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PubMed1999

Development and analytical characterization of cysteine-grafted polypyrrole films electrosynthesized on Pt- and Ti-substrates as precursors of bioactive interfaces.

The grafting of cysteine to polypyrrole(PPY)-coated platinum and titanium substrates has been investigated with the aim of developing innovative bioactive materials of interest for bone implants. Polypyrrole has been chosen as the coating polymer because of its suitability to be electrochemically grown directly onto metallic substrates, of any shape and dimension, leading to remarkably adherent overlayers. The effectiveness of grafting was monitored by X-ray photoelectron spectroscopy (XPS) which showed the presence of aminoacid residues onto the polymer surface. Information obtained by an accurate curve fitting of significant regions in the spectra (C1s, N1s, and O1s signals) and by a cross-check of peak area ratios, before and after the grafting process, gave evidence that cysteine forms covalent bonds to pyrrole rings, preferentially in beta-positions, via the sulfydryl group, leaving both amino and carboxylic functionalities available for further chemistry. The surface density of cysteine residues was evaluated by microgravimetric measurements performed by the electrochemical quartz crystal microbalance and was found suitable for the exploitation of these modified surfaces as bioactive systems. Some preliminary results are reported on the adhesion of neonatal rat calvarial osteoblasts onto titanium substrates after coating by a PPY film modified by a polypeptide having cysteine as a terminal residue and containing the Arg-Gly-Asp aminoacid adhesive sequence.

Amino Acid Sequence↗

PubMed1996

Initial attachment of human gingival fibroblast-like cells in vitro to titanium surfaces pretreated with saliva and serum.

Wound healing at the implant-soft tissue interface occurs in the presence of saliva and blood. The aim of this in vitro study was to investigate potential influence of saliva and serum on initial attachment of human gingival fibroblast-like cells to titanium (Ti) surfaces 10 x 10 mm large specimens were prepared from pure Ti, incubated for 1 h in either whole human saliva, fetal calf serum, their mixtures in proportions 75:25, 50:50 and 25:75, or buffer as control. Subsequently suspensions of human gingival fibroblast-like cells were applied in 4 separate assays to Ti surfaces for 40 min and cell attachment was evaluated by means of image analysis under reflected light microscopy. Significantly lower numbers of attached cells (p < 0.001) were found on all surfaces pretreated with saliva alone or in combination with serum. Pretreatment with serum alone showed no consistent enhancing effect on cell adhesion. These results suggest that exposure of implant necks to saliva during implant insertion or periimplantitis treatment might inhibit adhesion of gingival fibroblasts and thus indirectly support isolation of the implant by epithelial proliferation.

Animals↗

PubMed2002

Effect of metal alloy surface stresses on the viability of ROS-17/2.8 osteoblastic cells.

In this study we compared the effect of structural stresses and surface roughness on biocompatibility of NiTi- and Ti-alloy for ROS-17/2.8 osteoblastic cells. We suggest here that cell viability and cell attachment are linear functions of internal (structural) stress and subgrain size of the implant alloy. However, this is not the case with surface roughness. The two-phase state in these materials is characterized by different mean values of structural stresses (sigma) in alpha-martensite and beta-phase. We found a straight correlation between cell viability and sigma(beta)/sigma(alpha) ratio. Atomic force microscopy revealed that, even after equal surface polishing treatments, roughness varied significantly between the different alloys. The effect of the surface structure of the alloy on the osteoblastic ROS-17/2.8 cell survival rate was studied with combined calcein-ethidium-homodimer fluorescence labeling. The possible effects on cell attachment to substrate were studied by staining the focal contacts with paxillin antibody. All the NiTi surfaces were tolerated well and the cells attached most abundantly to the roughest NiTi surface but the smoothest Ti-alloy surface. However, other parameters of the material state, such as the surface stresses created by hot rolling seem to be responsible for some of the attachment and cell survival features observed in this study.

Alloys↗

PubMed2002

Machinability of cast commercial titanium alloys.

