• The korean journal of orthodontics
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• v.30 no.4 s.81
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• pp.483-490
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• 2000

The dental gold alloy shows a lower bond strength than the natural teeth in bracket bonding, and this can be a possible source of subsequent bond failure. This study aims to evaluate the effect of various gold alloy surface treatment techniques on shear bond strength between the orthodontic adhesives and the gold alloy and to find ways of increasing the bond strength. Two hundred and forty specimens made of the dental fold alloy were divided into twelve groups based on the combination of surface treatment methods(non-surface treatment, sandblasted, sandblasted plus tin-plated, and sandblasted plus intermediate adhesive) and adhesive systems (Ortho-one, Panavia 21, Superbond C&B). The specimens with bonded brackets were placed in distilled water at $37^{\circ}C$ for 24 hours and shear bond strength was measured by a universal testing machine. The results were as follows: 1. All surface-treated groups showed a significantly higher shear bond strength than non-surface-treated groups. 2. The sandblasted plus tin-plated group showed a significantly higher shear bond strength than the sandblasted group only when Panavia 21 was involved. 3. The sandblasted plus intermediate adhesive group showed a significantly higher shear bond strength than sandblasted group regardless of the type of adhesive used. 4. Of the three resin adhesive types, the Superbond C&B showed the highest bond strength, followed by Panavia 21 and Ortho-one. These findings suggest that a combination of sandblasting and intermediate resin treatment is desirable in order to enhance bracket bond strength regardless of adhesive types.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.26 no.2
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• pp.133-145
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• 1996

Aspirating or swallowing foreign bodies is a common occurrence. If they are wholly or partly radiopaque, their localization in and progress through the gastrointestinal tract can be more effective. Of the dental origin foreign materials swallowed, the most common things are fragments of anterior maxillary partial denture. But the radiopacity of denture base resins is not sufficient to determine the location of the objects. The purpose of this study was to develop a radiopaque dental acrylic resin, which has clinically detectible radiopacity with minimal change of mechanical properties and color. The radiopacity, color change(CIE 6..E) and microhardness of acrylic resins were determined after mixing barium sulfate or iodide compound. Thermocycling course was conducted to determine the change of characteristic of resins after using for a long time in the mouth. Five or ten percent of barium sulfate to total weight of cured material was mixed with heat curing dental acrylic resin or chemically curing orthodontic resin. In the case of iodide compound, the mixing ratio was two or three percent. After mixing the high radiopaque materials, resin was cured to 20×20×2 mm plate, polished with #600 sand paper and finally polished with Microcloth(Buehler). The specimens were thermocycled in 5 and 55 t distilled water for 2,000 times, and the measurement of radiopacity, color and Vickers hardness was repeated every 500 times thcrmocycling. The radiopacity of specimens on the X -ray films was measured with densitometer(X-rite). The color change was detennined with differential colorimeter(Model TC-6FX, Tokyo Denshoku), and the Vickers hardness number was measured with microhardness tester(Mitsuzawa). The following results were obtained : 1. All the three variables, the kinds of acrylic resins, the mixing or the kinds of high radiopaque materials and thermocycling, had combined effect on the radiopacity of the dental acrylic resins(p<0.0l). 2. The two variables, the mixing or the kinds of high radiopaque materials and thermocycling, influenced on the radiopacity of the dental acrylic resins(p<0.01). But the kinds of acrylic resins did not influence on the color change of mixed dental acrylic resins(p>0.05). 3. Each of the three variables, the kinds of acrylic resins, the mixing or the kinds of high radiopaque materials and thermocycling, influenced on the radiopacity of dental acrylic resins(p<0.0l). 4. The high radiopaque materials used in this study did not yield clinically usable radiopacity, and the color change was great after mixing those materials.

