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PubMed2001

Stent coating with titanium-nitride-oxide for reduction of neointimal hyperplasia.

BACKGROUND: Coronary stents prevent constrictive arterial remodeling but stimulate neointimal hyperplasia. Stainless steel induces a metallic foreign body reaction, which is absent for titanium. The hypothesis of the present study was that titanium renders the stent surface biologically inert, with reduced platelet and fibrinogen binding. METHODS AND RESULTS: Twelve pigs were instrumented with a stainless steel and 2 titanium-nitride-oxide-coated stents (TiNOX 1, ceramic; TiNOX 2, metallic). Animals were restudied after 6 weeks. Histological specimens of stented segments were analyzed by digital morphometry. Platelet adhesion and fibrinogen binding studies were performed in the perfusion chamber. Under in vitro conditions, TiNOX 1 showed reduced platelet adhesion (65+/-3%) compared with TiNOX 2 (72+/-5%; P<0.05) and stainless steel (71+/-4%; P<0.05). Platelet adhesion 48 hours after incubation with human plasma, however, was not different between TiNOX 1 (17+/-3%) and 2 (15+/-3%) but was significantly higher with stainless steel (23+/-2%; P<0.05). Fibrinogen binding was significantly reduced with TiNOX 2 (54+/-3%) compared with TiNOX 1 (82+/-4%, P<0.05) or stainless steel (100%, P<0.05). Histomorphometry revealed a significantly larger neointimal area in stainless steel (2.61+/-1.12 mm(2)) than in TiNOX 1-coated (1.47+/-0.84 mm(2), P<0.02) or TiNOX 2-coated (1.39+/-0.93 mm(2), P<0.02) stents. The reductions were 44% and 47%, respectively. CONCLUSIONS: TiNOX coating significantly reduces neointimal hyperplasia in stainless steel stents. The antiproliferative effect was similar for both TiNOX coatings, suggesting that the electrochemical properties are more important for attenuation of neointimal proliferation than the observed differences in platelet adhesion and fibrinogen binding.

Alloys↗
PubMed1995

Hydroxyl radical production and lung injury in the rat following silica or titanium dioxide instillation in vivo.

The hydroxyl radical (.OH) is a highly reactive oxygen free radical that has been implicated as a cause of lung injury following exposure to silica and silicates. Despite evidence that silica generates .OH in vitro, there has been no previous demonstration of in vivo production of .OH after exposure to nonfibrous mineral oxide dusts. We tested the hypothesis that instillation of silica into rat lungs is associated with greater .OH production and acute lung inflammation in vivo relative to the instillation of a less toxic nonsilicate particle, titanium dioxide. The production of .OH in the lungs following dust instillation was measured using sodium salicylate as an .OH trap. Seven days after dust exposure, the rats were given intraperitoneal salicylate, the lungs isolated, and salicylate hydroxylation products (2,3- and 2,5-dihydroxybenzoic acid), reflecting .OH, were measured. There was significantly more 2,3-dihydroxybenzoic acid in silica-exposed lungs compared with lungs instilled with titanium dioxide. In addition, the instillation of silica into rat lungs in vivo was associated with a greater acute inflammatory response. We conclude that following in vivo exposure, silica stimulates greater .OH production relative to the less toxic particle, titanium dioxide. These differences in .OH generation correspond to disparities in acute lung inflammation.

Animals↗
PubMed2005

Vapor-phase photo-oxidation of methanol over nano-size titanium dioxide clusters dispersed in MCM-41 host material part 2: catalytic properties and surface transient species.

