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At least 145 records · Page 8Linked to original sources
PubMed2006

Modulation of the human bone cell cycle by calcium ion-implantation of titanium.

Ca ion implantation of Ti surfaces has previously been reported to enhances osseointegration in vivo. Although the mechanisms underlying the response of bone cells to these novel surfaces still remain unclear, it is possible that Ca ion-implanted Ti (Ca-Ti) may influence the growth of new bone by modulating the progression of the cell cycle. In the present study we have, therefore, examined the precise effects of Ca ion-implantation of Ti on the bone-like MG-63 cell line in vitro. The results of flow cytometry analysis showed that this surface markedly enhanced the proportion of cells which expressed Ki-67, a cell proliferation-associated nuclear antigen, compared with cells grown on the non-implanted Ti (control) surface. In addition, cultures grown on Ca-Ti and synchronized at the G1/S boundary by hydroxyurea more rapidly re-entered and progressed through the S and G2/M phases of the cell cycle than their counterparts on Ti. Ca ion-implantation also significantly increased the numbers of mitotic cells. These results thus show that alteration of the surface chemistry of Ti by high-energy implantation with Ca ion was able to substantially modulate the progression of the bone cell cycle, and suggest a possible means of enhancing the response of bone cells to implant materials.

Adolescent↗
PubMed1996

[Wear characteristics of different metal-polyethylene beating surfaces. An experimental study of a new model of knee prosthesis].

PURPOSE OF THE STUDY: Wear of artificial components joint is the most important factor in long term durability. Only few studies have analysed in laboratory experimentation the quality of different alloys on the same type of prosthesis. MATERIAL: During the development of a new knee prosthesis, we studied the friction mechanisms of the metal/polyethylene (UHMWPE) couple and particularly the value of titanium alloy (Ti-6AI-4V) treatment using an ionic nitrogen implantation process (IMPLATEC). Two friction surfaces were studied in vitro: one in flexion-extension between femoral component and tibial plateau, the other in rotation between tibial plateau and "metal-back". METHODS: The implanted Ti-6AI-4V was compared with 316L stainless steel, cobalt chromium molybdenium alloy and with Ti-6AI-4V using a prosthesis of each configuration. The samples were tested on a TRIBOCUP friction machine during 3 x 10(6) cycles in Ringer 's solution. The friction couples were controlled every 200,000 cycles and the loss of polyethylene mass every 500,000 cycles. We have also evaluated the roughness and the rubbing surface macroscopically. RESULTS: The results analysis shows that friction couples such as Cobalt Chromium and implanted Ti-6AI-4V are weakest but implanted Ti-6AI-4V over time, tends to match the strength of Ti-6AI-4V without treatment. With implanted Ti-6AI-4V and with Cobalt Chromium alloy, the loss of polyethylene is slight comparatively to the stainless steel and non implanted Ti-6AI-4V. Surface analysis showed good protection of titanium alloy by ionic implantation especially in the femoral component where roughness is close (0.04 micron) to that of Cobalt Chromium alloy (0.07 micron). DISCUSSION: Our study confirms the results with pin-on-disk and cup-on-ball with results for the Ti-6AI-4V implanted and Cobalt Chromium alloys with protection of the metal surface and decrease of polyethylene wear comparatively to stainless steel and non implanted Ti-6AI-4V. CONCLUSION: Our conclusion is for this type of experimental device that the surface condition is satisfactory for such friction couples as implanted Ti-6AI-4V/polyethylene and Cobalt-chromium/polyethylene, with very similar results. However, the long-term durability of the nitrogen implanted on Titanium Alloy remains unknown.

Biodegradation, Environmental↗
PubMed2001

Effects of guided bone regeneration with non-resorbable and bioabsorbable barrier membranes on osseointegration around hydroxyapatite-coated and uncoated threaded titanium dental implants placed into a surgically-created dehiscence type defect in rabbit tibia: a pilot study.