• Journal of the Korean Chemical Society
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• v.55 no.1
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• pp.57-62
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• 2011

Sometimes inhabitants in remote areas have inadequate or no access to modern medicines or medical services. They can get benefit in term of the treatment against malaria by cultivating selected breeding of A. annua and making teas or decoctions from the plant materials following the proper way of tea preparation. In order to have the maximum extraction efficiency for artemisinin, different ways of tea preparations of A. annua were investigated by applying the developed DPP method and described in this article. Tea was prepared by three different ways (cooking, without cooking with/without shaking and microwave oven) with different times. From the results, it has been found that higher concentration of artemisinin (84.7%) can be attained by following the approach for tea preparation without cooking with shaking for 15 minutes (R.S.D. 2.34%). The concentration of artemisinin decreases with cooking more than 1.5 min in microwave oven. The utmost extraction (88.9% of artemisinin) is possible to extract by shaking with boiled 5% ethanol in distilled water (R.S.D. 2.28%).

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.4
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• pp.339-347
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• 2012

In previous studies, methods for enhancing cellular response on the Hydroxyapatite coated implant surface were described. In this study, the changes of surface characteristics such as surface roughness, contact angle, surface energy and surface morphology were observed when Hydroxyapatite coated Ti discs were immersed in NaCl solution for various time. Hydroxyapatite coated Ti discs were immersed in 0.9% NaCl solution for 7, 14 and 21 days at $37^{\circ}C$. The control group comprises dry identical discs not immersed in a solution. (n=3) All discs were dried in air completely and the surface roughness was measured using confocal laser scanning microscopy(CLSM). Static contact angle was recorded by video contact angle analyzer after dropping distilled water on the surface. The surface energy was calculated from contact angles of the three liquids. Surface was observed using a field emission-scanning electron microscope(FE-SEM). As a result, the surface roughness of immersed Hydroxyapatite coated Ti discs increased significantly and the contact angle decreased comparing with control group discs. The surface energy of immersed discs increased except for discs immersed for 14 days.

• Korean Journal of Food Science and Technology
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• v.37 no.5
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• pp.741-745
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• 2005

Pectin was dissolved in HCl, citric acid, and deionized distilled water (DW, 2%, v/v) and irradiated at different irradiation doses (2.5-50 kGy) by gamma ray to investigate its physicochemical characteristics and biological activity. Viscosity of pectin solution was significantly decreased by irradiation up to 10 kGy, then remained constant thereafter. Gamma-irradiation increased monosaccharide and polysaccharide levels up to 30-40 kDa. Electron donating ability of pectin solution was highest when DW was added and was increased by increasing irradiation dose (p<0.05). ${\beta}-Carotene$ bleaching assay revealed irradiation resulted in development of antioxidantive activity in pectin solution. Growth inhibition of cancer cell lines was observed in irradiated pectin solution in dose-dependent manner, with G36l showing the highest. Results suggested irradiation of pectin solution could be effective for preparation of functional pectin oligomer.

• Korean Journal of Food Science and Technology
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• v.17 no.5
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• pp.319-325
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• 1985

Agar was prepared from domestic agarophyte (Gelidium amansii) by a process of acid extraction. Optimal conditions in the acid treatment of the seaweed and the gelling properties of the agar thus prepared were investigated. The yield and gel strength of the control (the agar extracted with distilled water) showed 13,3% and 306g/$cm^2$, respectively. The yield of 38.7% was obtained when agar was extracted with 0.007N Hydorchloric acid while the gel strength of agar,511g/$cm^2$ was observed with the agar extracted with 0.005N Hydorchloric acid solution. The agar extracted with hydrochloric acid solution showed excellent properties of agar at the acid concentration range 0.005N-0.01N The cooking time of 60 min. was found to be effective to the yield and also to the gelling property of the agar and the cooking longer than 60 min. was proved to be destructive to agar. In general, yield and gelling properties of the agar obtained showed a close relation to the acid concentration and cooking time, but no consistent influence on the contents of ash and sulfur trioxide.

• Korean Journal of Food Science and Technology
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• v.44 no.4
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• pp.411-416
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• 2012

This study was carried out to investigate the effects of the extrusion process on the change of components in ginseng. The extraction yields from ginseng by distilled water extraction were highest in the extruded ginsengs, whereas it was lowest in the white ginseng. The contents of crude saponin were highest in the extruded ginseng, and they increased as the extrusion temperature was raised. The total contents of 11 kinds of ginsenosides increased in the order of red, white and extruded ginsengs. In particular, red ginseng showed higher contents of Rg1, Rg3 and Rb2, whereas Re was highest in white ginseng. In addition, the contents of Rg2, Rh1, Rh2 and Rg3 in the extruded white ginseng became higher. Free sugar contents were greatest in red ginseng. However, they were lowest in the extruded ginseng. White ginseng had a greater L value, whereas extruded ginseng demonstrated higher a and b values. In conclusion, the extraction yields, the contents of saponin, and ginsenoside-Rg2, Rh1, Rh2 and Rg3 were increased through the extrusion process.

