Titanium Ones Research Articles

Sintering of Incorporated Shape Memory Alloys into Functionally Graded Materials

Shape Memory Alloys (SMAs) have been investigated as one of the most full of promise smart materials in multi applications. Among the commercially obtainable Shape Memory Alloys, nickel–titanium (Nitinol or NiTi) ones are wonderful due to their outstanding performance and reliability. In addition to strain recovery, (Ni-Ti) be an attraction in several medical applications due to its biocompatibility, corrosion resistance and fatigue behavior. Low range of transition temperature was the main challenges in the fabrication of these materials. A novel method was introduced to improve the range of transition temperatures by incorporating the shape memory effect into functionally graded materials concept. Therefore, industrialization and implementing of NiTi functionally graded materials made by a powder metallurgy method were carried out through the current work. Two samples with different seven layers of NiTi/NiTi functionally graded materials were compacted using steel die and punch at the same compacted pressure and different sintered temperature. After inspect the different samples of NiTi/NiTi functionally graded materials under different fabrication conditions, the suitability fabrication regime was determined with the aid of microscopic observations. These materials are designed to have gradual or abrupt Microstructural or compositional variations within the body in one piece of material, these samples have been produced by powder metallurgy approach and the effect of composition for each layer studied on the XRD.

Sources of Reactive Oxygen and Nitrogen Species in Tissue Microenvironment of Hernioplasty Materials.

Titanium and polypropylene mesh endoprostheses were implanted into the rat abdominal cavity and the populations of cells migrating to their surface were analyzed. On both materials, the cells were presented mainly by macrophages that proliferated, activated, and fused to form multinuclear cells. Contact with the foreign surface triggered superoxide anion generation and myeloperoxidase synthesis by macrophages (these processes were more intense on polypropylene implants than on titanium ones) and stimulated production of nitric oxide by macrophage. It was hypothesized that the effects of free nitrogen and oxygen radicals lead to oxidation and destruction of the polypropylene endoprosthesis surface.

A systematic review of the clinical survival of zirconia implants.

ObjectivesThe aim of this review was to evaluate the clinical success and survival rates of zirconia ceramic implants after at least 1 year of function and to assess if there is sufficient evidence to justify using them as alternatives to titanium implants.Materials and methodsAn electronic search in MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Clinical Trials (CENTRAL) databases was performed in April 2015 by two independent examiners to retrieve clinical studies focusing on the survival rate of zirconia implants after at least 1 year of function. Implant survival was estimated using the overall proportion reported in the studies with a Clopper-Pearson 95 % confidence interval (random effect model with a Der-Simonian Laird estimate).ResultsFourteen articles were selected out of the 1519 titles initially screened. The overall survival rate of zirconia one- and two-piece implants was calculated at 92 % (95 % CI 87–95) after 1 year of function. The survival of implants at 1 year for the selected studies revealed considerable heterogeneity.ConclusionsIn spite of the unavailability of sufficient long-term evidence to justify using zirconia oral implants, zirconia ceramics could potentially be the alternative to titanium for a non-metallic implant solution. However, further clinical studies are required to establish long-term results, and to determine the risk of technical and biological complications. Additional randomized controlled clinical trials examining two-piece zirconia implant systems are also required to assess their survival and success rates in comparison with titanium as well as one-piece zirconia implants.Clinical relevanceZirconia implants provide a potential alternative to titanium ones. However, clinicians must be aware of the lack of knowledge regarding long-term outcomes and specific reasons for failure.

Improving Osteoblast Response In Vitro by a Nanostructured Thin Film with Titanium Carbide and Titanium Oxides Clustered around Graphitic Carbon.

