Corrosion behaviour of porous Ti intended for biomedical applications

Porous Ti implants are being developed inorder to reduce the biomechanical mismatch between theimplant and the bone, as well as increasing the osseointegrationby improving the bone in-growth. Most of the focusin the literature has been on the structural, biological andmechanical characterization of porous Ti whereas there islimited information on the electrochemical characterization.Therefore, the present work aims to study the corrosionbehaviour of porous Ti having 30 and 50 % ofnominal porosity, produced by powder metallurgy routeusing the space holder technique. The percentage, size anddistribution of the pores were determined by image analysis.Electrochemical tests consisting of potentiodynamicpolarization and electrochemical impedance spectroscopywere performed in 9 g/L NaCl solution at body temperature.Electrochemical studies revealed that samples presenteda less stable oxide film at increased porosity, morespecifically, the complex geometry and the interconnectivityof the pores resulted in formation of less protectiveoxide film in the pores.This study was supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalizac¸a˜o (POCI) with the reference project POCI-01-0145- FEDER-006941, Programa de Acc¸o˜es Universita´rias Integradas LusoFrancesas’ (PAUILF TC-12_14), and The Calouste Gulbenkian Foundation through ‘‘Programa de Mobilidade Acade´mica para Professores’’. The authors would also like to acknowledge Prof. Ana Senos (University of Aveiro) and Prof. Jose´ Carlos Teixeira (University of Minho) for the provision of the characterization facilities.info:eu-repo/semantics/publishedVersio

Comparative survey of selected Norfolk valley head fens

SIGLEAvailable from British Library Document Supply Centre- DSC:3425.823(NCC-CS--87) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Influence of the Manufacturing Process on the Corrosion and Mechanical Behavior of Esophageal Stents

Esophageal nitinol stents are an established method for treating swallowing difficulties caused by obstructing cancer. This raesearch investigates the influence of different qualities of raw metal alloys in combination with production technology on corrosion resistance in standardized simulated gastric fluid (SGF). Four different international stent manufacturers produced samples of their standard stents from nitinol sourced from three different alloy manufacturers. The stents were subjected to a 6-week immersion in SGF. During the immersion, the surface was studied at specified intervals using microscopy. The surface of the samples was also studied by X-ray Photoelectron Spectroscopy and after immersion the released ions were analyzed. Results demonstrated that both raw material and certain steps in the manufacturing process negatively affect corrosion resistance. Analysis of the SGF showed that the amount of nickel released is proportional to the degree of corrosion attack. Finally, current accepted standard test methods are inadequate for assessing susceptibility to corrosion by gastric acid and should take the low pH of the implanted environment into account. Conversely, certain measures in the manufacturing process are able to reduce the impact of the base material on corrosion susceptibility

Tailored degradation of biocompatible poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/calcium silicate/poly(lactide-co-glycolide) ternary composites: an in vitro study

Biodegradable materials, which are currently available for bone tissue regeneration, still have limitations regarding their degradation rate, mechanical stability and/or biological response. Thus, a novel generation of materials for bioactive bone scaffolds is needed that triggers hydroxyapatite formation and can be tailored to suit application-specific requirements. In this study we developed ternary bioactive composite materials composed of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), calcium silicate and poly(lactide-co-glycolide) (PHBV/CS/PLGA), which merged the good bioactivity of CS/PHBV composite and the improved degradation velocity of PHBV/PLGA blend. Bioactive character of all composites was proven by formation of hydroxyapatite-like crystals after already one week of incubation in simulated body fluid. Addition of PLGA significantly increased initial ultimate tensile strength (UTS0) and Young's modulus of the ternary composites from 14.3 ± 1.1 MPa (binary composite) to 22.3 ± 2.6 MPa and 1.23 ± 0.05 GPa up to 1.64 ± 0.14 GPa, respectively. Furthermore the degradation rate (measured as a decrease of UTS during degradation) could be successfully tailored and was in range of − 0.033 UTS0 to − 0.118 UTS0 MPa/week. The bioacceptance of the materials was proven in vitro using 2-D (conventional setup) and 3-D (multicellular spheroids) human bone marrow stromal cell cultures