We report in this paper on the ultraviolet-assisted vapor-phase oxidation of methanol at room temperature, with the help of nano-size clusters of titanium dioxide dispersed in an MCM-41 silicate matrix. The surface species formed during the adsorption/oxidation of methanol and the transformation that they undergo as a result of ultraviolet irradiation were monitored using in-situ Fourier transform infrared and thermal desorption spectroscopy techniques. Parallel experiments conducted on TiO2/MCM, bulk titania, and pristine MCM-41 samples helped in identifying the individual role of titanium dioxide and host matrix in these processes. The photo-catalytic oxidation of methanol, at concentrations of 0.1 to 1.1 mol% in air, gave rise to formation of CO2 and H2O as products, for both the TiO2/MCM and bulk TiO2 samples. No such reaction occurred on titania-free MCM. Furthermore, the rate of reaction depended upon the TiO2 content of a sample and also on the concentration of methanol in reaction mixture. Thus, the rate of conversion increased progressively with the increase in TiO2 loading from 5 to 21 wt% in TiO2/MCM samples, particularly for the experiments with high concentration of methanol. For low methanol concentration (0.1 mol%) in air, the effect of titania content in MCM was very small. The specific activity (per g of titania) of a sample, on the other hand, showed an inverse relationship with the loading of titanium dioxide in a sample. Infrared and temperature-programmed desorption results revealed that the mode of CH3OH adsorption and the reactivity of the transient species formed during the oxidation process were independent of the size of dispersed titania particles. Thus, the particles of approximately 2-6 nm size, present in TiO2/MCM, exhibited a chemisorption behavior similar to that of the bulk titania. The results of the present study provide strong evidence that the hydroxyl groups, both on the host matrix and at the titania sites, participate independently in the formation of methoxyl groups and at the same time promote the heterogeneous photo-catalytic oxidation of methanol molecules via formation of transient formate groups. Our results also show that the effect of titania crystallite size in the photo-catalytic properties relate mainly to the larger surface area and hence to the enhanced number of chemisorption sites, rather than to the changes in electronic properties.

Catalysis↗
PubMed1990

Adhesive bonding of titanium with a titanate coupler and 4-META/MMA-TBB opaque resin.

Adhesive bonding of titanium was evaluated with a titanate primer and adhesive opaque resin. The primer consisted of 2% isopropyl dimethacryloyl isostearoyl titanate in methyl methacrylate. The adhesive was 4-META/MMA-TBB opaque resin that contained 4-methacryloyloxyethyl trimellitate anhydride and was initiated by tri-n-butylborane derivative. Titanium discs were machined and blasted with aluminum oxide. They were primed and bonded together with the opaque resin. A shear test was performed after repeated thermocycles for investigation of the durability of the bond. The shear strength of the primed and 4-META resin-bonded specimens was 37.2 MPa after 50,000 thermocycles, with only a small decrease in bond strength. This was significantly higher than the control values. Thus, titanate primer and 4-META/MMA-TBB opaque resin may be used for the bonding of titanium in prosthodontic practice.

Acrylates↗
PubMed1995

Bacterial colonization on titanium, hydroxyapatite, and amalgam surfaces in vivo.

A study was conducted to evaluate qualitative and quantitative differences in bacterial colonization on titanium, hydroxyapatite, and amalgam surfaces in vivo. Six healthy adult individuals participated in the study. Two pieces each of titanium, hydroxyapatite, and amalgam of similar size were placed in cobalt-chromium splints and kept intra-orally in each individual for 10 min, and 1, 3, 6, 24, and 72 hrs. After removal of the splints, the pieces were rinsed in PBS and transferred to transport medium. After being vortexed, the samples were inoculated on selective and non-selective media for analyses of various facultative and anaerobic bacteria. During the experiment, total viable count increased on all surfaces. The investigated bacterial groups constituted, on average, approximately 60 to 99% of the total viable count on all three types of surfaces in each of the experiments, except in the 10-minute samples, when they constituted around 20 to 30%. Various streptococcal species predominated and usually constituted > 50% of total viable count. Similar colonization patterns of Streptococcus spp., Actinomyces naeslundii, Neisseria spp., Hemophilus parainfluenzae, Fusobacterium spp., and black-pigmented Prevotella spp. were seen at all three types of surfaces. No significant differences among the materials regarding colonization of investigated bacteria were found during the study period. This study failed to show any qualitative and quantitative differences in bacterial colonization among these materials. Titanium, hydroxyapatite, and amalgam do not seem to have a marked influence on the early colonization pattern in vivo.

