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J Lausmaa

Publications and source records attributed to J Lausmaa.

17 recordsLinked to original sources
PubMed1997

Glow discharge plasma treatment for surface cleaning and modification of metallic biomaterials.

Glow discharge plasma treatment is a frequently used method for cleaning, preparation, and modification of biomaterial and implant surfaces. The merits of such treatments are, however, strongly dependent on the process parameters. In the present work the possibilities, limitations, and risks of plasma treatment for surface preparation of metallic materials are investigated experimentally using titanium as a model system, and also discussed in more general terms. Samples were treated by different low-pressure direct current plasmas and analyzed using Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), atomic force microscopy, scanning electron microscopy, and light microscopy. The plasma system is a home-built, ultra-high vacuum-compatible system that allows sample introduction via a load-lock, and precise control of pressure, gas composition and flow rate, etc. This system allows uniform treatment of cylindrical and screw-shaped samples. With appropriate plasma parameters, argon plasma remove all chemical traces from former treatments (adsorbed contaminants and other impurities, and native oxide layers), in effect producing cleaner and more well-controlled surfaces than with conventional preparation methods. Removal (sputtering) rates up to 30 nm/min are possible. However, when inappropriate plasma parameters are used, the result may be increased contamination and formation of unintentional or undesired surface layers (e.g., carbides and nitrides). Plasma-cleaned surfaces provide a clean and reproducible starting condition for further plasma treatments to form well-controlled surface layers. Oxidation in pure O2 (thermally or in oxygen plasmas) results in uniform and stoichiometric TiO2 surface oxide layers of reproducible composition and thicknesses in the range 0.5-150 nm, as revealed by AES and XPS analyses. Titanium nitride layers were prepared by using N2 plasmas. While mild plasma treatments leave the surface microstructure unaffected, heavy plasma treatment can give rise to dramatic morphologic changes. Comparison of these results with corresponding analyses of commercial implants and electropolished and/or anodically oxidized samples shows that the plasma treatment offers superior control of the surface status. However, it is also shown that improper control of the plasma process can produce unwanted and irreproducible results.

Argon↗
PubMed1997

Adhesion and activation of platelets and polymorphonuclear granulocyte cells at TiO2 surfaces.

The initial reactions of two TiO2 surfaces with blood were investigated by short-time exposure to capillary blood and analysis of surface-adsorbed plasma proteins and surface-adhering cells by using immunofluorescence techniques. Antibodies directed against platelet membrane antigen and P-selectin were used to visualize platelet adhesion and activation. Acridine orange and anti-CD11b were used to detect adhesion and activation of polymorphonuclear granulocytes (PMNs). Antibodies against thrombospondin were used as markers for platelet alpha-granules. The fluorescence intensity was quantitated by computer-aided image analysis. Commercially pure, polished sheet titanium was oxidized in two different ways: (1) the natural oxide was dissolved with hydrofluoric acid and a new oxide layer was grown by oxidation in nitric acid, or (2) annealing was performed at 700 degrees C in air. Auger electron spectroscopy and x-ray photoelectron spectroscopy showed that both surfaces had similar composition consisting of TiO2 covered by a carbonaceous surface contamination layer. The thickness of the oxide layer was 4 nm on the acid-oxidized surface and 39 nm on the annealed surface. Optical profilometry and scanning electron microscopy showed that the acid-oxidized surface was rough and the annealed surface was smooth. The fibrinogen/prothrombin-thrombin ratio in the initial protein film differed between the surfaces. The number of adhering platelets was larger at the surface with a high surface concentration of adsorbed fibrinogen. Platelet activation (CD62) and priming of PMNs (CD 11b) were also significantly higher on the acid-oxidized surface. The results indicate that non-self recognition of biomaterials is an array of transient reactions comprising protein-material, protein-cell, and cell-cell interactions.

Biocompatible Materials↗
PubMed1996

Torque and histomorphometric evaluation of c.p. titanium screws blasted with 25- and 75-microns-sized particles of Al2O3.

