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At least 397 records · Page 22Linked to original sources

PubMed1993

Metal release from titanium fixtures during placement in the mandible: an experimental study.

Titanium screw taps and titanium fixtures were investigated by SEM before and after experimental use. Peri-implant bone surfaces were examined immediately after surgery and 5 months after implantation by SEM using the SE mode, backscattered electron imaging, and EDX analysis to detect titanium contamination of the bone specimens. The Ti content of the livers, kidneys, and lungs of six Göttingen minipigs, which had received two screw implants each, was determined using flameless atomic absorption spectroscopy and compared to a control group with no implants. Results showed that Ti particles were abraded and deposited on the bone surface during the preparation of implant beds. Five months after placement, particles were no longer observed on the bone surface next to the implants. Determination of the Ti concentration of the inner organs showed that the lungs contained the highest amount of titanium. The Ti content of the kidneys and livers was much lower. All values differed significantly from those of the control group (P < .01).

Alveolar Process↗

PubMed1989

Cobalt, chromium, and nickel concentrations in body fluids of patients with porous-coated knee or hip prostheses.

Co, Cr, and Ni concentrations were determined by electrothermal atomic absorption spectrophotometry in serum and urine specimens collected from a group of 28 patients at intervals of from 1 day to 2.5 years after total knee or hip arthroplasty with porous-coated prostheses fabricated of Co-Cr alloy (ASTM F-75-82). Two control groups were also tested: (a) 42 healthy adults and (b) 16 orthopaedic patients after total knee or hip arthroplasty with porous-coated prostheses fabricated predominantly of Ti-Al-V alloy (ASTM F-136-84). All prostheses contained polyethylene components to avoid metal-to-metal contact. Mean Co concentrations in serum and urine were slightly increased in patients with Co-Cr knee implants at 6-120 weeks after surgery, compared with (a) preoperative values, (b) corresponding values in patients with Co-Cr hip implants, and (c) corresponding values in control patients with Ti-Al-V knee and hip prostheses. Substantially increased Co levels were observed in serum and urine of two patients at 7 weeks and 22 months postarthroplasty, associated with loosening of the prostheses; one of the patients also had elevated Cr levels in serum and urine. Although ASTM F-75-82 and F-136-84 alloys contain very little Ni (less than 1.0 and less than 0.2% Ni, respectively, by wt), mean Ni concentrations in serum and urine were greatly increased at 1-2 days after implantation of Ti-Al-V and Co-Cr prostheses, diminishing by 2 weeks. The postoperative hypernickelemia and nickeluresis may reflect contamination of the operative field with Ni-containing particles from the drills, cutting jigs, and drilling jigs, or it may represent a previously unrecognized pathophysiological response to surgery.

Adult↗

PubMed2003

The effects of hydroxyapatite coating and bone allograft on fixation of loaded experimental primary and revision implants.

We used our established experimental model of revision joint replacement to examine the roles of hydroxyapatite coating and bone graft in improving the fixation of revision implants. The revision protocol uses the Søballe micromotion device in a preliminary 8-week period of implant instability for the presence of particulate polyethylene. During this procedure, a sclerotic endosteal bone rim forms, and a dense fibrous membrane is engendered, having macrophages with ingested polyethylene and high levels of inflammatory cytokines. At the time of revision after 8 weeks, the cavity is revised with either a titanium alloy (Ti) or a hydroxyapatite (HA) 6.0 mm plasma-sprayed implant, in the presence or absence of allograft packed into the initial 0.75 mm peri-implant gap. The contralateral limb is subjected to primary surgery with the same implant configuration, and serves as control. 8 implants were included in each of the 8 treatment groups (total 64 implants in 32 dogs). The observation period was 4 weeks after revision. Outcome measures are based on histomorphometry and mechanical pushout properties. The revision setting was always inferior to its primary counterpart. Bone graft improved the revision fixation in all treatment groups, as also did the HA coating. The sole exception was revision-grafted HA implants, which reached the same fixation as primary Ti and HA grafted implants. The revision, which was less active in general, seems to need the dual stimulation of bone graft and HA implant surface, to obtain the same level of fixation associated with primary implants. Our findings suggest that the combination of HA implant and bone graft may be of benefit in the clinical revision implant setting.