This study investigated the machinability of cast orthopedic titanium (metastable beta) alloys for possible application to dentistry and compared the results with those of cast CP Ti, Ti-6Al-4V, and Ti-6Al-7Nb, which are currently used in dentistry. Machinability was determined as the amount of metal removed with the use of an electric handpiece and a SiC abrasive wheel turning at four different rotational wheel speeds. The ratios of the amount of metal removed and the wheel volume loss (machining ratio) were also evaluated. Based on these two criteria, the two alpha + beta alloys tested generally exhibited better results for most of the wheel speeds compared to all the other metals tested. The machinability of the three beta alloys employed was similar or worse, depending on the speed of the wheel, compared to CP Ti.

Alloys↗

PubMed1978

Evaluation of couple/crevice corrosion by prosthetic alloys under in vivo conditions.

Alloys of cast Co-Cr-Mo, wrought Co-Cr-W, wrought, Co-Ni-Cr-Mo(MP35N), Ti-60% Al-4% V, and graphite were incorporated in specimens which simulated both a couple and a crevice corrosion condition. These specimens were implanted in a dog for 30 months. Post-sacrifice examination showed no substantial evidence of corrosion activity on the surfaces of the metals except for a tarnish film on the titanium alloy specimens. The presence of the tarnish film is taken as more evidence of corrosion activity and this correlated with a thicker average fibrous membrane, cellular activity in and near the fibrous membrane, and some increased vascularity. These must be regarded as preliminary observations.

Alloys↗

PubMed1997

Corrosion behaviour and mechanical properties of functionally gradient materials developed for possible hard-tissue applications.

Artificial hip joints have an average lifetime of 10 years due to aseptic loosening of the femoral stem attributed to polymeric wear debris; however, there is a steadily increasing demand from younger osteoarthritis patients aged between 15 and 40 year for a longer lasting joint of 25 years or more. Compliant layers incorporated into the acetabular cup generate elastohydrodynamic lubrication conditions between the bearing surfaces, reduce joint friction coefficients and wear debris production and could increase the average life of total hip replacements, and other human load-bearing joint replacements, i.e. total knee replacements. Poor adhesion between a fully dense substrate and the compliant layer has so far prevented any further exploitation. This work investigated the possibility of producing porous metallic, functionally gradient type acetabular cups using powder metallurgy techniques - where a porous surface was supported by a denser core - into which the compliant layers could be incorporated. The corrosion behaviour and mechanical properties of three biomedically approved alloys containing two levels of total porosity (>30% and <10%) were established, resulting in Ti-6Al-4V being identified as the most promising biocompatible functionally graded material, not only for this application but for other hard-tissue implants.

Journal Article↗

PubMed1981

Easy method for measurement of opening angle of Björk-Shiley valve with two computers. Proof of floating phenomenon of Björk-Shiley valve.

A new method for measuring the opening angle of Björk-Shiley valve (B-S valve) was reported in 1977. However, this method is complicated enough to permit quick calculation of the opening angle in multiple frames of one cinefilm. We devised a new method with using two computers (NAC Cardias GP 2000, TEXAS TI-59) for calculating the opening angle of the B-S valve. We measured the opening angle of 7 cases (they were all implanted B-S valves, 5 were mitral and 2 were aortic). Results are the following: (1) The maximum opening angle ranged from 54 degrees to 65 degrees and the mean value was 58.1 degrees. (2) We showed the floating phenomenon of B-S valve with our method. (3) We showed the accuracy of our method by measuring 10 times the same photograph of B-S valve. (4) We showed that our method is very accurate by comparing the values calculated by our method with those calculated directly from the valve which was removed from a patient. (5) It takes less than 30 minutes to calculate the opening angle of 60 frames (we took 60 frames of cine-film per minutes.

Aortic Valve↗

PubMed2005

Transforming growth factor-beta 1 (TGF-beta1) prevents the age-dependent decrease in bone formation in human osteoblast/implant cultures.

