Characterization of a new beta titanium alloy, Ti-12Mo-3Nb, for biomedical applications

In recent years, different beta titanium alloys have been developed for biomedical applications with a combination of mechanical properties including a low Young's modulus, high strength, fatigue resistance and good ductility with excellent corrosion resistance. From this perspective, a new metastable beta titanium Ti-12Mo-3Nb alloy was developed with the replacement of both vanadium and aluminum from the traditional Ti-6Al-4V alloy. This paper presents the microstructure, mechanical properties and corrosion resistance of the Ti-12Mo-3Nb alloy heat-treated at 950 degrees C for 1 h. The material was characterized by X-ray diffraction and by scanning electron microscopy. Tensile tests were carried out at room temperature. Corrosion tests were performed using Ringer's solution at 25 degrees C. The results showed that this alloy could potentially be used for biomedical purposes due to its good mechanical properties and spontaneous passivation. (c) 2011 Elsevier B.V. All rights reserved.

Influence of the substitutional solute on the mechanical properties of Ti-Nb binary alloys for biomedical use

Titanium alloys are widely used in the manufacture of biomedical implants because they possess an excellent combination of physical properties and outstanding biocompatibility. Today, the most widely used alloy is Ti-6Al-4V, but some studies have reported adverse effects with the long-term presence of Al and V in the body, without mentioning that the elasticity modulus value of this alloy is far superior to the bone. Thus, there is a need to develop new Ti-based alloys without Al and V that have a lower modulus, greater biocompatibility, and similar mechanical strength. In this paper, we investigated the effect of Nb as a substitutional solute on the mechanical properties of Ti-Nb alloys, prepared in an arc-melting furnace and characterized by density, X-ray diffraction, optical microscopy, hardness and elasticity modulus measurements. The X-ray and microscopy measurements show a predominance of the α phase. The microhardness values showed a tendency to increase with the concentration of niobium in the alloy. Regarding the elasticity modulus, it was observed a nonlinear behavior with respect to the concentration of niobium. This behavior is associated with the presence of the α phase.

Titanium surface topography after brushing with fluoride and fluoride-free toothpaste simulating 10 years of use

Objectives: To conduct a controlled study contrasting titanium surface topography after procedures that simulated 10 years of brushing using toothpastes with or without fluoride. Methods: Commercially pure titanium (cp Ti) and Ti-6Al-4V disks (6 mm circle divide x 4 mm) were mirror-polished and treated according to 6 groups (n = 6) as a function of immersion (I) or brushing (B) using deionised water (W), fluoride-free toothpaste (T) and fluoride toothpaste (FT). Surface topography was evaluated at baseline (pretreatment) and post-treatment, using atomic force microscope in order to obtain three-dimensional images and mean roughness. Specimens submitted to immersion were submerged in the vehicles without brushing. For brushed specimens, procedures were conducted using a linear brushing machine with a soft-bristled toothbrush. Immersion and brushing were performed for 244 h. IFT and BFT samples were analysed under scanning electron microscope with Energy-Dispersive X-ray Spectroscopy (EDS). Pre and post-treatment values were compared using the paired Student T-test (alpha = .05). Intergroup comparisons were conducted using one-way ANOVA with Tukey post-test (alpha = .05). Results: cp Ti mean roughness (in nanometers) comparing pre and post-treatment were: IW, 2.29 +/- 0.55/2.33 +/- 0.17; IT, 2.24 +/- 0.46/2.02 +/- 0.38; IFT, 2.22 +/- 0.53/1.95 +/- 0.36; BW, 2.22 +/- 0.42/3.76 +/- 0.45; BT, 2.27 +/- 0.55/16.05 +/- 3.25; BFT, 2.27 +/- 0.51/22.39 +/- 5.07. Mean roughness (in nanometers) measured in Ti-6Al-4V disks (pre/post-treatment) were: IW, 1.79 +/- 0.25/2.01 +/- 0.25; IT, 1.61 +/- 0.13/1.74 +/- 0.19; IFT, 1.92 +/- 0.39/2.29 +/- 0.51; BW, 2.00 +/- 0.71/2.05 +/- 0.43; BT, 2.37 +/- 0.86/11.17 +/- 2.29; BFT, 1.83 +/- 0.50/15.73 +/- 1.78. No significant differences were seen after immersions (p > .05). Brushing increased the roughness of cp Ti and of Ti-6Al-4V (p < .01); cp Ti had topographic changes after BW, BT and BFT treatments whilst Ti-6Al-4V was significantly different only after BT and BTF. EDS has not detected fluoride or sodium ions on metal surfaces. Conclusions: Exposure to toothpastes (immersion) does not affect titanium per se; their use during brushing affects titanium topography and roughness. The associated effects of toothpaste abrasives and fluorides seem to increase roughness on titanium brushed surfaces. (C) 2012 Elsevier Ltd. All rights reserved.

