• Progress in Medical Physics
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• v.16 no.4
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• pp.214-219
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• 2005

As part of Korean retinal prosthesis project, we have provided preliminary experimental results regarding voltage parameters for the stimulation of chemically degenerated rabbit retina. Since our APB-treated chemically degenerated retina is only ON-pathway blocked, now we switch our experiments to more appropriate retinal degeneration model, genetically degenerated retina model (RD mouse: rd/rd (C3H/HeJ)). Before studying with RD mouse, we started control experiments with normal SD rat to understand characteristics of retinal ganglion ceil activity with postnatal maturation in rodents. Ganglion cell activities were recorded with 8${\times}$8 multi-electrode array. Moving spontaneous bursts appeared until postnatal day of 15. During pre-eye opening period, no light evoked response appeared. After postnatal day of 2 weeks (post-eye opening period), ON-, OFF- and ON/OFF response appeared. The fractional distributions of ON, OFF, and ON/OFF ganglion cell is about $40\%,\;50\%$, and $5\%$. The percentage ($\%$) of light evoked response in each dorso-temporal, ventral, and dorso-nasal area of eye is about $50\%,\;37.5\%$ and $12.5\%$, respectively. We concluded that the optimal period for experiment in rodent is about postnatal day of 2${\~}$3 weeks.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.203-210
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• 2019

Purpose: The purpose of this study was to verify the effect of the abutment superimposition process on the final virtual model in the scanning process of single and 3-units bridge model using a dental model scanner. Materials and methods: A gypsum model for single and 3-unit bridges was manufactured for evaluating. And working casts with removable dies were made using Pindex system. A dental model scanner (3Shape E1 scanner) was used to obtain CAD reference model (CRM) and CAD test model (CTM). The CRM was scanned without removing after dividing the abutments in the working cast. Then, CTM was scanned with separated from the divided abutments and superimposed on the CRM (n=20). Finally, three-dimensional analysis software (Geomagic control X) was used to analyze the root mean square (RMS) and Mann-Whitney U test was used for statistical analysis (${\alpha}=.05$). Results: The RMS mean abutment for single full crown preparation was $10.93{\mu}m$ and the RMS average abutment for 3 unit bridge preparation was $6.9{\mu}m$. The RMS mean of the two groups showed statistically significant differences (P<.001). In addition, errors of positive and negative of two groups averaged $9.83{\mu}m$, $-6.79{\mu}m$ and 3-units bridge abutment $6.22{\mu}m$, $-3.3{\mu}m$, respectively. The mean values of the errors of positive and negative of two groups were all statistically significantly lower in 3-unit bridge abutments (P<.001). Conclusion: Although the number of abutments increased during the scan process of the working cast with removable dies, the error due to the superimposition of abutments did not increase. There was also a significantly higher error in single abutments, but within the range of clinically acceptable scan accuracy.

• Journal of Chest Surgery
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• v.30 no.9
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• pp.891-898
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• 1997

Between May 1984 and January 1996, 130 patients were replaced cardiac valve using 150 St. Jude Medical prosthetic valves(42 aortic, 68 mitral, 20 aortic and mitral valve replycements). Follow-up was 97.6% complete. The early mortality rate was 5.4%, and late mortality rate was 4.9%. The valve-related late mortality rate was 3.3%. Of late complications, there were 6 anticoagulant related hemorrhages, 4 thromboembolisms and 1 paravalvular leakage. Linearized rates of late complication and valve-related late mortality were as follows: total late complications, .1.68o per patient-year: anticoagulant related hemorrhages, 0.92% per patient-year: thromboembolism, 0.61% per patient-year: paravalvular leakage, 0.15% per patient-year: reoperation, 0.15% per patient-year: and valve-related late mortalities, 0.61% per patient-year. Actuar al event free rate at 10 years was 87.4 $\pm$ 3.2%. The overall actuarial survival rate was 90.4$\pm$2.7% at 5 years, 87.5$\pm$3.3% at 10 years. Ninety eight percent of the survivors were in the New York Heart Association functional class I or II at the end of follow-up. There was significant improvement of cardiothoracic ratio. In conclusion, this study suggests the excellent durability of the St. Jude Medical Heart valve and remarkable functional benefit for the majority of the patients. However, prosthesisrelated complications are still common. Outcome is strongly related to the patient's preoperative cardiac condition and to the adequacy of anticoagulation control.

