Corrosion and wear behavior of Ti-5Cu-xNb biomedical alloy in simulated body fluid for dental implant applications.

The present study examined the corrosion and tribological behavior of novel Ti-5Cu-xNb alloy synthesized via powder metallurgy as a new biomedical material in a simulated bodily fluid (SBF) solution. The electrochemical impedance spectroscopy (EIS) study reveals the formation of two protective layers on the surface of alloys during the test. The alloys spontaneously produce a passivating oxide coating on their surfaces, and the breakdown potential (1.14-1.17 V) and re-passivation current density (2.07-3.04 µAcm-2) were observed during the potentiodynamic polarization test. The highest corrosion resistance was observed for the alloy Ti-5Cu-10Nb (icorr = 21.44 nA-cm-2). The SEM and XPS analysis of the corroded surface showed the formation of oxide on the surfaces of the alloys. The samples were tested at 10 N, 15 N, and 20 N loads against the zirconia counterpart to investigate the effect of loading on friction and wear. The lowest coefficient of friction was obtained for Ti-5Cu-5Nb (0.25-0.41) at 20 N loading, while the maximum for Ti-5Cu-10Nb at 15 N load falls in the range of (0.71-0.25). Additionally, they present the wear rate in the range of (5.3 × 10-8-1.45 × 10-6 mm3/mm), in accordance with the change in microstructure and mechanical properties. However, the wear rate increases with the addition of niobium and reaches the maximum for Ti-5Cu-15Nb at 20 N loading condition, but it is relatively deficient compared to commonly used implant material. Therefore, it is suggested that this ß-type Ti-5Cu-xNb alloy is a promising candidate, more suitable than the commercially used Ti and Ti-6Al-4V for dental applications.

Microstructure, mechanical strength, chemical resistance, and antibacterial behavior of Ti-5Cu-x%Nb biomedical alloy.

Titanium-based biomedical alloys are susceptible as they are used as a substitute for human bone. In this study, titanium alloy, Ti-5Cu-x%Nb (x= 0, 5, 10, 15) (%wt) was developed by powder metallurgy route. The effect of alloying niobium with Ti-5Cu alloy and its effect on the microstructure, mechanical strength, corrosion resistance, and antibacterial properties have been evaluated. The results show that the sintered alloy has bothα-Ti and Ti2Cu phases. With increasing niobium content in the alloy,ß-Ti was also detected. Additionally, it was found that the micro-hardness and compressive strength of the studied alloy was better than commercially pure titanium (cpTi), while the Young's modulus was lower than cpTi. These properties are highly favorable for using this alloy to replicate the human cortical bone. The alloy was also tested for anticorrosive property in Ringer's solution. The antibacterial activity was also examined forStaphylococcus aureusandEscherichia colibacteria. The alloy showed promising anticorrosive and antibacterial ability.

Effect of nitrogen and cold working on structural and mechanical behavior of Ni-free nitrogen containing austenitic stainless steels for biomedical applications.

This investigation deals with the evaluation of structural and mechanical behavior of deformed (10% and 20% cold work) and annealed (at 1050°C for 15 min followed by water quenching) Ni-free high nitrogen austenitic stainless steels (HNSs). The microstructure was observed by optical micrograph and the mechanical properties were determined by macrohardness and tensile tests. Both stress strain behavior and work hardening behavior were evaluated. HNSs have smaller grain size as compared to low nitrogen steels and no formation of martensite was observed after 20% cold working. Further, it was found that hardness; yield strength and ultimate tensile strength of the steels linearly increases and elongation decreased with nitrogen content and degree of cold working. The strength coefficient was observed to be higher for the high nitrogen steels; it decreased to some extent with degree of cold working. The work hardening exponent was also observed to decrease with degree of cold working. Influence of nitrogen on mechanical properties was mainly related to its effect on solid solution strengthening. X-ray diffraction analysis of annealed as well as deformed alloys further confirmed no evidence for formation of martensite or any other secondary phases. SEM fractography of the annealed and deformed samples after tensile tests indicates predominantly ductile fracture in all specimens.

In-vitro long term and electrochemical corrosion resistance of cold deformed nitrogen containing austenitic stainless steels in simulated body fluid.