Titanium implants have been extensively used in orthopedic surgery and dentistry. Most of the patients who receive such implants are elderly with a compromised ability to heal and form new bone. By using an in vitro osteoblast/implant culture system, the potency of TGF-beta1 in enhancing mineralization of human osteoblast cultures from elderly subjects was investigated in this study. Primary human osteoblast (HOB) cells obtained from different age group human subjects [Young (Y), Middle (M), and Old (O)] were cultured on Ti alloy (Ti-6Al-4V) disks with or without continuous administration of 0.2 ng/mL TGF-beta1 in the medium for 2 or 4 weeks. TGF-beta1 significantly (p < 0.05) increased calcium content and the size of calcified nodules on implant disks in the O group, but had no effect on the Y or M groups. The number of calcified nodules was not different with or without TGF-beta1 in all age groups. As measured by Northern blot analysis and RT-PCR, TGF-beta1 significantly increased the expression of bone-specific extracellular matrix proteins, including alkaline phosphatase, Type I collagen, bone sialoprotein and osteocalcin, after both 2 and 4 weeks in the O group but not in the Y group. In conclusion, TGF-beta1 enhances mineralization on implant materials of osteoblast cultures from elderly human subjects.

Absorbable Implants↗

PubMed2005

Induction ovens and electromagnetic interference: what is the risk for patients with implantable cardioverter defibrillators?

Electromagnetic fields may interfere with normal implantable cardioverter defibrillator (ICD) function. Although the devices are effectively shielded and use exclusively bipolar leads, electromagnetic interference (EMI) remains a concern when patients are exposed to several household appliances. The aim of this study was to evaluate potential EMI risk of induction ovens, which are increasingly common in private households. In vitro measurements of an induction oven for private households GK 43 TI (V-Zug, Inc., Zug, Switzerland) showed that heating is regulated by increasing operating time from level 1 (100 ms/sec) to 5 (continuous operation). From levels 5 to 9 the magnetic field increases. Nineteen patients with left-sided implants of single- and dual-chamber ICD systems (8 Medtronic, 7 Guidant, and 4 St. Jude Medical) (18 males, 1 female), age (mean +/- SEM) 58 +/- 3 years, were included in this study. All patients were examined in standing position, bent over the cooking pot (minimal distance to the induction coil 25 cm), and with the cooking pot put eccentrically over the induction field at three different cooking levels (level 2, 5, and 9). The tests were repeated touching the cooking pot with one hand. Ventricular sensitivity was left unchanged. Ventricular tachycardia therapies were turned off in Medtronic and Guidant devices and ventricular sensing was continuously monitored in St. Jude Medical devices during testing. Interrogation of the devices after exposure did not show any inappropriate tachycardia detection, oversensing, or reprogramming. In conclusion, ICD patients can be reassured that EMI is unlikely to affect their devices if induction ovens are used in their kitchens.

Defibrillators, Implantable↗

PubMed2000

The effectiveness of mupirocin preventing Staphylococcus aureus in catheter-related infections in peritoneal dialysis.

The objective of this study was to evaluate the effectiveness of mupirocin on Staphylococcus aureus with regard to peritoneal dialysis (PD)-catheter exit-site infections (ESI), tunnel infections (TI), and peritonitis episodes (PE). The study was performed on 42 continuous ambulatory peritoneal dialysis (CAPD) patients (group I) treated from April 1998 to July 1999. These patients were instructed to apply mupirocin daily at the catheter exit site as part of their exit-site care. The control was the same group's historical infection data. Results were also recorded for a second group of 16 patients (group II) with newly implanted PD catheters were also instructed to apply mupirocin at the exit site daily. During the control period (before daily mupirocin application), group I recorded 16 episodes of ESI (0.30 episodes per patient-year), 6 episodes of TI (0.11 episodes per patient-year), 15 episodes of PE (0.28 episodes per patient-year), and one case of catheter removal (0.019 episodes per patient-year) owing to S. aureus exit-site infection coexisting with peritonitis. The rate of S. aureus exit-site infection during this period was 0.11 episodes per patient-year; of S. aureus tunnel infection, 0.057 episodes per patient-year; and of S. aureus peritonitis, 0.076 episodes per patient-year. During the mupirocin period, infections and peritonitis owing to S. aureus dramatically decreased (p < 0.01 and p < 0.001 respectively). The rate of S. aureus exit-site infection was 0.02 episodes per patient-year, with no S. aureus tunnel infections, and no catheter removals owing to S. aureus peritonitis. Similarly, in group II, no episodes were recorded of any ESI, TI, or PE owing to S. aureus, although 4 episodes of ESI (0.37 episodes per patient-year, 2 with other gram-positive bacteria, and 2 with gram-negative bacteria) and 8 PEs (0.75 episodes per patient-year) were seen. We conclude that mupirocin application provides excellent prophylaxis for catheter-related infections owing to S. aureus, and that reduction of these infections may improve the long-term survival of patients on CAPD.

