• Corrosion Science and Technology
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• v.8 no.2
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• pp.62-67
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• 2009

Ti and Ti-alloys have good biocompatibility, appropriate mechanical properties and excellent corrosion resistance. However, the widely used Ti-6Al-4V is found to release toxic ions (Al and V) into the body, leading to undesirable long-term effects. Ti-6Al-4V has much higher elastic modulus (100 GPa) than cortical bone (20 GPa). Therefore, titanium alloys with low elastic modulus have been developed as biomaterials to minimize stress shielding. The electrochemical behavior of surface-modified and MC3T3-E1 cell-cultured Ti-30(Nb,Ta) alloys with low elastic modulus have been investigated using various electrochemical methods. Surfaces of test samples were treated as follows: $0.3{\mu}m$ polished; $25{\mu}m$, $50{\mu}m$ and $125{\mu}m$ sandblasted. Specimen surfaces were cultured with MC3T3-E1 cells for 2 days. Average surface roughness ($R_a$) and morphology of specimens were determined using a surface profilometer, OM, and FE-SEM. Corrosion behavior was investigated using a potentiostat(EG&G PARSTAT 2273), and electrochemical impedance spectroscopy was performed (10 mHz to 100 kHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The microstructures of the Ti-30(Ta,Nb) alloys had a needle-like appearance. The $R_a$ of polished Ti-30Ta and Ti-30Nb alloys was lower than that of the sandblasted Ti alloy. Cultured cells displayed round shapes. For polished alloy samples, cells were well-cultured on all surfaces compared to sandblasted alloy samples. In sandblasted and cell-cultured Ti-30(Nb,Ta) alloy, the pitting potential decreased and passive current density increased as $R_a$ increased. Anodic polarization curves of cell-cultured Ti alloys showed unstable behavior in the passive region compared to non-cell-cultured alloys. From impedance tests of sandblasted and cell-cultured alloys, the polarization resistance decreased as $R_a$ increased, whereas, $R_a$ for cell-cultured Ti alloys increased compared to non-cell-cultured Ti alloys.

• Journal of Surface Science and Engineering
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• v.41 no.5
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• pp.232-239
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• 2008

The dental orthodontic mini-screw requires good mechanical properties and high corrosion resistance for implantation in the bone. The purpose of this study was to investigate the electrochemical characteristics of TiN and ZrN coated orthodontic mini-screws, mini-screws were used for experiment. Ion plating was carried out for mini-screw using Ti and Zr coating materials with nitrogen gas. Ion plated surface of each specimen w as o bserved with f ield emission scanning e lectron microscopy ( FE-SEM), e nergy dispersive x-ray spectroscopy (EDX), and electrochemical tester. The surface of TiN and ZrN coated mini-screw were more smooth than that of other kinds of non-coated mini-screw due to dercrease of machined defects. The corrosion current density of the TiN and ZrN coated mini-screw decreased compared to non-coated sample. The corrosion potential of TiN and ZrN coated mini-screw were higher than that of non-coated mini-screw in 0.9% NaCl solution. The pitting corrosion resistance increased in the order of ZrN coated, TiN coated and non-coated wire. Pitting potential of ZrN coated mini-screw was the highest in the other specimens.

• Journal of the Korean Society of Radiology
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• v.11 no.5
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• pp.371-377
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• 2017

General phantom for practical X-ray photography Practical phantom is an indispensable textbook for radiology, but it is difficult for existing commercially available phantom to be equipped with various kinds of phantom because it is an expensive import. Using 3D printing technology, I would like to make the general phantom for practical X-ray photography less expensive and easier. We would like to use a skeleton model that was produced based on CT image data using a 3D printer of FDM (Fused Deposition Modeling) method as a phantom for general X-ray imaging. 3D slicer 4.7.0 program is used to convert CT DICOM image data into STL file, convert it to G-code conversion process, output it to 3D printer, and create skeleton model. The phantom of the completed phantom was photographed by X - ray and CT, and compared with actual medical images and phantoms on the market, there was a detailed difference between actual medical images and bone density, but it could be utilized as a practical phantom. 3D phonemes that can be used for general X-ray practice can be manufactured at low cost by utilizing 3D printers which are low cost and distributed and free 3D slicer program for research. According to the future diversification and research of 3D printing technology, it will be possible to apply to various fields such as health education and medical service.

