Thin films of calcium phosphate and titanium dioxide by a sol-gel route: a new method for coating medical implants

Titanium is a commonly used biomaterial for dental and orthopaedic applications. To increase its ability to bond with bone, some attempts were made to coat its surface with calcium phosphate (CaP). This paper describes a new type of coating. Instead of a pure CaP layer, a mixing of titanium dioxide (TiO₂) and CaP is fabricated and deposited as a coating. These layers are deposited by a sol-gel route on pure titanium substrates using various pre-treatments. The method consists of mixing a solution of tetrabutyl ortho-titanate or a sol of titanium dioxide with a solution of calcium nitrate and phosphorous esters. This composite is deposited on to commercially pure titanium plates, mechanically polished or blasted with pure crystalline aluminum oxide, using the spin-coating technique. These coatings are then fired at 650 or 850°C for various times. The samples are characterized by X-ray diffraction for their crystallinity, X-ray photoelectron spectroscopy for their surface chemical composition and scanning electron microscopy for their topography. Samples treated at 850°C present a well-pronounced crystallinity, and a high chemical purity at the surface. The topography is strongly related to the viscosity of the precursor and the substrate pre-treatment. Possibilities to structure the outermost layer are presented. © 1999 Kluwer Academic Publishers     

Effect of chlorine on gold-titanium thin films

In this study the effect of a small concentration of chlorine on gold-titanium metallization was investigated. Samples were prepared by deposition of gold and titanium layers on a glass substrate. Samples were exposed at 75, 135 and 175° C for 53 days to an argon atmosphere and to an argon atmosphere containing 50 ppm chlorine. In all cases the electrical resistance of the exposed samples decreased and the addition of chlorine made this decrease even larger. Depending on the conditions, migration of the titanium atoms and formation of preferred oriented structure took place. At 135 and 175° C in the argon atmosphere containing 50 ppm chlorine, a very active migration of titanium atoms from the gold layer to the external surface of the samples was observed. Migration of titanium was not observed in the samples exposed to the pure argon atmosphere. This strongly suggests that chlorine acts as an agent bringing titanium from the gold layer to the external surface by a process known as chemisorption-induced segregation; on the surface titanium forms an oxide. When samples were exposed for 53 days at 175° C, preferred oriented structure in the gold layer was developed. Formation of the preferred oriented structure was neither conditioned nor related to the presence of chlorine in the atmosphere.     

Ta-10W/Ti的高温界面反应研究

采用多弧离子镀技术在金属钛表面成功制备出连续致密且厚度均匀的α-Ta相Ta-10W涂层。在900℃下分别对涂层进行高温氧化和真空扩散处理,通过XRD、SEM、EDS等分析测试手段对涂层的抗氧化性能及元素扩散行为进行研究。结果表明:在高温氧化过程中,存在氧化和扩散双重作用,涂层与基体间发生相互扩散且涂层表面形成氧化膜,致使涂层脆化,但涂层/基体界面处氧化不明显,说明Ta-10W涂层对基体起到了有效的抗氧化作用;在真空扩散过程中,Ta向基体中扩散较为剧烈且沿着逐渐趋直的α-Ti晶界进行扩散。     

钛表面固定纤维连接蛋白及其体外细胞培养

通过低温等离子聚合的方法,以丙烯酸为单体在钛表面沉积含有羧基的薄膜,以羧基为接入点固定纤维连接蛋白。样品表面用X射线光电子能谱、傅里叶红外光谱仪进行表征。将固定了纤维连接蛋白的样品进行体外细胞培养,所用的细胞为MG63骨瘤细胞,对照样为纯钛。结果表明, 钛表面聚丙烯酸薄膜能有效地固定纤维连接蛋白,并且固定纤维连接蛋白的样品能促进骨瘤细胞的生长和黏附,具有更高的成骨活性。      

Hydrogen content in titanium and a titanium–zirconium alloy after acid etching

Dental implant alloys made from titanium and zirconium are known for their high mechanical strength, fracture toughness and corrosion resistance in comparison with commercially pure titanium. The aim of the study was to investigate possible differences in the surface chemistry and/or surface topography of titanium and titanium–zirconium surfaces after sand blasting and acid etching. The two surfaces were compared by X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, scanning electron microscopy and profilometry.The 1.9 times greater surface hydrogen concentration of titanium zirconium compared to titanium was found to be the major difference between the two materials. Zirconium appeared to enhance hydride formation on titanium alloys when etched in acid. Surface topography revealed significant differences on the micro and nanoscale. Surface roughness was increased significantly (p < 0.01) on the titanium–zirconium alloy. High-resolution images showed nanostructures only present on titanium zirconium.     

