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At least 667 records · Page 37Linked to original sources
PubMed1994

Complex asparagine-linked oligosaccharides are required for morphogenic events during post-implantation development.

Complex asparagine (N)-linked oligosaccharides appear late in phylogeny and are highly regulated in vertebrates. Variations in these structures are found on the majority of cell-surface and secreted proteins. Complex N-linked oligosaccharide biosynthesis is initiated in the Golgi apparatus by the action of Mgat-1-encoded UDP-N-acetylglucosamine:alpha-3-D- mannoside beta-1,2-N-acetylglucosaminyltransferase I (GlcNAc-TI). To determine if these structures govern ontogenic processes in mammals, mouse embryos were generated that lacked a functional Mgat-1 gene. Inactivation of both Mgat-1 alleles produced deficiencies in GlcNAc-TI activity and complex N-linked oligosaccharides. Embryonic lethality occurred by day 10.5, thus establishing that complex N-linked oligosaccharides are required during post-implantation development. Remarkably, embryonic development proceeded into day 9 with the differentiation of multiple cell types. Complex N-linked oligosaccharides are important for morphogenic processes as neural tube formation, vascularization and the determination of left-right body plan asymmetry were impaired in the absence of a functional Mgat-1 gene.

Animals↗
PubMed2006

Titanium implant osseointegration with calcium pyrophosphate in rabbits.

The objective of this study was to characterize calcium pyrophosphate material, evaluate its in vitro cytotoxicity, and assess its ability to induce bone formation. X-ray diffraction (XRD) was used to determine crystallinity and phases present in material. Serial dilutions of extracts, from 10-day dissolution tests in modified Eagle's medium, were exposed for 24 h to mouse fibroblasts and cytotoxicity assessed via viable staining. In vivo performance was determined by placing Ti screws with and without calcium pyrophosphate agglutinated with marrow adipose tissue in the tibiae of eight rabbits. New bone formation around test and control implants was evaluated histomorphometrically by using three fluorochrome labels: alizarin, calcein, and tetracycline. After 8 postoperative weeks, the animals were killed and specimens were retrieved and processed for fluorescence and light microscopic analysis. Calcium pyrophosphate showed no cytotoxicity and the XRD showed that the main phase of the analyzed sample corresponded to beta-calcium pyrophosphate. The largest fluorochrome labeling area occurred during the fourth and fifth postoperative weeks, in both control and experimental groups. Histologically, the bone neoformation occurred in regions where the calcium pyrophosphate was resorbed. The morphometric analysis showed implants placed with calcium pyrophosphate resulted in smaller polyfluorochrome labeling area (p < 0.05).

Animals↗
PubMed1995

[Animal experiment study of titanium with surface coatings of (Ti,Nb)ON and (Ti,Zr)O].

Titanium is considered to be biocompatible as long as the passive layer of TiO2 which is formed within the body, is not destroyed mechanically by the shearing forces acting on implants during function. Mechanically stable hard coatings on the basis of the so-called refractory metals render titanium wear-and-tear-resistant, with the added advantage for its biocompatibility of keeping its the physical and electrochemical properties constant, even in the event of relative movement against hard or soft tissue. Biological testing of coated and uncoated titanium in experimental animals shows that the deposition of new bone on (Ti,Zr)O or (Ti,Nb)ON surfaces takes place in the same way as on the surface of titanium.

Alloys↗
PubMed2001

Analytical characterization of collagen- and/or hydroxyapatite-modified polypyrrole films electrosynthesized on Ti-substrates for the development of new bioactive surfaces.

The design and development of new bioactive surfaces on titanium-based materials employed in orthopedic implants is described. The new biosurfaces consist of thin polypyrrole films, directly grown on implant materials and modified by the inclusion of hydroxyapatite and/or collagen during the polymer electrodeposition step. The experimental procedure has been optimized in terms of loading and distribution of the bioactive components. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) investigations have been performed in order to control the effectiveness of film modifications. In particular, XPS has been used to check the presence of biocompounds in the surface and sub-surface region of the polymer film, which is a critical requisite for a positive interface interaction between the biomaterial and the surrounding tissue.

