Papers by Author: Yong Keun Lee

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Authors: Sang Hoon Rhee, Il Yong Chung, Yong Keun Lee, Bum Soon Lim, Yang Jo Seol
Abstract: Non-woven silica fabric was made by electro-spinning method for the potential application as a bone grafting material. The silica gel, the source material for electro-spinning, was prepared by the hydrolysis of tetraethyl orthosilicate in the presence of calcium salt, water, hydrochloric acid and ethanol. It was transferred to a syringe, which was connected to the high voltage supply generating a high electric field between the spinneret and the ground collecting drum. The silica fibers containing calcium were spun under the electric field of 2 KV/cm. Their diameters were in the range from about 0.3 μm to 8 μm. It was heat-treated at 300 oC for 3 hours. After soaking in the SBF for 1 week, low crystalline apatite crystals were observed to occur on their surfaces. From the results, it can be concluded that the non-woven silica fabric containing calcium made by electro-spinning method and then heat-treated has a bioactivity. It means it has a potential to be used as a bone grafting material because of its apatite-forming ability, high surface area to volume ratio and high porosity.
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Authors: Hanna Yoon, Yong Keun Lee, Bum Soon Lim, Sang Hoon Rhee
Abstract: Non-woven silica fabric was made by electro-spinning method for the application as a bone grafting material. The silica gel, the source material for electro-spinning, was prepared by the hydrolysis of tetraethyl orthosilicate in the presence of water, hydrochloric acid and ethanol. It was transferred to a syringe (spinneret), which was connected to the high voltage supply generating a high electric field between the spinneret and the ground collecting drum. The silica fibers were spun under the electric field of 2 KV/cm. Their diameters were in the range from about 100 nm to 5 µm. After soaking in the SBF for 4 week, low crystalline apatite crystals were observed to occur partly on their surfaces. From the results, it can be concluded that the non-woven silica fabric made by electro-spinning method has the apatite forming ability in the SBF and it means it has a potential to be used as a bone grafting material because of its apatite-forming ability, high surface area to volume ratio and high porosity.
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Authors: Seong Ho Choi, D.H. Baik, C.S. Kim, Chong Kwan Kim, Kyoung Nam Kim, Kwang Mahn Kim, Racquel Z. LeGeros, Yong Keun Lee
Abstract: The purpose of this study was to compare the bone regenerative effect of calcium phosphate glass and glass-ceramics in the system of CaO-CaF2-P2O5-MgO-ZnO, which is already reported that promoted the bone-like tissue formation in vitro and formed new bone in Sprague-Dawley rats. We prepared calcium phosphate glass and glass-ceramics with Ca/P ratio of 0.6 using the system CaO-CaF2-P2O5-MgO-ZnO and subsequently milled to 400 µm. 4×4 mm 1-wall intrabony defects of six beagle dogs were surgically created and used in this study. 8 weeks after transplantation of the prepared calcium phosphate glass and glass-ceramics in the experimental group 1 and 2, respectively, the animals were sacrificed. No root resorption or ankylosis were observed in all groups. It can be examined that the prepared glass-ceramics were more effective in alveolar bone regeneration with statistical signigicant difference. In cementum regeneration, both the prepared glass and glass-ceramics showed significantly different effect. However, there were no statistical significant difference neither in glass nor glass-ceramics in the amounts of junctional epithelium migration and connective tissue adhesion. Further study is required to control the flowability as well as reduce the absorption rate in vivo.
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Authors: Kwang Mahn Kim, Sang Bae Lee, Se Ho Lee, Yong Keun Lee, Kyoung Nam Kim
Abstract: Cytotoxicity test was essential for the pre-clinical evaluation of bioceramics. Proliferation assays such as MTT, XTT and WST-1 were commonly used for measuring biocompatibility. WST-1 was more convenient than MTT because of its water-solubility and storage condition. The calcium phosphate glass and β-TCP have been used for bone substitute, and some magnetic ferrites have been used for hyperthermic treatment. L929, mouse fibroblast cell, was the representative cell-line for in vitro biocompatibility test. The extracts of test samples were prepared by ISO10993-12:2002. The biocompatibilities of the extracts were measured by MTT and WST-1 assay and their pH were measured with pH meter. The cellular survival rate of CPG was the lowest and the results of the WST-1 test showed results similar to those of the MTT test. Thus, proliferation assays using WST-1 may be conveniently and routinely applicable to pre-clinical evaluation of bioceramics.
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Authors: Yeon Ung Kim, Min Chul Kim, Kyoung Nam Kim, Kwang Mahn Kim, Seong Ho Choi, Chong Kwan Kim, Racquel Z. LeGeros, Yong Keun Lee
Abstract: This study presents the manufacture of macroporous hydroxyapatite scaffolds with a small amount of calcium phosphate glass powder as sintering additives. Hydroxyapatite slurry was prepared by suspending the hydroxyapatite and glass powder in water. Polyurethane sponge was used to produce highly macroporous scaffolds. The rheological characteristic of the slurry was measured to identify the effect of adding calcium phosphate glass powder into hydroxyapatite slurry. Sintered scaffolds could be repeatedly coated to improve mechanical properties. Scaffolds prepared by single and double replication cycle process were characterized by density, porosity and compressive strength measurements by increasing amount of the calcium phosphate glass powder to the hydroxyapatite slurry, viscosity by increased more than same amount of pure hydroxyapatite, and the capillary force was similar to pure hydroxyapatite slurry. The compressive strength of the macroporous hydroxyxapatite scaffold containing the calcium phosphate glass powder showed higher value than that of pure hydroxyapatite at single replication cycle. SEM demonstrated that the microstructure of the scaffold became denser with the introduction of the calcium phosphate glass powder. The pore struts were thicker as replication cycle was increased.
