치과 급속 교정용 초내식성 스테인리스강 가공재의 특성

오근택,김영식,김경남 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.1

When stainless steels are used in the human body, the nickel ion released from the alloys over a short or long term can cause such adverse effects as allergies, dermatitis, asthma. Although the higher the corrosion resistance of stainless steels and the lower the nickel content, the better it is for the human body, since nickel has an essential role in the stabilization of the austenitic phase and the corrosion resistance of stainless steels, it is difficult to remove nickel completely. In this regard, the purpose of this study was to investigate corrosion resistance, cytotoxicity and mechanical properties of super stainless steels, and upon this basis, to evaluate their potential for orthodontic applications. Super austenitic stainless steels had higher content of nickel(17~20 wt%) than super duplex stainless steels (7~10 wt%) or super ferritic stainless steels (lower than 3 wt%). Super austenitic and duplex stainless steels had nitrogen content of above 0.2 w%. These steels had high Mo or W contents of which synergistic effect together with N increases localized corrosion resistance. In terms of hardness, super stainless steels exhibited higher value than 316L S. S. and two times higher than cp Ti(grade II). Austenitic and duplex stainless steels exhibited better mechanical properties. Super stainless steels exhibited low passive current density (3~4 μA/㎠) and similar potentiodynamic polarization behaviors among themselves. Thus, these steels are considered to have high corrosion resistance in the human body-simulated solution. Pitting corrosion occurred in 316L S. S.. A3 containing the highest nickel content, as well as SAF2507 exhibited none cytotoxicity, and the others, slightly. This indicates that the cytotoxicity has no direct relation with nickel content itself in these alloys. Super stainless steels with both high corrosion resistance and good biocompatibility are expected to be used for orthodontic applications by virtue of the passive film attribute enhanced by synergistic effect of Mo+N or by high addition effect of Cr+W.

교정학적 적용을 위한 초내식성 스테인리스강의 특성

오근택,김금진,황충주,박용수,김경남 大韓齒科器材學會 2001 대한치과재료학회지 Vol.28 No.3

Various kinds of orthodontic appliances have been developed for ideal tooth movement during orthodontic treatment. The orthodontic appliances made of metals are bands, arch wires, brackets and miniscrews as orthodontic anchorage. Generally, these appliances are made of stainless steel, pure titanium, Ni-Ti and TMA with the proper biocompatibility. However, localized corrosion of these materials can frequently occur in the particular environment. Super stainless steels, recently developed, have good corrosion resistance to reduce metal ion release induced by many kinds of corrosion. Recently, it has been reported that nickel ion release from orthodontic appliances affect the prevalence of nickel sensitization; however, there has been some controversy about nickel hypersensitivity to orthodontic appliances containing nickel. The purpose of this study was to evaluate and compare the microhardness, nickel ion release, corrosion resistance and cytotoxicity of 4 types of super stainless steels and 316L stainless steel as the control group according to nickel contents, and to determine the acceptability as the new material for various kinds of orthodontic appliances. All super stainless steels showed higher microhardness than 316L stainless steel, SR-3Mo showed especially the highest microhardness. In anodic polarization test, corrosion resistance was high in order of SR-50A, SFSS, SR-6DX, 316L stainless steel, SR-3Mo. There was no increase in nickel ion release from SR-50A, SR-6DX, 316L stainless steel with immersion time in artificial saliva; whereas there was some increase from SFSS and SR-3Mo with immersion time. All super stainless steels showed very low cytotoxicity regardless of nickel contents although SR-3Mo showed relatively higher cytotoxicity than the others. It is concluded that SR-50A among super stainless steels has the highest corrosion resistance and biocompatibility. It is undesirable to consider the alloys with high nickel content to release lots of nickel ion.

