• Journal of Technologic Dentistry
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• v.22 no.1
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• pp.79-88
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• 2000

The objective of this finite element method study was to analyze the stress distribution induced in a maxillary central incisor Ni-Cr base metal coping ceramic crowns with various margin design. Margin designs of crown in this experiment were knife-edge metal margin on chamfer finishing line of tooth preparation(M1), butt metal margin on shoulder finishing line(M2), reinforced butt metal margin on shoulder finishing line(M3), beveled metal margin on bevelde shoulder finishing line(M4). Two- dimensional finite element models of crown designs were subjected to a simulated biting force of 100N which was forced over porcelain near the lingual incisal edge. Base on plane stress analysis, the maxium von Miss stresses(Mpa) in porcelain venner was 0.432, in metal coping was 0.579, in dentin abutment was 0.324 for M1 model, and M2 model revealed in porcelain was 0.556, in metal coping was 0.511, in dentin was 0.339, and M3 model revealed in porcelain was 0.556, in metal coping was 0.794, in dentin was 0.383 for M4 model. All values of each material in metal-ceramic crown were much below the critical failure values.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.248-249
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• 2006

Direct Metal Laser Sintering (DMLS) has been utilized for prototype manufacturing of functional metal components for years now. During this period the surface quality, mechanical properties, detail resolution and easiness of the process have been improved to the level suitable for direct production of complex metallic components for various applications. The paper will present the latest DMLS technology utilizing EOSINT M270 laser sintering machine and EOSTYLE support generation software for direct and rapid production of complex shaped metallic components for various purposes. The focus of the presentation will be in rapid manufacturing of customized biomedical implants and surgical devices of the latest stainless steel, titanium and cobalt-chromium-molybdenum alloys. In addition to biomedical applications, other application areas where complex metallic parts with stringent requirements are being needed will be presented.

• Journal of Sensor Science and Technology
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• v.14 no.6
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• pp.423-429
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• 2005

In this paper, we proposed the fabrication process of the stable e-beam evaporation and the patterning of metals layer on the polydimethylsiloxane (PDMS) substrate. The metal layer was deposited under the various deposition rate, and its effect to the electrical and mechanical properties (e.g.: adhesion-strength of metal layer) was investigated. The influence of surface roughness to the adhesion-strength was also examined via the tape test. Here, we varied the roughness by changing the reactive ion etching (RIE) duration. The electrode patterning was performed through the conventional photolithography and chemical etching process after e-beam deposition of $200{\AA}$ Ti and $1000{\AA}$ Au. As a result, the adhesion strength of metal layer on the PDMS surface was greatly improved by the oxygen plasma treatment. The e-beam evaporation on the PDMS surface is known to create the wavy topography. Here, we found that such wavy patterns do not effect to the electrical and mechanical properties. In conclusion, the metal patterns with minimum $20{\mu}m$ line width was produced well via the our fabrication process, and its electrical conductance was almost similar to the that of metal patterns on the silicon or glass substrates.

• Journal of Biomedical Engineering Research
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• v.17 no.1
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• pp.11-18
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• 1996

The toxic metal ion release behaviour and the cytotoxicity of a super stainless steel (S.S.S, 22cr-20Ni -6Mo-0.25N) were investigated The measurement of the amount of static and wear- induced trace metal ion released from the steels was conducted in Hank's balanced salt solution using an electrothermal atomic absdrption spectrometry equiped with Uaphite furnace. And the in vitro cytotoxicity of the materials was assesed in cell culture. The static dissolution rates of Fe and Cr ions from the S.S.S were significantly lower than those of 316L SS. However, the Ni ion release from the S.S.S during the first 4 weeks was yester than that from 316L 55 by 15-45%. Also, the wear-in- duces dissolution rates from the steels were not correlated either with their elemental composition rates or with the static metal ion release rates. The S.S.S did not deteriorate the osteoblasts viability. And no toxic response was observed from the macrophages cultured for 7 days in RFMI 1640 medium immersed with the S.S.S specimens.

• Journal of Technologic Dentistry
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• v.24 no.1
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• pp.33-41
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• 2002

In dental prosthetics, the application of metal-ceramic restorations has steadily increased since their introduction. This is due to excellent esthetics in combination with high mechanical stability. In order to optimum bond strength between metal and ceramics, controlled oxidation of metal substructure is essential factor. Beryllium containing and beryllium free Ni-Cr alloys for metal-ceramic restorations were evaluated for the metal-ceramic bond strength by changing heat treatment for oxide formation. A mechanical three-point bending test was employed to evaluate the interfacial bond strength of metal-ceramic. In each metal, plate type specimens were used for mechanical three-point bending test. With Ni-Cr alloys for metal ceramics, mechanical three-point bending test showed that double degassing was more available preheat treatment method than another. It was found that beryllium containing Ni-Cr alloys are more effective than beryllium-free for metal-ceramic bond strength.