Animals↗

PubMed1990

Qualitative interfacial study between bone and tantalum, niobium or commercially pure titanium.

Tantalum (Ta), niobium (Nb) and commercially pure titanium (c.p. Ti) were sputtered on to the surfaces of polycarbonate plastic implants. After 3 month of insertion, in the tibial metaphysis of rabbits, the implants were removed with a surrounding bone collar and processed for light (LM) and electron microscopy (EM). By EM a zone of ground substance tens of nanometers wide without collagen filaments was noticed surrounding the Ta implants. Multinucleated macrophages could occasionally be recognized in the interface zone. Foreign body reactions were more striking at the Nb interface while no multinucleated macrophages were observed in the c.p. Ti interface. The ground substance layer had a thickness in the range of 40-60 nm for the Nb implants, whereas in c.p. Ti sections the collagen filaments were noticed 20-40 nm from the metal surface. There are more subtle differences between tantalum and c.p. titanium than between c.p. titanium and niobium which seems to be less well tolerated when implanted in bone.

Animals↗

PubMed1993

Osseous implant for studies of biomaterials using an in vivo electrochemical transducer.

The in vitro and in vivo electrochemical behavior of commercially pure titanium (cp Ti) was characterized using a specialized osseous implant in conjunction with electrochemical impedance spectroscopy (EIS) measurement techniques. Studies performed in vitro were used to verify the operation of the transducer and develop methods of deconvoluting EIS data. This method was subsequently used to describe an electrochemical equivalent circuit model of the surface oxide and electrical double-layer capacitance of cp Ti in the endogenous electrolyte found in the medullary compartment of a baboon tibia. Kinetic profiles of the double-layer capacitance and the polarization resistance were constructed from multiple in vitro and in vivo EIS measurements performed over 60 min at 0 V (reference Ag/AgCI) conditioning potential. The profiles demonstrated that the growth of surface oxides was biphasic, with rapid decrease in the double-layer capacitance occurring within 20 min and reaching steady-state conditions at approximately 40 min. These data suggested that a passive, stable biofilm formed on the cp Ti surface in vivo and in vitro.

Animals↗

PubMed1999

New experimental model to study the bone interface of endosseous implants: an in vitro three-dimensional model of cell culture.

To set up a three-dimensional culture model of endosseous implant material-osteoblast, titanium (Ti) discs were placed onto confluent cellular layers of human fetal osteoblasts that were cultured in calcifying conditions. Follow-up observations of living cells with phase-contrast microscopy and histological observations of the cell-Ti disc interface with ordinary microscopy and transmission electron microscopy were used to monitor and verify the formation of three-dimensional cellular structures at the osteoblast-Ti disc interface. These methods were further used to study osteoblast cell behavior during the early stage of bone healing in this three-dimensional cellular model. The follow-up observation showed that, upon the placement of the Ti disc, cells migrated from the cellular layer and attached to the rim of the disc, forming cell bridges. Cells continued to attach and orient throughout the culture time. A cellular multilayer at the osteoblast-Ti interface was formed, which resulted in the three-dimensional model. Furthermore, transmission electron microscopy observation showed that there was a mineralizing process at the osteoblast-Ti disc interface just like bone, which confirms the reality of this model. Histological observations with conventional microscopy demonstrated the interfacial relation between biomaterial and cells. If osteoblasts were replaced by other types of cells, this model could be used to study the other kinds of interfaces.

Cell Adhesion↗

PubMed1992

Joint replacement components made of hot-forged and surface-treated Ti-6Al-7Nb alloy.

We have developed a titanium-aluminium alloy with the inert alloying element niobium. The optimal composition was found to be Ti-6Al-7Nb (Protasul-100). This custom-made alloy designed for implants shows the same alpha/beta structure as Ti-6Al-4V and exhibits equally good mechanical properties. The corrosion resistance of Ti-6Al-7Nb in sodium chloride solution is equivalent to that of pure titanium and Ti-6Al-4V. This is due to a very dense and stable passive layer. Highly stressed anchorage stems of different hip prosthesis designs have been made from hot-forged Ti-6Al-7Nb. The polished surfaces of hip, knee and wrist joints made of Ti-6Al-7Nb and articulating against polyethylene are surface-treated by means of a very hard and 3-5 microns thick titanium nitride coating (Tribosul-TiN) or by oxygen diffusion hardening (Tribosul-ODH) to a depth of 30 microns.

