K. Baba

Photo‐induced hydrophilicity enhances initial cell behavior and early bone apposition

OBJECTIVEnThe anatase form of titanium dioxide (TiO(2)) exhibits photo-induced hydrophilicity when it is irradiated with ultraviolet (UV) light. In the present study, the effect of photo-induced hydrophilicity on initial cell behavior and bone formation was evaluated.nnnMATERIALS AND METHODSnPlasma source ion implantation method and post-annealing were employed for coating the anatase form of TiO(2) to the surface of the titanium disk and implant. Half of the disks and implants were illuminated with UV for 24 h beforehand, whereas the other halves were blinded and used as controls. Photo-induced hydrophilicity was confirmed by a static wettability assay. The effects of this hydrophilicity on cell behavior were evaluated by means of cell attachment, proliferation and morphology using pluripotent mesenchymal precursor C2C12 cells. Thereafter, bone formation around the hydrophilic implant inserted in the rabbit tibia was confirmed histomorphometrically.nnnRESULTSnThe water contact angle of the photo-induced hydrophilic disk decreased markedly from 43.5 degrees to 0.5 degree. Cell attachment and proliferation on this hydrophilic disk showed significant improvement. The cell morphology on this hydrophilic disk was extremely flattened, with an elongation of the lamellipodia, whereas a round/spherical morphology was observed on the control disk. The photo-induced hydrophilic implant enhanced the bone formation with the bone-to-metal contact of 28.2% after 2 weeks of healing (control: 17.97%).nnnCONCLUSIONnThe photo-induced hydrophilic surface used in the current study improves the initial cell reactions and enhances early bone apposition to the implant.

Enhanced Initial Cell Responses to Chemically Modified Anodized Titanium

BACKGROUNDnPreviously, we reported that anodized porous titanium implants have photocatalytic hydrophilicity. However, this effect was not always sufficient for the significant improvement of bone apposition.nnnPURPOSEnThe purpose of this study was to improve the photocatalytic properties of porous titanium implants by the fluoride modification of the anodized titanium dioxide (TiO(2)), and to investigate the initial cell response to it.nnnMATERIALS AND METHODSnThe ideal concentration of ammonium hydrogen fluoride (NH(4)F-HF(2)) used in this study was determined by a static water contact angle assay. The ideal concentration of NH(4)F-HF(2) was 0.175%, and experimental disks were treated with this concentration. A pluripotent mesenchymal cell line, C2C12, was cultured on the disks in order to investigate cell attachment, morphology, and proliferation.nnnRESULTSnCell attachment after 30 minutes of culturing was significantly higher for the ultraviolet-irradiated, fluoride-modified anodized TiO(2) (p < .05), and the simultaneous scanning electron microscope observation showed a rather flattened and extended cell morphology. The proliferation rate after 24 hours was also significantly higher for the fluoride-modified anodized TiO(2).nnnCONCLUSIONnFluoride chemical modification enhances the hydrophilic property of the anodized TiO(2) and improves the initial cell response to it.

Preparation and Properties of Ag-Containing Diamond-Like Carbon Films by Magnetron Plasma Source Ion Implantation

The doping effect of silver on the structure and properties of diamond-like carbon (DLC) films was investigated. The samples were prepared by a process combining acetylene plasma source ion implantation (high-voltage pulses of −10u2009kV) with reactive magnetron sputtering of an Ag disc. A mixture of two gases, argon, and acetylene was introduced into the discharge chamber as working gas for plasma formation. A negative high-voltage pulse was applied to the substrate holder, thus, accelerating ions towards the substrate. The chemical composition of the deposited films was modified by the respective gas flows and determined using X-ray photoelectron spectroscopy and secondary ion mass spectrometry. The silver concentration within the DLC films influenced the structure and the tribological properties. The surface roughness, as observed by scanning electron microscopy, increased with silver concentration. The film structure was characterized by Raman spectroscopy and X-ray diffractometry (XRD). The DLC films were mainly amorphous, containing crystalline silver, with the amount of silver depending on the process conditions. The tribological properties of the films were improved by the silver doping. The lowest friction coefficient of around 0.06 was derived at a low silver content.