• Investigative Magnetic Resonance Imaging
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• v.20 no.4
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• pp.215-223
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• 2016

Purpose: The management of metal-induced field inhomogeneities is one of the major concerns of distortion-free magnetic resonance images near metallic implants. The recently proposed method called "Slice Encoding for Metal Artifact Correction (SEMAC)" is an effective spin echo pulse sequence of magnetic resonance imaging (MRI) near metallic implants. However, as SEMAC uses the noisy resolved data elements, SEMAC images can have a major problem for improving the signal-to-noise ratio (SNR) without compromising the correction of metal artifacts. To address that issue, this paper presents a novel reconstruction technique for providing an improvement of the SNR in SEMAC images without sacrificing the correction of metal artifacts. Materials and Methods: Low-rank approximation in each coil image is first performed to suppress the noise in the slice direction, because the signal is highly correlated between SEMAC-encoded slices. Secondly, SEMAC images are reconstructed by the best linear unbiased estimator (BLUE), also known as Gauss-Markov or weighted least squares. Noise levels and correlation in the receiver channels are considered for the sake of SNR optimization. To this end, since distorted excitation profiles are sparse, $l_1$ minimization performs well in recovering the sparse distorted excitation profiles and the sparse modeling of our approach offers excellent correction of metal-induced distortions. Results: Three images reconstructed using SEMAC, SEMAC with the conventional two-step noise reduction, and the proposed image denoising for metal MRI exploiting sparsity and low rank approximation algorithm were compared. The proposed algorithm outperformed two methods and produced 119% SNR better than SEMAC and 89% SNR better than SEMAC with the conventional two-step noise reduction. Conclusion: We successfully demonstrated that the proposed, novel algorithm for SEMAC, if compared with conventional de-noising methods, substantially improves SNR and reduces artifacts.

• Biomaterials and Biomechanics in Bioengineering
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• v.1 no.3
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• pp.131-150
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• 2014

Vascular stenting has a great attention as a treatment for coronary arteries diseases as compared with percutaneous balloon angioplasty. In-stent restenosis and thrombosis are side effects resulting from using bare metal stent (BMS). Employing platelet therapy allowed to reduce the rate of thrombosis, however, the rate of restenosis remains a major problem. In 2002, drug-eluting stents (DESs) were introduced as an effort to reduce the restenosis. The commercially available DESs continue to suffer from coating defects that might lead to a series of adverse effects. Most importantly, multiple concerns remain regarding the polymer coating integrity on metal surfaces or the relation of polymer irregularities to longterm adverse events.

• Polymer(Korea)
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• v.33 no.6
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• pp.620-624
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• 2009

Biomedical metal implants have been used clinically for replacement, restoration, or improvement of injury bodies based on high mechanical properties, but it has some risks such as the inflammatory, late thrombosis, or restenosis due to the low biocompatibility and toxicity. In various techniques of surface treatment developed to preserve these drawbacks, this study examined the electrospray coating technology with biodegradable poly (lactic-co-glycoic acid) (PLGA) on metal surface. Based on fundamental examination of electrospraying and solution parameters, the surface morphology of coated film was closely related to the boiling point of solvent, in-flight distance, and droplet size. The thickness of polymer film was linearly proportional to the emerged volume. This result exhibits that the polymeric droplets were continuously deposited on the polymer film. Therefore, the electrospray coating technology might be applied into the fabrication of single/multi-layered polymer film in nano-/micro-thickness and the control of the topology for biomedical metal implants including stents.

• Biomedical Science Letters
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• v.10 no.4
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• pp.453-457
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• 2004

The welders and car painters are frequently exposed to heavy metals such as lead, zinc, cadmium and chromium, and those are a major source of heavy metal poisoning. This study was carried out to investigate the relationship of the heavy metal level in blood by age, working duration, and smoking status among 105 industrial workers and 88 general people in Gyeongnam province from October 2003 to October 2004. The heavy metal level in blood was analyzed by atomic absorption spectrophotometer. Mean blood lead level in exposed group and control group was 8.40±4.67μl/dl, 1.82±1.35μl/dl, respectively. Mean blood zinc level in exposed group and control group was 9.43±5.38 ㎍/ml, 2.89±1.79㎍/ml, respectively. Mean blood cadmium level in Exposed group and control group was 1.53±1.05μl/dl, 0.60±0.49 μl/dl, respectively. Mean blood chromium level in exposed group and control group was 0.89±0.76μl/dl, 0.68±0.63μl/dl, respectively. Lead, zinc, cadmium and chromium level in blood of exposed group was significantly higher than that of control group. In the comparison of smoking status, lead, zinc and cadmium level of smoker's was significantly higher than that of non-smoker's. Comparison of heavy metal level by age, lead, zinc, cadmium level in 40's, 50's (exposed group) in blood significantly higher than that of 20's, 30's. In exposed group, working duration has no significant difference. In conclusion, smoking was the most hazardous factor to elevate in blood heavy metal levels.

• Current Optics and Photonics
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• v.7 no.5
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• pp.569-573
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• 2023

We utilized terahertz time-domain spectroscopy (THz-TDS) to measure the thickness and electrical properties of nickel-chromium (Ni-Cr) films. This technique not only aligns well with traditional methods, such as haze-meter and transmission-densitometer measurements, but it also reveals the electrical properties and thickness of films down to a few tens of nanometers. The complex conductivity of the Ni-Cr thin films was extracted using the Tinkham formula. The experimental values closely aligned with the Drude model, indicating the reliability of our Ni-Cr film's electrical and optical constants. The thickness of Ni-Cr was estimated using the complex conductivity. These findings emphasize the potential of THz-TDS in quality control of metallic nanofilms, pointing toward an efficient and nondestructive test (NDT) for such analyses.