In Seop Lee

The biocompatibility of SLA-treated titanium implants

The titanium implant surface was sandblasted with large grits and acid etched (SLA) to increase the implant surface for osseointegration. The topography of the titanium surface was investigated with scanning electron microscopy (SEM) and a profilometer. The SLA implant demonstrated uniform small micro pits (1-2 microm in diameter). The values of average roughness (R(a)) and maximum height (R(t)) were 1.19 microm and 10.53 microm respectively after sandblasting and the acid-etching treatment. In the cell-surface interaction study, the human osteoblast cells grew well in vitro. The in vivo evaluation of the SLA implant placed in rabbit tibia showed good bone-to-implant contact (BIC) with a mean value of 29% in total length of the implant. In the short-term clinical study, SLA implants demonstrated good clinical performance, maintaining good crestal bone height.

Influence of nanocoated calcium phosphate on two different types of implant surfaces in different bone environment: an animal study

OBJECTIVEnThe purpose of this study was to evaluate the osseointegration of two different types of surfaces, smooth and roughened surface implants nanocoated with calcium phosphate (CAP) around different bone environment.nnnMATERIALS AND METHODSnFive male mongrel dogs were used in this study. The premolars and molars were extracted on both sides of the mandible. Eight weeks after extraction, implants were submerged on both sides of the mandible. On the left, CAP nanocoated roughened surface (RCAP) implants were installed whereas, the CAP nanocoated smooth surface (SCAP) implants were installed on the right side. The control group had no defect, on the other hand, three-wall intrabony defects were surgically created adjacent to the implant in the experimental group. The dogs were sacrificed after 12 weeks.nnnRESULTSnHistological and histomorphometrical analysis were performed with the specimen. The SCAP and RCAP implants showed good osseointegration with no statistical significance in the control group. Histologically, the SCAP group showed little resolution of the defect compared with the RCAP group. In the experimental groups, there was a significant difference in defect fill between SCAP and RCAP.nnnCONCLUSIONnWithin the limits of our study, it can be concluded that SCAP and RCAP implants show no difference in sufficient bone area whereas, CAP nanocoating on roughened implant surface may enhance osseointegration in deficient bone environment.

Iridium Oxide as a Stimulating Neural Electrode Formed by Reactive Magnetron Sputtering

Implantable neural prostheses form hybrid interfaces with biological constructs, and the application of electrical fields can restore functions of patients with neurological damages. The various stoichiometric compositions of iridium oxide were synthesized using reactive magnetron sputtering. The charge injection behavior of iridium oxide deposited with an O2/Ar ratio of 0.5 was similar to pure Ir. The charge density of iridium oxide increased with increasing O2/Ar ratio, and increasing thickness of iridium oxide.

Effects of Electrical Wave Form on Pore Size of Micro-Arc Oxidized TiO2 Film

The surface morphology of commercially pure titanium was investigated with varying electrical waveform. Controlling of electrical pulse width is effective to change pore sizes. Longer electrical pulse width was induced, larger size of pores were generated.

Neural Cells on Iridium Oxide

Iridium oxide was investigated as a material for the stimula ting neural electrode. Iridium oxide was formed by potential sweep of iridium film that was deposi ted on either Si wafer or silicone rubber with electron-beam evaporation. The rate of iridium oxide format ion was dependent on the upper and lower limits of potential sweep. The higher thickness of iri dium oxide produced the higher charge injection due to the reversible valence transition of iridium within oxide. Embryonic cortical neural cells formed neurofilament after 4-day culture on iridium oxi de, which indicated neural cells could adhere and survive on iridium oxide. Introduction Interaction between neurons and electrodes is very important for stim ulation or signal collection. The restoration of a variety of physiological functions by electricall y ctivating nerves serving paralyzed muscles has been of particular interest. The first application of functional electrical stimulation (FES) was by Liberson [1] who stimulated the peroneal nerve in adult hemipleg ia to correct drop foot during the swing phase of locomotion. For the rehabilitation of locomotion in parapl egics and hemiplegics, thirty-two electrodes are required and even more stimulations are demanded for the refined control [2]. A major problem limiting the widespread application FES has been the lack of stimulating electrodes that can be used for long-term precise multipoint stimulation of nerve s. Practical application requires miniaturized electrode geometry, which still demands high charge i njection capability over the suitable range in potential. Recently, iridium oxide was investigat ed s a candidate electrode material [3-6]. Iridium oxide shows electrochromic behavior, where a change of col r takes place between oxidative and reductive state of iridum. The color of iridium oxide st art changing from metallic to blue around 0.4 V (SHE) in 0.1 M H 2SO4, become darker and remains dark blue above near 0.9 V (SHE). The bleaching process occurrs during the cathodic sweep. The dar k blue became lightened around 1.0 V (SHE) and no blue color could be observed below 0.4 V (SHE). The double proton-electron injection mechanism has been proposed to explain the elect rochromism of the anodic iridium oxide film by Gottesfeld et al. [7]. They postulated the fol lowing reaction to describe the film conversion processes: Ir(OH)n Irx(OH)n-x + xH + + xe In this mechanism, during the coloration process, electrons are removed fr m the oxide across the metal-oxide interface by application of a suitable anodic potential to the metal substrate. Charge repulsion causes an equivalent amount of mobile positive charge carrier s (protons) to be ejected Key Engineering Materials Online: 2003-12-15 ISSN: 1662-9795, Vols. 254-256, pp 805-808 doi:10.4028/www.scientific.net/KEM.254-256.805