Biocompatible Materials↗
PubMed1996

Use of p-nitrophenyl chloroformate chemistry to immobilize protein on orthopedic biomaterials.

Biochemical surface modification involves covalently immobilizing biomolecules onto biomaterial surfaces to induce specific biological responses. This approach may be useful for enhancing the fixation of orthopedic implants. p-Nitrophenyl chloroformate (p-NPC) was used to immobilize protein on bulk samples of Co-Cr-Mo and Ti-6Al-4V. Activation of both materials was dependent on the concentration of p-NPC, with a maximum of approximately 1.5 active groups/nm2 of nominal surface area. Trypsin was used as a model protein because much is known about its structure and mode of action. Derivatization with 0.65 mg p-NPC/cm2 resulted in significantly greater enzymatic activity (7.4 BAEE [N-(alpha)-benzoyl-L-arginine ethyl ester hydrochloride] units) on the Co-Cr-Mo samples compared with higher concentrations of p-NPC (5 BAEE units) and with simple adsorption of trypsin (1.5 BAEE units). An activity of 10.5 BAEE units was measured on both adsorbed and p-NPC-activated Ti-6Al-4V, with the exception of samples derivatized with 1.95 mg p-NPC/cm2, on which activity was significantly lower (4 BAEE units). In probing the linkages between trypsin and biomaterial by treatment with chaotropic agents, guanidine hydrochloride (GuHCl) was observed to eliminate more enzymatic activity than was urea. On Co-Cr-Mo samples, GuHCl removed nearly all the trypsin activity, while urea significantly decreased the activity only at a concentration of 0.65 mg p-NPC/cm2. Treatment of Ti-6Al-4V samples with GuHCl caused a trend of decreasing activity with increasing concentration of p-NPC, whereas urea had no effect on immobilized trypsin activity.

Adsorption↗
PubMed2005

Characterization of surface modified Ti-6Al-7Nb alloy.

In the last years different types of surface modifications were developed with the aim of improving the osteointegration ability of titanium alloys. The chemical composition, crystallographic structure and morphology of a surface layer can be modified in order to obtain a better interaction between the implant, the cells and the organic fluids. The final goal is to obtain a more efficient bone growth also in critical clinical cases. In the present paper were reported several data about the characterization of the Ti-6Al-7Nb alloy treated by two innovative surface treatments. They consist of blasting, followed by a two step chemical etching and heat treatment performed in air or in vacuum. TEM, XRD and SEM investigations were performed in order to assess the structure and morphology of the modified surfaces. The surface chemical composition was investigated by XPS ad AES analyses. The ability to interact with physiological fluids was tested by immersion of the treated materials in an acellular simulated body fluid (SBF). Metal ion concentration analyses of the fluid and SEM observations of the samples were performed after different times of soaking. The mechanical characterization involved scratch and fatigue tests. The surface of treated samples shows chemical, structural and morphological modifications. The passivation pre-treatment has influence on the surface modification. The treated samples evidenced a quite low metal ion release and interact with SBF solution, showing a moderate bioactivity. A relevant decrease in fatigue strength was observed on modified samples.

Aluminum↗
PubMedDate not supplied

Examination of the bone-metal interface of titanium implants coated by the microwave plasma chemical vapor deposition method.