A comparison was made between screw-shaped c.p. titanium implants blasted with either 25- or 75-microns particles of Al2O3. The implant surfaces were investigated with respect to topography and composition before implantation in rabbit bone. Grit blasting with 25- or 75-microns particles produced two different surface roughnesses, but no significant difference in the surface composition for the two surfaces. After 12 weeks insertion time in the rabbit tibia and femur, a higher removal torque and more bone-to-metal contact was found for the implants blasted with 75-microns particles compared with the 25-microns-blasted ones.

Aluminum Oxide↗
PubMed1996

Bone response to surface-modified titanium implants: studies on the early tissue response to machined and electropolished implants with different oxide thicknesses.

The bone formation around titanium implants with varied surface properties is investigated. Machined and electropolished samples with and without thick, anodically formed surface oxides were prepared, surface characterized and inserted in the cortical bone of rabbits (1, 3 and 6 weeks). Scanning electron microscopy, scanning Auger electron spectroscopy and atomic force microscopy revealed marked differences in oxide thickness, surface topography and roughness, but no significant differences in surface chemical composition, between the different groups of implants. Light microscopic morphology and morphometry showed that all implants were in contact with bone and had a large proportion of bone within the threads at 6 weeks. The smooth, electropolished implants, irrespective of anodic oxidation, were surrounded by less bone than the machined implants after 1 week. After 6 weeks the bone volume as well as the bone-implant contact were lower for the merely electropolished implants than for the other three groups. Our study shows that a high degree of bone contact and bone formation are achieved with titanium implants which are modified with respect to oxide thickness and surface topography. However, the result with the smooth (electropolished) implants indicates that a reduction of surface roughness, in the initial phase, decreases the rate of bone formation in rabbit cortical bone.

Animals↗
PubMed1994

Titanium with different oxides: in vitro studies of protein adsorption and contact activation.

Adsorption of albumin (HSA) and fibrinogen (Fib) from human blood plasma onto titanium surfaces with varying oxide properties was studied with an enzyme-linked immunosorbent assay. The intrinsic activation of blood coagulation (contact activation) was studied in vitro using a kallikrein-sensitive substrate. The sample surfaces were characterized with Fourier transform Raman spectroscopy. Auger electron spectroscopy and atomic force microscopy. Low Fib and high HSA adsorption was observed for all titanium samples except for the radio frequency plasma-treated and water-incubated samples, which adsorbed significantly lower amounts of both. Oxide thickness and carbon contamination showed no influence on protein adsorption or contact activation. Smooth samples with a surface roughness (Rrms) < 1 nm showed some correlation between surface wettability and adsorption of Fib and HSA, whereas rough surfaces (Rrms > 5 nm) did not. To varying degrees, all titanium surfaces indicated activation of the intrinsic pathway of coagulation as determined by their kallikrein formation in plasma.

Adsorption↗
PubMed1994

Bone response to surface modified titanium implants: studies on electropolished implants with different oxide thicknesses and morphology.

In a series of experimental studies, bone formation was analysed around systematically modified titanium implants. In the present study, machined, electropolished and anodically oxidized implants were prepared, surface characterized and inserted in the cortical bone of rabbits (7 wks and 12 wks). SEM, scanning Auger electron spectroscopy and atomic force microscopy revealed no differences in surface composition but marked differences in oxide thickness, surface topography and roughness. Light microscopic morphology and morphometry showed that all implants were in contact with bone, and had a large proportion of bone within the threads. The smooth, electropolished implants were surrounded by less bone than the machined implants with similar oxide thickness, (4-5 nm) and the anodically oxidized implants with thicker oxides (21 nm and 180 nm, respectively) after 7 wks. These studies show that a high degree of bone contact and bone formation can be achieved with titanium implants which are modified with respect to oxide thickness and surface topography. However, it appears that a reduction of surface roughness may influence the rate of bone formation in rabbit cortical bone.

Animals↗
PubMed1994

Site-specific adhesion of Staphylococcus epidermidis (RP12) in Ti-Al-V metal systems.