Application of Hydrogen Peroxide Gas Plasma Method for Porous Polyurethane Sterilization

Tissue-engineering must be either manufactured aseptically or sterilized after processing. To extend protection of medical devices against microbial contamination, various sterilization methods have been suggested. Hydrogen peroxide gas plasma sterilization has been applied in hospitals worldwide for almost a decade. In this study, we investigated the sterilization efficacy of hydrogen peroxide gas plasma sterilizer with porous polyurethane sample. The result is suggested that hydrogen peroxide gas plasma can be applicable to the sterilization of polymer scaffold for tissue engineering materials.

Thinfilm Deposition and Characteristics of Calcium-Silicates Bioglass

Various composition of calcium-silicate thinfilms were deposited to the thickness of 1μm by electron-beam deposition. The composition was varied by changing the composition of source. The Si concentration of thinfilm was ranged from 25 at% to 85 at%, evaluated by EDS. The specimens were immersed into PBS solution at 37 °C. Changes of the morphology and calcium phosphate formation on the specimens were examined by SEM. If the concentration of calcium is high, the calcium phosphate was quickly formed on the specimen. However, the calcium phosphate formed on the high calcium oxide concentration exhibited very poor adhesion onto the substrate. There is a range of appropriate calcium oxide concentration to use as a surface modification method for dental or orthopedic implants.

Evaluation of Poly(Lactic-Co-Glycolic Acid) (65/35) Treated by Dielectric Barrier Discharge in Atmospheric Pressure

The surface properties of scaffolds are important since cell affinity is the most crucial factor to be concerned when the biodegradable polymeric material is utilized as a scaffold in tissue engineering. The surface of biodegradable non-porous poly (lactic-co-glycolic acid) (PLGA) scaffolds were treated by atmospheric pressure dielectric barrier discharge (APDBD). The wetting angle of APDBD treated PLGA were decreased from the untreated PLGA of 73° to 42°. FTIR-ATR analyses showed hydroxyl groups were not detected regardless of treated condition, but the intensities of both ether groups and carbonyl groups were increased with treatment time and oxygen flow rate. Treatment time and oxygen flux are equally effective to make the PLGA surface more hydrophilic.

Attachment and Proliferation of Human Dermal Fibroblasts onto ECM-Immobilized PLGA Films

In this study, human dermal fibroblast behaviors onto non-porous PLGA (75:25) films immobilized with 1, 10 and 100 µg/ml collagen (CN) or fibronectin (FN) were investigated according to different cell-seeding densities (1,000, 10,000 and 100,000 cells/ml). Cell attachment and proliferation were assessed using water soluble tetrazolium salt. The results indicated that 1 µg/ml of FN-immobilized PLGA film demonstrated significantly (p < 0.05) superior cellular attachment to the intact PLGA film after 4 hr of incubation. Moreover, the number of attached cells was shown to be directly proportional to that of initially seeded cells. After 48 hr, the cells showed significantly (p < 0.05) higher proliferation onto 1 or 10 µg/ml of FN-immobilized PLGA films than onto other PLGA films, regardless of the initial cell-seeding density. In terms of CN-immobilization, cell proliferation was appreciably increased but it was relatively lower than FN-immobilization. These results suggested that ECM-immobilization can enhance the cell affinity of hydrophobic scaffolds and be used to potential applications for tissue engineering by supporting cell growth.

The Hygrothermal Degradation on Mechanical Properties of Short-Fiber Reinforced Nylon

The hygrothermal degradation of glass fiber/nylon composite was investigated after aged at 25°C, 50°C, 75°C and 100°C up to 1 month of total exposure in aqueous solution. The effects of moisture absorption and thermal aging on mechanical properties are compared as functions of temperature, fiber volume and concentration of sodium chloride. The amount of water absorption increases when the aging temperature is increased and the concentration of NaCl is lowered. In general, the mechanical properties decrease with amount of water absorption. The degradation rate of various mechanical properties is different depending on the temperature, fiber volume and the concentration of NaCl. The diffusion mechanisms of water in short-fiber reinforced nylon are discussed as functions of fiber volume, molding conditions and concentration of sodium chloride.