Humans↗

PubMed1997

Solubility control of thin calcium-phosphate coating with rapid heating.

The thin calcium-phosphate (Ca-P) coatings produced by the ion-beam-mixing method instead of the plasma-spraying method have been found to be amorphous, resulting in films that easily dissolved in simulated body fluid. These coatings crystalized with conventional heat treatment in an electric furnace but tended to crack easily. Therefore, the purpose of this study was to find a suitable heat treatment that controls the solubility of Ca-P coatings without weakening their adhesion to titanium (Ti) substrate. Thin coatings (approximately 1 microm) were coated onto Ti substrates, followed by heat treatment in a conventional furnace and rapid heating by infrared radiation and laser radiation. X-ray diffraction analysis revealed untreated films to be amorphous but to become crystalline after being heated in a furnace at 500 degrees C, heated rapidly with infrared radiation higher than 600 degrees C and with laser radiation at output power of 10W. We evaluated solubility by estimating the film thickness after immersion in simulated body fluid for 5 weeks: Untreated films dissolved within 1 day. Coatings treated with infrared radiation at 600 degrees C dissolved minimally. Cracks were observed in coatings subjected to infrared radiation at 800 degrees C and furnace-heated at 500 degrees C. Coatings treated with laser radiation tended to dissolve easily, with non-uniform surface degradation. X-ray photoelectron spectroscopy analysis at the interface between the coating and the Ti substrate showed that cracks were the result of decreased Ca-implanted layers and too much growth of Ti-P compounds. No difference was recognized in the Ti-oxidation state among specimens. These data indicate that rapid, homogeneous, and comparatively low-temperature heating, such as defocused infrared radiation, controls Ca-P solubility and ensures the adherence of the coatings to the substrate.

Adhesiveness↗

PubMed1995

[Titanium porous-surface screw implant].

Titanium porous-surfaced screw implant was made by plasma-spray with Ti powder. The pore size was 80-300 microns. Two groups of implants were implanted in the mandibles of 15 dogs. Group A: porous-surfaced screw implant: Group B: smooth surface screw implant. The bone healing was evaluated by L. M. SEM. and shear strength testing. The results show that the osteo integration of two groups were completed after 12 weeks. The bone grew into porous surface. The shear strength of group A was significantly higher than that of group B.

Animals↗

PubMed2006

Enhancing surface free energy and hydrophilicity through chemical modification of microstructured titanium implant surfaces.

Roughness-induced hydrophobicity, well-known from natural plant surfaces and intensively studied toward superhydrophobic surfaces, has currently been identified on microstructured titanium implant surfaces. Studies indicate that microstructuring by sandblasting and acid etching (SLA) enhances the osteogenic properties of titanium. The undesired initial hydrophobicity, however, presumably decelerates primary interactions with the aqueous biosystem. To improve the initial wettability and to retain SLA microstructure, a novel surface modification was tested. This modification differs from SLA by its preparation after acid etching, which was done under protective gas conditions following liquid instead of dry storage. We hypothesized that this modification should have increased wettability due to the prevention of contaminations that occurs during air contact. The main outcome of dynamic wettability measurements was that the novel modification shows increased surface free energy (SFE) and increased hydrophilicity with initial water contact angles of 0 degrees compared to 139.9 degrees for SLA. This hydrophilization was kept even after any drying. Reduced hydrocarbon contaminations were identified to play a possible role in altered surface thermodynamics. Such surfaces aim to retain the hydrophilicity and natural high surface energy of the Ti dioxide surface until surgical implants' insertion and are compared in this in vitro study with structural surface variants of titanium to compare roughness and chemically induced wettability.

Acids↗

PubMed2003

Ion implantation: surface treatment for improving the bone integration of titanium and Ti6Al4V dental implants.

