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착색 용액을 적용한 치과용 유색 지르코니아의 색 안정성과 용출 성분 평가
석수황(Soo-Hweang Seok),이유미(Yu-Mi Lee),이상혁(Sang-Hyeok Lee),문학룡(Hag-Ryong Moon),양형철(Hyeong-Cheol Yang),임범순(Bum-Soon Lim) 대한치과재료학회 2014 대한치과재료학회지 Vol.41 No.3
The objective of this study was to evaluate the leaching components from the zirconia colored with various coloring liquids and color stability of the colored zirconia after accelerating aging. Commercially avaliable six coloring agents (AQU, BRU, DMA, LAV, RAI and INC) were tested. 3Y-TZP powder were used to prepare the disk-typed pre-sintered zirconia block. After application of coloring agents to pre-sintered zirconia block according to manufacturer’s instruction, final sintering was performed. XRD analysis was done to detect formation of secondary phases and phase transition of zirconia due to the addition of coloring agents. For the chemical stability test, ISO 6872:2008 was adopted and analytical equipments were used. ISO 7491:2000 was adopted for the color stability test. After accelerated aging treatments, color coordinates (CIE L<SUP>*</SUP>a<SUP>*</SUP>b<SUP>*</SUP>) were measured using spectrophotometer. Effects of coloring liquid on the microstructure of zirconia were not observed using XRD analysis, however, small peak of yittrium (Y) was observed in INC. In CTL and all experimental groups, Fe, Y, Mn and Ni ions were leached. Small amounts of Er, Co, and Cr ions were released from some experimental groups. The test of chemical stability in acetic acid solution did not affect the color stability of the colored zirconia (ΔE=0.06-0.69). After the accelerated aging treatment for 24 hrs, lightness (L<SUP>*</SUP>) and a<SUP>*</SUP> values showed the increasing behavior, but b<SUP>*</SUP> values did not show consistent changes. Color difference (ΔE) of CTL was 0.56, 1.61 for BRU, 1.26 for RAI, 1.16 for INC, 1.01 for DMA, 0.60 for AQU and 0.52 for LAV.
이중 지대주에서 티타늄 링크 높이가 지르코니아 지대주와의 유지력에 주는 영향
신홍수(Hong-Soo Shin),허수복(Soo-Bok Her),석수황(Soo-Hwang Seok),이유미(Yu-Mi Lee),임범순(Bum-Soon Lim) 대한치과재료학회 2013 대한치과재료학회지 Vol.40 No.3
The aim of present study was to evaluate the effects of link height and dental cements on the retention force between titanium link and zirconia abutment in the Ti-Zr bicomponent abutment system. Three different height (2.0, 2.5, and 3.0 mm with 0o taper) of titanium links (MonoDent, Korea) were machined and pertinent zirconia abutments (Acucera, Korea) were fabricated with CAD/CAM. One hundred thirty five titanium links and zirconia abutments were prepared. Zirconia abutments were cemented on their respective titanium links with three different types of dental cements, such as zinc phosphate (Fleck’s), resin-modified glass ionomer (RMGI, RelyX Luting 2), self-adhesive resin cement (RelyX U200). Specimens were stored in deionized water (37℃) for 24 hours until testing. Pull-off test was performed using a universal testing machine (Instron 4466, USA) with a crosshead speed of 1 mm/min. Fifteen specimens were tested at each experimental group. The data were analyzed using t-test and Newman-Keuls multiple comparisons test (p=0.05). RMGI showed the lowest retention force (p<0.05) and ZPC showed similar retention force with resin cement (p>0.05) regardless of link heights. For ZPC groups and self-adhesive resin cement groups, 3.0 mm height showed significantly higher retention force than both 2.5 mm and 2.0 mm groups which were not significantly different (p>0.05) For RMGI groups, the retention force increased significantly with increasing of link height (p<0.05). To obtain the proper retention in clinical situation, height of titanium link should be no less than 3.0 mm.