Staphylococcus epidermidis (RP12) adhesion patterns were studied on the following titanium (Ti)-aluminium (Al)-vanadium (V) metal systems: (i) microfabricated samples consisting of Ti, Al and V islands deposited onto Ti or V substrata, (ii) pure Ti, Al and V metals, and (iii) medical grade Ti6Al4-V alloy. All of these surfaces were covered with their respective oxides formed upon exposure of the metals to air. Quantitative analysis of the number of cells bound per unit area indicates that S. epidermidis (RP12) exhibits greatest adhesion to pure V surfaces. When exposed to surfaces having controlled spatial variations in chemical composition on the 10 microns scale (microfabricated samples), the bacteria preferentially populate V islands versus Ti or Al substrata. In the case of the biphasic Ti6Al4V alloy, the bacteria tend to adhere to V-rich, mixed phase regions and phase boundaries. These findings demonstrate that enhanced and preferential adhesion of S. epidermidis (RP12) occurs on V surfaces in Ti-Al-V metal systems and suggest that bacterial interactions are influenced by surface oxide composition.

Alloys↗
PubMed1994

Material-tissue interfaces: the role of surface properties and processes.

The introduction of a foreign material into living tissue--intentionally as in biomedical applications (implants, protheses, drugs) or unintentionally as when minerals or fibers are inhaled--results in the creation of interfaces between the material and the surrounding tissue. This article identifies and discusses the possible role of material surface properties and molecular processes occurring at such interfaces. For kinetic and thermodynamic reasons, surfaces are different from the corresponding bulk of the material, and contain reactive (unsaturated) bonds, which in turn lead to the formation of surface reactive layers (e.g., surface oxides on metals) and adsorbed contamination layers. The encounter with the biological environment leads to further surface reactions modifying the surface, and to the adsorption of water, ions, and biomolecules, which are continuously exchanged. The exact nature of the dynamic, adsorbed water, ions, and biomolecule coating in turn influences the behavior of cells approaching the material surface, and hence the tissue response.

Animals↗
PubMed1991

Preparation of ultra-thin oxide windows on titanium for TEM analysis.

Using submerged jet electropolishing, extremely thin (less than 10 nm), continuous, thermal oxide "windows" have been prepared on polycrystalline titanium (Ti). The preparation technique is described in detail. It has allowed a systematic investigation of the structure of thermal surface oxide layers on Ti in the thickness range 6-40 nm, corresponding to oxidation temperatures 100-450 degrees C. Auger electron spectroscopy was used for oxide characterization and for depth profiling to determine oxide thickness. The thinnest oxides, less than 10 nm, are amorphous, morphologically homogeneous, and with essentially no contrast in the transmission electron microscopy (TEM) pictures. As the oxide thickness is increased up to 40 nm, a texture corresponding to the grain structure of the oxidized metal becomes gradually more visible. At the same time the oxide becomes increasingly more crystalline. The results are compared with previously published corresponding results for thicker anodic oxides on Ti.

Microscopy, Electron↗
PubMed1990

Method for ultrastructural studies of the intact tissue-metal interface.

Samples were prepared for ultrastructural studies of the intact interface between metallic implants and tissue by transmission electron microscopy. The method is based on plastic embedding of implant and tissue and subsequent removal of the bulk metal by electrochemical dissolution (electropolishing), to facilitate preparation of ultrathin sections for transmission electron microscopy. Surface sensitive spectroscopy (Auger electron microscopy and X-ray photoemission spectroscopy) and transmission electron microscopy EDX results show that the method produces samples with an intact interface, containing the implant surface oxide and the adjacent tissue. Examples of application of the method on titanium, zirconium and aluminium implants in soft tissue are given.

Aluminum↗
PubMed1989

Ultrastructural differences of the interface zone between bone and Ti 6Al 4V or commercially pure titanium.