• Journal of Digital Convergence
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• v.14 no.10
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• pp.483-497
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• 2016

Purpose of this study is to compare and analyze effect of exercise intensity in complex training for 8 weeks on leptin, growth hormone, IGF-1, and body composition in middle school with intellectual disability. Subjects of this study were 26 middle school students, 9 in high-intensity group, 9 in middle-intensity group, and 8 in low-intensity group. To compare the difference from different exercise intensity, pre-value before training has been set as covariate and different exercise intensity has been set as independent variable, with changes in leptin, growth hormone, IGF-1, and body composition. Analysis of covariance (ANOVA) has been performed for data analysis and effect size ${\eta}^2$(eta) has been deduced. Result acquired from analyzed data is as following. First, when equal exercise has been imposed on middle school students with intellectual disability, in regard of exercise intensity, it was shown that leptin most decreased in middle-intensity, growth hormone most increased in middle-intensity, and IGF-1 increased in low-intensity. Second, in regard of body composition, low-intensity was most effective in increase of total body weight without fat. Decrease of body fat was most prominent in middle-intensity and increase of bone density, in low-intensity. Also, in further studies, study that differentiates subjects in gender and individual exercise performance is deemed mandatory.

• Imaging Science in Dentistry
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• v.35 no.3
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• pp.127-131
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• 2005

Purpose : We performed the present study to investigate whether osteotropic hormomes play roles on the nitric oxide (NO) production in culture of ROS 17/12.8 osteoblastic cells. Materials and Methods : The osteoblastic cell line ROS17/2.8 cells were cultured In F12 medium supplemented with $5\%$ fetal bovine serum (FBS) at $37^{\circ}C$ in a humidified atmosphere of $5\%\;CO_2$ in air. ROS17/2.8 cells were plated in 96-well plates at a density of $2-3\times10^3cells/well$ and grown to confluence. Then the cells were pretreated with osteotropic hormones (parathyroid hormone (PTH) 20-500 ng/mL, 1, 25-dihydroxycholecalciferol $(1,\;25[OH]_2D_3)$ 1-100 nM; prostaglandin $E_2 (PGE_2)$ 20-500 ng/mL in the medium supplemented with $0.4\%$ FBS for 72 hours and the cells were treated with cytokines $(TNF{\alpha}\;and\;IFN{\gamma})$ in phenol red-free F12 medium for an additional 48 hours. NO synthesis was assessed by measuring the nitrite anion concentration, the reaction product of NO, in the cell culture medium using Griess reagent. Results : PTH and $1,\;25[OH]_2D_3$ pretreatment induced a significant increase in NO production in the presence of $TNF{\alpha}\;and\;IFN{\gamma}.\;PGE_2$ slightly induced NO production compared to the control group. But, $PGE_2$ pretreatment did not affect in NO production in the presence of $TNF{\alpha}\;and\;IFN{\gamma}$. Conclusions : These results suggest that the actions of osteotropic hormones In bone metabolism may be partially mediated by NO in the presence of cytokines.

• Progress in Medical Physics
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• v.28 no.4
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• pp.207-217
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• 2017

For effective patient treatment in proton therapy, it is therefore important to accurately measure the beam range. For measuring beam range, various researchers determine the beam range by measuring the prompt gammas generated during nuclear reactions of protons with materials. However, the accuracy of the beam range determination can be lowered in heterogeneous phantoms, because of the differences with respect to the prompt gamma production depending on the properties of the material. In this research, to improve the beam range determination in a heterogeneous phantom, we derived a formula to correct the prompt-gamma distribution using the ratio of the prompt gamma production, stopping power, and density obtained for each material. Then, the prompt-gamma distributions were acquired by a multi-slit prompt-gamma camera on various kinds of heterogeneous phantoms using a Geant4 Monte Carlo simulation, and the deduced formula was applied to the prompt-gamma distributions. For the case involving the phantom having bone-equivalent material in the soft tissue-equivalent material, it was confirmed that compared to the actual range, the determined ranges were relatively accurate both before and after correction. In the case of a phantom having the lung-equivalent material in the soft tissue-equivalent material, although the maximum error before correction was 18.7 mm, the difference was very large. However, when the correction method was applied, the accuracy was significantly improved by a maximum error of 4.1 mm. Moreover, for a phantom that was constructed based on CT data, after applying the calibration method, the beam range could be generally determined within an error of 2.5 mm. Simulation results confirmed the potential to determine the beam range with high accuracy in heterogeneous phantoms by applying the proposed correction method. In future, these methods will be verified by performing experiments using a therapeutic proton beam.