Thin sol-gel-derived silica coatings on dental pure titanium casting.

The sol-gel dipping process, in which liquid silicon alkoxide is transformed into a solid silicon-oxygen network, can produce a thin film coating of silica (SiO(2)). The features of this method are high homogeneity and purity of the thin SiO(2) film and a low sinter temperature, which are important in the preparation of coating films that can protect metallic ion release from the metal substrate and prevent attachment of dental plaque. We evaluated the surface properties of dental pure titanium casting coated with a thin SiO(2) or SiO(2)/F-hybrid film by the sol-gel dipping process. The metal specimens were pretreated by dipping in isopropylalcohol solution containing 10 wt% 3-aminopropyl trimethoxysilane and treated by dipping in the silica precursor solution for 5 min, withdrawal at a speed of 2 mm/min, air-drying for 20 min at room temperature, heating at 120 degrees C for 20 min, and then storing at room temperature. Both SiO(2) and SiO(2)/F films bonded strongly (above 55 MPa) to pure titanium substrate by a tensile test. SiO(2(-)) and SiO(2)/F-coated specimens immersed in 1 wt% of lactic acid solution for two weeks showed significantly less release of titanium ions (30. 5 ppb/cm(2) and 9.5 ppb/cm(2), respectively) from the substrate than noncoated specimens (235.2 ppb/cm(2)). Hydrophobilization of SiO(2(-)) and SiO(2)/F-coated surfaces resulted in significant increases of contact angle of water (81.6 degrees and 105.7 degrees, respectively) compared with noncoated metal specimens (62.1 degrees ). The formation of both thin SiO(2) and SiO(2)/F-hybrid films by the sol-gel dipping process on the surface of dental pure titanium casting may be useful clinically in enhancing the bond strength of dental resin cements to titanium, preventing titanium ions release from the substrate, and reducing the accumulation of dental plaque attaching to intraoral dental restorations.

Temperature dependent properties of silicon containing diamondlike carbon films prepared by plasma source ion implantation

Silicon containing diamondlike carbon (Si-DLC) films were prepared on silicon wafer substrates by a plasma source ion implantation method with negative pulses superposed on a negative dc voltage. A mixture of acetylene and tetramethylsilane gas was introduced into the discharge chamber as working gases for plasma formation. Ions produced in the plasma are accelerated toward a substrate holder because of the negative voltage applied directly to it. After deposition, the films were annealed for 0.5 h in ambient air at temperatures up to 923 K in order to evaluate the thermal stability of the Si-DLC films. The films were analyzed by x-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy, and Raman spectroscopy. The surface morphology of the films and the film thickness were observed by atomic force microscopy and scanning electron microscopy. The mechanical and tribological properties were investigated by an indentation method and a ball-on-disk test. The results show the si...

Silicon carbide and amorphous carbon film formation by plasma immersion ion implantation: a comparison of methane and toluene as plasma forming gases

In the present study a comparison of two different hydrocarbon precursor gases, namely methane and toluene, on the formation of silicon carbide (SiC) and amorphous carbon (a-C:H) films by plasma immersion ion implantation (PIII) of silicon is made. The samples are analyzed by using Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS) for their element composition. XPS and Raman spectroscopy are applied to determine the bonding of silicon and carbon. Depending on the number of high voltage pulses the samples have been treated with, which corresponds to the ion fluence, it is possible to form stoichiometric SiC films without C layers on top of the wafers if methane is used as plasma forming species. For the same process conditions, CH4 PIII always results in thicker SiC and thinner a-C:H films compared with C7H8 PIII. Siue5f8C bond formation is proven by XPS. Raman spectroscopy shows the formation of a-C:H films for high pulse numbers for the case of a methane plasma, but already for small pulse numbers if toluene is used for plasma forming species.

