), and the width of keratinized tissue. Subsequently, the clinical attachment level (CAL) and the width of the attached gingiva were calculated. On bucco-oral cone-beam computed tomographic sections, the height and thickness of the crestal bone and the thickness of the alveolar bone were measured at different levels., Results: In general, the calculated mean changes of periodontal tissue and crestal/alveolar bone were only minimal. Significant mean changes included only GM and CAL on midoral aspects and the distance from the cementoenamel junction or restoration margin on midbuccal sites. CAL was further correlated with the thickness of the alveolar bone at 3 mm below the cementoenamel junction or restoration margin. None of the clinically and radiographically calculated mean changes were correlated with sex, biotype, or incision techniques. With regard to age, older patients showed significantly more gingival recession on the buccal aspect compared with younger individuals. Furthermore, mean changes of the midbuccal width of the attached gingiva were positively correlated with the healing outcome, whereas mean changes of the midoral GM and CAL were negatively correlated with the healing outcome., Conclusions: Within an observation period of 1 year, the marginal periodontium and its underlying bone structures did not suffer from significant changes after apical surgery., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Background: Critically ill patients may develop muscle weakness or paralysis during the course of sepsis and multiple-organ failure. We studied peripheral nerve and muscle disorders (NMD) in comatose patients., Method: Comatose patients who developed paralysis associated with absent deep-tendon reflexes had electroneuromyography (ENMG) and muscle-nerve biopsy specimens taken. Onset and duration of sepsis, multiple-organ dysfunction and failure, biochemical alterations, and drugs potentially interfering with nerve-muscle function were recorded., Findings: 24 patients became quadriparetic or quadriplegic; muscle changes were found in 23. Axonal neuropathy was found in eight of 22 patients examined. All patients had prolonged sepsis and multiple-organ dysfunction, but only 14 had multiple-organ failure. Drugs such as steroids, neuromuscular-blocking agents, and aminoglycosides were not responsible for paresis, and the part played by hyperglycaemia and hypoalbuminaemia is uncertain. Attending physicians predicted a fatal outcome in all cases, although six of seven survivors fully recovered within 115-210 days from the onset of paralysis., Interpretation: Comatose patients may become completely paralysed because of NMD. The diagnosis is important to avoid unnecessary investigations and unreasonably pessimistic prognosis. ENMG is essential for the diagnosis and for planning further clinical management. Biopsy needs to be done only when it is necessary to properly classify NMD.