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Yanggu, South Korea

Lim J.I.,Yonsei University | Lee Y.-K.,Denforus Co. | Shin J.-S.,Yonsei University | Lim K.-J.,Yonsei University
Journal of Biomaterials Science, Polymer Edition | Year: 2011

For tissue-engineering applications, a 3D porous chitosan scaffold was simply prepared from a mixture of acidic chitosan solution and sodium acetate particles as the porogen by a salt-leaching method. Differences in the porous structure in terms of pore morphology and interconnectivity between the salt-leached chitosan scaffold and phase-separated scaffold as the control were examined by using scanning electron microscopy, protein release and enzymatic degradation tests. A fibroblast (NIH-3T3) cell culture was performed for cell affinity evaluation. The chitosan scaffold prepared by salt-leaching showed good interconnectivity and improved mechanical properties. Furthermore, the chitosan scaffolds showed a high initial cell adhesion after 4 h cell culture and increased cell proliferation than the control. Thus, salt-leached chitosan scaffolds can be used for various tissue-engineering applications. © Koninklijke Brill NV, Leiden, 2011. Source

Lim J.I.,Yonsei University | Lim K.-J.,Yonsei University | Choi J.-Y.,Seoul National University | Lee Y.-K.,Denforus Co.
Microscopy Research and Technique | Year: 2010

Paraffin wax is usually used as an embedding medium for histological analysis of natural tissue. However, it is not easy to obtain enough numbers of satisfactory sectioned slices because of the difference in mechanical properties between the paraffin and embedded tissue. We describe a modified paraffin wax that can improve the histological analysis efficiency of natural tissue, composed of paraffin and ethylene vinyl acetate (EVA) resin (0, 3, 5, and 10 wt %). Softening temperature of the paraffin/EVA media was similar to that of paraffin (50-60°C). The paraffin/EVA media dissolved completely in xylene after 30 min at 50°C. Physical properties such as the amount of load under the same compressive displacement, elastic recovery, and crystal intensity increased with increased EVA content. EVA medium (5 wt %) was regarded as an optimal composition, based on the sectioning efficiency measured by the numbers of unimpaired sectioned slices, amount of load under the same compressive displacement, and elastic recovery test. Based on the staining test of sectioned slices embedded in a 5 wt % EVA medium by hematoxylin and eosin (H&E), Masson trichrome (MT), and other staining tests, it was concluded that the modified paraffin wax can improve the histological analysis efficiency with various natural tissues. © 2009 Wiley-Liss, Inc. Source

Lim J.I.,Yonsei University | Lee Y.-K.,Denforus Co. | Shin J.-S.,Yonsei University | Lim K.-J.,Yonsei University | Lim K.-J.,ProteomeTech Inc.
Materials Letters | Year: 2010

To improve the mechanical properties such as flexibility and bond strength of cyanoacrylates, poly(l-lactide-co-ε-caprolactone) (PLCL) copolymers were dissolved into 2 kinds of cyanoacrylates, ethyl 2-cyanoacrylate (EC) and allyl 2-cyanoacrylate (AC). Mechanical properties such as bond strength, bending-stress recovery, and crystallization intensity were measured. The optimal concentration for high bond strength was determined to be 8% PLCL (molar ratio 70:30). EC/8% PLCL (70:30) exhibited three times higher bond strength as compared with that of EC. Further, AC/8% PLCL (50:50) exhibited better bending recovery than other materials. These results indicate that cyanoacrylate/PLCL materials can be widely used as adhesives in various fields. © 2010 Elsevier B.V. All rights reserved. Source

Lim J.I.,Yonsei University | Lim K.-J.,Yonsei University | Lim H.-N.,Kyung Hee University | Lee Y.-K.,Denforus Co.
Journal of Materials Science | Year: 2010

Glass ionomer cement (GIC) has been successfully used in dental field for more than 40 years. Despite numerous advantages of GIC, low bond strength and slow setting rate limited conventional GICs for use only at low stress-bearing areas. To improve bond strength to tooth, two kinds of cyanoacrylates such as ethyl 2-cyanoacrylate (EC) and allyl 2-cyanoacrylate (AC) were added in a commercial GIC. Changes in setting time of cyanoacrylate-modified GICs (CMGICs) according to the concentration of cyanoacrylates and/or p-toluene sulfonic acid (TSA) was investigated using a rheometer. Shear bond strength to human dentin was measured. Biocompatibility was determined by the viability of fibroblasts. Optimal concentrations for EC and TSA were 5-10% of the GIC powder and 30% of the GIC liquid, respectively. EC-based CMGIC showed twofold increase of initial bond strength compared with conventional GIC. Also, AC-based CMGIC showed three times higher bond strength and similar biocompatibility compared with the GIC. Therefore, CMGIC materials can be widely applied in dental adhesive restoration field because they showed improved bond strength and proper setting time. © 2010 Springer Science+Business Media, LLC. Source

Yu B.,Kyung Hee University | Lim H.-N.,Kyung Hee University | Lee Y.-K.,Denforus Co.
Materials and Design | Year: 2010

This study determined the influence of nano- and micro-filler proportions on the stabilities of color, translucency and opalescence of experimental dental resin composites after wet thermocycling. Silane-coated nano- (mean: 40. nm) and micro-glass fillers (mean: 0.77 μm), in the ratios of 0:6 (N0M6), 1:5 (N1M5), 2:4 (N2M4), 3:3 (N3M3), 4:2 (N4M2), 5:1 (N5M1) and 6:0 (N6M0), were added to 1:1 mixed BisGMA and TEGDMA light curing resin matrix with a total content of 60. wt.% of the resin composites. Reflected and transmitted colors of cured specimens (1. mm in thickness) were measured before and after 5000 cycles of thermocycling with a spectrophotometer. A commercial dental resin composite with a filler content of 65. wt.% was used as a reference. As results, changes in color (ΔEab*), translucency (ΔTP) and opalescence (ΔOP) were in the range of 1.1-3.6, -4.5 to 0.1 and -3.7 to -0.7 units, respectively, all of which were influenced by the filler proportion (p<0.05). A hybrid composite (N4M2) and the nano-filled composite (N6M0) showed the smallest color change, while N4M2 alone showed the smallest translucency change (p<0.05). All the experimental composites showed significant changes in opalescence (p<0.05). Experimental hybrid composite containing 2:1 mixed nano- and micro- fillers showed the best stabilities in color and translucency. The micro-filled composite (N0M6) always showed higher translucency but lower opalescence than those of the hybrid and nano-filled composites. © 2010 Elsevier Ltd. Source

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