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PubMed2005

Electrochemical corrosion and metal ion release from Co-Cr-Mo prosthesis with titanium plasma spray coating.

The corrosion behavior of CoCrMo implants with rough titanium coatings, applied by different suppliers by either sintering or vacuum plasma spraying, has been evaluated and compared with uncoated material. The open-circuit potential, corrosion current and polarization resistance were determined by electrochemical techniques. The Co, Cr and Ti ions released from the samples into the electrolyte during a potentiostatic extraction technique were analyzed using ICP-MS. The Ti coatings from the different suppliers showed a different porous morphology, and the implants exhibited a distinct corrosion activity, underlining the importance of the coating process parameters. Among the titanium coated samples, the one with the sintered overcoat turned out to be the most resistant. Yet, on an absolute scale, they all showed a corrosion resistance inferior to that of uncoated CoCrMo or wrought titanium.

Biocompatible Materials↗

PubMed2002

Interface-mediated synthesis of hydroxyapatite.

Interfacing of water vapor and titanium was employed for a controlled synthesis of surface-supported hydroxyapatite. In this approach, a Ti surface was doped with Ca and P by ion implantation and then subjected to a hydrothermal treatment in a water vapor autoclave. Ion implantation served to prepare a reactive blend of finely dispersed reactants in a stoichiometric ratio incorporated within the network of an outermost layer of the substrate surface. Needle-like carbonate hydroxyapatite in an overlay was identified to deposit onto the surface. The results suggest interface-mediated thin film formation and phase transformation.

Biocompatible Materials↗

PubMed2005

Crystallographic texture for tube and plate of the superelastic/shape-memory alloy Nitinol used for endovascular stents.

The superelastic/shape-memory material, Nitinol, an approximately equiatomic alloy of Ni and Ti, is rapidly becoming one of the most important metallic implant materials in the biomedical industry, in particular for the manufacture of endovascular stents. As such stents are invariably laser-machined from Nitinol tubes or sheets rolled into tubes, it is important to fully understand the physical phenomena that may affect the mechanical behavior of this material. With tubing and plate, one major issue is crystallographic texture, which can play a key role in influencing the mechanical properties of Nitinol. In this article, we present a study on how geometry and heat treatment can affect the texture of Nitinol, with specific quantification of the texture of Nitinol tube used for the production of endovascular stents.

Alloys↗

PubMed2001

Platelet interactions with titanium: modulation of platelet activity by surface topography.

Endosseous implants initially come into contact with blood. Thus, the nature of the interactions between blood and implanted endosseous implants may influence subsequent bone healing events in the peri-implant healing compartment. We conducted studies to address the following question: Does implant surface microtexture modulate platelet activity? We used commercially pure Ti (cpTi) disks with four different surface finishes: dual acid-etched (DAE), 320 grit (320G) abraded, machined, and p1200 polished cpTi. Surfaces were characterized by scanning electron microscopy (SEM) and optical profilometry. The DAE and 320G surfaces presented more complex microtextures than the machined or polished surfaces. Platelet activities were measured by quantifying platelet adherence, platelet-derived microparticle (MP) formation, and P-selectin expression as function of surface type. Platelet adhesion, measured using a lactate dehydrogenase (LDH) assay. was increased on DAE and 320G surfaces compared to machined and polished surfaces (p < 0.05). M P formation and P-selectin expression, assayed by flow cytometry, also showed increased activation of platelets on DAE and 320G surfaces. Because increased activation of platelets may lead to up-regulation of osteogenic responses during bone healing, these results may explain the enhanced osteoconductivity known to occur with DAE cpTi surfaces in comparison with machined cpTi surfaces.

Blood Platelets↗

PubMed1986

Mechanical properties of porous metal total hip prostheses.

