• Restorative Dentistry and Endodontics
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• v.30 no.2
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• pp.121-127
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• 2005

A variety files made of stainless steel (S-S) or nickel-titanium (Ni-Ti) are used during endodontic treatment. The purpose of tt)is study was to evaluate the corrosion susceptibility of S-S and Ni-Ti endodontic files. Three brands of files were used for this study: $K-flex^{(R)}$ S-S files (Maillefer, USA), $Profile^{(R)}$ Ni-Ti files (Maillefer, USA), $K-3^{(R)}$ Ni-Ti files (SybronEndo. USA). 120 files of each brands (21mm, ISO size $\#20$) were divided into 12 groups according to 1) sterilization methods using Autoclave or Ethylene Oxide (E-O) gas, 2) Irrigation solutions using $5.25\%$ NaOCl or Saline, 3) the number of sterilization (1, 5, 10 times), After above procedures, each of the files was inspected by three examiners with a light microscope and camera at X25. Each file was judged and ranked according to the following criteria: 0;, no corrosion, 1; mild corrosion, 2; moderate corrosion, and 3; severe corrosion. The files of high score were examined under the Scanning Electron Microscope. Data were statistically analyzed with the Kruskal-Wallis test (p < 0.05). Most of the ten time-autoclaved files had showed mild to moderate corrosion. But, one or five time-autoclaved files did not show corrosive surface. NaOCl treatment and E-O gas sterilization did not influence on corrosion. There was a significant difference in corrosion susceptibility between sterilization methods and the number of autoclaving. However, there was no significant difference between brands and file materials.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.234-245
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• 2003

Most of the concrete bridge structures are exposed to damage due to the excessive traffic loading and the aging of the structure. The damage of concrete causes the further deterioration of the function in the concrete structure due to corrosion of the reinforced bars and decohesion between the concrete and the reinforced bar. The quick rehabilitation of the damaged concrete structures has become of great importance in the concrete structural system in order to avoid the further deterioration of the structures. Recently fiber sheets are used for strengthening the damaged concrete structures due to its many advantages such as its durability, non-corrosive nature, low weight, ease of application, cost saving, control of crack propagation, strength to thickness ratio, high tensile strength, serviceability and aesthetic. However, the lack of analytical procedures for assessing the nominal moment capacity by the fiber sheet reinforcement leads to difficulties in the effective process of decisions of the factors in the strengthening procedure. In this work, flexural strengthening effects by fiber sheets bonded on bottom face of the member are studied for the reinforced concrete T beam. In addition, auxiliary flexural strengthening effects by U-type fiber sheets bonded on bottom and side faces of the member to prevent delamination of the bottom fiber sheet are theoretically investigated. The analytical solutions are compared with experimental results of several references to verify the proposed approach. It is shown that the good agreements between the predicted results and experimental data are obtained.

• Journal of Chest Surgery
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• v.5 no.1
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• pp.45-56
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• 1972

Esophageal perforation is one of the most grave prognostic problems among thoracic and general surgical emergencies which necessitate urgent operative measures. In Korea,there are still many persons ingesting lye for suicidal attempt and thoracic surgeons in Korea have more chances to deal with lye burned esophagus with or without instrumental perforation than those in Western countries. Main cause of esophageal perforation in Korea is instrumental perforation in patients with lye stricture of the esophagus during diagnostic endoscopy or therapeutic bouginage. Other causes are corrosion of the esophagus due to ingestion of caustic agents, pathologic perforation, surgical trauma, stab wound and spontaneous rupture of the esophagus in our series. Therapeutic measures are various,and depend on duration of perforation, severity of its complications, pathology of perforated portion of the esophagus and degrees of inflammation at the point of perforation. The most important therapeutic measures are prevention of this grave condition during esophagoscopy, bouginage and surgical procedures on lungs and mediastinal structures and to make early diagnosis with prompt therapeutic measures. During the period of January, 1959, to December, 1971, the authors experienced 65 cases ofesophageal perforation including acquired esophagorespiratory fistula at Dept. of Chest Surgery, the National Medical Center in Seoul, and obtained following results in the series. 1. Female were 35 cases, and peak age incidence was 2nd and 3rd decades of life. 2. Among 65 cases, 43 were corrosive esophagitis or benign stricture of the esophagus due to caustic agents, 7 were patients with esophageal cancer. and there were 5 cases of esophageal perforation developed after pneumonectomy or pleuropneumonectomy. 3. Causes of perforation are instrumental perforation in 45, acute corrosion in 7, pathologic perforation in 7, surgical trauma in 3, stab wound in 2 cases, and one spontaneous rupture of the esophagus. 4. Most frequent sites of esophageal perforation were upper and mid thoracic esophagus, and 8 were cases with cervical esophageal perforation. 5. Complications of esophageal perforation were mediastinitis in 42, empyema or pneumothorax in 35, esophagorespiratory fistula in 12, retroperitoneal fistula or abscess in 5,pneumoperitoneum in 3, and localized peritonitis in 1 case. 6. Cases with malignant esophagorespiratory fistula were only 3 in the series which is predominant cause of acquired esophagorespiratory fistula in Western countries. 7. Various therapeutic measures were applied with mortality rate of 27.7% in the series. 8. In usual cases early treatment gave better prognosis, and least mortality rate in cases with perforation in mid thoracic esophagus. 9. Main causes of death were respiratory complications,acute hemorrhage with asphyxia, and septic complications. 10. Esophageal perforation developed after pneumonectomy gave more difficult therapeutic problems which were solved in only 1 among 5 cases.