Administration, Topical↗

PubMed2001

Observations at the articular surface of hip prostheses: an analytical electron microscopy study on wear and corrosion.

We used scanning electron microscopy in combination with X-ray microanalysis to evaluate Co-, Cr-, and Mo-based human femoral hip prostheses. In total, 23 retrieved implants and four new implants were included in this study. Scanning electron microscopy of the polished surface of all arthroplasties showed, in addition to the polishing marks, small round and angular holes or pits. Other types of surface irregularities were interpreted as wear or corrosion of the metal compound. In all cases studied, corrosion propagated from holes at the surface of the polished prosthesis heads, in some cases also along phase boundaries. X-ray microanalysis of the intact prosthetic surface showed a relative composition of the elements Co, Cr, and Mo, which was in agreement with the manufacturer's information (63:33:4%). However, X-ray microanalysis spot analysis of the surface holes showed deviation in the relative composition of the elements Co, Cr, and Mo and also the presence of Si, Ti, and Al. Furthermore, Ti and Al could be traced back at an artificially made fracture plane of a new prosthesis. Therefore, Ti and Al have to be present during the manufacturing process. These impurities in the metal prosthesis alloy may create a galvanic element with the Co, Cr, Mo alloy of the implant. If this is the case, such a galvanic element in combination with the electrolyte environment formed by body fluids, can induce galvanic corrosion with release of metal particles.

Arthroplasty, Replacement, Hip↗

PubMed1986

Effects of zinc oxide in an occlusive, adhesive dressing on granulation tissue formation.

The role of zinc in an occlusive, adhesive dressing (Zn-tape) was investigated in two experiments in the rat. In the first one Zn-tape was compared with a similar tape without zinc components and also with an inert plastic coated fabric with regard to the wound inflammatory reaction in excisional wounds. In the second experiment we attempted to assess possible systemic effects of zinc absorbed from Zn-tape-treated excisional wounds by studying the granulation tissue formation in subcutaneously implanted Ivalon sponges. The excisional wounds were treated with either the Zn-tape or a titanium tape in which the zinc oxide was replaced by an equivalent amount of titanium dioxide (Ti-tape). The granulation tissue produced was evaluated histologically, histochemically and biochemically. The plain adhesive mass and the Ti-tape elicited an intense inflammatory reaction as indicated both by high activities of alkaline phosphatases and histological examination. The Zn-tape reduced inflammatory processes in the granulation tissue of the excisional wounds. Zinc levels in serum and liver were raised in Zn-tape-treated animals. We conclude that zinc oxide in the Zn-tape affects inflammatory reactions in the granulation tissue of the wounds, possibly through a continuous release of zinc ions and by modifying the adhesive components of the Zn-tape. There was no evidence of a systemic effect of zinc absorbed from the excisional wounds on the granulation tissue formation in the implanted Ivalon sponges.

Acid Phosphatase↗

PubMed2002

[Evaluation of peribulbar soft tissue reactions to titanium mesh in experimental tests in animals].

Orbital fractures are often accompanied by periosteal rupture and oculomotor muscle injury from the orbital fissure (blowout fracture). During reconstruction, substitute material (biomaterial) restoring the orbit is placed on a bony shelf and brought into direct contact with muscles and indirect contact with the eyeball, optic nerve and lacrimal gland. Histological examination of orbital tissues following reconstruction with titanium mesh, not possible in humans, can be performed in a rat model. In spite of different anatomy, the rats orbit was found satisfactory for the purpose of this study. The eyeball is supported by oculomotor muscles, lying partly on the malar bone. The aim was to follow the reaction of periorbital soft tissues to titanium mesh in a rat model of inferior orbital wall injury simulating orbital muscle lesions in man caused by blowout fracture. Insertion of titanium mesh directly in contact with muscles reproduced the situation in the human orbit. The following soft tissues and organs were studied: striated oculomotor muscle (inferior rectus), sclera, choroid, optic nerve and lacrimal gland. The results were compared with sham-operated animals (titanium mesh not implanted). Two questions were addressed: Is the process of healing of orbital muscle injury affected by the titanium mesh? Is there any evidence of adverse effect on periorbital soft tissues or eye of titanium wear particles produced by contraction of orbital muscles? Buffalo rats of the 38th generation and smooth titanium mesh (Ti-6AI-4V alloy) measuring 0.2 x 8 x 8 mm were used.

