Vacuum arc deposition of nanostructured multilayer coatings for biomedical applications.

In recent years, the smart materials have attracted much attention due to their unusual properties such as shape memory effect and pseudoelasticity, being widely used for biomedical implants. These materials contain certain amounts of nickel, titanium and others which are not adequate for surgical implants and prosthesis. In the work reported here, two types of nonostructured multilayer coatings (TiN/ZrN, ZrN/Zr) used to prevent the ions release from shape memory alloys were investigated. For comparison, the TiN and ZrN monolayers were also examined. The films were deposited onto nickel-titanium based alloy (Ti-Ni-Nb) and Ni substrates by vacuum arc deposition technique under various deposition conditions. The concentrations of dissolved ions in Ringer solution for uncoated and coated Ni samples were determined to examine the benefic barrier effect of these coatings for ions release from shape memory alloys. In order to have a more complete characterization of the investigated coatings, other properties such as elemental and phase composition, morphology, texture, microhardness, and adhesion were studied. For all coatings, the concentrations of dissolved ions were lower that those measured in the case of the uncoated specimens. The nanostructured multilayer films exhibited the best mechanical and anticorrosive properties.

Influence of bilayer period on the characteristics of nanometre-scale ZrN/TiAIN multilayers.

In the last decade, considerable research effort was directed to the deposition of multilayer films with layer thicknesses in the nanometer range (superlattice coatings), in order to increase the performance of various cutting tools and machine parts. The goal of the present work was to investigate the main microstructural, mechanical and wear resistance characteristics of a superlattice coating, consisting of alternate multilayer ZrN/TiAIN films, with various bilayer periods (5 / 20 nm). The coatings were deposited by the cathodic arc method on Si, plain carbon steel and high speed steel substrates to be used as wear resistance surfaces. The multilayer structures were prepared by using shutters placed in front of each cathode (Zr and Ti+Al). The characteristics of multilayer structures (elemental and phase composition, texture, Vickers microhardness, thickness, adhesion, and wear resistance) were determined by using various techniques (AES, XPS, XRD, microhardness measurements, scratch, and tribological tests). A comparison with the properties of ZrN and TiAIN single-layer coatings was carried out.

A biodegradable AZ91 magnesium alloy coated with a thin nanostructured hydroxyapatite for improving the corrosion resistance.

The main aim of this study was to investigate the properties of an AZ91 alloy coated with nanostructured hydroxyapatite (HA) prepared by radio frequency (RF) magnetron sputtering. The bioactivity and biomineralization of the AZ91 magnesium alloy coated with HA were investigated in simulated body fluid (SBF) via an in vitro test. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analyses were performed. The samples were immersed in SBF to study the ability of the surface to promote the formation of an apatite layer as well as corrosion resistance and mass change of the HA-coated AZ91 alloy. Electrochemical tests were performed to estimate the corrosion behaviour of HA-coated and uncoated samples. The results revealed the capability of the HA coating to significantly improve the corrosion resistance of the uncoated AZ91 alloy.

Evaluation of Ag containing hydroxyapatite coatings to the Candida albicans infection.

In this research work, the synthesis of Ag doped hydroxyapatite coatings for dental or orthopedic implants was performed. The main goal was to determine the influence of Ag content on the roughness and antimicrobial performance of the prepared thin films. The films were deposited on Ti6Al4V alloy by means of RF magnetron sputtering. Those coatings were characterized by X-ray diffraction (XRD) and 3D surface profilometry. The antifungal activity after 1 and 7days of culture was evaluated in the presence of Candida albicans (ATCC - 10231). The increase of Ag content increased roughness and reduced the antifungal activity. The results showed that the Ag doped hydroxyapatite coatings can be a potential solution for the improvement of the antifungal activities of Ti based alloy.

Mechanical properties and biocompatibility of the sputtered Ti doped hydroxyapatite.

The hydroxyapatite enriched with Ti were prepared as possible candidates for biomedical applications especially for implantable devices that are in direct contact to the bone. The hydroxyapatites with different Ti content were prepared by RF magnetron sputtering on Ti-6Al-4V alloy using pure hydroxyapatite and TiO2 targets. The content of Ti was modified by changing the RF power fed on TiO2 target. The XPS and FTIR analyses revealed the presence of hydroxyapatite structure. The hardness and elastic modulus of the hydroxyapatite were increased by Ti addition. After 5 days of culture, the cell viability of the Ti-6Al-4V was enhanced by depositing with undoped or doped hydroxyapatite. The Ti additions led to an increase in cell viability of hydroxyapatite, after 5 days of culture. The electron microscopy showed the presence of more cells on the surface of Ti-enriched hydroxyapatite than those observed on the surface of the uncoated alloys or undoped hydroxyapatite.

Mycotic vaginitis caused by slow growth fungi.

The bacteriological and mycological investigations performed in a female diabetic patient, aged 72, with genital secretion and local discomfort revealed slowly growing fungi, identified as Saccharamyces heterogenicus in the cervix uteri secretion. The cultures performed on Sabouraud medium were positive after 48 hrs incubation in liquid medium and after 4 days in solid medium. The strain was sensitive to: Clotrimazole, Diflucan, Nizoral, Nystatin.

[A nutrient medium for culturing fungi based on a flores chamomillae infusion. I. The nutrient capacity and capacities for selecting and recovering fungi from clinical samples of a medium with a flores chamomillae infusion]. / Mediu nutritiv pentru cultivarea fungilor preparat pe baza de infuzie de Flores chamomillae. I. Capacitatile nutritive, selective si de recuperare a fungilor din probe clinice ale mediului cu infuzie de Flores chamomillae.