The forged condition is the strongest form of the Co-Cr-Mo and Ti-6Al-4V alloys used in orthopaedics. Both the Co-Cr-Mo alloy and the Ti-6Al-4V alloy lose strength when incorporated into porous implants. The strength loss in the Co-Cr-Mo alloy is a generalized condition and is largely a result of the microstructure of these cast and then gravity-sintered prostheses. The greatest fatigue strength achieved throughout these porous Co-Cr-Mo implants is that of the cast alloy. The strength loss in diffusion-bonded, porous titanium-alloyed implants is largely a result of notch sensitivity. This strength loss is not a generalized condition; it is localized on the implant to regions of porous coating attachment. In implant regions apart from the porous coatings, these titanium implants can have the strength of other wrought or forged titanium alloy implants. To achieve a functionally strong implant, porous implant design needs to account for these losses in material strength. Implant strength should be verified experimentally and communicated to the orthopaedic surgeon for assessment of implant adequacy for a particular patient. Patient weight, activity, and life expectancy are important elements in judging the adequacy of an implant's strength.

Alloys↗

PubMed1998

Evaluation of platelet adhesion and activation on materials for an implantable centrifugal blood pump.

A totally implantable centrifugal artificial heart has been developed in which a pivot bearing supported centrifugal pump is used as a blood pump. The following have been adopted as blood contacting materials in our pump: titanium alloy (Ti-6A1-4V) for the housing and impeller, alumina ceramic (Al2O3) for the male pivots, and ultrahigh molecular weight polyethylene (PE) for the female pivots. Greater antithrombogenicity is required for an implantable blood pump. To examine the thrombogenicity of these materials, we evaluated in vitro platelet adhesion and activation, which may play key roles in thrombogenesis on foreign surfaces. Ti-6A1-4V, Al2O3, and PE were compared with polycarbonate (PC), silicone carbide (SiC), and pure titanium (pTi). Platelet adhesion was assessed using monoclonal antibody (CD61) directed against glycoprotein IIIa. Platelet activation was evaluated by measuring P-selectin (GMP-140) released from irreversibly activated platelets. Each material with a surface area of 16.6 cm2 was incubated with 2.5 ml of plasma or 2.5 ml of heparinized fresh whole blood for 3 h at 37 degrees C. The optical density (OD) at a wavelength of 450 nm for CD61 was 0.93+/-0.35 in PC, 0.34+/-0.13 in PE, 0.27+/-0.13 in pTi, 0.26+/-0.01 in Al2O3, 0.21+/-0.04 in SiC, and 0.12+/-0.12 in Ti-6A1-4V. The GMP-140 levels of the tested materials were not significantly different from the control value (45.9+/-7.2 ng/ml). These results indicate that Al2O3, PE, and Ti-6A1-4V, which are incorporated into our implantable centrifugal pump, have satisfactory antithrombogenic properties in terms of platelet adhesion. However, platelet activation by any material was not observed under the static condition in this study.

Alloys↗

PubMed1993

Inflammatory reaction of rat striated muscle to particles of carbon fiber reinforced carbon.

1. Carbon fiber reinforced carbon (CFRC) was implanted in rats as particles measuring 30 microns or 11 microns, denoted as CFRC-A and CFRC-B, respectively. Titanium (Ti) and vitreous carbon (VC) were used as controls. Ti was used with the same particle size as CFRC (Ti-A or Ti-B). The VC particles measured 11 microns. All materials were separately sterilized on ethylene oxide before use. 2. One hundred and ten female Wistar rats, weighing 180 to 220 g, were divided into six groups of 4 to 5 animals each, according the time of the observation (1, 2, 4, 8, 16 and 52 weeks). 3. Under aseptic conditions, one 3-0 curette full of CFRC-A or CFRC-B was implanted into the right triceps surae muscle in each animal and the same quantity of Ti-A (paired with CFRC-A) or Ti-B or VC (paired with CFRC-B) was implanted into the left muscle. 4. Histological analysis did not show necrosis of muscular tissue nor exudative reaction during the acute phase. 5. During the chronic phase the particles induced a chronic inflammatory infiltration containing fibroblasts, macrophages and giant cells. VC and CFRC-B induced the lowest inflammatory infiltration and CFRC-A induced the highest one. 6. We suggest that the longer carbon fiber fragments contained in CFRC-A may be responsible for this more intensive reaction, which may restrict the medical use of the preparation.