Hydrogen Solubility in Palladium — Vanadium Alloys

The hydrogen absorption characteristics of Pd—V alloys containing up to 10.0 at.% V have been investigated at temperatures between 273 and 433 and hydrogen pressures up to 1000 Torr by means of pressure-composition isotherm measurements. The lower and the higher pressure solubilities of hydrogen decrease with increasing V content. The relative partial molar enthalpy of solution of hydrogen at infinite dilution becomes less exothermic with V content, and the partial molar entropy decreases with the solute content. The apparent

Silica coatings formed on noble dental casting alloy by the sol-gel dipping process.

The sol-gel dipping process, in which liquid silicon alkoxide is transformed into the solid silicon-oxygen network, can produce a thin film coating of silica (SiO2). The features of this method are high homogeneity and purity of the thin SiO2 film and a low sinter temperature, which are important in preparation of coating films that can protect from metallic ion release from the metal substrate and prevent attachment of dental plaque. We evaluated the surface characteristics of the dental casting silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy coated with a thin SiO2 film by the sol-gel dipping process. The SiO2 film bonded strongly (over 40 MPa) to Ti-implanted Ag-Pd-Cu-Au alloy substrate as demonstrated by a pull test. Hydrophobilization of Ti-implanted/SiO2-coated surfaces resulted in a significant increase of the contact angle of water (80.5 degrees) compared with that of the noncoated alloy specimens (59.3 degrees). Ti-implanted/SiO2-coated specimens showed the release of many fewer metallic ions (192 ppb/cm2) from the substrate than did noncoated specimens (2,089 ppb/cm2). The formation of a thin SiO2 film by the sol-gel dipping process on the surface of Ti-implanted Ag-Pd-Cu-Au alloy after casting clinically may be useful for minimizing the possibilities of the accumulation of dental plaque and metal allergies caused by intraoral metal restorations.

Hydrogen-induced metal atom rearrangements in pd3+χmn1−χ alloys with χ⩾0 using transmission electron microscopy, electrical resistivities and H2 solubilities

Abstract In this research we have characterized the products of the hydrogen-induced ordering of disordered and of L12−χ ordered Pd3+χMn1−χ alloys with χ⩾0. The long-period superstructure (L12−s) form is produced by a heat treatment at a temperature of about 700 K in vacuo. An L12 ordered form can be prepared by exposing Pd-Mn alloys to hydrogen (1 MPa or above) at temperatures of 500 K or above; this ordering is induced by hydrogen under conditions where ordering does not occur in its absence. After the alloys have transformed to their L12 form, they remain in this form if the hydrogen is removed at moderate temperatures. Large dislocation densities appear from the hydrogen-induced ordering of the disordered alloys; the density of these dislocations appears to decrease with increase in χ. Dislocations are also introduced by the disorder → L12−s transformation which occurs in vacuo. The mechanism of the hydrogen-induced ordering is unknown but it must be related to the lattice expansion caused by the hydrogen. It should be noted that not very much dissolved hydrogen is needed to cause these transitions, i.e. a hydride phase does not form.

Phase transformation in a dental PdCuGa alloy

Abstract Phase transformation behavior in a dental Pdue5f8Cuue5f8Ga alloy was studied by means of hardness tests, electrical resistivity measurements, X-ray diffraction and transmission electron microscopy. Annealing at 673 K produces two hardness peaks which correspond to the formation of a metastable phase with ordered fet structure and the precipitation of the equilibrium phases, α1(fcc) + α2(fcc) + Pd2Ga (orthorhombic), respectively. On the other hand, annealing at 873 K exhibits only one peak due to the precipitation of the equilibrium phases. The difference of the phase transformation between both annealings is interpreted in terms of the free energy.