The purpose of this study was to evaluate the effects of guided bone regeneration (GBR) with either a non-resorbable (ePTFE) or bioabsorbable barrier membrane (RSLT) on osseointegration and extent of bone formation around hydroxyapatite-coated (HA) and uncoated threaded titanium (Ti) dental implants placed into surgically-created dehiscence type defects in rabbit tibia. A dehiscence type bone defect, approximately 3 mm in width and height was surgically created on the outer surface of the bone in each tibia of 9 rabbits. For the conventional group, either a HA or a Ti implant was then placed at this site. After the same procedure was performed as in the conventional group, the implant site of the GBR group was covered with either an ePTFE or a RSLT. After 4 months, the rabbits were sacrificed. Specimens were prepared and examined histometrically. It was found that the mean percentage of osseointegration tended to increase in HA compared to Ti implants, both with and without membranes. There was a tendency that the extent of newly regenerated bone was higher in the GBR group than that in the conventional group.

Absorbable Implants↗
PubMed1998

[Cold deformation elements for attaching an implantable hearing aid transducer to ear ossicles or perilymph].

Development and short-term implantation results of the Tübingen implantable hearing aid (TI = Tübingen implant) have been presented. The TI is designed for patients with sensorineural hearing loss due to a malfunction of the cochlear amplifier. This can be identified by the presence of positive recruitment and the absence of TEOAE (transitory evoked otoacoustic emissions). The Tübingen implant functions in two ways: it allows electronic amplification of the auditory signal and electromechanical signal transduction into a micromechanical vibratory stimulus. There are two paths by which vibratory stimulus reaches the cochlea: (1) directly through a perforation in the stapes foot plate into the perilymph or (2) via the ossicular chain. Made of pure titanium, the casing of the helium-tight welded transducer includes the piezoelectric actuator. An implantable manipulator device is designed for transducer positioning and anchoring in the mastoid cavity. Usually, the transducer probe tip is directly coupled to the body of the incus. This functions without a special coupling device by utilization of an Erbium-YAG laser. Special anatomical situations or the loss of incus and/or stapes suprastructure, however, requires coupling of the vibratory signal to other points of the ossicular chain or to the perilymph. A major problem, however, was an intraoperative, irreversible link between the titanium probe tip and coupling elements. To overcome this problem, the coupling elements were made of gold. A crimp technique was developed, allowing the surgeon to induce cold deformation of the gold. The cold deformation technique (crimp) results in an irreversible coupling between the titanium probe tip and the golden coupling element.

Cochlear Implantation↗
PubMed1992

Acoustic emission during fatigue of porous-coated Ti-6Al-4V implant alloy.

Acoustic emission (AE) events and event intensities (e.g., event amplitude, counts, duration, and energy counts) were recorded and analyzed during fatigue loading of uncoated and porous-coated Ti-6Al-4V. AE source location, spatial filtering, event, and event intensity distributions were used to detect, monitor, analyze, and predict failures. AE provides the ability to spatially and temporally locate multiple fatigue cracks, in real time. Fatigue of porous-coated Ti-6Al-4V is governed by a sequential, multimode fracture process of: transverse fracture in the porous coating; sphere/sphere and sphere/substrate debonding; substrate fatigue crack initiation; slow and rapid substrate fatigue crack propagation. Because of the porosity of the coating, the different stages of fracture within the coating occur in a discontinuous fashion. Therefore, the AE events generated are intermittent and the onset of each mode of fracture in the porous coating can be detected by increases in AE event rate. Changes in AE event rate also correspond to changes in crack extension rate, and may therefore be used to predict failure. AE offers two distinct advantages over conventional optical and microscopic methods of analyzing fatigue cracks--it is more sensitive and it can determine the time history of damage progression. The magnitude of the AE event intensities increased with increasing stress. Failure mechanisms are best differentiated by analyzing AE event amplitudes. Intergranular fracture and microvoid coalescence generated the highest AE event amplitudes (100 dB), whereas, plastic flow and friction generated the lowest AE event amplitudes (55-65 dB). Fractures in the porous coating were characterized by AE event amplitudes of less than 80 dB.

Alloys↗
PubMed2004

Early detachment of titanium particles from various different surfaces of endosseous dental implants.