Animals↗

PubMed2006

Biomimetic implant coatings.

Biomaterials and tissue engineering technologies are becoming increasingly important in biomedical practice, particularly as the population ages. Cellular responses depend on topographical properties of the biomaterial at the nanometer scale. Structures on biomaterial surfaces are used as powerful tools to influence or even control interactions between implants and the biological system [; ]. The influence of nanometer sized surface structures on osteoblastlike cell interactions was tested with niobium oxide coatings on polished titanium slices (cp-Ti grade 2). The aim of the study was to investigate the influence of nanoscopic surface structures on osteoblast interactions in order to support collagen I production and cell adhesion. The coatings were done by means of the sol-gel process. The surface structure was adjusted by annealing of the metaloxide ceramic coatings due to temperature depended crystal growth. The applied annealing temperatures were 450, 550 and 700 degrees C for 1 h, corresponding to Ra-numbers of 7, 15 and 40 nm. The surfaces were characterized by means of AFM, DTA/TG, diffractometry and white light interferometry. The cell reactions were investigated concerning adhesion kinetics, migration, spreading, cell adhesion, and collagen I synthesis. The smooth surface (Ra=7 nm) resulted in the fastest cell anchorage and cell migration. The closest cell adhesion was reached with the surface structure of Ra=15 nm. The roughest surface (Ra=40 nm) impedes the cell migration as well as a proper spreading of the cells. The best results concerning cell adhesion and spreading was reached with an intermediate surface roughness of Ra=15 nm of the niobium oxide coating on cp-titanium slices.

3T3 Cells↗

PubMed2003

Quantitative analysis of osteoblast behavior on microgrooved hydroxyapatite and titanium substrata.

The effects of implant surface topography and chemistry on osteoblast behavior have been a research focus because of their potential importance in orthopedic and dental applications. This work focused on the topographic effects of hydroxyapatite (HA) and titanium (Ti) surface that had identical micropatterns to determine whether there was synergistic interaction between surface chemistry and surface topography. Surface microgrooves with six different groove widths (4, 8, 16, 24, 30, and 38 microm) and three different groove depths (2, 4, and 10 microm) were made on single crystalline silicon wafers using microfabrication techniques. Ti and HA thin films were coated on the microgrooves by radio-frequency magnetron sputtering. After that, human osteoblast-like cells were seeded and cultured on the microgrooved surfaces for up to 7 days. The cells' behavior was examined using scanning electron microscopy after cells were fixed and dehydrated. Statistical analysis was based on quantitative data of orientation angle, evaluating the contact guidance, and form index, describing cell shape or cell morphology changes. The contact guidance and cell shape changes were observed on the HA and Ti microgrooves. No difference in orientation angle between HA and Ti microgrooves was found. This might suggest that surface chemistry was not a significant influence on cell guidance. However, the form index analysis indicated an interaction between topographic effects and surface chemistry. Thus, conclusions about surface topographic effects on cell behavior drawn from one type of material cannot simply be applied to another type of material.

Durapatite↗

PubMed1996

Bone-bonding behavior of plasma-sprayed coatings of BioglassR, AW-glass ceramic, and tricalcium phosphate on titanium alloy.