The study suggests a new culture medium, of the Sabouraud type. The medium was tested for its nutritive and recovery properties of the fungi in clinical samples, in parallel to the classical medium Sabouraud with chloramphenicol (Sab. + C). The results obtained showed the following: the I.F.C. + C medium ensures optimum cultivation conditions of some fungi species, potentially pathogenic for man, has a high selectivity and the ability of making evident the fungi in different clinical samples at very near-related parameters practically identical with the parameters of the classical Sabouraud medium. These qualities, completed by the economical advantages and the availability of the raw material necessary for the preparation of the basic vegetal extract, recommend the use of the I.F.C. + C medium as a nutrient medium for isolation and cultivation of fungi.

Enhancement of the mechanical properties of hydroxyapatite by SiC addition.

Improvements of mechanical and anticorrosive properties, as well as superior osseointegration of the hydroxyapatite coated titanium alloy were reported in the last years by the addition of different elements (Si or Ti) into hydroxyapatite structure. The aim of this work was to prepare and to investigate the hydroxyapatite (HAP) coatings enriched with SiC in order to enhance the mechanical properties of HAP films. The coatings were deposited on Ti6Al4V alloy substrates by co-sputtering of HAP and SiC targets, using a magnetron sputtering system. The films were characterized in terms of elemental and phase composition, chemical binding, morphology and mechanical properties by EDS, XRD, FTIR, SEM, AFM, and nanoindentation. Overall, improved mechanical properties were found by adding SiC to the basic HAP structure.

Characterization of multi-principal-element (TiZrNbHfTa)N and (TiZrNbHfTa)C coatings for biomedical applications.

Multi-principal-element (TiZrNbHfTa)N and (TiZrNbHfTa)C coatings were deposited on Ti6Al4V alloy by co-sputtering of Ti, Zr, Nb, Hf and Ta metallic targets in reactive atmosphere. The coatings were analyzed for elemental and phase compositions, crystalline structure, morphology, residual stress, hardness, friction performance, wear-corrosion resistance and cell viability. For all the films, only simple fcc solid solutions with (111) preferred orientations were found, with crystallite sizes in the range 7.2-13.5 nm. The coatings were subjected to compressive stress, with values ranging from 0.8 to 1.6 GPa. The carbide coating with the highest carbon content (carbon/metal ≈1.3) exhibited the highest hardness of about 31 GPa, the best friction behavior (µ = 0.12) and the highest wear resistance (wear rate K=0.2×10(-6)mm(3)N(-1)m(-1)), when testing in simulated body fluids (SBFs). Cell viability tests proved that the osteoblast cells were adherent to the coated substrates, and a very high percentage of live cells were observed on sample surfaces, after 72 h incubation time.

[A comparative study of antibiogram methods employed in endodontic stomatological procedures]. / Studiu comparativ al metodelor de antibiograma, utilizate în stomatologia endodontica.

The study demonstrates the importance of the antibiogram in the determination of the sensitivity of microbiocenosis of the infected dental canals. The methods and the techniques for the sampling of the pathological products are presented. The classical technique for antibiograms, consisting in horizontal diffusimetry is compared with the modern method of double-layer diffusimetry which employs a "redox" indicator (C.T.T.-triphenyl-tetrazolium-2, 3, 5-chloride) which accelerates the lecture of the results by altering the colour of the culture medium. The study was carried out in 200 patients and showed that the antibiotics with the widest spectrum on the microbiocenosis of the infected dental canals were, by order of efficiency, the following: erythromycin, chloramphenicol, ampicillin, and tetracycline. Antibiograms should be done in the shortest possible time, and the time for the lecture of the results was reduced from 36-48 hours in the case of the classical antibiograms to 16-18 hours in the case of the rapid technique. The shortening of the working time allows for a more rapid individualization of the treatment, and the preparation of antibiotic-incorporating pastes that will reduce the number of procedures to 1-2 procedures in the simple form of the pulp gangrene and to 3-4 procedures in the cases of complicated pulpal gangrene.

[Secondary active-evolutive cavitary pulmonary tuberculosis of the apicodorsal segment of the left upper lobe associated with bronchial tuberculosis and bronchial geotrichosis]. / Tuberculoza pulmonara secundara activ-evolutiva cavitara segment apicodorsal lob superior stâng asociata cu tuberculoza bronsica si geotricoza bronsica.

A case of active pulmonary secondary tuberculosis associated with bronchial tuberculosis and bronchial geotrichosis is presented. This association is infrequent. Favoring factors: local and general immunodepression (recurrent infection with pyogenic germs, rubella, neutropenia, aggressive antibiotherapy, iron deficiency). The diagnosis was based mainly on the bacteriological sputum examination for bK (smear and culture) and the mycologic examination (smear and culture) of the bronchial aspiration, identifying Geotrichum candidum. The treatment consisted of antituberculous and antimycotic drugs, bronchodilators, bronchial aspirations and local endoscopic administration of antimycotic drugs.

[Studies of oral microbiocenosis. III. Incidence of microorganisms of the Mycoplasma genus]. / Studii de microbiocenoza orala. Nota III. Incidenta microorganismelor din genul Mycoplasma.

Microorganisms of the Mycoplasma genus were found in the washing fluids of the oral cavity in 2% of healthy youths, and in 57.1% of patients with parodontal lesions: 25.7% in the buccal fluid, 17.1% in the dental tartar and 34.2% in the gingiva exsudate. Microplasma was not found in dental caries and in the radicular canals with pulpar gangrene. Although these microorganisms were frequently found in subjects with parodontal lesions they cannot be implicated with certainty in their aetiology.