IntroductionRecently, we introduced a new deposition method, based on Ion Plating Plasma Assisted technology, to coat titanium implants with a thin but hard nanostructured layer composed of titanium carbide and titanium oxides, clustered around graphitic carbon. The nanostructured layer has a double effect: protects the bulk titanium against the harsh conditions of biological tissues and in the same time has a stimulating action on osteoblasts.ResultsThe aim of this work is to describe the biological effects of this layer on osteoblasts cultured in vitro. We demonstrate that the nanostructured layer causes an overexpression of many early genes correlated to proteins involved in bone turnover and an increase in the number of surface receptors for α3β1 integrin, talin, paxillin. Analyses at single-cell level, by scanning electron microscopy, atomic force microscopy, and single cell force spectroscopy, show how the proliferation, adhesion and spreading of cells cultured on coated titanium samples are higher than on uncoated titanium ones. Finally, the chemistry of the layer induces a better formation of blood clots and a higher number of adhered platelets, compared to the uncoated cases, and these are useful features to improve the speed of implant osseointegration.ConclusionIn summary, the nanostructured TiC film, due to its physical and chemical properties, can be used to protect the implants and to improve their acceptance by the bone.

Effect of low temperature annealing on the wear properties of NITINOL

NiTi shape memory alloy is a wonder material that is a solution looking for problems. The material finds wide biomedical applications like endodontic files for root canal treatment and cardiovascular stents. This material has rendered the surgical procedure simple compared to that with the existing Stainless Steel (SS) or titanium ones. NiTi as an endodontic file would cause less discomfort to the patients in comparison to that with far stiffer SS or titanium ones. Here nearly equi-atomic 50:50 commercial NiTi rods were subjected to low temperature aging at 300 to 450°C. The wear resistance of the as-received and the heat-treated samples was studied using adhesive wear tests on hardened steel counter face. Abrasive wear tests were run against Alumina disc to simulate the working of endodontic drills and files against dental hard and soft tissues. The abrasive wear resistance is expected to be proportional to the Vickers Hardness of the material and is high for the 450°C heat-treated sample. A correlation between the mechanical properties and microstructures of this material is attempted

A comparative study on the polymerization of 1-octene promoted by vanadium and titanium complexes supported by phenoxyimine and salen type ligands

Polymerizations of 1-octene were carried out in the presence of vanadium and titanium complexes bearing salen-type or phenoxyimine ligands activated with various co-catalysts. Vanadium complexes turned out active only in conjunction with MAO, whereas the titanium ones were active in combination with Al(i-Bu)3/Ph3CB(C6F5)4. The activity of all catalysts was moderate or low and it was dependent on the ligand type: bis(phenoxyimine) complexes were more active than the salen ones. Both vanadium and titanium catalytic systems produced poly(1-octene)s possessing atactic structures with [mmmm] sequences in the range from 12 to 56 % at room temperature. A temperature decrease to 0.5 °C for the reaction catalyzed by the vanadium catalyst led to poly(1-octene) of [mmmm] = 70 %. The 1H NMR analysis showed that unsaturated end groups were present in poly(1-octenes) which were introduced to the polymer chains as a results of various chain transfer reactions. In case of vanadium catalysts, vinylidene and vinylene end groups were present in polymer products. For titanium catalyst, vinyl and tri-substituted unsaturated groups were present in poly(1-octenes) in addition to the end groups as mentioned before.

Influence of tightening procedures and lubrication conditions on titanium screw joints for lightweight applications

In recent years, the need for lighter vehicles led to the widespread of lightweight alloys, such as titanium, also in the field of threaded fasteners. Unluckily, the replacement of steel bolts with titanium ones, usually suggested because of their favourable ratio between strength and weight, is not quite straightforward. The coefficient of friction, a key parameter in bolted joints design, changes drastically when switching from steel to titanium. Some results concerning the frictional behaviour of bolted joints involving titanium screws are here presented: friction and torque coefficients were calculated, according to ISO 16047, for joints made up of a hexagon socket head screw made of titanium alloy (Ti–6Al–4V), a bush made of aluminium alloy (EN AW 7075 T6) and a steel nut (ISO 4032). Data were collected by performing several tightening tests on ad-hoc designed specimens, which allowed the evaluation of the different tribological behaviour of the same joint under three different conditions of lubrication (dry, Teflon® added oil, and ceramic paste). 20 repeated tightenings (re-tightenings) have been analysed in order to simulate some maintenance operations. The DOE method was applied to manage the tests, while the results were analysed by the ANOVA and P-value methods. Out of the two lubricants examined, the ceramic paste showed the best results in terms of friction coefficients constancy throughout the re-tightening operations, as well as the best protection of the thread and underhead surfaces against wear.