Animals↗

PubMed2003

[Analysis of clinical application for various types of esophageal stents made in China].

BACKGROUND & OBJECTIVE: Dysphagia is the main clinical symptom of the patients with esophageal carcinoma. The stent placement in esophagus is an effective method to resolve dysphagia.There are many types of stents. Through comparing observation of the stents made in China, which is the stainless steel "Z" stent, the Ni-Ti wire mesh-like stent, and the covered or uncovered-stent, the authors analyzed the clinical application of various types of esophageal stents in the treatment of malignant esophageal stricture. METHODS: The various types of esophageal stents were implanted into 40 patients with esophageal carcinoma. 13 cases for stainless steel "Z" stents, 27 cases for Ni-Ti wire mesh-like stents(24 cases were the covered stents and 16 cases were uncovered). All the patients were not operated with the dilation of balloon before stent placement. RESULTS: The esophageal stents were successfully implanted into 40 patients without complication of operation. Stainless steel "Z" stent were all dilated immediately at the time of operation, and all the 13 patients had obvious intra-breastbone pain after operation, which lasted 10-20 days. Although Ni-Ti wire mesh-like stents could not dilate completely in operation, all these can be dilated completely after 1 to 3 days; nine cases of them had obvious intra-breastbone pain, which lasted 3-5 days. In all these, 7 cases were the covered-stents and 2 cases uncovered. In 9 cases, tracheoesophageal fistulas were blocked completely. There was barium sulphate retention between the covered-stent implanted to the patients without tracheoesophageal fistula and the dilated esophagus. CONCLUSION: The clinical adaptability of the Ni-Ti wire mesh-like stent is better than that of the stainless steel "Z" stent. For the patients with tracheoesophageal fistula, the first choice is covered-stent, while for the patients without tracheoesophageal fistula, uncovered-stent is better. The dilation of balloon is not necessary before the stent placement.

Aged↗

PubMedDate not supplied

Histologic evaluation of bone-implant contact of immediately loaded transitional implants after 6 to 27 months.

PURPOSE: Transitional implants (TIs) were developed as a method of providing fixed provisional restorations for the implant patient who wishes to avoid removable temporary restorations during implant healing. Success of TIs depends on achieving sufficient osseointegrated bone-to-implant contact (BIC) during the provisional prosthesis phase. To date, little data are available on the degree of BIC of these implants in function. The purpose of this study was to histologically evaluate the BIC of TIs following various periods of loading. MATERIALS AND METHODS: Histologic analysis of 33 immediately loaded implants from 21 patients was performed. All TIs had turned machined surfaces and were made of commercially pure titanium (grade 1). These transitional implants were in function for an average of 10.8 months (range: 6 to 27 months). Before the definitive restoration was provided, all of the TIs were removed with trephine drills and sent for hard tissue histomorphometric analysis. RESULTS: The average percentage of BIC was 52.9% +/- 13.81% (range 25.1% to 83%). DISCUSSION: Although TIs are traditionally removed when the definitive implants are restored, the BIC and clinical integration of the TIs in the present study may suggest a change in TI protocol. Studies are indicated to examine long-term use of TIs as sole support or in conjunction with definitive implants in definitive implant-supported restorations. CONCLUSION: The percentage of BIC achieved with TIs was similar to that documented in the literature for conventional turned, machine-surfaced implants.

Dental Implantation, Endosseous↗

PubMed1989

[SEM observation of the interface between hydroxyapatite ceramic and metal compound implant materials].

This article described the results of interface between HAP ceramic and metal compound system when the bio-glass burning method was used with Scanning Electro-microscope (SEM). According to the results, the author concluded that as a method of forming compound implant system, bio-glass is a good vehicle between HAP and Co-Cr alloy; Ti alloy; and Ni-Cr alloy when the burning method was used.