교정용 스테인리스강 선재의 내식성에 미치는 응력 제거 열처리 조건의 영향

오근택,전용석,황충주,김경남 대한치과기재학회 2001 대한치과재료학회지 Vol.28 No.2

Heat treatment is applied to orthodontic wires in order to relieve the stress that results from cold working and the orthodontists manipulations. In this study, 4 types of wires were heat-treated in an air, argon or vacuum environment, and were either cooled in a furnace or a water bath. Corrosion properties of the heat-treated wires were investigated by potentiodynamic method. The difference of corrosion resistance between the wires heat-treated in an ambient according to cooling methods was not significant. After heat-treated in an ambient, both water-cooled and furnace-cooled wires had a similar and low corrosion resistance. The difference of corrosion resistance between the wires heat-treated n a vacuum environment with cooling methods was significant. After heat-treated in a vacuum, the furnace-cooled wires had high corrosion resistance, but the water-cooled wires low. After heat-treated in a vacuum, argon, or air environments, the water-cooled wires had low corrosion resistance. It was considered because the irregular and unstable film was formed on the surface of the wires when cooled in a water bath. The control wires showed a low current density and high pitting potential, but most of the heat-treated wires did high current density and low pitting potential except for the wire heat-treated in vacuum and then cooled in a furnace. Conclusively, orthodontic wires are considered to have to be heat treated in vacuum condition or inert gas environment and then to be cooled in a furnace in order to inhibit surface oxidation, minimize the decrease of corrosion resistance and improve the mechanical properties.

대구지역 산업연관모형에 의한 산업구조분석 : 섬유산업과 성장 유망산업을 중심으로

이춘근,여택동,김영재 한국경상학회, 한국국민경제학회 2003 경제연구 Vol.21 No.4

본 연구는 한국은행에서 작성한 전국 산업연관표를 연구목적에 따라 재분류 통합하여 비조사법에 의해 대구지역 산업연관모형을 작성하고, 이를 토대로 지역산업의 산업연관구조를 분석하고 대구지역에 대한 산업정책적 시사점을 도출하고자 한다. 특히 본 연구에서는 대구지역의 주요 전통산업이 섬유산업이며 그 중에서도 폴리에스터 직물제조가 주종을 이루고 있으므로, 섬유산업을 4개 부문(방적, 직조 및 섬유가공업, 편조업, 의복 및 장신품, 기타 섬유제품)으로 세분하여 대구지역 산업연관표를 작성하고 이를 이용하여 지역산업의 연관구조를 분석하고자 한다. 그리고 대구지역 산업연관모형을 이용한 산업구조분석 결과에 따라 대구지역 지역 전통산업인 섬유산업과 성장유망산업에 관한 산업정책적인 함의를 제시하고자 한다. 특히 본 연구에서는 대구지역의 성장유망산업을 선정함에 있어 입지계수법, 지역 산업연관모형과 같은 지역경제 분석기법을 이용하여 분석한 결과를 반영하여 검토하고자 한다. This paper analyzes the industrial structure in Daegu area. employing the regional input-output model. First, this paper explores the current situation of the regional economy and industrial structure in Daegu and attempts to examine the textile industry which has been a key industry in Daegu region. Second, this paper employs the input-output model to show the linkage effects of both forward and backward directions in the whole industry of Daegu region. Particularly, this paper analyzes the structure of Daegu's textile industry. while considering more categorized sub-divisions of the textile industry in order to investigate the structure of that industry. Lastly, this paper intends to provide the industrial policy implications for the local government as well as the central government. Moreover, the current paper intends to present some fruitful policy implications for the Milan Project that would help enhance the international competitiveness of the textile and apparel industry and thus revive the regional economy in Daegu.