The influence of carbon content on the characteristics of V–C–N coatings deposited by combined magnetron sputtering and ion implantation (CMSII)

Hard coatings based on transitional metal compounds have received over the years a large interest due to their relative ease of synthesis and outstanding mechanical properties. These advantages make them excellent candidates for industrial applications. Less attention has been paid to vanadium compounds (nitrides and carbides), comparatively than to titanium ones, and the properties of vanadium compounds have not been completely explored yet. This paper reports on the synthesis of vanadium carbonitride coatings produced by a magnetron sputtering deposition method assisted by a high voltage discharge. Chemical composition, phase structure and morphology were determined by using GDOES (Glow Discharge Optical Emission Spectrometry), XRD (X-ray Diffraction) and SEM (Scanning Electron Microscopy) techniques. Coatings with a thickness in the range 10–15 µm and Vickers microhardness up to 3800 HV0.05, depending on the deposition parameters, have been obtained. The wear properties of the coated samples were evaluated using a pin-on-disc tribometer under oil lubricated conditions.

Surface species structure and activity in NO decomposition of an anatase-supported V–O–Mo catalyst

The paper concerns the evolution of surface species of a V–O–Mo/anatase catalyst in the course of its thermal treatment in oxidising and/or reducing conditions. The catalyst was obtained by the sol–gel method. The structure of its surface was investigated by XPS and Raman spectroscopy. The fresh catalyst consists of anatase nanocrystallites with some vanadium and molybdenum ions substituted for titanium ones and molybdenum oxide islands on their surfaces. A V/Mo 5O 14 solid solution-containing V atoms in its channels, as well as MoO 3 and anatase with some surface vanadia species are present on the catalyst surface. The reduction of anatase to TiO 2− x and of MoO 3 to Mo 5O 14, accompanied by inward vanadium diffusion occurs during the catalyst interaction with ammonia at 523 K. The oxidation of the TiO 2− x but not Mo 5O 14 and V reappearance in the surface channels take place during the interaction of the reduced catalyst with molecular oxygen. However, the oxidation of Mo 5O 14 to MoO 3 occurs under the influence of atomic oxygen, formed by NO decomposition at 423 K. It is accompanied by the surface vanadia species formation. The activity of V ions of these species in NO decomposition is lower than of the surface interstitial ones.

Modification of the photocatalytic activity of Pd/TiO2 and Zn/TiO2 systems through different oxidative and reductive calcination treatments

Two different solids consisting of Pd or Zn-containing titania systems (metal/titanium nominal ratio of 1%) were submitted to diverse oxidative and reductive calcination treatments and tested for gas-phase selective photooxidation of 2-propanol. As regards the Pd system, reduction at low temperature (≤500°C) resulted in a gradual increase in catalytic activity which was ascribed to the gradual reduction of bulk palladium to Pd0. Thermal treatment of the system at high temperature (850°C) in static air, air flow or hydrogen flow led to a decrease in activity as the result of the sharp decrease in surface area. Nevertheless, those systems containing Pd0 only were more active than the one consisting of Pd+PdO. Finally, Pd-system overcame Pd migration to the surface on reduction at 850°C which resulted in a significant increase in selectivity to acetone up to 97% for a time on stream of 5h. As regards the Zn-containing system, none of the applied treatments resulted in improvement in photocatalytic activity. It seems that the most favourable situation for photocatalysis is that on which Zn atoms are substituting titanium ones in the lattice, whereas segregation of Zn to form small ZnO clusters is especially detrimental to activity.

