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조주영(Joo-Young Cho),김원기(Won-Gi Kim),최환석(Hwan-Suk Choi),이호종(Ho-Jong Lee),최한철(Han-Cheol Choe) 한국표면공학회 2010 한국표면공학회지 Vol.43 No.3
NiTi alloy has been used for orthodontic wire due to good mechanical properties, such as elastic strength and frictional resistance, combined with a high resistance to corrosion. Recently, these wire were coated by polymer and ceramic materials for aesthetics. The purpose of this study was to investigate surface characteristics of polymer coated NiTi alloy wire for orthodontics using various instruments. Wires (round type and rectangular type) were used, respectively, for experiment. Polymer coating was carried out for wire. Specimen was investigated with field emission scanning electron microscopy(FE-SEM), energy dispersive x-ray spectroscopy(EDS) and atomic force microscopy(AFM). The phase transformation of non-coated NiTi wire from martensite to austenite occurred at the range of 14~15℃, in the case of coated wire, it occurred at the range of 16~18℃. Polymer coating on NiTi wire surface decreased the surface defects such as scratch which was formed at severe machined surface. From the AFM results, the average surface roughness of non-coated and coated NiTi wire was 13.1 ㎚, and 224.5 ㎚, respectively. From convetional surface roughness test, the average surface roughness of non-coated and coated NiTi wire was 0.046 ㎛, and 0.718 ㎛, respectively.
신생아 외과환아의 술후 합병증 및 사망율에 관한 임상적 분석
최한철,윤영국,이영하,장수일 慶北大學校 醫科大學 1992 慶北醫大誌 Vol.33 No.2
1981년 1월부터 1990년 12월까지 만 10년간 경북대학교 의과대학 소아외과에서 수술받은 생후만1개월 미만의 신생아수술 92예에 대하여 신생아수술의 합병율, 사망율 및 이에 관여하는 인자를 관찰한 결과를 요약하면 다음과 같다. 성별비는 남아 67예, 여아 25예로(남:여=2.9:1)로 남아에 많았고 입원당시 연령은 24hr 이내가 30.4%, 72hr 이내가 58.7%, 일주일이내가 73.9%였다. 질환별로는 복벽균열이 평균 1.18일로 가장 빨랐으며 유문협착증이 24.5일로 가장 늦은 경우였으며 가장 흔한 질환은 항문직장기형(30.4%)이었다. 미숙아는 92예중 12예(13.0%)였으며 입원시 체중으로 저체중아는 19예(20.6%)였고, 전체환자의 평균체중이 2825gm였으며 질환별 평균체중은 식도무공증이 2338gm으로 가장 낮았다. 술후합병증은 92예의 환자중 29예(31.5%)에서 있었으며 가장 흔한 술후합병증은 창상감염으로 12예(13.0%)에서 있었으며, 질환별 합병증발생율은 식도무공중이 75.0%로 가장 높은 합병증 발생율을 보였으며, 그 다음이 복벽균열로 66.7%였으며 항문직장기형이 28예중 3예로 (10.7%)로 가장 낮았다. Stage Ⅰ이 41.4%(34예중 14예), Stage Ⅱ가 25.8%(58예중 15예)의 술후합병율로 Stage Ⅱ가 낮은 경향을 보였으나 유의한 차이는 없었다. 92예중 16예(17.4%)가 사망하였으며, 질환별사망율로는 공장 및 회장폐쇄증이 9예중 4예(44%)로 가장 높았으며 항문직장기형이 28예중 3예(10.7%)로 가장 낮았으며, 가장 흔한 사망원인은 폐혈증이었다(41.3%). Stage Ⅰ이 26.4%(34예중 9예), Stage Ⅱ가 12.0%(58예중 7예)의 술후사망율로 Stage Ⅱ가 낮은 경향을 보였으나 유의한 차이는 없었다. 사망에 영향을 미치는 요인으로는 미숙아, 저체중아, 저체온이 있었다(P<0.05). A clinical analysis on ninety-two surgical neonates who underwent neonatal surgery from Jan. 1981 to dec. 1990 at Kyungpook National University was carried out in order to observe factors which affected the postoperative morbidity and the mortality. Of these 92 patients, the male and female ratio was 2.9:1. Age on admission was younger in cases with gastroschisis or with omphalocele or with jejunoileal atresia. Average body weight on admission was 2825gm and was lowest in patient with esophageal atresia, 2338gm. The postoperative complications appeared 29cases(31.5%) among 92 cases and the most common complication was wound infection, 12cases(13.0%). Esophageal atresia presented highest morbidity (75%), secondly gastroschisis (66.7%) and anorectal malformation presented lowest morbidity(10.7%). The complication rate of Stage Ⅰ, 41.1%(14 cases among 34 cases) seemed to be higher than that of Stage Ⅱ, 25.8% (15 cases among 58 cases) but statistically not significant. The mortality rate was 17.4%(16 deaths among 92 cases) and jejunoileal atresia presented highest mortality (44%), and anorectal malformation presented lowest mortality(10.7%). The most common cause of death was sepsis, 7 cases(41.3%). The mortality rates of Stage Ⅰ, 26.4% (9 cases among 34 cases) seemed to be higher than that of Stage Ⅱ 12.0% (7 cases among 58 cases) but statistically not significant. The present results suggested that factors which significantly affected the postoperative mortalities were prematurity, low birth weight and hypothermia.