Adult↗
PubMed2006

Biocompatibility of supercritical CO2-treated titanium implants in a rat model.

Supercritical phase CO2 is a promising method for sterilizing implantable devices and tissue grafts. The goal of this study is to evaluate the biocompatibility of titanium implants sterilized by supercritical phase CO2 in a rat subcutaneous implantation model. At 5 weeks post implantation titanium implants sterilized by supercritical phase CO2 produce a soft tissue reaction that is comparable to other methods of sterilization (steam autoclave, ultraviolet light radiation, ethylene oxide gas, and radio-frequency glow-discharge), as indicated by the thickness and density of the foreign body capsule, although there were some differences on the capillary density. Overall the soft tissue response to the implants was similar among all methods of sterilization, indicating supercritical phase CO2 treatment did not compromise the biocompatibility of the titanium implant.

Alloys↗
PubMed1985

Retention and tissue binding of titanium in the rat.

The fate of a soluble form of titanium (Ti) was studied in rats injected intraperitoneally with 1 microgram of Ti per rat as [44Ti]ammonium oxalotitanate (IV). After 16 h the Ti concentration in all tissues tested was of the order of 0.5 ng/g wet weight. After 19 days the Ti concentration increased in most tissues, especially in spleen, femur and kidney. By this time 55 ng had been excreted both via urine and faeces and the Ti concentration in blood plasma (mainly associated with plasma proteins) was three times lower than at 16 h postinjection. Chromatographic separation of the day 19 liver cytosol showed the ability of biological macromolecules to incorporate Ti compounds. Ti-labelled 'titanic acid' and 'titanium phosphate' showed low solubility which was, however, higher in human serum than in water and sodium chloride solution. The chromatographic profiles of plasma from incubated human blood in vitro with [44Ti]titanium oxalate showed the capacity of plasma proteins to complex Ti compounds. The results indicated that the long retention of Ti in the body may be due to its ability to form biocomplexes with cellular constituents.

Animals↗
PubMed2002

Non-constrained titanium-polyethylene total endoprosthesis in the treatment of hallux rigidus. A prospective clinical 2-year follow-up study.

BACKGROUND AND AIMS: To evaluate the outcome in a prospective 2-year follow-up study of a non-constrained titanium-polyethylene total endoprosthesis (ReFlexion) in the treatment of hallux rigidus. MATERIAL AND METHODS: Ten patients with painful hallux rigidus were treated with a non-constrained titanium-polyethylene total endoprosthesis (ReFlexion). The American Orthopaedic Foot and Ankle Society (AOFAS) scoring was used preoperatively and at follow-up. RESULTS: At 2-year follow-up, the AOFAS scoring shbwed 5 instances of excellent, 1 of good, 2 of fair, and 2 of poor outcome. Eight patient were subjectively satisfied and 2 dissatisfied. Five of the patients were painless, 4 had mild, occasional pain, and 1 had moderate, daily pain in the first metatarsophalangeal joint. The mean VAS was 7.6 (SD 2.0) preoperatively and 1.1 (SD 1.4) at 2-year follow-up (p < 0.001). Extension increased by a mean of 25 (13-38) degrees and flexion by a mean of 15 (2-35) degrees (p < 0.001). Eight patients had no activity limitations, while 1 had mild and 1 moderate limitations. Alignment of the metatarsophalangeal joint was good in 7 cases, but some degree of valgus malalignment was seen in 2 and symptomatic malalignment in 1. Complications included one subluxation of a prosthesis, one recurrence of severe valgus alignment and one superficial wound infection. Radiological loosening of one cementless phalangeal component was seen at follow-up. CONCLUSION: The non-constrained titanium-polyethylene total arthroplasty gave satisfactory 2-year outcome in 60% of the patients. It is an alternative treatment for hallux rigidus in low demand patients. We do not recommended it for athletes and young people, because high forces acting on the prosthesis may cause a failure.

Adult↗
PubMed2004

Antibacterial titanium plate anodized by being discharged in NaCl solution exhibits cell compatibility.