携载蛋白质的氧化钛纳米管表面成骨细胞行为

通过阳极氧化技术,在光滑钛表面制备一层管径约100nm的纳米管,并选用小牛血清白蛋白（BSA）和纤维连接蛋白（FN）以及两种蛋白的混合溶液（BF）进行蛋白吸附试验。将吸附蛋白后的试样进行细胞培养,所用细胞为MC-3T3E1成骨细胞株,结果表明,较光滑钛吸附蛋白前后的纳米管试样显示出更好的成骨活性,同时,吸附单组分纤维连接蛋白的纳米管试样能更好地促进成骨细胞的黏附和生长,具有更高的生物活性。     

An alternative method for manufacturing high-strength CP Ti–SiC composites by accumulative roll bonding process

For the first time, the accumulative roll bonding (ARB) process was used as an effective alternative method for manufacturing Ti–SiC composites and compared with the monolithic ARBed Ti. High-strength monolithic commercially pure titanium (CP Ti) and CP Ti–SiC composites with effective uniform reinforcement distribution were fabricated by this process. The tensile test, Vickers hardness measurements and SEM observations were done for the characterization of materials. A significant increase in yield and tensile strength and a drastic decrease in elongation were observed by applying 8 cycles of ARB process. An unexpectedly slight decrease of yield and tensile strength along with elongation was observed after the sixth ARB cycle for the monolithic sample. It was attributed to the weakening of the bond between the titanium layers in the final cycles. Strength of the composite samples was higher than that of the monolithic sample and did not decrease in the final ARB cycles. This was caused by the significantly improved distribution of SiC particles in the titanium matrix.     

Mechanical and ellipsometry measurements of thin TiN layer prepared by PIII

Titanium nitrides have good mechanical, biomedical and optical properties, therefore they are used to harden and protect cutting and sliding surfaces and as a non-toxic exterior for bio-medical applications. Nitrogen plasma immersion implantation (PIII), in which the diffusion of nitrogen from low pressure r.f. plasma is combined with the implantation of nitrogen ions at energies up to 30 kV, is an effective tool for nitriding titanium and titanium alloys. In this work, samples of pure titanium were nitrided by PIII at different negative high voltage pulses. The properties and the characteristics of the processed samples were evaluated using X-ray diffraction (XRD), Auger electron spectroscopy (AES), ball-on-disk type tribometer, surface profilemeter, and ellipsometry measurements. The results show that, the wear resistance of the untreated sample in comparison to the PIII treated samples is extremely poor and the friction coefficient for the PIII treated samples is decreased to the half value in comparison to the untreated titanium, this attributed to the formation of the solid solution titanium α-Ti(N) and the cubic TiN phases. Ellipsometric measurements were carried out on the PIII treated samples at different negative high voltage pulses. A three layers model was used to fit the calculated data to the experimental ellipsometric spectra. The thickness, surface roughness and refractive index increase with increasing the negative high voltage pulses. The refractive index at 550 nm increases from 1.83 to 2.09 as the negative high voltage pulses increases from 10 to 30 kV.     

Quantitative comparison of screw-shaped commercially pure titanium and zirconium implants in rabbit tibia

Screw-shaped implants with an outer diameter of 3.7 mm and a total length of 8 mm were made from rods of commercially pure titanium (c.p. Ti) and commercially pure zirconium (c.p. Zr). Prior to insertion in rabbit tibia for 12 weeks, the surface roughness of two randomly chosen c.p. Ti and two c.p. Zr machined implants of the batch were numerically and visually described with a TopScan 3-D system. Irrespective of implant material, they demonstrated rather similar surface roughnesses, for example, the R _a and R _q values (that describe the average deviation from the mean line) were 0.79 and 1.18 for c.p. Ti versus 0.56 and 0.86 for c.p. Zr. Each rabbit had four implants inserted; two made of c.p. Ti in one leg and two made of c.p. Zr in the other. The bone tissue reactions to the materials were qualitatively and quantitatively examined. Removal torque tests were performed on the distal implants and histomorphometrical evaluations of the proximal ones. No qualitative or quantitative bone differences were observed. Removal torque measurements demonstrated a mean of 26.2 N cm±9.6 for c.p. Ti versus a mean of 25.9 N cm±7.1 for the c.p.Zr implants. Histomorphometrical comparisons of the bone-to-metal contact revealed a mean of 29 ±10.2% for c.p. Ti and a mean of 19±5.5% for the c.p. Zr samples. The mean bone area in the threads around the c.p. Ti samples was 49±16.6% compared to 43±7.9% for the c.p. Zr group. Commercially pure titanium and zirconium implants seemed to be well accepted by the bone bed after 12 weeks of insertion in rabbit bone.     