Titanium (Ti) endosseous dental screws with different surfaces (smooth titanium--STi, titanium plasma-sprayed-TPS, alumina oxide sandblasted and acid-etched--Al-SLA, zirconium oxide sandblasted and acid etched--Zr-SLA) were implanted in femura and tibiae of sheep to investigate the biological evolution of the peri-implant tissues and detachment of Ti debris from the implant surfaces in early healing. Implants were not loaded. Sections of the screws and the peri-implant tissues obtained by sawing and grinding were analysed by light microscopy immediately after implantation (time 0) and after 14 days. All samples showed new bone trabeculae and vascularised medullary spaces in those areas where gaps between the implants and host bone were visible. In contrast, no osteogenesis was induced in the areas where the implants were initially positioned in close contact with the host bone. Chips of the pre-existing bone inducing new peri-implant neo-osteogenesis were surrounded by new bone trabeculae. The threads of some screws appeared to be deformed where the host bone showed fractures. Ti granules of 3-60 microm were detectable only in the peri-implant tissues of TPS implants both immediately after surgery and after 14 days, thus suggesting that this phenomenon may be related to the friction of the TPS coating during surgical insertion.

Animals↗
PubMed2004

In vitro biocorrosion of Ti-6Al-4V implant alloy by a mouse macrophage cell line.

Corrosion of implant alloys releasing metal ions has the potential to cause adverse tissue reactions and implant failure. We hypothesized that macrophage cells and their released reactive chemical species (RCS) affect the alloy's corrosion properties. A custom cell culture corrosion box was used to evaluate how cell culture medium, macrophage cells and RCS altered the Ti-6Al-4V corrosion behaviors in 72 h and how corrosion products affected the cells. There was no difference in the charge transfer in the presence (75.2 +/- 17.7 mC) and absence (62.3 +/- 18.8 mC) of cells. The alloy had the lowest charge transfer (28.2 +/- 4.1 mC) and metal ion release (Ti < 10 ppb, V < 2 ppb) with activated cells (releasing RCS) compared with the other two conditions. This was attributed to an enhancement of the surface oxides by RCS. Metal ion release was very low (Ti < 20 ppb, V < 10 ppb) with nonactivated cells and did not change cell morphology, viability, and NO and ATP release compared with controls. However, IL-1beta released from the activated cells and the proliferation of nonactivated cells were greater on the alloy than the controls. In summary, macrophage cells and RCS reduced the corrosion of Ti-6Al-4V alloys as hypothesized. These data are important in understanding host tissue-material interactions.

Alloys↗
PubMed2006

Host inflammatory response to NiCr, CoCr, and Ti in a soft tissue implantation model.

The inflammatory response to nickel chromium (NiCr), cobalt chromium (CoCr), and titanium (Ti) implants at 7 and 28 days was investigated using real-time PCR analysis along with histological and immunohistochemical staining. Contrasting inflammatory profiles were found in response to the different metal compositions. The inflammatory profile induced by CoCr remained consistent and elevated during the 28-day period with high cell counts associated with the implants and a progressive recruitment of T lymphocytes. The response to NiCr was also elevated, but with an initially low T-lymphocyte infiltration that increased by the later time period. Ti indicated an early increased inflammatory response that had reduced by 28 days. Changes in gene expression demonstrated that Ti induced very low levels of expression of the three inflammatory cytokine genes. NiCr initiated a significant upregulation in gene expression for IL-6 and TNF-alpha. CoCr resulted in the highest upregulation of IL-2 indicative of T-lymphocyte activation to this material.

Animals↗
PubMed2001

In vitro mechanical integrity of hydroxyapatite coatings on Ti-6Al-4V implants under shear loading.

A new test method for the mechanical behavior of coatings on metal substrates under shear loading has been developed. Finite element simulations show that this new test method provides an almost identical shear load on the coatings to that of the conventional test. Using the new method, the static and fatigue behavior of plasma-sprayed hydroxyapatite (HA) coatings on Ti-6Al-4V substrates were studied at room temperature as a function of processing conditions. The results of the static tests show that the nominal interface shear strength is in the range of 25 approximately 40 MPa. The fatigue resistance to cyclic shear loading was characterized by shear stress amplitude versus cycle-to-failure for the samples that failed within 1010(7)cycles, and by residual nominal interfacial shear strength for the samples that survived 1010(7)cycles. The experimental results indicate that a threshold level of shear stress amplitude exists for introducing fatigue damage to HA coatings. AES and XPS studies indicated that bonding between the coating and substrate does not occur over about 12 percent of the area of the interface while bonding in the contact area of the interface is mainly mechanical interlocking. A failure mechanism of interfacial microflaw coalescence is suggested.

Alloys↗
PubMed2003

Macrophages related to dental implant failure.