PURPOSE: Diamond layers can be plated with microwave plasma chemical vapor deposition (MWP-CVD) treatment on metal bases such as titanium-aluminum-vanadium alloy (Ti-6Al-4V). The bonding strength of the diamond layer to the metal base is very high, so that no fissures and partial loss of coating take place-well known phenomena that may occur with other coatings in tribologic material testing. In an experimental study using 40 New Zealand White rabbits, a new method for coating implant material was tested for stability of the bone-metal interface. MATERIALS AND METHODS: The results of histomorphometric and biomechanical evaluation of coated and uncoated probes implanted in the distal femur of 40 rabbits were compared. The animals were divided into 3 groups, with observation times of 42, 84, and 168 days. RESULTS: The bone-implant contact was 5% to 18% less in coated than in uncoated probes. Only the early group, with 42 days healing time showed significant differences. Values for the pull-off force of uncoated material were about 3 to 4 times higher than coated material (diamond layer = 2.7 microm). The force increased 2 to 3 times when 200-nm coatings were tested. Electron microscopy detected undercuts of the rough surface that were obturated by diamond when the coating was too thick. DISCUSSION: Diamond-coated material seems to have no corrosion problems in contrast to all other known implant material. CONCLUSION: An inert diamond layer on a metal base can become osseointegrated. Biomechanical stability increased by thinning the diamond coating.

Alloys↗
PubMed2004

Posterior cervical laminoplasty using a new plating system: technical note.

BACKGROUND: Laminoplasty is well described in the Japanese literature as a surgical option for treating ossification of the posterior longitudinal ligament (OPLL). The open door technique has gained increasing popularity in the United States and Europe to treat not only OPLL but also cervical stenotic myelopathy. An obstacle to its widespread use is the lack of a suitable fixation plate to adequately secure the fractured lamina to the lateral mass. Our objective was to demonstrate the advantages of a novel miniplate (Ti-Mesh LP system; Medtronic Sofamor Danek, Memphis, TN, USA) that is ideally suited for fixing the lamina to the lateral mass. METHODS: We used the Ti-Mesh LP miniplate system to perform laminoplasties on five patients, all male, with a mean preoperative Nurick score of 2.8. Four patients had congenital cervical stenosis with myelopathy and one had OPLL. Open door laminoplasties were performed on all patients. The plates were implanted with a claw positioned on the trapdoor lamina and a flat plate on the lateral mass. RESULTS: The system was implanted successfully in all patients. The mean number of levels fixated was 4.4. There were no intraoperative or postoperative complications after >5 months follow-up. CONCLUSIONS: The new Ti-Mesh LP cranial miniplate and screw system facilitates posterior cervical laminoplasty procedures by eliminating the need to contour cranial miniplates for use in the cervical spine. Its unique claw construct and angled design are ideal for holding a trapdoor laminoplasty in the open position. We have used this system successfully and without complications to perform decompressive posterior cervical laminoplasties in five patients.

Aged↗
PubMed2002

Ceramic and PMMA particles differentially affect osteoblast phenotype.

There is increasing evidence that wear debris particles present in periprosthetic tissues have direct effects on osteoblasts. The nature of the cell response varies with the chemistry of the particle and the number of particles. Most studies have used Ti, Ti-6Al-4V, and ultrahigh molecular weight polyethylene (UHMWPE) particles since these materials are most frequently used in implants and as a result, these particles predominate in peri-prosthetic tissues. Ceramics have also been used successfully as load-bearing surfaces in implants for years, although it is unknown how wear debris from these surfaces may contribute to aseptic bone loss. Further, particles resulting from polymethylmethacrylate (PMMA) cements used for fixation may also be involved in aseptic loosening of implants, but how these particles may affect bone formation is unknown. In the present study, we examined whether aluminum oxide (Al2O3), zirconium oxide (ZrO2), and PMMA particles exert effects on osteoblast proliferation, phenotypic expression, and local factor production, and if so, whether the effects were specific to the particle type. ZrO2 particles were produced in a custom-made axial mixer in which ZrO2 containers were filled with ZrO2 bars and 95% ethanol and then rotated continuously at room temperature. PMMA particles were prepared in a ZrO2 roller mill. Al2O3 was produced and provided by Aesculap AG. Particles were endotoxin-free with equivalent circle diameters <3 microm; Al2O3 particles were significantly smaller than ZrO2 or PMMA particles. Particle suspensions were added to confluent cultures of MG63 osteoblast-like cells after diluting them 1:100, 1:10, and 1:1 with culture medium. Cells were incubated with the particles for 24 h. Transmission electron microscopy showed that MG63 cells phagocytosed Al2O3 particles and exhibited ultrastructural changes consistent with cytotoxicity. This was supported by biochemical changes as well. Proliferation, alkaline phosphatase activity, and TGF-beta1 levels were decreased. ZrO2 and PMMA particles increased proliferation and alkaline phosphatase specific activity. The effect of ZrO2 on alkaline phosphatase was targeted to matrix vesicles, the effect of PMMA was greater on the cells. All particles increased prostaglandin E2 production. These results show that Al2O3, ZrO2, and PMMA particles elicit direct effects on osteoblasts and that cell response depends on the particle type. None of the particles tested had the same effect as noted previously for UHMWPE: increased proliferation and decreased alkaline phosphatase. These results may indicate that the response of peri-prosthetic tissues to wear particles may be modulated by the relative contributions of the various particle types present.

