Plasma Source Ion Implantation Method Research Articles

Effects of Mg-ion and Ca-ion implantations on P. gingivalis and F. nucleatum adhesion

The purpose of this study was to evaluate the effects of ion implantation on Porphyromonas gingivalis (P. gingivalis) and Fusobacterium nucleatum (F. nucleatum) bacterial adhesion. Titanium (Ti) discs of 15 mm diameter and 1 mm in thickness (n = 42, 7 per group) were fabricated. Magnesium (Mg) and calcium (Ca) ions were implanted into the Ti surfaces using a plasma-source ion-implantation method. The roughness, chemistry, morphology, and contact angle of the titanium surfaces were analyzed using scanning electron microscopy, Rutherford back-scattering spectroscopy, Auger electron spectroscopy, and contact angle meter. P. gingivalis and F. nucleatum strains were cultured in anaerobic conditions at 37°C for 72 hours, and all titanium specimens were dipped in the bacterial suspension at 37°C for 24 hours. Specimens were examined at 1,000× magnification using a fluorescence microscope. The number and total area of bacteria in each of 10 separate fields were determined by computer imaging analysis method. The resulting data was analyzed to assess the significance of observed differences based on the method of the surface treatment, ion implantation. The number of P. gingivalis and F. nucleatum attached to the Mg-(927 and 227, respectively) and Caionimplanted (1325 and 231, respectively) surfaces were greater than those attached to the non-implanted surfaces (306 and 98, p <.001). Total area occupied by P. gingivalis adhesion was greater than those of F. nucleatum in the Mgand Caion-implanted surfaces (p <.001). The types of ion and bacteria did not affect the amount of bacterial adhesion. Ion implantation enhanced the adhesions of P. gingivalis and F. nucleatum. Non-specific bonding derived from the electrostatic force affected by positively charged ions might be the predominant factor in bacterial adhesion. The possibility of specific bonding could not be ruled out in the Ca-ion- implanted surface.

The effects of Mg‐ion implantation and sandblasting on Porphyromonas gingivalis attachment

The purpose of this study was to evaluate the effect of titanium surface treatment on Porphyromonas gingivalis bacterial attachment. Titanium disks of 15 mm in diameter and 1 mm in thickness (n=40) were subjected to mechanical grinding, or sandblasting. Magnesium (Mg) ions were implanted onto the titanium surface using a plasma source ion implantation method. The structure, chemistry, and surface morphologies of the titanium surfaces were analyzed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy and Auger electron spectroscopy. Surface roughness was measured using a laser profilometer. Half of the titanium disks in each group were dipped in saliva for 24 h. All of the titanium specimens were rinsed with distilled water. A P. gingivalis strain was cultured in anaerobic conditions at 37°C for 72 h, and all titanium specimens were dipped in the bacterial suspension at 37°C for 24 h. Specimens were examined at × 3000 magnification using a SEM. The number of bacteria in each of 10 separate fields was determined by directly counting the number of bacterial colonies that adhered to each specimen. The mean values were calculated afterward. The resulting data were analyzed to assess the significance of observed differences based on the method of the surface treatment, ion implantation, and saliva dipping. The amount of P. gingivalis attached to the sandblasted specimens was greater than that on the ground specimens (P<0.001). Moreover, surfaces with Mg-ion implantation had more attachments than nonimplanted surfaces (P<0.001). Saliva dipping acted synergistically with surface roughness and chemical composition of the specimens. Chemically modified surface increase the attachment of a major periodontopathic bacterium, P. gingivalis.

Bone response of Mg ion‐implanted clinical implants with the plasma source ion implantation method

This study examined the bone response of magnesium (Mg) ion-implanted implants produced using a plasma source ion implantation method. The surface characteristics were evaluated by scanning electron microscopy, Auger electron spectroscopy, X-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy. The screw-type titanium implants were treated with resorbable blasting media (RBM) and divided into one control group (RBM implants) and three test groups (Mg ion-implanted implants with different retained Mg doses). Twenty-four implants from each group were placed into the tibiae of 24 New Zealand white rabbits. After allowing 6 weeks for healing, the removal torque (RTQ) was measured and the implants were subjected to histomorphometric analysis. The surface roughness and surface morphology of the test groups were similar. The Mg ion-implanted implants with a 2.3 x 10(15) ions/cm(2) retained dose showed a significantly higher RTQ than the other implants. Histomorphometric analysis indicated that the bone contact of this group was superior to the other groups. The bone response of Mg ion-implanted implant showed results superior or similar to an RBM-treated implant. The optimal Mg ion concentration that induced the strongest osseointegration was approximately 9%.

