Jin-Kyung Lee

Antimicrobial Efficacy of a Polymeric Chlorhexidine Release Device Using In Vitro Model of Enterococcus faecalis Dentinal Tubule Infection

This study aimed to assess the antimicrobial efficacy of a novel polymeric chlorhexidine-controlled release device as an intracanal medicament. One hundred cylindrical dentin blocks prepared from human single-rooted teeth were inoculated with Enterococcus faecalis for 3 weeks. The intracanal medicaments tested were calcium hydroxide, a polymeric chlorhexidine-controlled release device (PCRD), a polymeric controlled release device without chlorhexidine (CHx), 0.2% CHx solution, and sterile saline. Dentin samples (at 200-mum and 400-mum depths) were collected from the medicated canal lumens after 1 week of medication with sterile LightSpeed files and placed in growth medium. Bacterial growth was assessed spectrophotometrically by analysis of optical density (OD) after 24 hours of incubation. The OD values at both depths were significantly lower in the PCRD group than in the other experimental groups (P < .001). These results indicate that a PCRD can be an effective intracanal medicament against E. faecalis.

Calcium Hydroxide Inactivates Lipoteichoic Acid from Enterococcus faecalis

Calcium hydroxide is a widely used endodontic medicament for eliminating viable bacteria and inactivating virulence factors. Enterococcus faecalis, a pathogenic gram-positive bacterium, has been associated with refractory apical periodontitis. Because lipoteichoic acid (LTA) is a major virulence factor of gram-positive bacteria, we examined whether calcium hydroxide could detoxify LTA from E. faecalis. An enzyme-linked immunosorbent assay showed that calcium hydroxide-killed E. faecalis was less potent than heat-killed bacteria in stimulating the release of tumor necrosis factor-alpha by a murine macrophage line, RAW 264.7 (P < 0.05). Pretreatment of LTA with calcium hydroxide remarkably abrogated the ability of LTA to induce the release of tumor necrosis factor-alpha (P < 0.05). Furthermore, calcium hydroxide-treated LTA was not able to stimulate Toll-like receptor 2, which recognizes functionally intact LTA. These results suggest that calcium hydroxide could detoxify LTA, resulting in attenuation of the inflammatory responses to E. faecalis and its LTA.

Chlorhexidine Gluconate Attenuates the Ability of Lipoteichoic Acid from Enterococcus faecalis to Stimulate Toll-like Receptor 2

Chlorhexidine gluconate (CHX) has been widely used as a canal irrigant or an intracanal medicament on account of its antibacterial substantivity. This in vitro study aimed to determine if CHX attenuates the inflammatory activity of Enterococcus faecalis and its major virulence factor, lipoteichoic acid (LTA). An enzyme-linked immunosorbent assay showed that CHX-killed E. faecalis was less potent than heat-killed E. faecalis in the production of tumor necrosis factor alpha (TNF-alpha) by a murine macrophage cell line, RAW 264.7 (p < 0.05). Interestingly, pretreatment of LTA with 2% CHX for 6 hours or with 0.2% CHX for 24 hours almost eliminated the TNF-alpha inducibility (p < 0.05). Furthermore, CHX abrogated the ability of LTA to stimulate Toll-like receptor 2, resulting in the attenuated induction of TNF-alpha expression. Collectively, our results suggest that CHX can inactivate LTA of E. faecalis leading to the alleviation of inflammatory responses induced by E. faecalis and its LTA.

Monolithic photorefractive molecule with excellent transparency in the visible region

9-(2-Ethyl-hexyl)-3-[2-(4-methanesulfonyl-phenyl)vinyl]-9H-carbazole (EHCS) was synthesized as a monolithic photorefractive molecule forming low Tg(∼25 °C) organic glass. It showed distinct photoconductivity due to the carbazole moiety and the optical nonlinearity by the push–pull structure. The EHCS glass showed excellent optical quality and great stability as the ethylhexyl group effectively suppressed the crystallization in the films. Also, the extremely simple structure of EHCS contributed to a very high chromophore concentration. This single-component photorefractive glass of EHCS showed large net gain (56.3 cm−1) and diffraction efficiency (12%). Photorefractivity of EHCS glass was greatly improved by doping with a small amount (<1%) of 2,4,7-trinitrofluorenone (TNF). The two-beam coupling gain of samples with TNF was 113 cm−1 and the diffraction efficiency was 29%.

Reviewing Korea's Strategic Plan of Adaptation and Mitigation for Sustainable Development and Climate Change

This article introduces Koreas Five Year Green Growth Plan (FYGGP) as the national policy portfolio framework, assesses the weakness of FYGGP using the Adaptation Policy Framework (APF)s principals, and proposes three ideas to improve FYGGP. The first idea is setting up the Total Management System for Climate Changes (TMSCC) that consists of an effective integration process with existing authorities and plans; strong institutional support; monitoring and evaluation processes; and responsive adjusting mechanisms. The second idea is effectively applying the inventory of TMSCC to decide and modify the national policy. The TMSCC needs an independent agent under the Korean Presidential Committee which can coordinate and manage it, so that sustainability indicators and standards of judgment for mitigation can be developed and announced. The final idea is taking a systematic evaluation that can upgrade the TMSCC, linked with policy directions, as a suitability evaluation about TMSCC itself needs a process making the system; an efficiency evaluation needs a process modifying the system and a process applying policy scenarios; an accuracy evaluation needs a process forecasting policy effects and climate change impacts. This evaluation cycle can help achieve the national objectives.

Fluorescent topographic nanopatterns by fluorophore-functionalized diblock copolymers

We demonstrated the fabrication of fluorophore-functionalized nanopatterns with topographic features. To obtain fluorescent nanopatterns, diblock copolymers having fluorophores in one of the blocks were synthesized by the reversible addition fragmentation chain transfer polymerization and were annealed by solvent vapor, resulting in perpendicular or parallel cylindrical nanopatterns functionalized with fluorophores, depending on the annealing solvent. Then, by etching one of the copolymer blocks, we were able to produce fluorescent topographic nanopatterns. Furthermore, Au nanorods selectively loaded in the nanometer-sized valley of the pattern effectively altered the fluorescence of the topographic nanopattern.

Clinical study of shade improvement and safety of polymer-based pen type BlancTic Forte whitening agent containing 8.3% Carbamide peroxide

This clinical study evaluated the whitening effect and safety of polymer based-pen type BlancTis Forte (NIBEC) containing 8.3% carbamide peroxide. Twenty volunteers used the BlancTis Forte whitening agent for 2 hours twice a day for 4 weeks. As a control. Whitening Effect Pen (LG) containing 3% hydrogen peroxide was used by 20 volunteers using the same protocol. The change in shade (, color difference) was measured using (DeguDent) before, during, and after bleaching (2 weeks, 4 weeks, and post-bleaching 4 weeks). A clinical examination for any side effects (tooth hypersensitivity or soft tissue complications) was also performed at each check-up. The following results were obtained. 1. Both the experimental and control groups displayed a noticeable change in shade () of over 2. No significant differences were found between the two groups (p > 0.05), implying that the two agents have a similar whitening effect.2. The whitening effect was mainly due to changes in a and b values rather than in L value (brightness). The experimental group showed a significantly higher change in b value, thus yellow shade, than the control (p