Effect of Zr Addition on the Corrosion of Ti in Acidic and Reactive Oxygen Species (ROS)-Containing Environments

The effect of systematic Zr additions on the corrosion behavior of Ti was studied in both acidic and Reactive Oxygen Species (ROS) containing environments, including macrophage cell culture, simulating inflammation associated with metallic implants. Electrochemical measurements on commercially-pure (CP) Ti, Zr and TiZr alloys showed that increasing Zr additions progressively enhanced Ti passivity in both acidic (HCl) and oxidative (H2O2) environments. However, a Ti50Zr alloy was found with increased pitting susceptibility.Corrosion was also evaluated using mass-spectrometry to determine metal ion release following exposure of the alloys to THP-1 macrophage cell cultures, transformed into either their M1 (inflammatory states) or M2a (tissue repair states) phenotypes. The magnitude of ion release was reduced with increasing Zr contents, consistent with electrochemical observations. Nevertheless, optimized Zr content in Ti should balance both passivity and pitting resistance

Temperature-Dependence Corrosion Behavior of Ti6Al4V in the Presence of HCl

Ti alloys have been widely used in biomedical field due to good compatibility and corrosion resistance. However, corrosion-related failures of implanted Ti devices and prostheses have been regularly reported within the medical literature. The corrosion of Ti alloys has attracted much attention in vivo and in vitro. In the current study, the corrosion behavior of Ti6Al4V alloy was investigated using surface analysis and electrochemical tests. Corrosion of Ti6Al4V in 2 M hydrochloric acid is temperature dependent within the temperature range studied. It has found that the steady state current density at −510 mV vs. SCE (the primary passivation potential at the physiological temperature of 37°C) becomes higher with increasing temperature. The α phase of Ti6Al4V is preferentially dissolved relative to the β phase after potentiostatic measurement at primary passivation potential in 2 M HCl at 37°C. This investigation provides novel and useful information for Ti corrosion-related failures of biomedical implants and prostheses.</p

The effect of location/site on polished human enamel after mechanical and chemical wear

OBJECTIVE: To compare profilometry and microhardness of polished occlusal and buccal human enamel following a mechanical and chemical wear regime.METHODS: Enamel from polished human molars were sectioned into buccal and occlusal surfaces and randomly allocated into two groups (n=10) and then exposed to 0.3% citric acid at pH 2.7 for 10, 20, 40 and 60 mins each followed by abrasion with non-fluoridated toothpaste for 240 strokes in a reciprocating brushing machine. A white light profilometer with a spot size of 12 um measured mean step-height following each cycle. Microhardness indentations were conducted following the final cycled 60 mins erosion/abrasion using 0.01, 0.02, 0.1, 0.5 and 2.5 kgf indentation load. Statistical disparity were evaluated using a two-way ANOVA and post-hoc Sidak's multiple comparisons tests at α = 0.05.RESULTS: After erosion/abrasion, the mean (SD) step-heights on occlusal and buccal surfaces were not significantly different until 60 mins, when occlusal surfaces exhibited greater step-heights, 32.9 µm (2.8) and 31.1 µm (1.8) and p=0.02, respectively. Buccal and occlusal microhardness was statistically lower following erosion/abrasion at loads of 0.01 kgf (p=0.0005) and 0.02 kgf (p=0.0006) but no significant differences were observed in the microhardness between the surfaces at any loads.CONCLUSION: The occlusal and buccal surfaces were not statistically different for microhardness or step height suggesting the susceptibility to wear is not related to the anatomy and structure of the tooth and is more likely related to other factors such as the environment.CLINICAL SIGNIFICANCE: The study emphasizes that a notable difference in wear between occlusal and buccal enamel surfaces emerges only after prolonged exposure to simultaneous chemical and mechanical stress. This finding necessitates a preventive dental approach that accounts for both the duration of exposure and environmental factors.</p

Effects of Scavenging, Entrainment, and Aqueous Chemistry on Peroxides and Formaldehyde in Deep Convective Outflow over the Central and Southeast U.S.