Alkaline Phosphatase↗
PubMed2005

Response of osteoblastic cells to titanium submitted to three different surface treatments.

In the complex process of bone formation at the implant-tissue interface, surface properties are relevant factors modulating osteoblastic function. In this study, commercially pure titanium (cp Ti) samples were prepared with different surface characteristics using chemical attack with a sulfuric acid/hydrochloric acid based solution (treatment A); chemical attack plus anodic oxidation using phosphoric acid (treatment B); and chemical attack plus thermal oxidation followed by immersion in a sodium fluoride solution (treatment C). The samples were characterized by scanning electron microscopy (SEM), contact profilometry and contact angle. The biological performance of the prepared surfaces was evaluated using mice osteoblastic cell cultures for up to 21 days. Cells seeded on the different titanium samples showed similar behavior during cell attachment and spreading. However, cellular proliferation and differentiation were higher for samples submitted to treatments A and C (p < or = 0.05; n = 3), which were less rough and showed surface free energy with smaller polar components.

Animals↗
PubMedDate not supplied

Glow discharge plasma treatment of titanium plates enhances adhesion of osteoblast-like cells to the plates through the integrin-mediated mechanism.

PURPOSE: Initial adhesion of cells to implant surfaces and subsequent behavior of the cells are important determinants for biocompatibility of the implants. It was previously reported that both adhesion of MC3T3-E1 osteoblast-ike cells to titanium (Ti) plates and their differentiation into more mature cells on the plates were stimulated by treatment of the plates with glow discharge plasma (GDP). However, the mechanisms of these processes have not yet been identified. In this study, the adhesion and differentiation mechanism of osteoblast-like cells to Ti with and without GDP were investigated. MATERIALS AND METHODS: The adhesion and differentiation mechanism of MC3T3-E1 osteoblast-like cells to Ti, with and without GDP, were investigated by cultivation in serum-free medium and use of a competitive inhibition test to examine the influence of extracellular matrix proteins contained in the serum and to identify cell binding proteins. In addition, the amount of fibronectin adsorption on each Ti plate was investigated by enzyme-linked immunosorbent assay and fluorescein isothiocyanate labeling. Furthermore, the stress fiber formation and morphology of cells on each plate were evaluated microscopically. RESULTS: Adherent cells on Ti plates, with and without GDP, were significantly reduced in serum-free conditions and the presence of RGDS (Arg-Gly-Asp-Ser) peptides. Fibronectin adsorption on titanium plates was increased by GDP. Furthermore, stress fiber formation of cells was extremely progressive on the Ti plates treated with GDP and was not observed on the cells inhibited by RGDS peptide. DISCUSSION: These results suggest that RGDS containing serum proteins have a major role in regulating specific adhesion of cells to Ti, and GDP promoted cell adhesion and differentiation on Ti by increasing the adsorption of proteins. CONCLUSION: According to this study, the adhesion and differentiation mechanism of osteoblast-like cells to Ti, with and without GDP, can be obtained.