• Journal of Chest Surgery
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• v.29 no.4
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• pp.373-380
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• 1996

Prevention of thromboembolism is the most important task in the development of bioconpatible small caliber artificial vascular graft. In normal vessels, vascular endothelial cells maintain homeosatsis by secreting numerous factors. The aim of this study is to develope a method which Improves biocompatibility of small caliver polyurethane graft using endothelial cell culture technique, and ev luate the efTectiveness of extracelluar matrix for endothelization which was produced by cultured fibroblast. Methods ; Multiporous polyurethane tube of 3 mm diameter, 0.3 mm thickness was manufactured for vascular graft. Three mongrel dogs were intubated and internal jugular veins removed. Extracelluar matrix produced by cultured flbrobast which was obtained from dog's internal jugular vein were coated to the polyurethane graft. Then, endothelial cells extracted from Jugular vein were cultured and fixed on the extracelluar matrix layer of vascular graft. Endothelial cell coated vascular grafts were implanted to the carotid arteries of experimental dogs as interposed autograft. Implanted grafts were removed after 3 and 6 weeks. As a control, PTFE graft was interposed on carotid artery. These experiments demonstrated that extracelluar matrix produced by fibroblast can afford a base for endothelial cell linings of polyurethane graft. Although thrombosis were developed on autografted en othelial cell coated graft, 33% opening was noticed, and showed less adhesion to adjacent tissue layer. These findings suggest that fiboblast produced extracelluar matrix which can be used for edothelial cell lining vascular graft, and by improving the cultured endothelial cell function, there will be a new modality for reducing thrombosis on small vascular graft.

• Journal of Technologic Dentistry
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• v.22 no.1
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• pp.179-198
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• 2000

Since dental prosthesis is made possible only when dental technicians give themselves to the study of knowledge and the acquisition of updated skills, continuing education is of great importance in that it makes up for the efforts of dental technicians. Accordingly, continuing education relates to a system designed to contribute to the enhancement of the talents of dental technicians and the dental health of the nation. Specialized knowledge and information may work as the best weapon to preserve their jbs. This is true of this modern society where no one can expecth to survive without acquiring knowledge and information constantly for work is getting more classified and more divirsifide. This paper is dedicated to take a look at the current condition of the continuing education of dental technicians and to come up with measure to make general evaluation and to improve continuing education. This research resorts to 609 questionnaires among 6433 copies save unfaithfully responded 34 copos with 6.431 dental technicians as the subjects enrolled in the Dental technician Association. The collected questionnaires consist of 365 dental technicians living in Seoul and of 244 ones, Which account for 11.8 percent of dental technicians enrolled in the association. Because dental technicians live more in local areas than Seoul, the generalization of this survey leaves something to be desired. I have come up with the following findings. 1. 6,431 dental technicians, or 36.3 percent of an total of 14,956 licensed dental technicians, were admitted as numbers of the Dental Tachnician Association as of October 31, 1999. In the '98 continuing education. 4,141 dental technicians among 4,711 dental technicians got relevant training, and in the '99 continuing education, 4,075 technicians, or 75.9 percent of 5,365 technicians got relevant training while 1,290 technicians or 24.2 percent, fail to get relevant training. 2. The survey has it that 38.1 percent of dental technicians are ignorant of the laws on continuing education, and that technicians staying in local communities(146 persons, or 61.6%) take more part in education than those living in the capital of Korea(159 persons, or 146%), and that the older they are, the more money they earn, the more carrer they have, the higher position they hold, the more part they take in education 3. According to the survey, those who have the experience of getting training more than three times account for 52 persons(16.8%) in Seoul and 47 persons(22.4%) in local districts(p<0.01). In terms of sanctions in relation to continuing education, 26 dental technicians(4.6%) say that they have ever gotten sanctions, and 533 dental technicians(95.4%) say that they haven't. And those who were absent from continuing education(72 technicians : 13.51%) didn't get any sanction. 4. In terms of the degree of understanding continuing education, local technicians(46.8% : 110 persons) have a higher understanding of continuing education than their countparts staying in Seoul(36.0% : 130). Continuing education is not the ultimate goal itself. It should be changed to motivate those who get education to be willing to take part in contunuing education, and to help dental technicians in a practical and specific way. And the branch societies should be developde to engage in more specialized and classified expert fields. Of course, the curriculum should be so selected that the conceptions of dental technicians may be reflected to the maximum extent, and the ultimate effores should be made to effect diversity in the ways of educational methods and to perfect the preparation of continuing education on the part of instructors. Regulations should be established in relation to continuing education with a veiew to enhancing the participation of continuing education and its effectiveness. The supervision of the Ministry of Health and Welfare is of great importance in this context. The regulation of continuing education is not administrative regulation, but the expression of national will to guarantee the medical service of the nation at highest level. Therefore, it is necessary that the Ministry of Health and Welfare should change their understanding of the needs for the continuing education of dental experts, and that the expertise of government employees in charge of continuing education should be expanded. It goes without saying that the government should suppory continuing education in a financial way so as to supply the person in charge of public welfare and control the quality of national medicine.