Deep convective transport of gaseous precursors to ozone (O3) and aerosols to the upper troposphere is affected by liquid- and mixed-phase scavenging, entrainment of free tropospheric air, and aqueous chemistry. The contributions of these processes are examined using aircraft measurements obtained in storm inflow and outflow during the 2012 Deep Convective Clouds and Chemistry (DC3) experiment combined with high resolution (dx <= 3 km) WRF-Chem simulations of a severe storm, an airmass storm, and a mesoscale convective system (MCS). The simulation results for the MCS suggest that formaldehyde (CH2O) is not retained in ice when cloud water freezes, in agreement with previous studies of the severe storm. By analyzing WRF-Chem trajectories, the effects of scavenging, entrainment, and aqueous chemistry on outflow mixing ratios of CH2O, methyl hydroperoxide (CH3OOH), and hydrogen peroxide (H2O2) are quantified. Liquid-phase microphysical scavenging was the dominant process reducing CH2O and H2O2 outflow mixing ratios in all three storms. Aqueous chemistry did not significantly affect outflow mixing ratios of all three species. In the severe storm and MCS, the higher than expected reductions in CH3OOH mixing ratios in the storm cores were primarily due to entrainment of low background CH3OOH. In the airmass storm, lower CH3OOH and H2O2 scavenging efficiencies (SEs) than in the MCS were partly due to entrainment of higher background CH3OOH and H2O2. Overestimated rain and hail production in WRF-Chem reduces the confidence in ice retention fraction values determined for the peroxides and CH2O

Pectin coating of titanium and polystyrene surfaces modulates the macrophage inflammatory response

Titanium has been used with success for bone anchoring of dental implants. However, when implant surfaces are exposed to the oral environment, the progression of peri-implantitis triggered by specific oral bacteria has been reported. Bacterial colonization of implants leads to prolonged immune cell activation and bone resorption. A new strategy to improve implant biocompatibility and prevent peri-implantitis is to develop pectin surface nanocoatings. These plant-derived polysaccharides are promising candidates for surface nanocoatings of titanium implants due to their osteogenic and anti-inflammatory properties. Therefore, the aim of the study was to evaluate the in vitro effect of nanocoating with plant-derived rhamnogalacturonan-I (RG-I) on pro- and anti-inflammatory responses of primary human monocyte-derived macrophages (HMDMs) induced by Escherichia coli LPS and Porphyromonas gingivalis bacteria. In the present study, two different types of surface materials, tissue culture polystyrene (TCPS) plates and titanium (Ti) discs, coated with pectic polysaccharides, potato unmodified RG-I (PU) and potato dearabinanated RG-I (PA), have been examined. The inflammatory responses of HMDMs after E. coli LPS/P. gingivalis stimulation were investigated through gene expression measurements of pro- and anti-inflammatory cytokines. The results showed that PU and PA decreased expression of the proinflammatory genes tumour necrosis factor-alpha (TNFA), interleukin-1 beta (IL1B) and interleukin-8 (IL8) in activated HMDMs cultured on TCPS/Ti surfaces. In contrast, the effects on anti-inflammatory interleukin-10 (IL10) gene expression were not significant. The results indicate that RG-Is should be considered as a candidate for organic nanocoatings of titanium implant surfaces in order to limit host proinflammatory responses and improve bone healing. DOI: http://dx.doi.org/10.5281/zenodo.125054

Diagnostic accuracy of post-mortem MRI for thoracic abnormalities in fetuses and children

OBJECTIVES: To compare the diagnostic accuracy of post-mortem magnetic resonance imaging (PMMR) specifically for non-cardiac thoracic pathology in fetuses and children, compared with conventional autopsy. METHODS: Institutional ethics approval and parental consent was obtained. A total of 400 unselected fetuses and children underwent PMMR before conventional autopsy, reported blinded to the other dataset. RESULTS: Of 400 non-cardiac thoracic abnormalities, 113 (28 %) were found at autopsy. Overall sensitivity and specificity (95 % confidence interval) of PMMR for any thoracic pathology was poor at 39.6 % (31.0, 48.9) and 85.5 % (80.7, 89.2) respectively, with positive predictive value (PPV) 53.7 % (42.9, 64.0) and negative predictive value (NPV) 77.0 % (71.8, 81.4). Overall agreement was 71.8 % (67.1, 76.2). PMMR was most sensitive at detecting anatomical abnormalities, including pleural effusions and lung or thoracic hypoplasia, but particularly poor at detecting infection. CONCLUSIONS: PMMR currently has relatively poor diagnostic detection rates for the commonest intra-thoracic pathologies identified at autopsy in fetuses and children, including respiratory tract infection and diffuse alveolar haemorrhage. The reasonable NPV suggests that normal thoracic appearances at PMMR exclude the majority of important thoracic lesions at autopsy, and so could be useful in the context of minimally invasive autopsy for detecting non-cardiac thoracic abnormalities. KEY POINTS: • PMMR has relatively poor diagnostic detection rates for common intrathoracic pathology • The moderate NPV suggests that normal PMMR appearances exclude most important abnormalities • Lung sampling at autopsy remains the "gold standard" for pulmonary pathology