• Childhood Kidney Diseases
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• v.10 no.2
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• pp.142-151
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• 2006

Purpose : Growth retardation is one of the serious problems in children with nephropathy requiring long-term steroid therapy. We observed the efficacy and safety of recombinant human growth hormone(rhGH) on the growth in children with long-term steroid therapy. Methods : We studied 60 children(male 47, female 13) with nephropathy who received rhGH(1 U/kg/week) for more than 0.5 years($1.39{\pm}1.12$). Their mean age was 11.0 years($11.17{\pm}2.62$). They received steroid therapy from January 1987 through July 2005, and the mean duration of steroid therapy was $4.32{\pm}2.97$ years. Among the patients, there were 32 nephrotic syndrome, 9 IgA nephropathy, 4 mesangial proliferative glomerulonephritis, 4 focal segmental glomerulosclerosis, 2 Henoch $Sch\ddot{o}nlein$ nephritis, 2 Alport syndrome and 7 other cases. Data were gathered on the growth parameters, such as growth velocity, height standard deviation score(SDS), IGF-1, IGFBP-3, bone mass density(BMD) and general chemistry changes. Results : Height velocity increased significantly with rhGH therapy from $3.29{\pm}1.95$ to $8.66{\pm}3.75$(cm/yr) and height SDS decreased from $-0.72{\pm}0.93$ to $-1.04{\pm}0.86$ at one year after steroid therapy but increased to $-0.55{\pm}0.96$ at one year after rhGH administration(P<0.05). BMD improved from $0.71{\pm}0.14$ to $0.79{\pm}0.15g/cm^2$(P<0.05). IGF-1 increased from $445.09{\pm}138.01$ to $506.62{\pm}181.31ng/mL$(P<0.05). IGFBP-3 decreased from $4073.75{\pm}700.78$ to $3933.61{\pm}789.25ug/L$ numerically, but there was no statistically significant difference(P=0.533). Conclusion : The administration of rhGH in the short stature patients who received long-term steroid therapy showed improvement in growth parameters such as SDS, growth velocity, and BMD without significant side-effects or changes in the biochemical parameters.

• Journal of Korean Neurosurgical Society
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• v.42 no.5
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• pp.371-376
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• 2007

Objective : Balloon kyphoplasty can effectively relieve the symptomatic pain and correct the segmental deformity of osteoporotic vertebral compression fractures. While many articles have reported on the effectiveness of the procedure, there has not been any research on the factors affecting the deformity correction. Here, we evaluated both the relationship between postoperative pain relief and restoration of the vertebral height, and segmental kyphosis, as well as the various factors affecting segmental deformity correction after balloon kyphoplasty. Methods : Between January 2004 and December 2006, 137 patients (158 vertebral levels) underwent balloon kyphoplasty. We analyzed various factors such as the age and sex of the patient, preoperative compression ratio, kyphotic angle of compressed segment, injected PMMA volume, configuration of compression, preoperative bone mineral density (BMD) score, time interval between onset of symptom and the procedure, visual analogue scale (VAS) score for pain rating and surgery-related complications. Results : The mean postoperative VAS score improvement was $4.93{\pm}0.17$. The mean postoperative height restoration rate was $17.8{\pm}1.57%$ and the kyphotic angle reduction was $1.94{\pm}0.38^{\circ}$. However, there were no significant statistical correlations among VAS score improvement, height restoration rate, and kyphotic angle reduction. Among the various factors, the configuration of the compressed vertebral body (p=0.002) was related to the height restoration rate and the direction of the compression (p=0.006) was related with the kyphotic angle reduction. The preoperative compression ratio (p=0.023, p=0.006) and injected PMMA volume (p<0.001, p=0.035) affected both the height restoration and kyphotic angle reduction. Only the preoperative compression ratio was found to be as an independent affecting factor (95% CI : 1.064-5.068). Conclusion : The two major benefits of balloon kyphoplasty are immediate pain relief and local deformity correction, but segmental deformity correction achieved by balloon kyphoplasty does not result in additional pain relief. Among the factors that were shown to affect the segmental deformity correction, configuration of the compressed vertebral body, direction of the most compressed area, and preoperative compression ratio were not modifiable. However, careful preoperative consideration about the modifiable factor, the PMMA volume to inject, may contribute to the dynamic correction of the segmental deformity.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.2
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• pp.257-264
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• 2018