Implant surfaces should be modified to achieve excellent cell compatibility as well as antibacterial activity. Our previous study demonstrated that titanium plates anodized by being discharged in NaCl (Ti-Cl) exhibited high antibacterial activity. Since Ti-Cl was prepared with a NaCl solution, we hypothesized that Ti-Cl would exhibit low toxicity toward cells. The aims of this study were to characterize the surface of Ti-Cl and investigate the cell compatibility (MC3T3-E1 and L929 cells) of Ti-Cl. The results demonstrated that, since the TiCl(3) formed on the Ti-Cl surface was hydrolyzed into HCl, HClO, and TiOH after immersion in pure distilled water, TiCl(3) contributed to the antibacterial activity of Ti-Cl. On the other hand, TiO formed on the Ti-Cl surface enhanced cell extension and cell growth through a larger adsorption of fibronectin compared with the pure titanium control. These findings suggest that antibacterial titanium is a promising material for use in dental implant systems.

3T3 Cells↗
PubMed2005

Apatite/amelogenin coating on titanium promotes osteogenic gene expression.

Osteoblast differentiation and extracellular matrix production are pivotal processes for implant osseointegration or bone tissue engineering. We hypothesized that a biomimetic coating on titanium surfaces, consisting of apatite and amelogenin, would promote such processes. Human Embryonic Palatal Mesenchymal pre-osteoblasts were used as a model for the evaluation of cell adhesion and spreading patterns, as well as mRNA expression of certain osteoblastic gene products. Real-time PCR showed significant (p < 0.05) increase in expression of type I collagen, alkaline phosphatase, and osteocalcin from cells grown on titanium with an apatite/amelogenin composite, as compared with that from cells grown on a pure titanium or apatite coating only. Osteocalcin expression was specifically stimulated by amelogenin added to the culture media. Enhanced attachment and cell spreading were also observed. The biomimetic coating promoting cell adhesion and osteoblast differentiation may have great potential for future dental and biomedical applications.

Alkaline Phosphatase↗
PubMed2004

Endurance of aneurysm clips: mechanical endurance of Yaşargil and Spetzler titanium aneurysm clips.

OBJECTIVE: To determine whether repeated use weakens titanium aneurysm clips, making them unsafe for clinical use. METHODS: Nine Yaşargil (titanium alloy) and five Spetzler (pure titanium) clips were subjected to clinically relevant maneuvers, and the effects on the closing force were assessed. Clips were considered unsafe if 1) the blades crossed, 2) the clips failed to close completely, or 3) the blood pressure could open them. RESULTS: Yaşargil and Spetzler clips significantly (P < 0.01 for both) weakened, by 18.9% and 26.1%, respectively, after 10 minutes of sustained maximal opening. After 100 open-close cycles, Spetzler clips showed no change in closing force, but the closing force of Yaşargil clips decreased significantly (P < 0.01), by a further 12.0%. CONCLUSION: Repeated use weakens Spetzler and Yaşargil clips. All Spetzler and all but one Yaşargil clips were deemed safe for clinical use at the end of the experiments.

Alloys↗
PubMed2005

Titanium cage-assisted polymethylmethacrylate reconstruction for cervical spinal metastasis: technical note.

OBJECTIVE: Reconstruction and stabilization of the cervical spine after vertebrectomy is an important goal in the surgical management of spinal metastasis. The authors describe their reconstruction technique using a titanium cage-Silastic tube construct injected with polymethylmethacrylate (PMMA) augmented by an anterior cervical plate. The surgical results using this technique are reviewed. METHODS: Six patients ranging from 43 to 70 years of age underwent resection of metastatic tumor in the cervical spine followed by cage-assisted PMMA reconstruction of the anterior spinal column. The following reconstruction technique was performed. A Silastic tube is incised longitudinally and placed circumferentially around a titanium cage with the opening facing anteriorly. The cage-Silastic tube construct is carefully tapped into the corpectomy defect and filled with PMMA. The final construct is then augmented with anterior cervical plate fixation. RESULTS: Two patients required additional posterior stabilization with lateral mass screws and rods. All patients achieved immediate stabilization, restoration of vertebral body height and normal lordosis, and preservation of the ability to walk independently. Five patients experienced significant palliation of biomechanical neck pain. There were no complications of neurological worsening, postoperative hematoma, wound infection, subsidence, graft dislodgement, or construct failure during a follow-up period of 1 to 19 months (mean, 6.8 mo). CONCLUSION: Titanium cage-assisted PMMA reconstruction augmented with an anterior cervical plate is an effective means of reconstruction after tumor resection in patients with cervical spinal metastasis. The Silastic tube holds the PMMA within the cage and protects the spinal cord from potential thermal injury.