Interventions for replacing missing teeth:prostheses for the edentulous mandible

OBJECTIVES: This is a protocol for a Cochrane Review (intervention). The objectives are as follows: To evaluate the benefits and harms of removable and fixed prostheses for people with edentulous mandibles. To explore whether equity impacts the benefits and harms of removable and fixed prostheses for people with edentulous mandibles, particularly in relation to the age and economic status of wearers.</p

A synergistic effect of albumin and H2O2 accelerates corrosion of Ti6Al4V

The synergistic effect of albumin and H2O2 on corrosion of titanium alloy Ti6Al4V in physiological saline was investigated with long-term immersion tests and electrochemical methods. It was found that in the presence of both albumin and H2O2, the rate of metal release in immersion tests was far higher than in the presence of either species alone. Electrochemical polarisation curves and potentiostatic tests showed that H2O2 increased both the rates of the anodic and cathodic reactions, whilst albumin significantly decreased the rate of the cathodic reaction and slightly decreased the rate of the anodic reaction. The synergistic effect of albumin and H2O2 during immersion tests was attributed to the effect of adsorption of albumin in lowering the rate of the cathodic reaction and thus lowering the open circuit potential into the active region of titanium where complexation by H2O2 increased the corrosion rate. The corrosion attack was found to be greater in the β-phase of the alloy. The findings suggest that current standard tests in physiological or phosphate-buffered saline may underestimate the rate of corrosion in the peri-implant environment, in which albumin is the predominant protein, and reactive oxygen species such as H2O2 can occur as a result of inflammatory reactions in response to surgery, infection, or implant corrosion products.STATEMENT OF SIGNIFICANCE: Corrosion of many biomedical implant materials occurs in the body leading to adverse biological responses. Several components of the environment into which a metal implant is placed including proteins and products of cellular physiology, been shown to modify corrosion resistance. Previously all studies on such components including the common protein albumin and the inflammatory product H2O2 have considered the effects of these species in isolation. For the first time we report a synergistic interaction between albumin and H2O2 significantly accelerating corrosion of Ti6Al4V at physiological pH and temperature. This is attributed to an increased rate of the anodic reaction caused by H2O2 complexation of Ti, suppression of cathodic reaction by albumin adsorption shifting OCP to the active region of Ti6Al4V.</p

Paternal low protein diet programs preimplantation embryo gene expression, fetal growth and skeletal development in mice

Defining the mechanisms underlying the programming of early life growth is fundamental for improving adult health and wellbeing. While the association between maternal diet, offspring growth and adult disease risk is well-established, the effect of father's diet on offspring development are largely unknown. Therefore, we fed male mice an imbalanced low protein diet (LPD) to determine the impact on post-fertilisation development and fetal growth. We observed that in preimplantation embryos derived from LPD fed males, expression of multiple genes within the central metabolic AMPK pathway was reduced. In late gestation, paternal LPD programmed increased fetal weight, however, placental weight was reduced, resulting in an elevated fetal:placental weight ratio. Analysis of gene expression patterns revealed increased levels of transporters for calcium, amino acids and glucose within LPD placentas. Furthermore, placental expression of the epigenetic regulators Dnmt1 and Dnmt3L were increased also, coinciding with altered patterns of maternal and paternal imprinted genes. More strikingly, we observed fetal skeletal development was perturbed in response to paternal LPD. Here, while offspring of LPD fed males possessed larger skeletons, their bones comprised lower volumes of high mineral density in combination with reduced maturity of bone apatite. These data offer new insight in the underlying programming mechanisms linking poor paternal diet at the time of conception with the development and growth of his offspring