Argon↗
PubMed2005

Bioactivity of titanium following sodium plasma immersion ion implantation and deposition.

Bio-activation of titanium surface by Na plasma immersion ion implantation and deposition (PIII and D) is illustrated by precipitation of calcium phosphate and cell culture. The bioactivity of the plasma-implanted titanium is compared to that of the untreated, Na beam-line implanted and NaOH-treated titanium samples. Our data show that the samples can be classified into two groups: non-bioactive (untreated titanium and beam-line Na implanted titanium) and bioactive (Na-PIII and D and NaOH-treated titanium). None of the four types of surfaces exhibited major cell toxicity as determined by lactate dehydrogenase (LDH) release. However, the LDH release was higher on the more bioactive PIII and NaOH-treated surfaces. From a morphological point of view, cell adherence on the NaOH-treated titanium is the best. On the other hand, the cell activity and protein production were higher on the non-bioactive surfaces. The high alkaline phosphatase activity per cell suggests that the active surfaces support an osteogenic differentiation of the bone marrow cells at the expense of lower proliferation. The use of Na-PIII and D provides an environmentally cleaner technology to improve the bioactivity of Ti compared to conventional wet chemical processes. The technique is also particularly useful for the uniform and conforming treatment of medical implants that typically possess an irregular shape and are difficult to treat by conventional ion beam techniques.

Animals↗
PubMed2006

Mesenchymal stem cell adhesion and spreading on microwave plasma-nitrided titanium alloy.

Improved methods to increase surface hardness of metallic biomedical implants are being developed in an effort to minimize the formation of wear debris particles that cause local pain and inflammation. However, for many implant surface treatments, there is a risk of film delamination due to the mismatch of mechanical properties between the hard surface and the softer underlying metal. In this article, we describe the surface modification of titanium alloy (Ti-6Al-4V), using microwave plasma chemical vapor deposition to induce titanium nitride formation by nitrogen diffusion. The result is a gradual transition from a titanium nitride surface to the bulk titanium alloy, without a sharp interface that could otherwise lead to delamination. We demonstrate that vitronectin adsorption, as well as the adhesion and spreading of human mesenchymal stem cells to plasma-nitrided titanium is equivalent to that of Ti-6Al-4V, while hardness is improved 3- to 4-fold. These in vitro results suggest that the plasma nitriding technique has the potential to reduce wear, and the resulting debris particle release, of biomedical implants without compromising osseointegration; thus, minimizing the possibility of implant loosening over time.

Cell Adhesion↗
PubMed2001

Substrate affects the initial attachment and subsequent behavior of human osteoblastic cells (Saos-2).

Interaction between implant materials and bone cells contributes to the clinical success of dental implants. The object of this study was to investigate the initial attachment and subsequent behavior of human osteoblastic cells (Saos-2) to pure titanium (Ti), hydroxyapatite (HA), and glass. We, therefore, performed a time-course study for examining the area, attachment rate, distribution of focal adhesion kinase (FAK) vinculin, and actin, and the motility of Saos-2 cells on the materials. On Ti, cell area increased gradually, whereas on HA, cells spread quickly, but quitted spreading at 12 h after cell seeding. The number of cells on HA was greater than on the other materials. On Ti, the numbers of FAK- and vinculin-positive focal adhesions increased continuously. On HA, although the number of FAK-positive focal adhesions also increased continuously, the number of vinculin-positive focal adhesions decreased. Furthermore, actin staining showed that the cells on HA poorly formed stress fibers with weak polarity, whereas the cell on Ti possessed well-defined polarized stress fibers. On HA, cells started extension earlier than on Ti, motility was inactive, and the cells settled on the materials. These results suggest that the earlier settling of osteoblasts on HA might result in earlier osteogenesis on HA than other materials.

Actins↗
PubMedDate not supplied

The implant-supported telescopic prosthesis: a biomechanical analysis.