Commercially pure (CP) titanium and Ti 6Al 4V alloy were sputtered onto polycarbonate plastic implants to analyse hard tissue reactions to the two metals. The implants were inserted in the tibial metaphyses of five rabbits. Three months later they were removed and processed for light microscopy (LM) and transmission electron microscopy (TEM) investigations. At the LM level, disordered woven bone was seen in the interface zone of Ti 6Al 4V, whereas organized bone was observed in direct contact with the CP titanium implants. TEM examination of Ti 6Al 4V sections revealed a 500-1000 A thick collagen-free proteoglycan layer compared to 200-400 A for CP titanium. A surface analysis test was performed to compare the magnetron sputtered film with bulk Ti 6Al 4V alloy. This test revealed no major differences between the experimental implant and the bulk alloy. More natural-like tissue reactions were observed to CP titanium than to Ti 6Al 4V alloy.

Alloys↗
PubMed1988

Biomaterial and implant surfaces: on the role of cleanliness, contamination, and preparation procedures.

Material specificity in implant-tissue interactions derives primarily from the surface properties (chemical composition, microstructure, etc.) of the implant. This article addresses several questions related to implant and biomaterial surfaces: What is the status of real implant surfaces (composition, cleanliness, contamination, microstructure, etc.), and how does it vary with preparation procedures? Can the surface status be varied and analyzed in a controlled manner? How significant are surface status variations for in vivo function? And so on. We discuss clean surfaces, how they are contaminated, and how the contamination may affect the properties. We also discuss different preparation procedures, such as conventional machining, plasma treatment, and sterilization. Three important conclusions are drawn: (i) The surface status of a particular implant material may vary widely depending on its preparation and handling history. (ii) The surface status of implants is expected to be important for in vivo function, and should thus be controlled and standardized. (iii) It is usually not possible to predict how a change in surface status will affect the long-term, in vivo function of an implant.

Biocompatible Materials↗
PubMed1988

Surface spectroscopic characterization of titanium implants after separation from plastic-embedded tissue.

The method of plastic embedding of tissue and implant and subsequent separation of plastic and implant for preparing sections of tissue adjacent to solid metallic implants relies on a successful separation of the embedment and the implant. In this work, the surface of machined Ti implants has been analysed in order to investigate to what extent plastic remnants exist on the implant after separation. SEM and AES analyses show that at least 70% of the implant surface is free of plastic remnants to a proximity of 10 nm or less from the implant surface. The method is simple and suitable for both light and transmission electron microscopy of the interface tissue.

Bone Screws↗
PubMed1986

Characterization of surface roughness in titanium dental implants measured with scanning tunnelling microscopy at atmospheric pressure.

Characterization of the surface topography of implant materials is important for understanding tissue response. We have measured, for the first time, the topography of titanium surfaces used in osseointegrated dental implants. Scanning tunnelling microscopy (STM) which provides 3D real space images was used. In addition to clinical samples, electropolished and anodically oxidized surfaces were also measured. Clinical samples are rather inhomogeneous in character showing grooves and steps with a maximum depth of 0.11 micron. Micropores with an average diameter of about 30 nm are also present. Electropolished samples are rather homogeneous and very smooth, showing steps of 1 to 5 nm in height. The measurements were performed under atmospheric conditions at a resolution in the subnanometer range.

Dental Implantation, Endosseous↗
PubMed1985

Accelerated oxide growth on titanium implants during autoclaving caused by fluorine contamination.

Titanium implants were occasionally found to be strongly discoloured after autoclaving. The discolouration is shown to be due to an accelerated growth of the surface oxide that covers the implants. Oxide thicknesses up to 650 A have been observed, i.e. more than ten times thicker than on normal implants. By applying surface sensitive spectroscopies (SIMS and XPS or ESCA) it is also shown that these oxide films contain considerable amounts of fluorine, alkali metals and silicon. Screening tests with alkali-halide solutions identify fluorine as the impurity responsible for the accelerated oxide growth. Discolouration after autoclaving can be observed for fluorine contaminations down to the ppm level. In those cases where discolouration was observed in the clinical situation, the source of fluorine was the textile cloths in which the titanium implant storage box had been wrapped during the autoclaving procedure. The cloths contained residual Na2SiF6 which had been used as an additive to the rinsing water used in the last step of the cloth laundry procedure. Since the biocompatibility of titanium implants is closely related to their surface oxides it is advisable to avoid all sources of fluorine in the implant preparation procedures.

Color↗