Dental implants subjected to surface treatment have shown better bone integration than implants which have only been turned (machined). Three main types of treatment are presently available: the addition of material or coating, the removal of material, and surface modification. Ion implantation corresponds to the third approach. A histomorphometric study is made following the rabbit tibial bone placement of 88 commercial dental implants of pure titanium and Ti6AI4V subjected to surface treatment in the form of different ion implants (C+, CO+, N+, Ne+). Light microscopic, scanning electron microscopic (SEM), electron microsonde (EDS) and X-ray photoelectron spectroscopy (XPS) studies were made. The results indicate improved bone integration (expressed as percentage bone-implant contact) in those specimens subjected to ion implantation versus the non-treated controls, the difference being statistically significant for the groups treated with C+ and CO+. In these groups, XPS showed a Ti-O-C junction (bone-implant interface) involving covalent type bonds, these being stronger and more stable than the ion-type bonds usually established between the titanium oxide and bone.

Alloys↗

PubMed1996

The influence of the chemical composition and surface of the implant on infection.

The influence of the localization and size of orthopaedic implants on infection has been analyzed extensively, but the influence of implant shape and chemical composition has rarely been studied, and the influence of the surface has only been described in one single report. Several experimental studies have tried to compare the incidence of infection for different materials. PMMA usually appears as the implant material most prone to causing infection, while titanium (Ti) and cobalt-chromium (CoCr) are the materials most resistant to infection. On the polished surface of cylinders implanted in rabbit femora, it took 40 times more inoculum to produce a clinical infection than it took for porous CoCr implants. The polished surface implants required 2.5 times more inoculum than porous Ti to produce infection.

Animals↗

PubMed2004

In vivo behavior and mechanical stability of surface-modified titanium implants by plasma spray coating and chemical treatments.

The geometric design and chemical compositions of an implant surface may have an important part in affecting early implant stabilization and influencing tissue healing. In this study, in vivo behavior and mechanical stability in implants of three surface designs, which were smooth surface (SS), rough titanium (Ti) surface by plasma spray coating (PSC), and alkali- and heat-treated (AHT) Ti surface after plasma spray coating, were compared by histological and mechanical analyses. Surface morphologies of the implants were observed by optical microscopy and scanning electron microscopy. Chemical compositional surface changes were investigated by energy dispersive spectroscopy. The implants were inserted transversely in a dog thighbone and evaluated at 4 weeks of healing. At 4 weeks of healing after implantation in bone, the healing tissue was more extensively integrated with an AHT implant than with the implants of smooth (SS) and/or rough Ti surfaces (PSC). The bone bonding strength (pull-out force) between living bone and implant was observed by a universal testing machine. At 4 weeks' healing after implant placement in bone, the pull-out forces of the SS, PSC, and AHT implants were 235 (+/-34.25), 710 (+/-142.25), and 823 (+/-152.22) N, respectively. Histological and mechanical data demonstrate that appropriate surface design selection can improve early bone growth and induce an acceleration of the healing response, thereby improving the potential for implant osseointegration.

Animals↗

PubMed2005

Ti(IV) binds to human serum transferrin more tightly than does Fe(III).

The binding of titanium(IV) to human serum transferrin in 50 mM Tris with 20 mM bicarbonate and 10 mM citrate at pH 7.4 was studied by UV/vis kinetics and by isothermal titration calorimetry. Ti(IV) citrate, [Ti(C6H4O7)3]8-, employed in this study was previously characterized and delivers the metal to transferrin rapidly, allowing the quantification of the intrinsic binding constants for Ti(IV) to the C- and N-sites of transferrin. The results after correcting for blood plasma conditions (pH 7.4, [HCO3-] = 27 mM) reveal that Ti(IV) binds with greater affinity (log K = 26.8 and 25.7) than Fe(III) (log K = 22.5 and 21.4) to transferrin, a finding not previously observed for other examined metal ions. The strength of metal binding to transferrin correlates with the Lewis acidity of the metal. Ti(IV) is more Lewis acidic than Fe(III) and is nearly the same size. The study also reveals that Ti(IV) binds more tightly to one site than the other, and this difference is due to both entropic and enthalpic contributions. The study has implications for the role of transferrin in the anticancer activity of Ti(IV) drugs and the serum binding of Ti(IV) ions released from implants or imaging reagents.

Binding Sites↗

PubMed2001

Corrosion behavior of PIRAC nitrided Ti-6Al-4V surgical alloy.