교정용 스테인리스강 선재의 기계적 특성에 미치는 응력제거 열처리 조건의 영향

오근택,황충주,김경남 대한치과기재학회 2001 대한치과재료학회지 Vol.28 No.1

Heat treatment is applied to orthodontic wires in order to relieve the stress that results from cold working and the orthodontist's manipulations for making loops, helical springs and archforms. Conventionally, the wires are heat-treated for a few minutes at higher temperature in an ambient. In this study, 4 types of wires were heat-treated in an air, argon or vacuum environment, and were either cooled in a furnace or a water bath. Mechanical properties of the heat-treated wires were investigated. Stress relief heat treatment increased the microhardness, strength and Young's modulus of the orthodontic wires. The increased factions of microhardness, maximal strength, yield strength and Young's modulus of the orthodontic wires by the heat treatment were approximately 0.4∼22.9%, 2.9∼14.8%, 3.7∼14.4% and 2.5∼9.0%, respectively. Yield strength and microhardness of the heat-treated wires were significantly different with the cooling methods. Microhardness and yield strength of the water-cooled wires were lower than those of the furnace cooled wires. It was considered because thermal stress was introduced to the wire by the rapid cooling. Stress relief heat treatment in and ambient oxidized the surface of the wires, and mechanical properties and surface cleanness of the water-cooled wires were lower than those of the furnace-cooled wires. Conclusively, orthodontic wires have to be heat-treated in vacuum condition or inert gas environment after plastic deformation and to be cooled in the furnace, in order to inhibit surface oxidation, minimize the decrease of corrosion resistance and improve the mechanical properties.

어린 가토에서 자가 연골 이식후 연골성장에 관한 실험적 연구

권택근,김태연,정전은,이동진 대한성형외과학회 1992 Archives of Plastic Surgery Vol.19 No.3

Does free transplanted autologous cartilage grow? Until now many autors have published different results about the growth potential of cartilage. Some authors have produced in their study that transplanted cartilages were able to grow, but others showed contradicting results. In this study, authors obtained cartilages from young rabbits'ear, 10 by 10mm in size and divided them into two groups ; the first group was cartilages with perichondrium and the second group was cartilages stripped perichondrium. We transplanted both groups of cartilages in the posterior nuchal area of rabbits. Then numbers of specimens of each group were evaluated and compared for assessment of cartilage growth. After observaton for six months, we took the cartilages from the posterior nuchal area and examined the surface area, the thickness, and the weight and finally confirmed the growth potential of the cartilage by histologic study. The results are as follows : 1, The surface area, the thickness, and the width of the transplanted cartilages were increased significantly in gross specimens and their measured values were statistically significant and cartilages with perichondrium showed more growth than cartilages stripped perichondrium 2. In histologic studies, we observed increased surface activities with numerous proliferatng cells and found no abnormal features compared with normal cartilages. Cartilages with pericondrium were thicker than cartilages with stripped perichondrium

골내 고정 장치용 초내식성 오스테나이트 및 듀플렉스 스테인리스강 가공재의 특성

오근택,강국진,박용수,김경남 大韓齒科器材學會 2003 대한치과재료학회지 Vol.30 No.3

Nickel is one of the most common causes of allergic contact dermatitis and hypersensitivity. In case of stainless steel as biomaterials, the higher the corrosion resistance and the lower the nickel content, the better it is or the human body. However, because nickel plays an essential role in the stabilization of the austenitic phase and the corrosion resistance of stainless steel, it is difficult to remove the nickel from the constituents of stainless steels completely. Therefore, the purpose of this study was to investigate corrosion resistance, cytotoxicity, and mechanical property of super stainless steels, which had high corrosion resistance by synergistic effect of Mo(or W) and N, with respect to nickel content and to evaluate their potential for orthodontic applications. Super austenitic stainless steel(SR-50A) had high nickel content of 22% and super duplex stainless steels nickel contents of 6~10%. Super austenitic and duplex stainless steels had nitrogen contents of above 0.2%. Also, these steels had high Mo or W contents which were able to increase the localized corrosion resistance. In terms of hardness, super stainless steels, which had Vickers hardness values of 374~400 Hv in cold-rolled state and 186~285 Hv in annealed state, exhibited higher values than 316L S. S.. Duplex stainless steels exhibited higher mechanical properties than austenitic stainless steels. In terms of corrosion resistance, super stainless steels exhibited lower passive current density(2.3~3.8 ㎂/cm^2) than pure Ti(6.6㎂/cm^2) in the body-simulated solution and similar potentiodynamic polarization behaviors. Pitting corrosion occurred in 316L S. S. but not in the others. Thus these steels were considered to have high corrosion resistance in the human body. In terms of cytotoxicity, SR-5OA and SAF2507 exhibited none cytotoxicity and the others slight. This results indicated that the cytotoxicity of alloys containing nickel had no relation with nickel content because SR-5OA with the highest nickel content exhibited none cytetoxicity In conclusion, it is considered that super stainless steels with high corrosion resistance and good biocompatibility can be used for orthodontic applications because of the enhanced passive film by high addition of Mo, W, N, etc.