Microstructural evolution in ultrafine-grained titanium processed by high-pressure torsion under different pressures

A grade 2 commercially pure (CP) titanium was processed by high-pressure torsion (HPT) at pressures of 3.0 and 6.0 GPa in order to achieve improved strengths. The microhardness values for these Ti samples were plotted against the imposed strain, and the plots show that a higher saturation microhardness of 320 Hv is achieved for the sample processed at 6.0 GPa compared to a microhardness of 305 Hv when using a pressure of 3.0 GPa. The omega ω-phase has been reported in some earlier HPT investigations of pure titanium, but it was not detected in this investigation even after processing at 6.0 GPa. The absence of the ω-phase is attributed to the relatively high level of oxygen (0.25 wt%) in these CP titanium samples. The higher saturation hardness for the 6.0 GPa sample is consistent with the smaller average grain size of ~105 ± 12 nm compared with the measured grain size of ~130 ± 18 nm after processing with an imposed pressure of 3.0 GPa.     

Comparison of titanium soaked in 5 M NaOH or 5 M KOH solutions

Commercially pure titanium plates/coupons and pure titanium powders were soaked for 24 h in 5 M NaOH and 5 M KOH solutions, under identical conditions, over the temperature range of 37° to 90 °C. Wettability of the surfaces of alkali-treated cpTi coupons was studied by using contact angle goniometry. cpTi coupons soaked in 5 M NaOH or 5 M KOH solutions were found to have hydrophilic surfaces. Hydrous alkali titanate nanofibers and nanotubes were identified with SEM/EDXS and grazing incidence XRD. Surface areas of Ti powders increased > 50–220 times, depending on the treatment, when soaked in the above solutions. A solution was developed to coat amorphous calcium phosphate, instead of hydroxyapatite, on Ti coupon surfaces. In vitro cell culture tests were performed with osteoblast-like cells on the alkali-treated samples.     

Does sodium fluoride in bone cement affect implant fixation Part II: Evaluation of the effect of sodium fluoride additions to acrylic bone cement and the fixation of titanium implants in ovariectomized rabbits

Bone integration of threaded implants made of cured polymethylmethacrylate containing sodium fluoride or commercially pure (c.p.) titanium were studied in normal and estrogen deficient New Zealand white rabbits. Nine had been ovariectomized through laparoscopy and nine served as controls. Four weeks after the ovariectomy two threaded implants made of cured bone cement with or without sodium fluoride addition were inserted in each tibia. One threaded commercially pure titanium implant was inserted in each patello–femoral joint flush to the cartilage. Six weeks after implant insertion measurement of the peak removal torque necessary to loosen the implants and light microscopical histomorphometrical investigations of tissue integration were performed. In the ovariectomized rabbits addition of sodium fluoride to the cement resulted in increased area of bone in the threads (p=0.04), but no corresponding effect could be noted in the controls. The removal torque was lower in the ovariectomized rabbits compared to the non-ovariectomized when comparing implant with sodium fluoride addition (p=0.02). The bone tissue response and the removal torque of the titanium implants were not influenced by ovariectomy in these rabbits. ©2002 Kluwer Academic Publisher     

Characteristics of powder metallurgy pure titanium matrix composite reinforced with multi-wall carbon nanotubes

By using pure titanium powder coated with un-bundled multi-wall carbon nanotubes (MWCNTs) via wet process, powder metallurgy (P/M) titanium matrix composite (TMC) reinforced with the CNTs was prepared by spark plasma sintering (SPS) and subsequently hot extrusion process. The microstructure and mechanical properties of P/M pure titanium and reinforced with CNTs were evaluated. The distribution of CNTs and in situ formed titanium carbide (TiC) compounds during sintering was investigated by optical and scanning electron microscopy (SEM) equipped with EDS analyzer. The mechanical properties of TMC were significantly improved by the additive of CNTs. For example, when employing the pure titanium composite powder coated with CNTs of 0.35 mass%, the increase of tensile strength and yield stress of the extruded TMC was 157 MPa and 169 MPa, respectively, compared to those of extruded titanium materials with no CNT additive. Fractured surfaces of tensile specimens were analyzed by SEM, and the uniform distribution of CNTs and TiC particles, being effective for the dispersion strengthening, at the surface of the TMC were obviously observed.     