P-29 Mechanical characteristics of spectacle frames made of gum metal

Most metal frame spectacles are now made of titanium alloy. Recently, however, frames made of gum metal have started to be produced. Gum metal is a new material having a low Young's modulus, high strength and high elastic deformation. This report compares the mechanical characteristics of the full-rim and rimless spectacles made of gum metal on the market and the conventional titanium frames by using recent measuring and analytical techniques. Using the finite element method (FEM), the authors preformed detail analysis of the mechanical characteristics of these frames. Consequently, gum metal frames were found to fit slightly better than titanium ones. Irrespective of the material they are made from, however, rimless spectacles have greater risk of lens damage and require a structure that can effectively mitigate the temple opening force by the improvement of end pieces and hinges.

Collagen I‐coated titanium surfaces: Mesenchymal cell adhesion and in vivo evaluation in trabecular bone implants

The goal of the study was the evaluation of the effect of modification of titanium implants by acrylic acid surface grafting-collagen I coupling. Tests were performed on titanium samples treated by galvanostatic anodization to create a porous surface topography. Surface characterization by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) confirms the biochemical modification of the surface and shows a surface topography characterized by pores mostly below 1 mum diameter. In vitro evaluation involving human mesenchymal cells shows enhanced cell growth on collagen coated surfaces as compared to titanium ones. Four weeks in vivo evaluation of implants in rabbit femur trabecular bone shows improvements of bone-to-implant contact, while improvement of bone ingrowth is slightly not significant (p = 0.056), when compared to the control. Overall, these data indicate that integration in trabecular, or cancellous, bone can be enhanced by the surface collagen layer, confirming previous findings obtained by modification of machined surfaces by the same approach in cortical bone implants.

Effect of Core Diameter and Surface Treatment on the Retention of Resin Composite Cores to Prefabricated Endodontic Posts

With advances in adhesive dentistry and current emphasis on esthetic restorations, dowel systems have been developed to take advantage of these new techniques. Of interest when using these systems is the interaction between core materials and post materials. This investigation compared the tensile retentive force of two resin composite core materials to two metallic and one non-metallic prefabricated endodontic posts. Two dimensions of core build-up and two post-surface treatments were tested. One hundred twenty posts (stainless steel, titanium alloy, and glass fiber-impregnated resin) were secured in a jig with 4 mm of the post extending into a cylindrical matrix. The matrix formed cylinders with diameters of 3 and 5 mm into which resin composite was inserted. The posts were treated or not treated with a bonding agent. After storage for 24 hours at 100% humidity, five specimens per condition were tested in an Instron testing machine at a crosshead speed of 0.5 mm/min. Failure loads were recorded in kilograms and failure modes were observed under light microscopy (40 x). Four-way analysis of variance and multiple comparison testing were used to compare means at the 0.05 level of significance. The means and standard deviations of tensile loads were calculated. All variables were significant in either main effects or interactions ( p<0.05). Fisher's PLSD intervals for post, core, treatment, and diameter were 2.0, 1.6, 1.6, and 1.6 kg, respectively. In most cases, the retentive force recorded for metallic posts was higher than that of glass fiber posts. Titanium posts had higher retentive forces than did the stainless steel posts. For metallic posts, 5-mm cores provided higher forces than 3-mm cores. In the glass fiber group, core diameter was not significant. For core materials, Build-It gave higher results with stainless steel posts, and FluoroCore gave higher results with the titanium ones. The surface treatment results were mixed. In the metallic post groups the adhesive failure data ranged between 80% and 100%, whereas in the glass fiber post groups, adhesive failures ranged between 60% and 70%. Within the limitations of this study, the metallic post groups always provided higher tensile retentive forces, with the titanium post groups showing higher retentive forces than the stainless steel ones. In the glass fiber post groups, different core diameters did not affect retention values.