초내식성 스테인리스강 선재와 브라켓의 내식성 및 금속 이온 용출 특성

오근택,정경진,황충주,박용수,김경남 大韓齒科器材學會 2001 대한치과재료학회지 Vol.28 No.4

Metallic orthodontic appliances are known to release metal ions in an oral cavity. It is not advisable that toxic corrosion products derived from the appliances is absorbed into the body. Metal ions release from orthodontic appliances is known to have large effects on the result of orthodontic treatment and systemic health. Metal bracket and wire were made of super stainless steel(S32050) with high corrosion resistance. The corrosion resistance and ion release property of S32050 and conventionally used appliances were examined. Four types of wire were ligated in either super stainless steel(SB) or Tomy bracket(TB) with O-ring, and then each group was immersed in an artificial saliva at 37℃ for 12 weeks. Amount of released metal ions was measured with immersion time by graphite furnace atomic absorption spectroscopy and surface morphology was investigated. S32050 showed the low passive current density of about 1 μA/㎠ and the stable passive region to a high potential in artificial saliva. S32050 appliances did hardly release nickel ions in artificial saliva. S32050 wire(SRW) and NiTi wire(NW) didn't show significant difference of Ni ion release with immersion time, meanwhile, Remanium wire(RW) showed significant difference in 12 weeks. Ni ion releasce from the brackets didn't show any significant difference with immersion time and between SB and TB. Amounts of Ni ion released from TB-SRW showed significant difference in 12 weeks, those from TB-RW showed significant difference from 4 weeks later and highest release among all groupsin12weeks. TB-NW released little Ni ion for all immersion time and showed significant difference from 4 weeks later, TB-TW(TMA wire) showed significant difference in 12 weks. SB-SRW didn't show any significant difference and SB-RW signigicant difference in 12 weeks,but lower compared with TB group. SB-NW and SB-TW didn't show any significant difference. Corrosion products didn't be observed in mostly groups during the immersion time, except that in TB-RW, they were observed on the bracket surface between O-ring and wire from 8 weeks later. Super stainless steel wire had good corrosion resistance compared with stainless steel wire, and it is believed that it can be used as orthodontic material for bracket and wire.