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Authors: D.H. Min, M.J. Kim, J.H. Yun, C.S. Kim, Yong Keun Lee, Seong Ho Choi, Kyoung Nam Kim, Chong Kwan Kim
Abstract: This study evaluated periodontal repair and biomaterial reaction following implantation of a newly fabricated calcium phosphate block bone with chitosan membrane on the regeneration of 1-wall intrabony defects in the beagle dogs. The surgical control group received a flap operation only, while the experimental group I was treated with a chitosan nonwoven membrane only and the experimental group II was treated with a chitosan nonwoven membrane and a calcium phosphate block bone. The subjects were sacrificed 12 weeks after surgery and a comparative histometric analysis was done. No root resorption or ankylosis were observed in the experimental group. Mann-Whitney U test showed that the experimental group II produced statistically significant higher gain in connective tissue adhesion, new cementum regeneration and new bone formation. Based on histological results, the calcium phosphate block bone successfully functioned as a osteoconductive scaffold for invading cells of host.
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Authors: J.K. Kang, Yong Keun Lee, Kwang Mahn Kim, Kyoung Nam Kim
Abstract: Dental impression materials are used to register or reproduce the form and relationship of the teeth and oral tissues. They should not be torn when removing from the wet mouth after setting. Nowadays, silica is widely used as filler to overcome the low mechanical strength of the dental impression materials. The purpose of this study was to synthesize high strength glass in the system of MgO-CaO-Al2O3-SiO2 and investigate its usefulness according to ISO standard after mixing with addition silicone. Commercial products, Contrast, Examix, Express, and Perfect-F were selected as control group. When the prepared glass filler was introduced in addition silicone impression material, tear strength was drastically increased significantly than that of the control group, keeping the consistency. All experimental groups showed higher tear stength than that of control groups. As the amount of filler content increases, tear strength was increased. Strain in compression, recovery from deformation, and linear dimensional change were satisfied the ISO standard either all the experimental or control groups. Therefore, calcium-substituted magnesium aluminosilicate glass in the system of 12.5MgO-17.5CaO-20Al2O3-50SiO2 is expected the useful filler in the light body of addition silicone impression materials.
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Authors: Min Chul Kim, Kyoung Nam Kim, Kwang Mahn Kim, Seong Ho Choi, Chong Kwan Kim, Racquel Z. LeGeros, Yong Keun Lee
Abstract: The development of phosphate glasses for use in orthopaedic implants has attracted much interest because their chemical and physical properties make them suitable for use as bone-bonding materials. We prepared various compositions of CaO-P2O5-MO or CaO-P2O5-M2O (M: K, Li, Na, Mg, Zn) glasses to measure ion release, solubility and bioactivity. The compositions with (Ca,M)/P molar ratio 0.6 were fixed P2O5 mol% content at 45.45 mol%, and varying MO or M2O mol% at 10, 20 and 30 mol%. Ca2+ ion release properties were investigated in 0.1M potassium acetate with pH 6 at 37oC by immersing 50 mg of powder into 100 ml of acidic buffer solution. The highest and lowest extent of released Ca2+ ion was observed for composition with 10 mol% of K2O and 30 mol% of MgO, respectively. The weight loss in distilled water at 37oC was measured. Solubility increased with decreasing CaO content, but decreased with increasing MgO content. Bioactivity in the simulated body fluid at 37oC was measured.
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Authors: Sang Hoon Rhee, Yong Keun Lee, Bum Soon Lim
Abstract: The effect of silica content in the PMMA/silica nano-composite on the mechanical properties and the growth behavior of apatite crystals were investigated. The PMMA/silica nano-composites with different silica content were synthesized through the sol-gel reaction with triethoxysilane end-capped PMMA and tetraethyl orthosilicate (TEOS). The compressive strength showed its maximum value when the content of TEOS was 20 wt% while the elastic modulus showed its maximum value when the content of TEOS was 60 wt%. The growth behavior of the apatite crystals following the cell culture showed different response according to the silica content. As increasing the TEOS content, the shape of the apatite crystals changed from globule-like structure to fiber-like one.
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Authors: Sang Hoon Rhee, Yong Keun Lee, Bum Soon Lim
Abstract: A bioactive chitosan-siloxane nano-hybrid material was newly developed and evaluated for the potential application as a bone graft material. The chitosan which can be dissolved in organic solvent was synthesized by the reaction with phtalic anhydride (Ph-Chitosan) and it was then reacted with 3-isocyanatopropyl triethoxysilane (Si-Chitosan) in dimethylformamide. Following this, the Si-Chitosan was hydrolyzed and condensed to yield a hybrid sol-gel material (Si-O-Chitosan). The gelation was carried out for 1 week at ambient condition in a covered Teflon mold with a few pinholes and then dried under vacuum at room temperature for 48 h. The bioactivity of the chitosan nano-hybrid material was evaluated by examining the apatite forming ability in the simulated body fluid (SBF). The surface microstructure and functional groups of the specimen was analyzed by field emission scanning electron microscopy and Fourier transformed infrared spectroscopy, respectively. The crystal phases of the specimen before and after the bioactivity testing were analyzed by thin film X-ray diffractometry. Newly developed chitosan nano-hybrid material showed apatite-forming ability in the SBF within 1 week soaking and this ability was believed to come from the silanol group formed on the surface of Si-O-Chitosan and calcium salt which increased the ionic activity product of apatite in the SBF.
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