불소 전처치와 후처치가 교정용 브라켓의 접착강도에 미치는 영향
양유경(Yu-Kyoung Yang),석수황(Soo-Hweang Seok),이유미(Yu-Mi Lee),양형철(Hyeong-Cheol Yang),임범순(Bum-Soon Lim) 대한치과재료학회 2014 대한치과재료학회지 Vol.41 No.3
The purpose of this study was to evaluate the effects of the periodic topical fluoride application before (APF gel) and after (fluoride varnish) bracket bonding, on the shear bond strength of orthodontic brackets bonded to bovine teeth. Eighty permanent mandibular incisors of bovine with whole enamel and no decalcification, cracks, or fractures were used. After being extracted, the teeth were kept in a 0.1% tymol solution for disinfection for 1 week. Forty bovine teeth were untreated (CTL, EXP-1), and 40 teeth were pre-treated with 1.23% APF gel about 14 times during 28 days (EXP-2, EXP-3), and XRD analysis was performed to detect the formation of new crystal. After orthodontic bracket adhesion, each groups were divided into 2 subgroups. One subgroup was untreated (CTL, EXP-2) and stored in deionized water (37 ℃) for 28 days, and the other subgroup was treated with fluoride varnish for 4 times during 28 days (EXP-1, EXP-3). SBS test and ARI evaluation were performed, and the data were analyzed using Newman-Keuls multiple comparisons test (p=0.01). Calcium fluoride as well as fluorapatite crystals were formed on the bovine surface after periodical APF gel treatment. Pre-treatment with APF gel caused significant decrease of bond strength and different ARI scores compared to the control group. Post-treatment with fluoride varnish after bracket bonding resulted in significant decrease of bond strength also, however, the strength was higher than the clinically recommended values (6-8 MPa). Both pre-treatment and post-treatment with fluoride agents showed similar SBS and ARI score to the groups with only pre-treatment and no further worsening was observed. Therefore, the post-treatments of fluoride can be suggested after bracket bonding for reduced caries and white spot formations with maintaining proper bonding durability.
이라크 전쟁과 한반도 안보 이라크 전쟁과 북한 핵문제 해법 다자외교
이석수 ( Seok Soo Lee ) 국방대학교 안보문제연구소 2003 국방연구 Vol.46 No.2
This study is designed to discuss measures to resolve the North Korea`s nuclear issue. It places focus on the development since the Iraq War. Before the War, North Korea and the United States maintained hard-line policies, confronting with each other. While North Korea asked bilateral negotiation with the United States, the United States preferred multilateral approach to the issue. Since the end of the Iraq War, North Korea began to show its willingness to join multilateral negotiation to discuss the nuclear issue. Apart from North Korea`s policy shift, China became very active as a broker to arrange multilateral meeting. As a result, three-party meeting was convened in April in Beijing. However, the meeting was aborted due to the severe confrontation between Pyongyang and Washington. In August, six-party talk took place in Beijing, including North and South Korea, the United States, China, Japan, and Russia. In the talk, representatives from six countries gave keynote speeches concerning how to resolve the North Koreas nuclear problems. But participants failed to draw a joint statements. China, the host country, summarized common elements of six keynote speeches to promote negotiation. After the first round of six-party talk, President Bush became softer, mentioning the collective security guarantee. North Korea responded positively to Bush`s proposal. Since then, it was expected that the second round of six-party talk was imminent. The Iraq war provided a momentum of multilateral diplomacy. Despite little progress of the multilateral diplomacy, it cannot be ignored that multilateral talk itself is a meaningful step to resolve the North Korea`s nuclear issue in a ?peaceful manner.
무선 홈네트워크 구현을 위한 UWB와 60㎓ 대역 무선 통신 기술의 활용방안과 시장전망
홍석수(Seok-Soo Hong),박종훈(Jong Hun Park),이동주(Dong-Joo Lee),이재섭(Jaesup Lee),홍정완(Jung-Wan Hong),이창훈(Chang-Hoon Lie) 한국전자거래학회 2008 한국전자거래학회지 Vol.13 No.2
컴퓨터와 디지털 미디어 기기의 발전으로 인해 무선 홈네트워크 구축 시 전송이 요구되는 정보의 용량이 증가함에 따라 이를 처리할 수 있는 새로운 무선 통신 기술이 요구되고 있는 상황에서 UWB와 60㎓ 대역 무선 통신 기술이 그 대안으로 활발히 연구되고 있다. 본 연구에서는 UWB와 60㎓ 대역 무선 통신 기술의 국내외 동향과 특징을 알아보고, 무선 홈네트워크에서의 역할과 그 구현방안을 제안하였다. 끝으로 UWB와 60㎓ 대역 무선 통신 기술의 주된 서비스 분야로 예상되는 WPAN과 HDMI의 시장 전망에 대해 서술하였다. The demand of wireless communication system is increasing due to the development of computers and other digital media appliances. In particular, new wireless communication technology is necessary for implementation of home network since a lot of data transmission is occurred. Recently, two wireless communication technologies, Ultra Wide Band(UWB) and 60㎓ band wireless communication technology, have being developed for high-speed data transmission and Wireless Personal Area Network(WPAN). In this paper, we study the present development condition of these two technologies and a role of them in home network. We also suggest the method to implement the home network using all wireless communication technologies. At the end, we outlook the market of WPAN and High Definition Multimedia Interface(HDMI).