Key Engineering Materials Vols. 361-363

Abstract: Surface titanium oxide (TiO2) films were fabricated on implant titanium (Ti) at low temperatures by electron-cyclotron-resonance (ECR) plasma oxidation. The relationship among the oxidization conditions, crystal structure, morphology and osteoconductive property were investigated. Although crystallized TiO2 film was not prepared by thermal oxidation at 300°C, crystallized rutile-type TiO2 film was formed by ECR plasma oxidation at 300°C. Rough morphology was observed in the substrate surface oxidized by ECR plasma. Mixtures of octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD) were observed after calcification. The XRD peak intensities of the OCP and DCPD formed on the ECR plasma oxidized Ti were larger than those of calcified on the thermal oxidized Ti. ECR plasma oxidation at low temperature would induce osteoconductive calcium phosphate on implant Ti.

Abstract: A nanoporous calcium phosphate (CaP) coating on metallic surfaces is presented. The coating consists of a stack of (a) a TiNbN layer deposited by physical vapor deposition and acting as diffusion barrier against allergenic ions, (b) a SiO2 xerogel layer providing good adhesion properties and designing the nanoporosity of the outer CaP layer (c) precipitated electrochemically. SEM results verified a homogeneous nanoscale porous structure of the CaP coating. It is characterized by a high adhesion strength. If applied to stent covering the nanoporous CaP coating has promising properties to initiate rapid endothelium formation and reduced risk of restenosis.

Abstract: The surface oxide films were prepared by Electron Cyclotron Resonance (ECR) plasma oxidation on Ti substrates. Octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD) peaks were formed after calcification by supersaturated calcium and phosphate solutions. Calcification ability was enhanced with increasing the oxidation time and the total pressure of ECR plasma treatment during oxidation. The results demonstrated that the calcium phosphate nucleation and the deposition can be controlled by various ECR plasma conditions.

Abstract: The corrosion behavior of titanium alloys and 316L stainless steel has been evaluated and compared with coated materials. The corrosion current and the corrosion rate were evaluated by electrochemical techniques. The ions release from titanium alloys and 316L stainless steel were analyzed using ICP-MS and the HA coatings were observed using FTIR analysis.

Abstract: The aim of this paper was to find and establish the contact: biomaterial implant (TiAlZr) - coated with biologically active molecules; and the correlation between surface characteristics and their efficiency.

Abstract: The present work is focused on the stability of bioactivated CoCr alloy in biological environment (buffered saline solution (PBS), lactic acid, citric acid). The chemical and electrochemical deposition was characterized by electrochemical methods (open circuit potential, cyclic voltametry), scanning electronic microscope (SEM), x-ray diffractometer (XRD), inductively coupled plasma/mass spectrometry (ICP/MS) and citotoxicity test. The results prove a good electrochemical stability in all cases.

Abstract: Since 1952 when Branemark first reported osseointegration of titanium (Ti) with bone, many academic and industrial research activities have endeavored to improve the efficacy of Ti or Ti alloy (Ti6Al4V) by modifying the chemistry, topography and design of the implant surface. Strong bonding between implant and host tissue minimize the micromovements that promote fibrous tissue formation at the implant interface that may lead to implant failure. Surface design include lateral holes perpendicular to the implant axis, grooves, variations of spacings between ridges, etc. Physico-mechanical means of surface modification is by grit-blasting with various abrasives (alumina, silica, apatitic abrasive), laser ablation, spark discharge, etc. Chemical modifications include: acid etching, treatment with alkali, treatment with fluoride, coating with titanium or with calcium phosphate (by plasma spray, electromagnetic sputtering, electrochemical deposition). A review of studies on Ti or Ti alloy implants with different surfaces showed the following methods to enhance osseointegration and greater bone formation: (1) grit-blasting with apatitic abrasive; (2) acid-etching with mixed acids; (3) adjusting plasma-spray parameter to get a higher HA/ACP ratio in the coating; (4) employing electrochemical deposition (with pulse modulation) or precipitation to obtain thin coating with homogeneous composition; and/or (5) Ftreatment.

Abstract: The aim of this study was to create a nano-structured coating using Plasma Thermal Spraying (PTS). This process consists in introducing pre-agglomerated nanosized particles in a high-temperature and high-velocity gas jet and projected them onto the substrate to form, layer by layer, a nanostructured coating. In order to retain nanometer grain sizes in the deposited coating through specific PTS technologies, a thermal field and velocity distribution in the plasma jet are analytically calculated. A finite element analysis is employed to calculate the thermal field evolution inside the agglomerated particles and the thermal induced internal stress distribution is determined. The parameters determined by the theoretical analysis are used for experimental coatings. The average crystallite size of nano-hydroxyapatite powder was 90nm. After deposit via Plasma Thermal Spraying (PTS) process and followed by a 2 hours heat treatment to reduce amorphous fraction, the experimental deposited coating shows that it retains the nanometer crystallite sizes. The substructure of nanocrystals was evaluated at about 120nm in size. Such a nanocoating may play the role of nucleation site to bone, allowing a faster stabilization of the implant.

Abstract: This study was carried out to assess the bone response to alkali-modified titanium implant surface (Bio surface), using histomorphometric investigation on an animal model. The mean net contribution of the Bio surface to the increase in bone implant contact (BIC) with reference to the turned, machined surface was evaluated at 7.94 % (BIC/week), within the first five weeks of healing. The contribution was expressed as the difference in the osseointegration rates (
BIC/
'healing time) between the implants with alkali modified surface (Bio surface) and those with turned, machined surface. The surface characteristics that differed between the implant surfaces, i.e. surface morphology, specific surface area, contact angle, hydroxylation/hydration, may represent factors that influence the rate of osseointegration.

Abstract: Phase stability of 3 mol% yttria stabilized polycrystalline zirconia ceramics (3Y-TZP) was evaluated by aging test in water vapor environment and Raman spectroscopic technique. In our previous study, it has been confirmed that phase stability was improved by controlling sintering temperature. In this study, we pointed our attention and evaluated the influence of surface conditions related to machining and to heat treatment, thus monitoring the changes in phase transformation fraction and residual stress on the material surface. From the results of aging test, an increase in monoclinic fraction was observed for grinded surfaces as compared with polished surfaces. Samples subjected to heat treatment after machining showed improved phase stability. A Vickers indentation print was also introduced on a 3Y-TZP surface, and the relationship between surface condition and low temperature aging was evaluated in the neighborhood of the print. We found that the residual stress fields induced in phase-transformed areas were enhanced during low temperature aging, and that phase stability was improved by heat treatment.