Dental Alloys↗

PubMed1996

Preparation of bioactive Ti and its alloys via simple chemical surface treatment.

A simple chemical method was established for inducing bioactivity of Ti and its alloys. When pure Ti, Ti-6A1-4V, Ti-6A1-2Nb-Ta, and Ti-15Mo-5Zr-3A1 substrates were treated with 10M NaOH aqueous solution and subsequently heat-treated at 600 degrees C, a thin sodium titanate layer was formed on their surfaces. Thus, treated substrates formed a dense and uniform bonelike apatite layer on their surfaces in simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. This indicates that the alkali- and heat-treated metals bond to living bone through the bonelike apatite layer formed on their surfaces in the body. The apatite formation on the surfaces of Ti and its alloys was assumed to be induced by a hydrated titania which was formed by an ion exchange of the alkali ion in the alkali titanate layer and the hydronium ion in SBF. The resultant surface structure changed gradually from the outermost apatite layer to the inner Ti and its alloys through a hydrated titania and titanium oxide layers. This provides not only the strong bonding of the apatite layer to the substrates but also a uniform gradient of stress transfer from bone to the implants. The present chemical surface modification is therefore expected to allow the use the bioactive Ti and its alloys as artificial bones even under load-bearing conditions.

Alkalies↗

PubMed2002

A scanning electron microscopy study of human osteoblast morphology on five orthopedic metals.

Despite the long-standing use of metals as orthopedic implants there still are unsolved problems with these materials and open questions about their behavior in a biological environment. Cell-culture studies provide a useful tool for investigations. In addition to the determination of biochemical or molecular biological parameters, the morphology of adhering cells reflects their interaction with the substrata. This article describes an investigation of the morphology of human osteoblasts on stainless steel, cobalt chromium alloy, commercially pure titanium, Ti-6Al-4V, and Ti-6Al-7Nb with surface designs similar to those used as clinical implants. A cell culture plastic surface was used as a control material. The materials were examined by scanning electron microscopy at different points of time. The cells spread, proliferated, and formed nodules on all test substrates in a time-dependent manner, without signs of a disturbing influence from any of the materials. On the smooth surfaces the cells showed a flattened fibroblast-like morphology and only slight differences could be detected. Therefore, the cellular morphology seems not to be markedly affected by the different chemical material compositions. In contrast, the titanium alloy with a rough, sandblasted surface induced a three-dimensional growth. This three-dimensional cellular network could be the basis for the known earlier differentiation of osteoblasts on rough surfaces in vitro and a better osseointegration in vivo.

Bone Substitutes↗

PubMed2001

Notch sensitivity of titanium alloy, commercially pure titanium, and stainless steel spinal implants.

STUDY DESIGN: This is a biomechanical study comparing the fatigue life of stainless steel (SS), titanium alloy (TI), and commercially pure titanium (CP) rods that were notched using techniques essential to spine surgery. OBJECTIVES: To show the difference in fatigue life of the three rods and the effect on fatigue life of marks caused by techniques unavoidable in spine surgery. SUMMARY OF BACKGROUND DATA: Past studies have shown a decrease in the fatigue life of titanium when there is a defect or notch in the surface. This has been demonstrated with spinal and fracture implants, prosthetic joints, and in the materials science literature. Previous authors have recommended avoidance of techniques that mark the surface of titanium implants. METHODS: Four Texas Scottish Rite Hospital rods of each metal were prepared in four different ways: 1) no notch, 2) a French bender notch, 3) a top-loading connector--left on, 4) a top-loading connector--removed. The rods were fatigued in four point bending up to 1 million cycles. Before fatigue testing, two samples of each preparation were examined with electron microscopy. RESULTS: No SS rods failed. No TI rods without a notch or connector removed failed. One TI rod with the connector left in place failed (106,635 cycles). Three of the TI rods in the French-bender group failed (average, 87,663 cycles). One CP rod without a notch failed (358,957 cycles). No CP rods with the connector left in place failed. All CP rods with the connector removed failed (average, 230,094 cycles). All CP rods in the French bender group failed (average 120,817 cycles). The following differences were significant (P < 0.05): SS-TI and SS-CP in the French bender group; SS-CP and TI-CP in the connector removed group. Electron micrographs performed before fatigue testing showed cracks in the TI and CP rods that were marked with the French bender. CONCLUSION: Caution is recommended when bending TI or CP rods, or placing a connector and removing it when using CP rods in situations in which fatigue failure is a concern.