This work was focused on the evaluation of the corrosion behavior of deformed (10% and 20% cold work) and annealed (at 1050 °C for 15 min followed by water quenching) Ni-free high nitrogen austenitic stainless steels (HNSs) in simulated body fluid at 37°C using weight loss method (long term), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. Scanning electron microscopy (SEM) was used to understand the surface morphology of the alloys after polarization test. It has been observed that cold working had a significant influence on the corrosion resistant properties of these alloys. The weight loss and corrosion rates were observed to decrease with increasing degree of cold working and nitrogen content in the alloy. The corrosion resistance of the material is directly related to the resistance of the passive oxide film formed on its surface which was enhanced with cold working and nitrogen content. It was also observed that corrosion current densities were decreased and corrosion potentials were shifted to more positive values. By seeing pit morphology under SEM, shallower and smaller pits were associated with HNSs and cold worked samples, indicating that corrosion resistance increases with increasing nitrogen content and degree of cold deformation. X-ray diffraction profiles of annealed as well as deformed alloys were revealed and there is no evidence for formation of martensite or any other secondary phases.

Effect of cold working on biocompatibility of Ni-free high nitrogen austenitic stainless steels using Dalton's Lymphoma cell line.

The aims of the present work are to explore the effect of cold working on in-vitro biocompatibility of indigenized low cost Ni-free nitrogen containing austenitic stainless steels (HNSs) and to compare it with conventionally used biomedical grade, i.e. AISI 316L and 316LVM, using Dalton's Lymphoma (DL) cell line. The MTT assay [3-(4,5-dimethythiazol 2-yl)-2,5-diphenyltetrazolium bromide] was performed on DL cell line for cytotoxicity evaluation and cell adhesion test. As a result, it was observed that the HNS had higher cell proliferation and cell growth and it increases by increasing nitrogen content and degree of cold working. The surface wettability of the alloys was also investigated by water contact angle measurements. The value of contact angles was found to decrease with increase in nitrogen content and degree of cold working. This indicates that the hydrophilic character increases with increasing nitrogen content and degree of cold working which further attributed to enhance the surface free energy (SFE) which would be conducive to cell adhesion which in turn increases the cell proliferation.

A review on nickel-free nitrogen containing austenitic stainless steels for biomedical applications.

The field of biomaterials has become a vital area, as these materials can enhance the quality and longevity of human life. Metallic materials are often used as biomaterials to replace structural components of the human body. Stainless steels, cobalt-chromium alloys, commercially pure titanium and its alloys are typical metallic biomaterials that are being used for implant devices. Stainless steels have been widely used as biomaterials because of their very low cost as compared to other metallic materials, good mechanical and corrosion resistant properties and adequate biocompatibility. However, the adverse effects of nickel ions being released into the human body have promoted the development of "nickel-free nitrogen containing austenitic stainless steels" for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel and emphatically the advantages of nitrogen in stainless steel, as well as the development of nickel-free nitrogen containing stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength, better corrosion and wear resistance and superior biocompatibility in comparison to the currently used austenitic stainless steel (e.g. 316L), the newly developed nickel-free high nitrogen austenitic stainless steel is a reliable substitute for the conventionally used medical stainless steels.

Outcome of parapneumonic empyema.

OBJECTIVE: Empyema thoracis is known to have variable age group affection, causative agents and controversy regarding primary mode of management. To look into current demography, bacteriology and treatment outcome. METHODS: Prospective study made on admitted cases of parapneumonic empyema from July 2001 to June 2003. All cases were treated with chest tube drainage, parenteral antibiotics or thoracotomy in multiloculated or non-improving cases. RESULTS: 0.8% (C.I. 0.6-1.0) of total pediatric admission had empyema, who were more likely to be females (P< 0.05), under-weight (P< 0.05) compared to children admitted for other reasons. Staphylococcus aureus is still the commonest isolate (13.2%). All cases received antibiotics prior to hospitalisation. Majority of cases (90.5%) could be successfully managed with antibiotics and chest tube drainage alone. 9.4% cases needed thoracotomy. 5.8% cases needed salvage thoracotomy following non-improvement with chest tube drainage. Fever remission time and duration of hospital stay were comparable in both groups. Thoracotomy cases required antibiotics for shorter period (P=0.04). Two cases died due to reasons other than mode of management. Radiological and lung function recovery was excellent in most of the cases. CONCLUSION: Chest tube drainage is a safe, efficacious primary method of empyema management.