Surface characterization

The biocompatibility of commercially pure titanium and its alloys is closely related to their surface properties, with both the composition of the protecting oxide film and the surface topography playing an important role. Surfaces of commercially pure titanium and of the two alloys Ti–6Al–7Nb and Ti–6Al–4V (wt %) have been investigated following three different pretreatments: polishing, nitric acid passivation and pickling in nitric acid–hydrogen fluoride. Nitric acid treatment is found to substantially reduce the concentration of surface contaminants present after polishing. The natural 4–6 nm thick oxide layer on commercially pure titanium is composed of titanium oxide in different oxidation states (TiO2, Ti2O3 and TiO), while for the alloys, aluminium and niobium or vanadium are additionally present in oxidized form (Al2O3, Nb2O5 or V-oxides). The concentrations of the alloying elements at the surface are shown to be strongly dependent on the pretreatment process. While pickling increases the surface roughness of both commercially pure titanium and the alloys, different mechanisms appear to be involved. In the case of commercially pure titanium, the dissolution rate depends on grain orientation, whereas in the case of the two alloys, selective -phase dissolution and enrichment of the -phase appears to occur. © 1999 Kluwer Academic Publishers     

Nanostructured severe plastic deformation processed titanium for orthodontic mini-implants

Titanium mini-implants have been successfully used as anchorage devices in Orthodontics. Commercially pure titanium (cpTi) was recently replaced by Ti-6Al-4 V alloy as the mini-implant material base due to the higher strength properties of the alloy. However, the lower corrosion resistance and the lower biocompatibility have been lowering the success rate of Ti-6Al-4 V mini-implants. Nanostructured titanium (nTi) is commercially pure titanium that was nanostructured by a specific technique of severe plastic deformation. It is bioinert, does not contain potentially toxic or allergic additives, and has higher specific strength properties than any other titanium applied in medical implants. The higher strength properties associated to the higher biocompatibility make nTi potentially useful for orthodontic mini-implant applications, theoretically overcoming cpTi and Ti-6Al-4 V mini-implants. The purposes of the this work were to process nTi, to mechanically compare cpTi, Ti-6Al-4 V, and nTi mini-implants by torque test, and to evaluate both the surface morphology and the fracture surface characteristics of them by SEM. Torque test results showed significant increase in the maximum torque resistance of nTi mini-implants when compared to cpTi mini-implants, and no statistical difference between Ti-6Al-4 V and nTi mini-implants. SEM analysis demonstrated smooth surface morphology and transgranular fracture aspect for nTi mini-implants. Since nanostructured titanium mini-implants have mechanical properties comparable to titanium alloy mini-implants, and biocompatibility comparable to commercially pure titanium mini-implants, it is suggestive that nanostructured titanium can replace Ti-6Al-4 V alloy as the material base for mini-implants.     

Osseointegration behavior of novel Ti–Nb–Zr–Ta–Si alloy for dental implants: an in vivo study

This study aimed to evaluate the effects of Ti–Nb–Zr–Ta–Si alloy implants on mineral apposition rate and new BIC contact in rabbits. Twelve Ti–Nb–Zr–Ta–Si alloy implants were fabricated and placed into the right femur sites in six rabbits, and commercially pure titanium implants were used as controls in the left femur. Tetracycline and alizarin red were administered 3 weeks and 1 week before euthanization, respectively. At 4 weeks and 8 weeks after implantation, animals were euthanized, respectively. Surface characterization and implant-bone contact surface analysis were performed by using a scanning electron microscope and an energy dispersive X-ray detector. Mineral apposition rate was evaluated using a confocal laser scanning microscope. Toluidine blue staining was performed on undecalcified sections for histology and histomorphology evaluation. Scanning electron microscope and histomorphology observation revealed a direct contact between implants and bone of all groups. After a healing period of 4 weeks, Ti–Nb–Zr–Ta–Si alloy implants showed significantly higher mineral apposition rate compared to commercially pure titanium implants (P?<?0.05), whereas there was no significant difference between Ti–Nb–Zr–Ta–Si alloy implants and commercially pure titanium implants (P?>?0.05) at 8 weeks. No significant difference of bone-to-implant contact was observed between Ti–Nb–Zr–Ta–Si alloy implants and commercially pure titanium implants implants after a healing period of 4 weeks and 8 weeks. This study showed that Ti–Nb–Zr–Ta–Si alloy implants could establish a close direct contact comparedto commercially pure titanium implants implants, improved mineral matrix apposition rate, and may someday be an alternative as a material for dental implants.     