• Journal of Chest Surgery
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• v.41 no.2
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• pp.223-228
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• 2008

Background: The aim of this study is to confirm that peripheral blood sampling for measuring of serum immunoglobulin can predict immunological changes after xenograft implantation. Material and Method: Between March 2006 and January 2007, 19 patients were enrolled (10 xenograft implantation group, 9 control group). Through 3 peripheral blood samples, we measured changes in serum immunoglobulin G and M levels preoperatively, and 2 and 10 days postoperatively. Result: In both groups, serum immunoglobulin levels showed similar changes-they decreased 2 days postoperatively, then increased up to the baseline levels 10 days postoperatively. However, this postoperative change of immunoglobulin G and M was not significantly different in absolute value or pattern between the 2 groups (Ig G; p-value=0.393, Ig M; p-value=0.193). Conclusion: We could not predict immunological changes after xenograft implantation by measuring serum immunoglobulin levels by simple blood sampling. Direct checking of ${\alpha}$-Galactose antibody may confirm an immunological reaction after xenograft implantation.

• Journal of Technologic Dentistry
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• v.14 no.1
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• pp.67-79
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• 1992

This study was conducted to analyze the dental care utilization pattern of the city residents. An interview and questionnaire survey was carried for 1008 people who lived in Kimchun-city, Kyungsangpook-do, from february 1 to March 30, 1992. The summarized results are as follows : The rate of persons who experienced the oral disease was 32.7 per 100 persons during 1 year and it was highest in the age group of 20$\sim$29. During 1 year period, 90.3% of the cases had treated the perceived oral disease, 9.7% had done no action. 65.8% had treated experienced oral disease at dental clinics. The rate of person who dad experienced dental prosthesis during ten-year period was 37.5% among 18year and older, and it was higher in male as compared to female and it was highest in age group of 40$\sim$64 year old. The rate of person who had treated dental prosthetics by the unauthorized illegally was 27.0%, and the reason for it was cheap-price free(44.2%). Of the person who dad treated dental prosthetics by the unauthorized illegally, 64.3% had satisfied and 4.3% had done out of use, while each was 80.1%, 2.7% at dental clinics. The rate of persons with missing teeth was 18.0%. Of the persons with missing teeth, 57.6% did not treat the missing teeth due to economic reason and 89.6% hopped treating the dental prosthetics at dental clinics. In consideration of above finding, we may conclude that oral health community program to prevent oral diseases should be intensified, oral health education to raise oral health knowledge should be performed periodically and the control of unlicensed activities should be enforce at community health center and allows benefits for prosthetics.

• Journal of Oral Medicine and Pain
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• v.33 no.3
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• pp.279-294
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• 2008

This study aimed to make an analysis of the occlusion in the state of muscle fatigue produced by excessive mouth opening and clenching during the dental treatment to control the dental pain and to evaluate the sensory nerve in the muscle pain state. Most of the reasons why patients visit the dental office result in pain-either conceivably the dental origin pain or the non-dental origin pain. The dental offices have many therapeutic actions to produce the masticatory muscle fatigue for the treatment. Dental treatment with long minutes of mouth opening can cause some headaches, masticatory muscle pain and mouth opening difficulties. Patients with mastication problems who visits a dental office to alleviate pain run against another unexpected pain with other aspects. This study uses T-scan II system(Tekscan Co., USA) for the evaluation on the occlusal pattern in the experimental muscle fatigue after clenching, opening the mouth excessively and chewing gum. The occlusal contact pattern is analyzed by the contact timing, namely first, intercuspal, maximum and end point of contact. This inspection was performed at frequencies of 2000Hz, 250 Hz and 5 Hz before and after each experimental muscle pain was produced to 24 subjects who had normal occlusion without the orthodontic treatment or a wide range of the prosthesis by using $neurometer^{\circledR}$ CPT/C(Neurotron, Inc. Baltimore, Maryland, USA). The measuring sites were mandibular nerve experimental muscle fatigue respectively. This study could obtain the following results after the assessment of occlusion and sensory nerve of the experimental muscle fatigue. 1. There were the fastest expression after the excessive mouth opening in muscle fatigue and after tooth clenching in muscle pain. In the visual analog scale that records the subjective level, there was the highest scale after the clenching in the muscle fatigue in jumping off the point of pain. 2. Tooth contact time, contact force, relative contact force on the point of the first contact had no difference, and there were decreases in the contact force after the excessive mouth opening on intercuspal position point, after the excessive mouth opening and the gum chewing on the point of the maximum, and in the contact time after all the experimental muscle fatigue state on the point of the end contact. 3. There was no statistic significance in the current perception threshold before and after the experimental muscle fatigue. 4. There was no significant difference in the contact number, the maximal contact number on the point of the first contact, and the contact number after the mouth opening and gum chewing on the point of the intercuspal position and the contact number after the experimental muscle fatigue on the maximum point, and showed significant decreases. In conclusion, it was found that the occlusal pattern can cause the changes on the case of the clinical muscle weakness by intra-external oral events. It was important that the sedulous attention to details is required during dental treatment in case of excessive mouth opening, mastication and clenching.