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 silicon containing DLC films were amorphous and the surface roughness of the Si containing DLC films was very smooth and no special structure was observed. Integrated intensity ratios ID/IG of Raman spectroscopy of the Si containing DLC films decreased with Si content. The Raman spectra showed that the structure of the Si-free DLC film changed to a graphitelike structure with increasing annealing temperature, whereas that of the 24 at. % Si containing DLC films did not change at the maximum temperature used in this study. A very low friction coefficient was obtained for the 13 at. % Si containing DLC film. The surface roughness and the hardness of the films changed with increasing annealing temperature. The formation of Si oxide in a near surface layer was confirmed by XPS and it prevents further oxidation of the inside of the film. Heat resistivity of DLC films can be improved by Si addition into the DLC films.

Mechanical and electrical properties of diamond-like carbon films deposited by plasma source ion implantation

Diamond-like carbon (DLC) films were prepared by a plasma source ion implantation method with superposed negative pulse and negative DC voltage. Acetylene gas was used as working gas for plasma formation. A negative DC voltage and a negative pulse voltage were superposed and applied to the substrate holder. The DC voltage was changed in the range from 0 to −4.8kV and the pulse voltage was changed from −18 to −13.2kV. The films were annealed in the range of 200–450°C for 1h. The surface morphology of the films and the film thickness were observed by atomic force microscopy and scanning electron microscopy. The film structure was characterized by Raman spectroscopy. The hardness of DLC films was evaluated by an indentation method. Measurement of the electrical resistivity was performed using a four-point probe station. Furthermore, a ball-on-disc test with 2N load was employed to obtain information about the friction properties and sliding wear resistance of the films.The surface of the DLC films was very smooth and featureless. The deposition rate was changed with the DC voltage and pulse conditions. Integrated intensity ratios ID/IG of Raman spectroscopy and electrical resistivity of the DLC films changed with DC voltage. The electrical resistivity decreased with increasing ID/IG ratio. The ID/IG ratio was increased and the electrical resistivity was decreased with annealing temperature owing to graphitization. Very low friction coefficients around 0.05 were obtained for as-deposited films.

Antibacterial metal implant with a TiO2‐conferred photocatalytic bactericidal effect against Staphylococcus aureus

AbstractPhotocatalysis with anatase Titanium dioxide (TiO2) under ultraviolet A (UVA) has a well recognized bactericidal effect. There have been a few reports, however, on the effects of photocatalysis on bio‐implant‐related infections. The purpose of present study was to evaluate the photocatalytic bactericidal effects of anatase TiO2 on Staphylococcus aureus (S. aureus) associated with surgical site infections.TiO2 films were synthesized on commercially pure titanium substrates and SUS316 stainless steel using a plasma source ion implantation method followed by annealing. The chemical composition of the surface layers was determined using GXRD and XPS. The disks were seeded with cultured S. aureus and exposed to UVA illumination from black light. The bactericidal effect of the TiO2 films was evaluated by counting the survived colonies statistically.A structural gradient anatase type TiO2 layer formed on all substrates. The viability of the bacteria on the photocatalytic TiO2 film coated on titanium was suppressed to 7.0% at 30 minutes and 5.5% at 45 minutes, whereas that on a similarly coated stainless steel was suppressed to 45.8% at 30 minute and 28.6% at 45 minutes (ANOVA: p &lt; 0.05). Complete bacterial inactivation was achieved after 90 minutes on titanium and after 60 minutes on stainless steel. The photocatalytic bactericidal effect of TiO2 is useful for sterilizing the contaminated surfaces of bioimplants. Copyright © 2008 John Wiley &amp; Sons, Ltd.

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

The 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. Plasma 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. The 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%). The photo-induced hydrophilic surface used in the current study improves the initial cell reactions and enhances early bone apposition to the implant.