Adult↗
PubMed2003

Radiation absorbed doses at compact bone-titanium interfaces in diagnostic radiography: a Monte Carlo approach.

OBJECTIVES: The aim of this study was to estimate the radiation absorbed dose at cortical tissue-implant interfaces in diagnostic radiology. METHODS: Since our interest was the radiation dose at an interface (cortical bone-implant interface), a Monte Carlo simulation was considered to be the most suitable method for studying the problem. The Monte Carlo code employed was MCNP4B. A phantom consisting of soft tissue, cortical bone, an implant and air, with appropriate chemical compositions and densities, was described in the code. The implant simulated had a commercial name of ASTM67, grade 2 and was 1.9 mm wide. The incident photon beam was divergent of 20 cm x 20 cm at a source-to-phantom distance of 40 cm. Two energy spectra were employed (70 kVp and 100 kVp, 0.5 mm Al internal filtration) and their photon fluence distribution against energy was described in the code with an energy interval of 5 keV. The computations that led to radiation dose calculations had a spatial resolution of 0.01 cm (100 microm) to allow a detailed radiation dose distribution across the cortical bone-titanium interface. Monte Carlo runs took place both with and without an implant in the phantom and, in each case, 120 million photon histories were followed, leading to a radiation dose statistical fluctuation between 5% and 10%. RESULTS: The ratio of radiation dose with implant to dose without implant against depth allows a direct estimate of the effect of the implant on the radiation dose to the cortical bone surrounding the implant. At a distance >or=100 microm there was no radiation dose increase due to the titanium implant. However, in contact with the implant (i.e. the first layers of cells) there was a sharp radiation dose increase as high as 3.5 times the radiation dose compared with when the implant was absent. Also, the newly formed bone inside the implant's tiny hole received a radiation dose close to 50% of the radiation dose without the implant owing to high absorption by the implant itself. CONCLUSIONS: Assuming that the patient received five radiographic images over a 6-month period, the maximum radiation dose at the cortical bone-titanium interface was estimated to be less than 20 mGy (0.02 Gy).

Absorption↗
PubMed1998

Anti-inflammatory properties of titanium in the joint environment. An experimental study in rats.

Little is known about the tissue reactions to various implant materials which coincide with an inflammatory reaction. We used the avridine arthritis rat model to evaluate the tissue response in the synovial, interstitial and subcutaneous tissues after implant insertion. Quantitative immunohistochemistry showed that normal joint synovial tissue is dominated by ED2-positive resident macrophages. Polyethylene implants induced a much stronger foreign-body reaction than titanium implants, as measured by the number of interfacial ED1-positive macrophages. The tissue response to titanium and polyethylene was also vastly different in arthritic synovial tissue compared with control tissue. It is likely that these biomaterials interact differently with inflammatory cells or intermediary compounds. It may be that arthritic synovial tissue produces reactive oxygen intermediates (free radicals) with which titanium has a unique anti-inflammatory interaction in vitro.

Abdominal Muscles↗
PubMed2003

Microvascular response of striated muscle to metal debris. A comparative in vivo study with titanium and stainless steel.