Alloys↗

PubMed1980

An electrophysiological analysis of sleep and respiration of rats breathing different gas mixtures: diaphragmatic muscle function.

The effects of breathing 21% O2, 21% O2 + 5% CO2, 10% O2 + 4% CO2 and 10% O2 on the sleep-waking rhythm, respiratory rate, diaphragmatic EMG, inspiratory (Ti) and expiratory (Te) times were studied in rats. They carried chronically implanted electrodes to permit polygraphic recordings of the ECoG, EOG and dorsal neck and integrated diaphragmatic EMG activity. Average respiratory rates, independent of state of consciousness varied depending on the gas mixture breathed. Sleep-waking times, expressed as percentages, were determined as a function of the gas mixture breathed. Oxygen deficiency caused PS deprivation which was partially alleviated by the addition of 4% CO2. Diaphragmatic EMG activity decreased during PS when rats breathed gas mixtures rich in CO2 but increased when they breathed 10% O2. In general, at a given frequency of breathing, Ti was shorter during PS than during SWS except when rats breathed 10% O2. It is concluded that: (1) regardless of the state of consciousness hypoxia is a more potent stimulus of respiratory rate than hypercapnia, (2) diaphragmatic effort is reduced when rats breathe CO2 enriched gas mixtures but is increased by hypoxia due to changes in upper airway resistance, and (3) low O2 content of an inspired gas disrupts the inspiratory and expiratory off-switch mechanisms, this disruption being prevented by the addition of CO2.

Animals↗

PubMed2002

Quantitation of platelet adhesion to Ti and DLC-coated Ti in vitro using (125)I-labeled platelets.

Measurement of platelet adhesion in vitro is a good indicator of its reactivity to implant devices in vivo. Platelets were labeled with I-125 without affecting its normal morphology and function and the labeled platelets were suspended in platelet poor plasma and exposed to Ti and diamond like carbon-coated (DLC) Ti discs, under dynamic conditions, using a parallel plate flow chamber. The test materials were washed, dried, exposed to a phosphor screen and scanned to get the images. The number of platelets that adhered to Ti was found to be higher than those that adhered to DLC coated Ti sample, irrespective of the shear stress which was varied between 2 and 16 dynes/cm(2).

Blood Platelets↗

PubMed1997

Biochemical surface modification of Ti-6Al-4V for the delivery of protein to the cell-biomaterial interface.

Biochemical surface modification involves delivery of biomolecules to the tissue-implant interface to induce desired cell and tissue responses. We have previously had success in immobilizing and retaining bioactive molecules on Co-Cr-Mo but not on Ti-6Al-4V. The purpose of this study was to modify the gamma-aminopropyltriethoxysilane (APS) scheme to enable successful attachment of protein to the surface of Ti-6Al-4V. Ti-6Al-4V samples were silanized with organic (acetone) solutions of APS and dried at increasing temperatures. Concentrations resulting in 2-4 NH2 per nm2 of nominal surface area were incubated in physiological saline for up to 96 hr to assess retention of amino groups. A model protein, trypsin, was coupled to silanized Ti-6Al-4V via glutaraldehyde. The samples were then incubated in saline, and the activity of residual immobilized enzyme was quantified. After drying at 45, 80, or 115 degrees C, the NH2 groups were lost from the surface by 24 hr of incubation in saline. On samples dried at 150 degrees C, with 4% APS, the number of NH2 groups increased after 8 hr and remained relatively constant through 96 hr. Likewise, at 150 degrees C with 2% APS the surface density of NH2 groups reached a maximum at 24 hr and remained relatively constant up to 96 hr. When incubated for 96 hr, Ti-6Al-4V with 4% APS and dried at 150 degrees C retained approximately 31% of the activity initially immobilized, whereas protein on 45 degrees C or adsorbed samples was lost by 24-48 hr.