최한철,고영무,정재헌,신종연,김일선,최성욱,정효수 대한치과기재학회 1999 대한치과재료학회지 Vol.26 No.4
Dental magnetic materials have been applied to removable prosthetic appliances, maxillofacial prostheses, obturator and dental implant but they still have some problems such as low corrosion resistance in oral environments. To increase the corrosion resistance of dental magnetic materials, surfaces of Sm-Co and Nd-Fe-B based magnetic materials were plated with TiN and then electrochemical corrosion test were performed in 4 kinds of electrolyte solutions(0.9% NaCl. 1% lactic acid, 0.05% HCl and modified Fusayama's artificial saliva). From this study, corrosion behavior, amount of elements released, mean average surface roughness values and the changing of mean surface microhardness values were measured comparing with control group of non-sputtered plating magnetic materials. The results were as follows: 1. TiN layer coated on magnet grows into preferred direction with lamellar structure and its thickness is 3.0㎛. 2. Sm-Co base magnetic materials coated with TiN have good corrosion resistance in 1% lactic acid and their pitting corrosion can not be seen. 3. Nd-Fe-B base magnetic materials coated with TiN showed good tendency of corrosion resistance in 0.05% HCl solution. 4. The amount of elements released from both Sm-Co and Nd-Fe-B base magnetic materials coated with TiN were more significantly decreased than that of uncoated magnetic materials. 5. The mean surface roughness values of both Sm-Co and Nd-Fe-B base magnetic materials coated with TiN were smooth than that of uncoated magnetic materials after corrosion test. 6. The decreasing rate of microhardness of both Sm-Co and Nd-Fe-B base magnetic materials coated with TiN were lower than that of uncoated magnetic materials after corrosion test. 7. Dental magnetic materials coated with TiN produced various corrosion products such as TiO, TiO₂, Ti₂O₃on the surface and resulted in better corrosion resistance than uncoated magnetic materials. In conclusion, it is considered that the corrosion problem of dental magnetic materials could be solved to some extent by EB-PVD with TiN on the surface of dental magnetic materials.
전자빔 진공증착을 이용한 치과용 임플란트재의 표면 전처리법에 따른 HA 코딩효과
고영무,최한철,최낙찬 大韓齒科器材學會 2002 대한치과재료학회지 Vol.29 No.4
The dental implant materials require good mechanical properties, such as fatigue strength, combined with a high resistance to corrosion. For increasing fatigue resistance and delaying onset of stress corrosion cracking, shot-peening has been used for over 50 years to extend service life of metal components, However, there is no information on the electrochemical behavior of shot-peened and hydroxyapatite(HA) coated Ti-6Al-4V alloys. To increase fatigue strength, good corrosion resistance, and biocompatibility, the electrochemical characteristics of Ti/TiN/HA coated and shot-peened Ti-6Al-4V alloys by EB-PVD have been researched by various electrochemical method in 0.9%NaCl The coated layer and surface showed the formation of dense and uniform surface in the case of TiN/HA and Ti/TiN/HA film coated samples. The hardness of shot-peened Ti-6Al-4V alloys(SPA) increased as SP treatment time increased. Electrochemical measurements showed that, in the case of shot-peened Ti-6Al-4V alloys, the corrosion and pitting potential increased due to the SP induced removal of defects, such as inclusion, scratch, and pore on the surface, whereas passivation and active current density decreased as the SP time increased. For the HA coated samples, pitting and repassivation potential increased in the order of Ti/TiN/Ha > TiN/HA > Ti/HA > HA coated SPA. Results suggest that the best pitting corrosion behavior is shown by Ti/TiN/HA coated SPA with a fatigue strength and biocompatibility.