Wear products of metal implants are known to induce biological events which may have profound consequences for the microcirculation of skeletal muscle. Using the skinfold chamber model and intravital microscopy we assessed microcirculatory parameters in skeletal muscle after confrontation with titanium and stainless-steel wear debris, comparing the results with those of bulk materials. Implantation of stainless-steel bulk and debris led to a distinct activation of leukocytes combined with a disruption of the microvascular endothelial integrity and massive leukocyte extravasation. While animals with bulk stainless steel showed a tendency to recuperation, stainless-steel wear debris induced such severe inflammation and massive oedema that the microcirculation broke down within 24 hours after implantation. Titanium bulk caused only a transient increase in leukocyte-endothelial cell interaction within the first 120 minutes and no significant change in macromolecular leakage, leukocyte extravasation or venular diameter. Titanium wear debris produced a markedly lower inflammatory reaction than stainless-steel bulk, indicating that a general benefit of bulk versus debris could not be claimed. Depending on its constituents, wear debris is capable of eliciting acute inflammation which may result in endothelial damage and subsequent failure of microperfusion. Our results indicate that not only the bulk properties of orthopaedic implants but also the microcirculatory implications of inevitable wear debris play a pivotal role in determining the biocompatibility of an implant.

Animals↗
PubMed2004

Corrosion of cemented titanium femoral stems.

Cemented titanium stems in hip arthroplasty are associated with proximal cement-stem ebonding and early failure. This was well publicised with the 3M Capital hip. However, corrosion in this setting has been reported with only one stem design and is less widely accepted. We present a series of 12 cemented titanium Furlong Straight Stems which required revision at a mean of 78 months for thigh pain. At revision the stems were severely corroded in a pattern which was typical of crevice corrosion. Symptoms were eliminated after revision to an all-stainless steel femoral prosthesis of the same design. We discuss the likely causes for the corrosion. The combination of a titanium stem and cement appears to facilitate crevice corrosion.

Aged↗
PubMed2005

The effect of bisphosphonates and titanium particles on osteoblasts: an in vitro study.

In an attempt to increase the life of cementless prostheses, an hydroxyapatite-coated implant which releases a bisphosphonate has been suggested as a drug-delivery system. Our in vitro study was designed to determine the maximum dose to which osteoblasts could be safely exposed. Our findings demonstrated that zoledronate did not impair the proliferation of human osteoblasts when used at concentrations below 1 microm. Murine cells can be exposed to concentrations as high as 10 microm.A concentration of 0.01% of titanium particles did not impair the proliferation of either cell line. Zoledronate affected the alkaline phosphatase activity of murine osteoblasts through a chelation phenomenon. The presence of titanium particles strongly decreased the alkaline phosphatase activity of murine osteoblasts. We did not detect any synergic effect of zoledronate and titanium particles on the behaviour of both human and murine osteoblasts.

Alkaline Phosphatase↗
PubMed2006

Urinary and serum titanium: assessment as an indicator of exposure to ammonium citratoperoxotitanate (IV) and its influence on renal function.

Ammonium citratoperoxotitanate IV (TAS-FINE) is a water-soluble titanium complex used to synthesize a photocatalytic titanium(IV) oxide film. This study was aimed to investigate the LD50, dose-response, time-course response, and renal toxicity of TAS-FINE using an animal model. Serum titanium (S-Ti) and its 24-h urinary excretion (U-Ti) were determined by inductively coupled plasma-argon emission spectrometry (ICPAES) after a single oral TAS-FINE administration to male Wistar rats. The LD50 of TAS-FINE was 7.97 g/kg body weight in 24 h, and its half-life was 3.78+/-1.28 d for S-Ti and 2.19+/-0.09 d for U-Ti. Although TAS-FINE was not easily absorbed in the gastrointestinal tract, it was distributed into the bloodstream in a dose-dependent manner. Within 24 h, 0.189% of administrated Ti was excreted via urine. It was speculated that TAS-FINE formed conjugates with serum constituents that resulted in nephrotoxicity resulting from an allergic reaction. The observed indices in this study were revealed to be good indicators for TAS-FINE exposure. The analytical method and animal model described in this study will help to further elucidate details about human exposure to TAS-FINE, which in recent times has become an occupational and environmental toxicant of concern.

Acetylglucosaminidase↗