타이타늄 임플란트와 상부구조물의 갈바닉 쌍의 전기화학적 특성

오근택,김명화,최병갑,김경남 大韓齒科器材學會 2003 대한치과재료학회지 Vol.30 No.1

For the aesthetic and functional restoration of edentulous patients, recently dental implants have been used widely. Dental implants and restorative alloys are required with the high corrosion resistance. Suprastructure and implant with different compositions, which are in electrical contact, may develop galvanic or coupled corrosion problems. Besides galvanic corrosion, crevice and pitting corrosion may occur in the marginal gap or the gap between dental implant assemblies. In this study, Ti implants, gold, silver-palladium, cobalt-chromium and nickel-chromium suprastructures were used to investigate their galvanic and crevice corrosion of suprastructure/Ti implant couples. Potentiodynamic and potentiostaic testing were performed in artificial saliva at 37℃. Potentiodynamic testing was carried out at the potential scan rate of 1 ㎷/sec and in the range of -600∼1600 ㎷(SCE). Potentiostatic testing such as open circuit potential and current densities at -250, 0 and 250 ㎷(SCE) was performed for 5000 seconds in artificial saliva. After electrochemical testing, the surface and cross-sectional morphologies of the samples were observed using optical microscopy. Potentiodynamic test results indicated that suprastructure/Tim implant couples exhibited the passive current density range of 0.5∼12 ㎂/㎠, Ti abutment/Tim implant and gold/Tim implant couples exhibited relatively low passive current density, Co-Cr/Tim implant couples the highest. Co-Cr and Ni-Cr/Tim implant couples showed the breakdown potentials of 700 and 570 ㎷(SCE), respectively. Open circuit potentials of silver, Ti abutment, gold, Ni-Cr and Co-Cr/Ti implant couples were -93.2±93.9, -123.7±58.8, -140.0±80.6, -223.5±35.1, and -312.7±29.8, respectively and stable according to immersion time. The couples exhibited cathodic current densities at -250 ㎷(SCE), especially, gold and silver alloys showed the high cathodic current densities of ±3.18 and ±6.63 ㎂/㎠, respectively. At 250 ㎷(SCE), Ti abutment/Ti implant couples exhibited the lowest current density of 9.48×10^-2 ㎂/㎠, and gold, Ni-Cr, Co-Cr and silver/Ti implant couples exhibited 0.313, 1.27, 5.60 and 8.06 ㎂/㎠, respectively. The couples exhibited relatively low current densities at 0 ㎷(SCE). The photographs after electrochemical testing showed crevice or pitting corrosion in the marginal gap and suprastructure surface. Although Co-Cr/Ti implant couples among the tested samples had the possibility of the galvanic corrosion, its degree was not significant.

식도암에서 외부방사선치료와 근접방사선치료의 병용요법

남택근,나병식,오윤경 조선대학교 부설 의학연구소 2002 The Medical Journal of Chosun University Vol.27 No.2

Background and Objectives: To evaluate the role of brachytherapy following external radiotherapy by retrospective analysis in view of survival and prognostic factors in esophageal carcinoma. Materials and Methods: From Apr. 1999 to Dec. 2000, a total of 28 patients, who were diagnosed as esophageal carcinoma, were treated by curative external radiotherapy followed by brachytherapy with or without chemotherapy. Eligible primary tumors were located in the thoracic esophagus and lymphatic metastases were restricted to supraclavicular or mediastinal nodes. External radiotherapy was performed by 6 MV or 10 MV X-ray and the range of doses was 50.0 Gy - 59.4 Gy (median; 54.9) to primary tumors. One week later, the intraluminal brachtherapy (IB) was performed by high-dose rate remote controlled afterloader with radioisotope of ^192Ir. Fraction size of IB was 2~5 Gy, twice a week and delivered up to total doses of 3 Gy~ 20 Gy (median; 12). Twenty-one patients were treated by concurrent chemotherapy with the agents of cisplatin and 5-FU. Cisplatin, 75 ㎎/㎡, was given on the first day of weeks 1, 5, 8, 11 and 5-FU, 1,000 ㎎/㎡, was administered as a continuous infusion for the first 4 days of each course. Results: The estimated median survival time was 15 months and 1, 2, 3-year survival rates were 60.7%, 27.5%, 9.2%, respectively. The median survival time (MST) of the patients with stage II (n=9), III (n=17), IVA (n=2) were 20, 15, 5 months, respectively (p=0.68). The MST of the patients with complete response vs partial response were 21 vs 14 months, respectively (p=0.12). The MST of patients younger than 60 years vs older were 22 vs 12 months, respectively (p=0.07). The MST of patients with ECOG performance index 1 vs 2 were 16 vs 10 months, respectively (P=0.06) Tile Mn of patients treated by concurrent chemotherapy vs untreated were 20 vs 12 months, respectively (p=0.07). Four patients (14.3%) suffered massive hematemesis after brachytherapy and one patient with local recurrence salvaged by esophagectomy had mediastinal abscess. Of 21 patients treated by concurrent chemoradiothetapy, one patient had pancytopenia and other two patients had severe leukopenia. Conclusion: This study showed no better outcomes of brachytherapy boost after external radiotherapy than historical results of external radiotherapy alone. Concurrent chemotherapy might have more significant therapeutic role rather than brachytherapy boost and the employment of brachythelapy should be considered with great caution in the treatment of esophageal carcinoma.