Fatigue Reliability of 3 Single-Unit Implant-Abutment Designs

Objectives: Because the mechanical behavior of the implant-abutment system is critical for the longevity of implant-supported reconstructions, this study evaluated the fatigue reliability of different implant-abutment systems used as single-unit crowns and their failure modes. Methods and Materials: Sixty-three Ti-6Al-4V implants were divided in 3 groups: Replace Select (RS); IC-IMP Osseotite; and Unitite were restored with their respective abutments. Anatomically correct central incisor metal crowns were cemented and subjected to separate single load to failure tests and step-stress accelerated life testing (n = 18). A master Weibull curve and reliability for a mission of 50,000 cycles at 200 N were calculated. Polarized-light and scanning electron microscopes were used for failure analyses. Results: The load at failure mean values during step-stress accelerated life testing were 348.14 N for RS, 324.07 N for Osseotite, and 321.29 N for the Unitite systems. No differences in reliability levels were detected between systems, and only the RS system mechanical failures were shown to be accelerated by damage accumulation. Failure modes differed between systems. Conclusions: The 3 evaluated systems did not present significantly different reliability; however, failure modes were different. (Implant Dent 2012;21:67-71)

Radiative association of Ti and O atoms

Rate coefficients for the radiative association of titanium and oxygen atoms to form the titanium monoxide (TiO) molecule are estimated. The radiative association of Ti(F-3) and O(P-3) atoms is dominated by an approach along the C-3 Delta potential energy curve, accompanied by spontaneous emission into the X-3 Delta ground state of TiO. For temperatures ranging from 300-14 000 K, the total rate coefficients are found to vary from 4.76 x 10(-17) to 9.96 x 10(-17) cm(3) s(-1), respectively.

On the electrical conductivity of Ti-implanted alumina

Ion implantation of metal species into insulators provides a tool for the formation of thin, electrically conducting, surface layers with experimenter-controlled resistivity. High energy implantation of Pt and Ti into alumina accelerator components has been successfully employed to control high voltage surface breakdown in a number of cases. In the work described here we have carried out some basic investigations related to the origin of this phenomenon. By comparison of the results of alumina implanted with Ti at 75 keV with the results of prior investigations of polymers implanted with Pt at 49 eV and Au at 67 eV, we describe a physical model of the effect based on percolation theory and estimate the percolation parameters for the Ti-alumina composite. We estimate that the percolation dose threshold is about 4 x 10(16) cm(-2) and the maximum dose for which the system remains an insulator-conductor composite is about 10 x 10(16) cm(-2). The saturation electrical conductivity is estimated to be about 50 S/m. We conclude that the observed electrical conductivity properties of Ti-implanted alumina can be satisfactorily described by percolation theory. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3697900]

O gerente de projetos de TI em organizações com níveis de maturidade diferenciados

A literatura sobre gestão de projetos mostra, de forma recorrente, a importância da figura do gerente no desempenho dos projetos. O presente artigo apresenta os resultados de um levantamento (survey) do papel do gerente de projetos de TI como elemento condicionante do desempenho desses projetos. Os resultados encontrados mostram que a relação do gerente de projetos com o desempenho dos projetos é alterada pelo nível de maturidade da organização executante em gestão de projetos. Nas organizações com menor maturidade existe uma relação muito mais forte do perfil do gerente com o desempenho dos projetos.Isso sugere que as organizações que conseguem estimular sua maturidade em gestão de projetos criam condições para que o desempenho de seus projetos fique menos dependente da ação individual dos gerentes.

Dynamical Elastic Moduli of the Ti-13Nb-13Zr biomaterial alloy by mechanical spectroscopy

Dynamical Elastic Moduli of the Ti-13Nb-13Zr biomaterial alloy were obtained using the mechanical spectroscopy technique. The sample with heat treatment at 1170K for 30 minutes and water quenched with subsequent aging treatment at 670 K for 3 hours (TNZ + WQ + 670 K/3 h), was characterized through decay of free oscillations of the sample in the flexural vibration mode. The spectra of anelastic relaxation (internal friction and frequency) in the temperature range from 300 K to 625 K not revealed the presence of relaxation process. As shown in the literature, the hcp structure usually does not exhibit any relaxation due to the symmetry of the sites in the crystalline lattice, but if there is some relaxation, this only occurs in special cases such as low concentration of zirconium or saturation of the stoichiometric ratio of oxygen for zirconium. Dynamical elastic modulus obtained for TNZ + WQ + 670 K/3 h alloy was 87 GPa at room temperature, which is higher than the value for Ti-13Nb-13Zr alloy (64 GPa) of the literature. This increment may be related to the change of the proportion of α and β phases. Besides that, the presence of precipitates in the alloy after aging treatment hardens the material and reduces its ductility.

On Ti-18Si-6B and Ti-7.5Si-22.5B powder alloys prepared by high-energy ball milling and sintering

Recently, a new ternary phase was discovered in the Ti-Si-B system, located near the Ti6Si2B composition. The present study concerns the preparation of titanium alloys that contain such phase mixed with α-titanium and other intermetallic phases. High-purity powders were initially processed in a planetary ball-mill under argon atmosphere with Ti-18Si-6B and Ti-7.5Si-22.5B at. (%) initial compositions. Variation of parameters such as rotary speed, time, and ball diameters were adopted. The as-milled powders were pressureless sintered and hot pressed. Both the as-milled and sintered materials were characterized by X-ray diffraction, scanning electron microscopy and energy-dispersive spectrometry. Sintered samples have presented equilibrium structures formed mainly by the α-Ti+Ti6Si2B+Ti5Si3+TiB phases. Silicon and boron peaks disappear throughout the milling processes, as observed in the powder diffraction data. Furthermore, an iron contamination of up to 10 at. (%) is measured by X-ray spectroscopy analysis on some regions of the sintered samples. Density, hardness and tribological results for these two compositions are also presented here.