The current study focused on doping of hydroxyapatite (HA) with constant yttrium (Y(3+) ) and varying fluoride (F(-) ) compositions to investigate its microstructure, microhardness, and biocompatibility. HA was synthesized by precipitation method and sintered at 1100°C for 1 h. Y(3+) and F(-) ion dopings resulted in changes in densities. In x-ray diffraction analysis, no secondary phase formation was observed. Lattice parameters decreased upon ion substitutions. Scanning electron microscopy (SEM) results showed that ion addition resulted in smaller grains. In Fourier transform infrared spectroscopy analysis, F(-) ion substitution was confirmed. HA doped with 2.5% Y(3+) and 1% F(-) exhibited the highest microhardness. Y(3+) and F(-) ions improved Saos-2 cell proliferation on discs in Methylthiazolyldiphenyl-tetrazolium (MTT) assay. In SEM analysis, cells attached and proliferated on all disc surfaces. Alkaline phosphatase (ALP) assay showed that cell differentiation on the discs was improved by doping HA with an optimum F(-) amount. Dissolution tests revealed that structural stability of HA was improved with F(-) ion incorporation. The dissolution behavior of fluoridated samples exhibited a parallel pattern with the cell proliferation and differentiation behavior on these samples. Overall, this work shows that fluoride and yttrium cosubstitution into HA HA2.5Y1F was the most promising material for biomedical applications.
Farklı geometrilere ve yüzey özelliklerine sahip üç set Nikel-Titanyum (NiTi) şekil hafızalı alaşımının (ŞHA) biyouyumluluğu, nitel ve nicel in vitro deneylerle incelenmiştir. Deneylerde kullanılan alaşımların bir seti levha, diğer iki seti ise farklı yarıçaplarda silindirik geometriye sahip örneklerdir. Hücre kültürü deneyleri öncesinde yapılan yapısal elektron mikroskobu ve profilometre incelemelerinde örneklerin geometrilerine bağlı olarak farklı yüzey özellikleri gösterdiği saptanmıştır. Yapısal karakterizasyon işlemlerinin devamında yapılan in vitro deneylerde ise, yüzey özelliklerinin şekil, dağılım ve derinliğinin hücre yapışması ve çoğalma davranışları üzerindeki etkileri elektron mikroskobu incelemeleri ve hücre sayımı deneyi ile araştırılmıştır. Sonuçlar örnek geometrisi ve yüzey pürüzlülüğünün ilk hücre yapışması açısından belirleyici faktörler olduğunu ortaya çıkarmıştır. Bununla birlikte, birbiriyle bağlantılı hücre ağlarının oluşumu açısından, yüzey oluklarının derinliği ve organizasyonunun daha kritik olduğu gözlemlenmiştir. Genel olarak bu çalışma, metalik biyomalzemelerin biyouyumluluğunun; yüzey özelliklerinin manipülasyonu, özellikle de yüzey karakteristiklerinin dağılım ve derinliğinin değiştirilmesi yoluyla geliştirilebileceğini göstermektedir.
This article presents a new multiscale modeling approach proposed to predict the impact response of a biomedical niobium-zirconium alloy by incorporating both geometric and microstructural aspects. Specifically, the roles of both anisotropy and geometry-based distribution of stresses and strains upon loading were successfully taken into account by incorporating a proper multiaxial material flow rule obtained from crystal plasticity simulations into the finite element (FE) analysis. The simulation results demonstrate that the current approach, which defines a hardening rule based on the location-dependent equivalent stresses and strains, yields more reliable results as compared with the classical FE approach, where the hardening rule is based on the experimental uniaxial deformation response of the material. This emphasizes the need for proper coupling of crystal plasticity and FE analysis for the sake of reliable predictions, and the approach presented herein constitutes an efficient guideline for the design process of dental and orthopedic implants that are subject to impact loading in service.
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