This in vitro project investigated load transfer through screw-retained telescopic prostheses. Three Brånemark System implants incorporating strain gauges were embedded in an aluminum block. Telescopic prostheses that included 1 mesial and 1 distal cantilever were fabricated over 1 central EsthetiCone and 2 Ti-Adapt abutments. The buffering capacity of the cement in a combined screw-retained/cemented prosthesis was studied. The degree of misfit of the prostheses could be adjusted by applying shims of various thicknesses under the EsthetiCone. Load distribution was measured while a 50-N load was applied in turn over each implant and each cantilever. The results showed that tightening the central prosthetic screw widened the load distribution. The cement accommodated misfits between the layers of the telescope, significantly reducing bending moments on some supporting implants. The system exhibited a degree of tolerance to misfit and can provide a versatile prosthodontic option.

Biomechanical Phenomena↗
PubMed2006

Laser induced multi-scale textured zirconia coating on Ti-6Al-4V.

A textured coating of zirconia on Ti-6Al-4V alloy was produced using pulsed laser based processing technique. Scanning electron microscope observations coupled with fractal analysis revealed the multi-scale nature of the textured coating. Both stylus based profilometric measurements and fractal analysis indicated non-linear nature of the relationship between laser processing speed at constant pulse frequency (10 kHz) and roughness of the textured coating. The textured coatings produced with all the three processing speeds (40, 160, 290 cm/min) were fractal over certain length scales. Processing at 40 cm/min resulted in structures that are fractal across a large number of length scales where as higher processing speeds resulted in fractality over fewer length scales. The processing speed influenced the zirconia content in the coating and the phase transformation within Ti-matrix of the coating. Within the coating, while zirconia content decreased the amount of retained beta-Ti increased with increase in processing speed. Such physical and chemical transformations are desired in a titanium bio-implant for effective contact with protein, cells and tissues at various length scales and its effective chemical performance in bio-environment.

Alloys↗
PubMed2005

Comparison of metal release from various metallic biomaterials in vitro.

To investigate the metal release of each base and alloying elements in vitro, SUS316L stainless steel, Co-Cr-Mo casting alloy, commercially pure Ti grade 2, and Ti-6Al-4V, V-free Ti-6Al-7Nb and Ti-15Zr-4Nb-4Ta alloys were immersed in various solutions, namely, alpha-medium, PBS(-), calf serum, 0.9% NaCl, artificial saliva, 1.2 mass% L-cysteine, 1 mass% lactic acid and 0.01 mass% HCl for 7d. The difference in the quantity of Co released from the Co-Cr-Mo casting alloy was relatively small in all the solutions. The quantities of Ti released into alpha-medium, PBS(-), calf serum, 0.9% NaCl and artificial saliva were much lower than those released into 1.2% L-cysteine, 1% lactic acid and 0.01% HCl. The quantity of Fe released from SUS316L stainless steel decreased linearly with increasing pH. On the other hand, the quantity of Ti released from Ti materials increased with decreasing pH, and it markedly attenuated at pHs of approximately 4 and higher. The quantity of Ni released from stainless steel gradually decreased with increasing pH. The quantities of Al released from the Ti-6Al-4V and Ti-6Al-7Nb alloys gradually decreased with increasing pH. A small V release was observed in calf serum, PBS(-), artificial saliva, 1% lactic acid, 1.2% l-cysteine and 0.01% HCl. The quantity of Ti released from the Ti-15Zr-4Nb-4Ta alloy was smaller than those released from the Ti-6Al-4V and Ti-6Al-7Nb alloys in all the solutions. In particular, it was approximately 30% or smaller in 1% lactic acid, 1.2% L-cysteine and 0.01% HCl. The quantity of (Zr + Nb + Ta) released was also considerably lower than that of (Al + Nb) or (Al + V) released. Therefore, the Ti-15Zr-4Nb-4Ta alloy with its low metal release in vitro is considered advantageous for long-term implants.

Biocompatible Materials↗