• KSBB Journal
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• v.21 no.2
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• pp.151-156
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• 2006

Vitamin-C is one of the typical bioactive substances widely used in the cosmetic and pharmaceutical applications. It is well known that the bioavailability of vitamin-C decreases with time because it is spontaneously oxidized in the presence of oxygen. In this study, vitamin-C inclusion complexes were prepared by formulating vitamin-C with 2-hydroxypropyl-${\beta}$-cyclodextrin (HP-${\beta}$-CD) to protect vitamin-C from being oxidized. Vitamin-C inclusion complexes were prepared by a solvent evaporation method using a rotary evaporator and various solvents of different dielectric constant such as ethanol, methanol and distilled deionized water to investigate the effect of solvent polarity on the stability of vitamin-C. To estimate the stability of inclusion complexes, samples were stored in a 50 mM phosphate buffer solution of pH 7.0 for 24 hours at $25{\pm}0.1^{\circ}C$ and the degradation rate of vitamin-C was calculated using a high performance liquid chromatography. The stability of vitamin-C was observed to improve with the increase of solvent polarity.

• Journal of the Korea Convergence Society
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• v.8 no.9
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• pp.127-133
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• 2017

The purpose of this study is to confirm the effect of natural tooth whitening using fruits that can be easily accessed in real life by increasing interest in tooth whitening in modern society. Twenty premolar teeth were divided into five groups (n=4). Strawberry (A), lemon (B), banana skin (C), baking soda (D) and whitening toothpaste (E) were treated with a toothbrush on the enamel surface. The tooth surface was treated with a toothbrush at the same time for 3 minutes for breakfast, lunch, and dinner, then washed with sterile distilled water, and stored in saline solution. This procedure was repeated for 4 weeks, and the color change of teeth was observed at intervals of one week. After 4 weeks, there was a significant difference in tooth color change after 3 weeks(p<0.05). Among them, strawberry and lemon showed higer effects to whitening toothpaste. It is believed that strawberries and lemons have a higher whitening effect than whitening toothpaste. Whitening toothpaste may be replaced with a safe natural whitening effect using strawberries and lemons instead of chemical ingredients that may be harmful to human body.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.6
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• pp.664-672
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• 1993

The purpose of this study was to investigate the effect of alcohol administration on selenium concentration and cell morphology in tissurs of rats fed with the different levels of selenium (Se) and vitamin E. Seventy two male rats of Sprague-Dawley strain weighing about 58~62g were divided into 12 groups. The dietary Se levels were 0mg(L-), 0.4mg(C-) and 10mg(H-), and the dietary vitamin E levels were 0mg(-L) and 150mg(-C) per kg diet, respectively. Alcohol-adminstrated groups(--A) received the triple distilled potable water solution containing 10% of ethanol from the 3rd week of experimental periods. The obtained experimental results are summarized as follows. Se concentration in blood and urine made difference in accordance with Se level in diet and tended to be low in alcohol administrated groups. Se concentration in liver and kidney was also directly proportional to the dietary Se level, and it tended to be low in each alcohol group, but Se concentration in kidney tended to be increased by alcohol administration. Myocardium in rats showed lysosome increasing, fat droplet, mitochondrial swelling, and in particular, bad intracellular edema, in H-group fed with high Se and in L-group with low Se. It also showed such phenomena in the alcohol administrated group. In HC-group fed with excessive Se and normal vitamin E. there appeared no noticeable change in liver tissue. However, in the alcohol administrated HCA-group, there came out fat droplet. Especially, in the alcohol administrated LLA-group, not fed with sufficient Se and vitamin, E, there were found lysosome increasing and a number of fat droplet.