PURPOSE: The aim of this study was to evaluate, histologically and quantitatively, the presence of macrophages loaded with metallic particles in the periimplant soft tissues of failed titanium (Ti) dental implants. MATERIALS AND METHODS: The study was performed on sections of metallic Ti implants embedded in methyl methacrylate resin that exhibited macrophages in the soft tissues contiguous with the implant. The volume of periimplant soft tissue was evaluated, and the number of macrophages was determined. The particles within macrophages were analyzed by energy-dispersive x-ray analysis. RESULTS: Macrophages were more abundant in the zone adjacent to the metallic implant as compared with the zone further away from the implant. Energy-dispersive x-ray analysis revealed the presence of Ti within macrophages. CONCLUSIONS: Macrophages loaded with Ti particles can be associated with a corrosion process. The method proposed would allow for the objective evaluation of the presence of macrophages associated with dental implants and other orthopedic materials that contain Ti or other metals.

Cell Count↗
PubMed1992

Hydroxyapatite coating modifies implant membrane formation. Controlled micromotion studied in dogs.

We studied the influence of controlled micromovements between bone and porous titanium alloy implants with and without hydroxyapatite coating. A dynamically loaded unstable device producing approximately 150-microns axial translation of knee implants during each gait cycle was developed. Stable implants served as controls. Matched stable and unstable implants with either porous titanium (Ti) or hydroxyapatite (HA) coating surrounded by a gap of 0.75 mm were inserted into the weight-bearing regions of the medial femoral condyles in 14 mature dogs. Histologic analysis after 4 weeks showed a fibrous membrane surrounding both types of implants subjected to micromovements, whereas various amounts of bone ingrowth was obtained in the stable implants. The membrane around unstable HA implants was thinner than that around unstable Ti implants. Islands of fibrocartilaginous tissue characterized the membrane around unstable HA implants, whereas fibrous connective tissue surrounded unstable Ti implants. The collagen concentration of the fibrous membranes was higher around unstable HA implants compared with Ti implants. Instability reduced the shear strength of the implants. However, the shear strength of unstable HA implants exceeded that of the Ti implants, both unstable and stable. The greatest shear strength was obtained by stable HA implants, i.e., tenfold greater than that of stable Ti implants. The gap-healing capacity around stable HA implants increased toward the HA surface, and was greater than that around Ti implants. Our study demonstrates that micromovements between bone and implant inhibit bone ingrowth and lead to the development of a fibrous membrane. The superior fixation of unstable HA implants compared with unstable Ti implants may be ascribed to the presence of fibrocartilage, a higher collagen concentration, and radiating orientation of collagen fibers in the membrane. The strongest mechanical anchorage and the greatest amount of bone ingrowth was obtained by stable implants coated with hydroxyapatite.

Alloys↗
PubMed2001

Surface analysis of Ti-15Zr-4Nb-4Ta alloy after implantation in rat tibia.

A new Ti-15Zr-4Nb4Ta alloy without V was implanted in rat tibiae for 6-48 weeks. The new bone formation surrounding the Ti implant in bone marrow, surface analysis of the Ti alloy after implantation, and metal concentrations in dried bone tissue containing new bone were investigated. New bone was well formed around the Ti-15Zr-4Nb-4Ta alloy implanted in bone marrow. The mean thickness of the new bone increased up to 24 weeks after implantation, and changes in the mean thickness thereafter, up to 48 weeks. were very small. The number of corrosion pits observed in the Ti-6Al-4V extra low interstitial (ELI) alloy surface tended to be slightly more than that of the Ti-5Zr-4Nb-4Ta alloy implant. The concentrations of metal elements in the bone tissue containing the new bone tended to increase slightly more than in bones without the implant.

Alloys↗
PubMed1993

Mechanical properties of a Ti-6A1-4V dental implant produced by electro-discharge compaction.

Cylindrical, porous-surfaced implants were fabricated from Ti-6A1-4V atomized powders by an electro-discharge compaction technique (EDC). Input energy (1-2.5 kJ/g powder) was used to produce implant compacts having a solid core surrounded by a porous layer. The solid core size, neck size between core and particle, neck size between particles, and pore size in the porous layer varied as input energy was changed. Compression tests were carried out to evaluate the mechanical properties of the EDC compacts. The yield strength ranged from 270 to 530 MPa and the ultimate compressive strengths ranged from 390 to 600 MPa. The yield strengths for solid core, core-particle and particle-particle interfaces remained constant at 755 MPa regardless of input energy. The endurance limits estimated from these results were 190-310 MPa, which were higher than the reported values for sintered titanium implants. Microhardness testing revealed that hardness was independent of input energy and the position where the testing indentation was applied. The average hardness of the compacts was 3430 MPa.