Osteopetrosis is characterized by impaired osteoclast function and increased bone density. Infantile osteopetrosis is a severe form of the disease and has characteristics such as diffusely sclerotic skeleton, pancytopenia, cranial nerve entrapment, infection susceptibility, and abnormal craniofacial appearance. Patients with infantile osteopetrosis often experience developmental delay, and may have a short life span. A 14-month-old girl with osteopetrosis presented to the department of pediatric dentistry. Incipient caries on deciduous incisors were observed. The patient revisited 4 years of age. Besides medical problems, oral complications such as growth retardation, narrow upper arch, crowding, dental caries, and abnormal tooth development were observed. After consultation with her pediatrician, dental treatments were performed on the deciduous molars under sedation after a prophylactic antibiotic injection. At a periodic follow-up, multiple deciduous teeth were treated and extracted, and oralrehabilitation with a removable partial denture was initiated. Patient with osteopetrosis are highly susceptible to infection because of their compromised immune system and problems associated with wound healing that lead to osteomyelitis or sepsis development. Active participation in dental care for sugar intake management and proper oral hygiene are obligatory.

• Journal of Technologic Dentistry
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• v.30 no.1
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• pp.25-31
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• 2008

Cp-Ti and Ti-6Al-4V alloys commonly used dental implant materials, particularly for orthopaedic and osteosynthesis because of its suitable mechanical properties and excellent biocompatibility. This alloys have excellent corrosion behavior in the clinical environment. The first factor to decide the success of dental implantation is sufficient osseointegration and high corrosion resistance between on implant fixture and its surrounding bone tissue. In this study, in order to increase corrosion resistance and biocompatibility of Cp-Ti and Ti-6Al-4V alloy that surface of manufactured alloy was coated with TiN by RF-magnetron sputtering method. The electrochemical behavior of TiN coated Cp-Ti and Ti-6Al-4V alloy were investigated using potentiodynamic (EG&G Co, PARSTAT 2273. USA) and potentiostatic test (250mV) in 0.9% NaCl solution at 36.5 $\pm$ 1$^{\circ}C$. These results are as follows : 1. From the microstructure analysis, Cp-Ti showed the acicular structure of $\alpha$-phase and Ti-6Al-4V showed the micro-acicular structure of ${\alpha}+{\beta}$ phase. 2. From the potentiodynamic test, Ecorr value of Cp-Ti and Ti-6Al-4V alloys showed -702.48mV and -319.87mV, respectively. Ti-6Al-4V alloy value was higher than Cp-Ti alloy. 3. From the analysis of TiN and coated layer, TIN coated surface showed columnar structure with 800 nm thickness. 4. The corrosion resistance of TiN coated Cp-Ti and Ti-6Al-4V alloys were higher than those of the non-coated Ti alloys in 0.9% NaCl solution from potentiodynamic test, indicating better protective effect. 5. The passivation current density of TiN coated Cp-Ti and Ti-6Al-4V alloys were smaller than that of the noncoated implant fixture in 0.9% NaCl solution, indicating the good protective effect resulting from more compact and homogeneous layer formation.