Hard titanium nitride (TiN) coatings were obtained on the surface of Ti-6Al-4V alloy using an original PIRAC nitriding method, based on annealing the samples under a low pressure of monatomic nitrogen created by selective diffusion of N from the atmosphere. PIRAC nitrided samples exhibited excellent corrosion resistance in Ringer's solution in both potentiodynamic and potentiostatic tests. The anodic current and metal ion release rate of PIRAC nitrided Ti-6Al-4V at the typical corrosion potential values were significantly lower than those of the untreated alloy. This, together with the excellent adhesion and high wear resistance of the TiN coatings, makes PIRAC nitriding an attractive surface treatment for Ti-6Al-4V alloy surgical implants.

Journal Article↗

PubMed2001

Titanium powder sintering for preparation of a porous functionally graded material destined for orthopaedic implants.

This work focuses on basic research into a P/M processed, porous-surfaced and functionally graded material (FGM) destined for a permanent skeletal replacement implant with improved structural compatibility. Based on a perpendicular gradient in porosity the Young's modulus of the material is adapted to the elastic properties of bone in order to prevent stress shielding effects and to provide better long-term performance of the implant-bone system. Using coarse Ti particle fractions the sintering process was accelerated by silicon-assisted liquid-phase sintering (LPS) resulting in a substantial improvement of the neck geometry. A novel evaluation for the strength of the sinter contacts was proposed. The Young's modulus of uniform non-graded stacks ranged from 5 to 80 GPa as determined by ultrasound velocity measurements. Thus, the typical range for cortical bone (10-29 GPa) was covered. The magnitude of the Poisson's ratio proved to be distinctly dependent on the porosity. Specimens with porosity gradients were successfully fabricated and characterized using quantitative description of the microstructural geometry and acoustic microscopy.

Journal Article↗

PubMed2004

Fibroblast attachment to smooth and microtextured PET and thin cp-Ti films.

Improving the biological performance of engineered implants apposing interfacing tissues is a critical issue in Biomaterials Science and Engineering. Micromotion at the soft tissue-implant interface has been shown to sustain an inflammatory response. To eliminate micromotion, it is desirable to promote cellular and extracellular matrix adhesion to the implant surface. Surfaces are modified topographically or chemically to effect cellular adhesion and to influence cellular interactions and function. Previous studies have identified the specific topographical characteristics that appear to elicit cellular attachment. This in vitro study compares the independent effects of surface chemistry and topography on fibroblast-test specimen proximity. Titanium (Ti) was sputter-coated in stepwise, increasing thickness (20-350 nm) onto a series of either smooth or microtextured polyethylene terephthalate (PET), resulting in a stepwise change from a PET surface to a Ti surface. The series was evaluated in a 3-day fibroblast culture with transmission electron microscopy (TEM) for cell-test specimen proximity. Fibroblast proximity to the coverslip surface increases, as the Ti thickness increases, on either smooth or textured test specimens. Furthermore, fibroblasts were firmly attached to the ridge tops on the coated textured test specimens. Therefore, fibroblast apposition is strongly enhanced by microtextured surfaces and Ti rather than smooth surfaces and PET.

Animals↗

PubMed2006

Coating of titanium implants with collagen, RGD peptide and chondroitin sulfate.

Coating of orthopaedic implants with extracellular bone matrix components was performed to enhance bone healing. Titanium pins of 0.8mm diameter were coated with type I collagen (Ti/Coll), RGD peptide (Ti/RGD) or type I collagen and chondroitin sulfate (Ti/Coll/CS). Uncoated pins (Ti) served as control. The pins were inserted as intramedullary nails into the tibia of male adult Wistar rats. Six specimens of each group were retrieved at 4, 7, 14 and 28 days. All implants healed uneventfully without adverse reactions. ED 1-positive macrophages appeared in higher numbers around Ti/RGD at day 4 and around Ti at day 14 after implantation (p < 0.05). TRAP-positive osteoclasts and precursors were abundant around Ti/Coll/CS at day 7 (p < 0.05). A significant increase in osteopontin-positive osteoblasts was seen around Ti/Coll/CS implants at days 7 and 14, and around Ti/RGD at day 14 (p < 0.05). At day 28, 62% of Ti, 76% of Ti/Coll, 85%* of Ti/RGD and 89%* of Ti/CoIl/CS (*p < 0.05) implants were covered with newly formed lamellar bone. The addition of extracellular matrix components significantly enhances bone remodelling in the early stages of bone healing around Ti implants, eventually leading to increased new bone formation at the implant surface after 4 weeks.

Animals↗