Aluminum↗
PubMed1990

Stress enhancement and fatigue susceptibility of porous coated Ti-6Al-4V implants: an elastic analysis.

An elastic stress analysis of porous-coated implant surfaces was performed using the finite element method. Three-hundred-microns-diameter metal beads sinter bonded onto an implant surface were modeled with sinter neck radii of 5, 10, 20, and 50 microns. Smooth-surface, single-bead, single-layer, and double-layer systems were analyzed. The finite element models were loaded to simulate bone-bead contact forces and lateral hip implant tensile forces. Results showed that, for a single bead sinter-bonded onto an implant surface, concentration of stress occurs either at the base of the sinter neck or within the neck itself, depending on the type of load applied. Under lateral hip implant tensile loads, a maximum stress concentration factor of 1.97 was obtained for a single bead sinter-bonded onto a implant surface. Addition of a single layer of beads onto the implant surface resulted in a significant increase in stress at the most proximal and distal ends of the porous layer, with a maximum stress concentration factor of 4.3. Addition of a second layer of beads did not significantly increase the magnitude of the stress concentration occurring at the ends of the porous layer. The results of this study provide stress concentration factors for porous coatings with sinter necks of known dimensions under loading conditions similar to those present along the lateral surface of a hip prosthesis.

Alloys↗
PubMed2006

Frequency effect in fretting wear of Co-28Cr-6Mo versus Ti-6Al-4V implant alloys.

A piezo-electrically driven fretting testing device has been constructed and fretting release and release rates have been determined with highest accuracy, using a radiotracer technique. First results on the fretting release and release rate of titanium alloy fretting pads against cobalt-chrome alloy fatigue specimens are reported. The frequency dependency of fretting release has been determined between 1 and 8 Hz and shows higher release rates for low frequencies, thus indicating that accelerated testing of materials and components of artificial joints must be analyzed extremely carefully. The present experiments under simple conditions present a base-line study for step-wise applying more complex and realistic testing conditions and for using radiotracer methods to quantify fretting release in simulated testing of artificial hip- and knee-prostheses.

Alloys↗
PubMed1999

Surface characterization of implant materials c.p. Ti, Ti-6Al-7Nb and Ti-6Al-4V with different pretreatments.

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 alpha-phase dissolution and enrichment of the beta-phase appears to occur.

Journal Article↗
PubMed2006

Heterotopic bone formation around sintered porous-surfaced Ti-6Al-4V implants coated with native bone morphogenetic proteins.

PURPOSE: Coating endosseous dental implants with growth factors such as bone morphogenetic proteins (BMPs) may be one way to accelerate and/or enhance the quality of osseointegration. The purpose of this study was to investigate in the murine muscle pouch model whether sintered porous-surfaced titanium alloy implants coated with BMPs would lead to heterotopic bone formation around and within the implant surface geometry. MATERIALS: Porous-surfaced dental implants were coated with partially purified native human BMPs, with or without a carrier of Poloxamer 407 (BASF Corp., Parsippany, NJ), placed in gelatin capsules and implanted into the hindquarter muscles of mice. Mice were euthanized after 28 days. Sections of retrieved specimens were subsequently prepared for morphometric analysis of bone formation using backscatter electron microscopic images. RESULTS: Human BMPs, either with or without the carrier of Poloxamer 407, led to bone formation within and outside of the sintered porous implant surface. When the sintered implant surface region was subdivided into inner and outer halves, similar levels of bone ingrowth and contact were seen in the 2 halves. Evidence of bone formation to the depth of the solid implant core (i.e., the deepest level possible) also was seen. DISCUSSION AND CONCLUSIONS: Sintered porous-surfaced dental implants can be used as substrate for partially purified BMPs in the murine muscle pouch model. With the addition of these osteoinductive factors, the porous implant surface supported bone formation within the surface porosity provided, in some instances, all the way to the solid implant core. The addition of growth factors to a sintered porous surface may be an efficient method for altering locally the healing sequence and quality of bone associated with osseointegration of bone-interfacing implants.

Alloys↗