The bone-bonding behavior of three kinds of bioactive ceramics coated on titanium alloy by the plasma-spray technique was investigated. Titanium alloy (Ti-6A1-4V) coated with BioglassR (45S5), apatite-wollastonite containing glass ceramic (AW), or beta-tricalcium phosphate (TCP) was prepared, and rectangular specimens were implanted into the tibial bones of mature male rabbits, which were sacrificed 8 or 24 weeks after implantation. The tibiae containing the implants were dissected out and subjected to detachment tests to measure the failure load. The bone-implant interface was investigated by Giemsa surface staining, contact microradiography, and scanning electron microscopy-electron probe microanalysis (SEM-EPMA). Eight weeks after implantation, the failure loads for implants coated with BioglassR, AW, and TCP were 1.04 +/- 0.94, 2.03 +/- 1.17, and 3.91 +/- 1.51 kg, respectively, and 24 weeks after implantation, the respective failure loads were 2.72 +/- 1.33, 2.39 +/- 1.30, and 4.23 +/- 1.34 kg. Failure loads of AW- and TCP-coated implants did not increase significantly with time. After the detachment test, breakage of the coating layer was observed. Bioactive ceramics can act as stimulants that induce bonding between bone and metal implants. However, failure load of metal implants coated with the bioactive ceramics was lower than that of bulk AW or TCP. It appears impossible to obtain a higher failure load using a bioactive-ceramic coating on titanium alloy. Histologically, the coating layer was found to become detached from the metal implant and the bone tissue bonded to the coating layer. SEM-EPMA observation revealed breakage of the coating layer, although bonding between bone and the coating layer was evident. A Ca-P-rich layer was observed at the interface between bone and the AW coating, and a Ca-P-rich and a Si-rich layer were observed at the interface between bone and the BioglassR coating. For clinical application, it would seem better to use coated metal implants for short-term implantation. However, there is a possibility of breakage of the coating layer because of both dissolution of the bioactive ceramic and mechanical weakness at the interface between the coating layer and the metal implant.

Alloys↗

PubMed1999

Comparison of Zeeman Background Corrected Atomic Absorption Spectrometric and Inductively Coupled Plasma Mass Spectrometric detection of trace elements in electrothermally vaporized serum.

There is continued interest in the measurement of degradation products of metallic implants in biological tissues and fluids. A study was conducted to compare analytical results obtained by the Zeeman Background Corrected Atomic Absorption Spectrometric and Inductively Coupled Plasma Mass Spectrometric techniques on a uniform set of triple-element (Ti, Al, and V) spiked human serum specimens over concentration ranges up to 20 ppb (20 ng/ml). The results indicate that the two methods are comparable. The positive and negative aspects of each method of instrumental analysis are discussed.

Biocompatible Materials↗

PubMed2003

In vitro corrosion behavior of bioceramic, metallic, and bioceramic-metallic coated stainless steel dental implants.

OBJECTIVES: The most common metals and alloys used in dentistry may be exposed to a process of corrosion in vivo that make them cytotoxic. The biocompatibility of dental alloys is primarily related to their corrosion behavior. The aim of this work was to evaluate the corrosion behavior and thus the biocompatibility of the uncoated and coated stainless steels and compare the effect of type of coatings on corrosion behavior. METHODS: Three types of coatings, hydroxyapatite (HA), titanium (Ti), and a double-layer HA/Ti on AISI 316L stainless steel were made. HA coating was produced using plasma-spraying technique and Ti coating was made using physical vapor deposition process. In order to perform a novel double-layer composite coating, a top layer of HA was plasma-sprayed over a physical vapor deposited Ti layer on AISI 316L stainless steel. Structural characterization techniques including XRD, SEM and EDX were used to investigate the microstructure, morphology and crystallinity of the coatings. Electrochemical potentiodynamic tests were performed in physiological solutions in order to determine and compare the corrosion behavior of the coated and uncoated specimens as an indication of biocompatibility. RESULTS: Double-layer HA/Ti coating on AISI 316L SS had a positive effect on improvement of corrosion behavior. The decrease in corrosion current densities was significant for these coated specimens and was much lower than the values obtained for uncoated and single HA coated specimens. Ti coating on AISI 316L SS also has a beneficial effect on corrosion behavior. The results were compared with the results of corrosion behavior of HA coated commercially pure titanium (cpTi) and uncoated cpTi. SIGNIFICANCE: These results demonstrated that the double-layer HA/Ti coated 316L SS can be used as an endodontic implant and two goals including improvement of corrosion resistance and bone osteointegration can be obtained simultaneously.

Biocompatible Materials↗