An Antibacterial Surface on Dental Implants, Based on the Photocatalytic Bactericidal Effect

It is well known that the moderately roughened surfaces of dental implants enhance direct bone-implant contact. However, rough implant surfaces, as compared to smooth surfaces, are thought to pose a higher risk of bacterial infection when exposed to the oral cavity. This study was focused on evaluating the photocatalytic bactericidal effects of anatase titanium dioxide (TiO(2)) on gram-negative anaerobic bacteria known to be associated with periimplantitis. A film of photocatalytic anatase TiO(2) was added onto the surface of commercially pure titanium disks by plasma source ion implantation (PSII) followed by annealing. The photocatalytic properties of the film were confirmed by the degradation of methylene blue. Actinobacillus actinomycetemcomitans and Fusobacterium nucleatum cells were incubated anaerobically and seeded on the disk. The disks were then exposed to ultraviolet A (UVA) illumination from black light in an anaerobic environment. After illumination, the number of viable cells was counted in terms of colony-forming units. The anatase TiO(2) film added by the PSII method and annealing exhibited a strong photocatalytic reaction under UVA illumination. The viability of both types of bacteria on the photocatalytic TiO(2) film was suppressed to less than 1% under UVA illumination within 120 minutes. The bactericidal effect of the TiO(2) photocatalyst is of great use for sterilizing the contaminated surface of dental implants.

Properties of TiN coating on 45 # steel for inner surface modification by grid-enhanced plasma source ion implantation method

Using a new inner surface modification method named GEPSII (grid-enhanced plasma source ion implantation), which is designed for inner surface modification of tubular work pieces, we successfully produced polycrystalline TiN coating on 0.45{%} C steel (45# steel) samples. Compared with the uncoated 45# steel sample, the electrochemical corrosion test on the coated 45# steel samples presents evident improvement in their corrosion resistance. Two implanted voltages, direct current (–2kV) and pulsed negative voltage (–10kV), are applied on the substrates. It is shown that the direct current implantation is more effective than the pulsed implantation in the surface corrosion resistance. AES depth profile shows that coating thickness is about tens of nanometres. The preferred orientations expressed by peaks at (111) and (200) can be seen clearly in XRD patterns.

Application of oxygen ion implantation to titanium surfaces: effects on surface characteristics, corrosion resistance, and bone response.

The surface oxide layer of titanium plays a decisive role in determining biocompatibility. However, there are some reports demonstrating that the natural oxide film may not be sufficiently protective in the aggressive biologic environment. The goal of this study was to examine the effectiveness of a thick oxide layer on corrosion resistance in vitro and the bone formation around titanium implants in vivo. A plasma source ion implantation (PSII) method was used to increase the thickness of the surface oxide layer. Several instruments were employed to confirm the surface properties before and after the surface modification. Potentiodynamic polarization measurements in a phosphate-buffered saline (PBS) solution were carried out to investigate corrosion resistance in vitro. Bone formation around this surface-modified specimen was examined in a rabbit model and assessed in histomorphometry. Improved corrosion resistance was demonstrated by the potentiodynamic polarization measurements. Light microscopic histomorphometry showed that all implants were in contact with bone and had some proportion of bone within the threads at 4 weeks; however, there were no significant differences compared with as-machined controls. The results indicate that in spite of improved corrosion resistance in vitro, a thick oxide layer fabricated with the PSII method does not influence early bone formation around titanium implants in vivo.

Inner surface reaction and modification of titanium alloy by a new plasma source ion implantation method

The inner surface of a cylindrical titanium alloy target was successfully implanted with nitrogen ion using a new plasma source ion implantation method. By means of x-ray photoelectron spectroscopy and x-ray diffraction, the reactive phases and their chemical state in the implanted layer were investigated. In order to characterize the modification effect and its uniformity, the retained dose and the microhardness at seven different positions along the axis on the inner surface of the cylindrical target were measured, respectively. The experimental results show that a TiN reactive phase was formed in the implanted layer, which contributed to the improvement of inner surface microhardness. The root-mean-square deviations of retained dose and microhardness measured along the axis of the target are less than 9% and 4%, respectively, which are well within an acceptable tolerance range for metallic applications of ion implantation.

Inner surface modification of 40Cr steel cylinder with a new plasma source ion implantation method

Cylindrical targets of 40Cr steel were immersed in a nitrogen plasma with density 1×1010 cm−3 and implanted at an energy of 30 keV. In order to characterize the inner surface modification effect and the dose uniformity achievable with a new plasma source ion implantation method, the axial distributions of the microhardness, and the implantation dose on the inner surface of the targets were measured, respectively. The experimental results demonstrate that the inner surface of materials can be effectively modified with our method and the measured root-mean-square variations of the retained dose and the microhardness along the axis of the target are well within the acceptable tolerance range for nonsemiconductor applications of ion implantation when the ratio of length to diameter does not exceed 10.