Alloys↗

PubMed1997

Study on plasma-spraying coating bioactive ceramics onto silicon nitride surface as composite endosteal implants.

The successful key of endosteal implants depends on the properties of implant materials which are very important for oral implantology at the present. Because silicon nitride has high strength and hydroxylapatite (HA) and flourapatite (FA) have good biocompatibility. In this paper, we apply silicon nitride as base material. Plasma spray HA, FA onto its surface as composite endosteal implants. Physical and chemical properties test, includes X-ray diffraction (XRD), scanning electronic microscope (SEM), EDAX and bonding strength test (push-out test). The results indicate: after plasma-spraying coating, crystalline phase of HA and FA unchanged and form a lot of pores among the crystal particles. Those pores benefit bone growing into them. It is very important for implants to be fixed in bone for long time, Ca/P ratio has no significant change. Bonding strength test results indicate: Si3N4-HA 23.6MPa, Si3N4-FA 27.12 MPa are higher than that of Ti-HA 15.07 MPa. On the basis of these studies, they are kinds of ideal implant materials.

Apatites↗

PubMed1996

Effect of titanium surface roughness on chondrocyte proliferation, matrix production, and differentiation depends on the state of cell maturation.

Although it is well accepted that implant success is dependent on various surface properties, little is known about the effect of surface roughness on cell metabolism or differentiation, or whether the effects vary with the maturational state of the cells interacting with the implant. In the current study, we examined the effect of titanium (Ti) surface roughness on chondrocyte proliferation, differentiation, and matrix synthesis using cells derived from known stages of endochondral development. Chondrocytes derived from the resting zone (RCs) and growth zone (GCs) of rat costochondral cartilage were cultured on Ti disks that were prepared as follows: HF-HNO3-treated and washed (PT); PT-treated and electropolished (EP); fine sand-blasted, HCl-H2SO4-etched, and washed (FA); coarse sand-blasted, HCl-H2SO4-etched, and washed (CA); or Ti plasma-sprayed (TPS). Based on surface analysis, the Ti surfaces were ranked from smoothest to roughest: EP, PT, FA, CA, and TPS. Cell proliferation was assessed by cell number and [3H]-thymidine incorporation, and RNA synthesis was assessed by [3H]-uridine incorporation. Differentiation was determined by alkaline phosphatase specific activity (AL-Pase). Matrix production was measured by [3H]-proline incorporation into collagenase-digestible (CDP) and noncollagenase-digestible (NCP) protein and by [35S]-sulfate incorporation into proteoglycan. GCs required two trypsinizations for complete removal from the culture disks; the number of cells released by the first trypsinization was generally decreased with increasing surface roughness while that released by the second trypsinization was increased. In RC cultures, cell number was similarly decreased on the rougher surfaces; only minimal numbers of RCs were released by a second trypsinization. [3H]-thymidine incorporation by RCs decreased with increasing surface roughness while that by GCs was increased. [3H]-Uridine incorporation by both GCs and RCs was greater on rough surfaces. Conversely, ALPase in the cell layer and isolated cells of both cell types was significantly decreased. GC CDP and NCP production was significantly decreased on rough surfaces while CDP production by RC cells was significantly decreased on smooth surfaces. [35S]-sulfate incorporation by RCs and GCs was decreased on all surfaces compared to tissue culture plastic. The results of this study indicate that surface roughness affects chondrocyte proliferation, differentiation, and matrix synthesis, and that this regulation is cell maturation dependent.

Animals↗