Separation of europium from aqueous solutions using Al3+- and Fe3+-doped zirconium and titanium phosphates

The sorption of europium from aqueous solutions (Eu-concentration: 10 to 250 mg/l) by Fe3+- and Al3+-doped zirconium- and titanium-phosphates was investigated using a batch technique and 152Eu tracer. The initial pH of the solutions was adjusted to 3, 4, 5 and 6. All investigations were performed under constant ionic strength, I=0.15 established by NaCl. Although zirconium phosphates generally showed a higher Eu-uptake capacity than the titanium ones, all investigated materials possessed the ability to remove considerable amounts of europium from aqueous solutions. The Eu-sorption properties of the studied phosphate materials seem to be not especially affected by the type of trivalent cations used for the doping (i.e., Al3+or Fe3+).

Experience with Cyberknife ™

Request for temporary removal of orthodontic appliances due to medical conditions that require magnetic resonance (MR) imaging is not uncommon in daily practice in the field of orthodontics. This may be at the expense of time and cost. Metal Orthodontic appliances cause more signal loss and image distortion as compared to ceramic and titanium ones. Stainless steel and large brackets in addition to the oriented miniscrews in relation to the axis of magnetic field may cause severe signal loss and image distortion. Moreover, gradient echo and frequency-selective fat saturation MR protocols are more susceptible to metal artifacts. The spin echo and fat-suppression protocols, low magnetic field strength (e.g., 1.5 Tesla vs. 3 Tesla), small field of view, high-resolution matrix, thin slice, increased echo train length and increased receiver band width could be applied to lessen the metal artifacts in MR images. The larger the distance between an appliance and desired location to be imaged, the lower the distortion and signal loss. Decision to remove brackets should be made based on its composition and desired anatomic location. In this review, first the principles of MR imaging are introduced (Part-I) and then the interactions of orthodontic appliances and magnetic field are farther discussed (Part-II).

Failure Analyses of Polymer Matrix Composite (PMC) Honeycomb Sandwich Joint Panels

The objective of this paper is to investigate the structural behavior and material failure characteristics of polymer-matrix composite (PMC) honeycomb sandwich joint panels under several transverse loads which resulted in web bending as typically experienced by aircraft wing skin. Several PMC honeycomb sandwich joint panels were fabricated as part of the demonstration test elements to provide structural concepts for the High-Speed Civil Transport (HSCT) wing. Test elements were preliminarily designed and sized under design-integration trade studies (DITS) task. Test elements selected for this study included two PMC honeycomb sandwich joint panels; one panel consisted of a honeycomb sandwich wing skin bolted joint by two fiber-reinforced composite spar caps to a honeycomb sandwich spar web; the other panel had the same structural concept except that the composite spar caps were replaced with the titanium ones. Essential components in the sandwich construction were composite face sheets, honeycomb cores, and core-to-facing bonding material. By statically loaded test elements to failure in room temperature, the test was designed to simulate flight load condition of 15 psi fuel over pressurization against the wing spar during supersonic maneuver. Geometric linear and nonlinear finite element models were constructed to simulate the structural behaviors of these test panels. Failure theories such as the Yeh-Stratton, Tsai-Wu, Tsai-Hill, and Maximum Stress and Strain criteria were utilized to predict the first ply failure and the results were compared with experimental data.

Local Bonding States of Titanium and Germanium-doped Tetragonal Zirconia Polycrystal and Their Correlation to High Temperature Ductility

bond with oxygen ions rather than Zr‐O bond. Covalency of TZP is more increased by solution of germanium ions than that of titanium ones. In superplastic deformation of TZP, an addition of GeO2 or TiO2 enhances tensile ductility of TZP. Germanium ion is more effective to improve ductility than titanium. The increment of covalency is in a good agreement with the improvement of elongation to failure in doped TZP. Dopant cations segregate at grain boundaries and form no secondary phase. Assuming that a dopant effect on chemical bonding states in grain boundaries is similar to that in grain interior, segregation of germanium or titanium ion increases covalent bonding strength nearby grain boundaries. Such increasing of covalency is likely to enhance cohesion of grain boundaries. The enhancement of grain boundary cohesion suppresses intergranular failure during tensile deformation at elevated temperatures. This must be the reason why an addition of GeO 2 and TiO2 is effective to improve the high temperature ductility of TZP. Our calculation suggests that the covalency nearby grain boundaries have a critical role in the tensile ductility of TZP.

Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly l-lactide (PLLA). Part II: practical properties of miniscrews and miniplates

Miniscrews and miniplates made of forged composites composed of raw hydroxyapatite (u-HA) particles (particle size 0.2–20 μm, averaging 3.0 μm, Ca/p=1.69 and containing CO 3 2−) and a poly l-lactide (PLLA, M ̄ v : about 180 kDa, containing residual 0.05 wt% lactide) with osteological bioactivity such as direct bonding to bone and osteoconductivity, total resorbability and radiopacity were examined for various mechanical properties in order to evaluate their usefulness for cranio-, oral and maxillo-facial as well as plastic and reconstructive surgeries with PLLA-only or titanium devices. The composites containing u-HA particles at 30 wt% for miniscrews and 40 wt% for miniplates were selected based on total mechanical strengths and bioactivity, respectively. It was found that the composite devices generally had slightly different mechanical properties than forged PLLA-only devices of which strengths are ranked the highest among the reinforced PLLA-only ones that having been used in many clinical cases to date, in spite of their approximate 2 or 3 times lower absolute strengths than those of titanium ones. However, a remarkable distinction that makes the composite miniplates stand above the titanium ones was confirmed on their fatigue resistance to alternate bendings such that they retained 70% of their initial strength even after 60 times without revealing any damage, whereas the metallic devices fully broke off at only 8 times. This behavior was similar to that of forged PLLA-only devices but is unique as composites made of organic polymers divided by inorganic particles. In addition, profile plates such as L-, T-, X, T, C-, Mesh-, Box-, and Barhole types which were processed by forging twice exhibited nearly directional isotropy in strength and could be deformed in situ at ordinary temperatures to adjust their shapes along the surface undulations of the skull, mandible, maxilla, zygomatic bone and the like without thermoforming and did not return to their original shapes inside an alive body due to the high PLLA’s T g (65°C) over an alive body temperature (37°C). Since it had already been confirmed in previous papers that these stiff and tough composites have the osteological bioactivity which is missing from both PLLA-only and titanium ones, and radiopacity which is wanting in PLLA-only ones, these various small and thin screws and plates have conclusively less objectionable practicality for use in oral-maxillo and craniofacial as well as plastic and reconstructive surgeries.

Porous bone implants

Porous conical implants made by sintering micro-spheres made from bioactive and bio-compatible glasses have been tested mechanically as well as in vivo by inserting the implant through the cortical bone into the bone marrow. The behaviour is compared to a reference implant made by sintering micro-spheres of metallic titanium. Due to capillary forces the implant pores were filled with bone marrow fluid when inserted. An extended bone ingrowth occurred in the cones of bioactive glass, in the titanium ones only in the cortical area. Further, the factors influencing the formation of a chemical bond between glass and living tissue are discussed.

Electrochemistry in Near-Critical and Supercritical Fluids. 9. Improved Apparatus for Water Systems (23−385 °C). The Oxidation of Hydroquinone and Iodide

The apparatus for electrochemical measurements in high-temperature water has been improved by replacing the alumina tube reactor with an oxidized titanium tube, producing a more rugged reactor. All metal fittings were replaced by titanium ones, decreasing corrosion problems. The working electrodes are Pt disks (radius, 14 μm) fabricated by sealing Pt−Ir wires in a high PbO-containing glass. This glass has the advantage over borosilicate glass in showing lower conductivity at temperatures above 230 °C, better corrosion resistance, and a coefficient of thermal expansion well-matched to Pt. Well-defined steady-state cyclic voltammograms for the oxidation of iodide ion and hydroquinone were obtained in (initially 23 °C) 0.2 M NaHSO4 solutions over a temperature range 23−385 °C. Diffusion coefficients (D) were determined from the limiting currents. The experimental D values were in excellent agreement with those calculated from the Stokes−Einstein equation and viscosity values for water at the relevant temperatures and pressures.