Microwave-hydrothermal process for the synthesis of rutile

The synthesis of pure rutile titanium dioxide is not an easy achievement, as the crystallization process generally leads to mixtures of two or even three phases; moreover the synthetic processes normally used by industry require harsh reaction conditions. We carried out the synthesis of titanium dioxide from an aqueous titanium tetrachloride solution under microwave irradiation in the reaction time range of 5-120 min. We mostly obtained mixtures of rutile and anatase, but obtained single-phase rutile after a 2-h treatment at 160 °C; transmission electron micrographs revealed well-dispersed spherical nanoparticles. We also investigated the effects of dilution and addition of a dispersant (polyvinylpyrrolidone) on phase crystallization and particle shape.     

Surface modification of titanium by hydrothermal treatment in Mg-containing solution and early osteoblast responses

Surface modification on titanium was carried out in order to improve its bioactivity. Pure titanium was hydrothermally treated in distilled water and 0.1 M MgCl₂ solutions at 200°C for 24 h. Surface morphology, roughness, wettability and chemical composition were characterized before and after treatment. Bovine serum albumin was used as model to study protein adsorption. MC3T3-E1 cells were cultured and initial cell attachment, morphology, proliferation were evaluated. After hydrothermal treatment, nano-sized precipitations were observed and samples showed superhydrophilicity. Magnesium (Mg) was immobilized into titanium surface by hydrothermal treatment. Protein adsorption was significantly increased on Mg-containing samples. Cell attachment was improved and cell spreading was enhanced on Mg-containing samples compared with untreated or those treated in distilled water. Increased early cellular attachment on the MgTi surface resulted in subsequent increase of number of proliferated cells. Hydrothermal treatment in MgCl₂ solution was expected to be an effective method to fabricate titanium implant with good bioactivity.     

Commercially pure titanium and Ti6AI4V implants with and without nitrogen-ion implantation: surface characterization and quantitative studies in rabbit cortical bone

Nitrogen-ion implantation is a surface modification of interest for biomedical materials. In this study screw-shaped commercially pure titanium and Ti6AI4V alloy implants were nitrogen-ion implanted and analysed by scanning electron microscopy (SEM) and scanning Auger electron spectroscopy (AES). The surface topography was essentially similar for treated and non-treated samples. AES survey spectra showed an incorporation of nitrogen into the surface of the nitrogen-ion treated commercially pure titanium and Ti6AI4V implants, as judged by the ratio between the intensities of the peaks at 390 and 420 eV. AES depth profiles revealed a similar oxide thickness (7.5 nm) for the nitrogen-ion implanted and the non-treated samples. In nitrogen-ion implanted screws nitrogen was detected up to depths of about 150 nm below the surface, with a maximum nitrogen concentration at about 50 nm. Light microscopic examination of the 10 m-thick ground sections 3 months after the insertion of nitrogen-ion implanted and non-treated commercially pure titanium and Ti6AI4V screws in the proximal tibial methaphysis of rabbits showed that bone filled a large portion of the area within the threads. A fibrous capsule was not observed. Light microscopic morphometry did not reveal any statistically significant differences in bone-metal contact or bone area within the threads of nitrogen-ion treated and non-treated implants. The mirror-image analysis showed that for all implants examined significantly more bone was present immediately outside than inside the threads. The results from this study indicate that nitrogen-ion implanted, screw-shaped, commercially pure titanium and Ti6AI4V implants heal as well in cortical bone as non-treated samples.     

Study on double-glow plasma niobium surface alloying of pure titanium

A niobium modified layer on a pure titanium surface was obtained by means of a double-glow plasma surface alloying technique. Microstructure and phases resident in the alloy layer were analyzed. The processing parameters and effects of cathode sputtering before the diffusion process were also studied. The results show that the surface niobium content in the modified layer is similar to that in the Ti-45Nb alloy, and decreases gradually from the surface into the underlying substrate. The oxidation behavior of the modified pure titanium at 900 °C was noticeably improved after the niobium alloying process. Characterization was performed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The oxidation mechanism is also discussed.