• 대한치과의사협회지
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• 제48권2호
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• pp.113-118
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• 2010

Titanium and titanium alloys are the most common materials used for dental and biomedical implants, owing to their biocompatibility and favourable mechanical properties. However infection of the region surrounding a dental implant by pathogenic microorganisms is a significant factor in implant failure. Prevention and control of microbial colonization of implant surfaces is considerable interest to the biomedical community. One important strategy is to render the implant surface antibacterial by impeding the formation of biofilm. A number of approaches have been proposed for this purpose. Therefore, we reviewed the researches of antibacterial coatings on titanium implants in this articles.

• 대한치과의사협회지
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• 제47권11호
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• pp.758-768
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• 2009

Purpose : Schulte introduced immediate implant cases in 1970s, since then many patients have been treated by immediate implants. The aim of this study was to evaluate the cumulative survival rate of immediate implant and to analyze various factors associated with survival of immediate implant in a 8-year period retrospectively. Materials and methods : From May, 2000 to October, 2007, 77 implants were placed in 63 patients immediately after tooth extraction at Department of Periodontology, Yonsei University Hospital. The implant survival rate was analyzed using a life-table analysis. After delivery of prosthesis, along 1 year of observation period, all implants were evaluated clinically and radiographically. Results : Among 77 implants, 59 were placed in maxilla and 18 in mandible. The most common site of the implantation was Mx anterior (65%). The overall survival rate was 94.8% over a mean follow-up period of $44.2{\pm}21$ months and the 8-year cumulative survival rate was 94.6%. Failure occurred in 4 implants, all of which were due to early failures. None of the following factors were significantly associated with the survival of immediate implants: advanced surgical technique including bone graft and guided bone regeneration, the types of implants, causes of tooth loss, and types of prosthesis. Conclusion : On the basis of 8-year life time analysis, immediate implant placement can be considered a safe and predictable treatment mordality.

• Journal of Yeungnam Medical Science
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• 제1권1호
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• pp.13-23
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• 1984

Acute renal failure refers to a rapid reduction in renal function that usually occurs in an individual with no known previous renal disease. Development of a complication of acue renal failure in critically ill surgical patients is not unusual, and it causes high morbidity and mortality. Acute renal failure can be divided as Pre-renal (functional), Renal (organic), and Post-renal (obstructive) azotemia according to their etiologies. Early recognition and proper correction of pre-renal conditions are utter most important to prevent an organic damage of kidney. These measures include correction of dehydration, treatment of sepsis, and institution of shock therapy. Prolonged exposure to ischemia or nephrotoxin may lead a kidney to permanent parenchymal damage. A differential diagnosis between functional and organic acute renal failure may not be simple in many clinical settings. Renal functional parameters, such as $FENa^+$ or renal failure index, are may be of help in these situations for the differential diagnosis. Provocative test utilyzing mannitol, loop diuretics and renovascular dilators after restoration of renal circulation will give further benefits for diagnosis or for prevention of functional failure from leading to organic renal failure. Converting enzyme blocker, dopamine, calcium channel blocker, and propranolol are also reported to have some degree of renal protection from bioenergetic renal insults. Once diagnosis of acute tubular necrosis has been made, all measures should be utilized to maintain the patient until renal tubular regeneration occurs. Careful regulation of fluid, electrolyte, and acid-base balance is primary goal. Hyperkalemia over 6.5 mEq/l is a medical emergency and it should be corrected immediately. Various dosing schedules for medicines excreting through kidney have been suggested but none was proved safe and accurate. Therefore blood level of specific medicines better be checked before each dose, especially digoxin and Aminoglycosides. Indication for application of ultrafiltration hemofilter or dialysis may be made by individual base.

• Journal of Periodontal and Implant Science
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• 제36권3호
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• pp.683-691
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• 2006

This study is an analysis of distribution of patients who installed Implantium implant in Yonsei University Dental Hospital and types of implant site for about 1 years recall check and success rate. 164 implants were installed to 52 patients in this study. It shows the conclusion below. 1. Patients at the age of 40s and 50s were 65% of all implant cases and average number of implant was 4 (man), and 2.7 (woman). 75 implants were operated on maxilla and 89 were mandible. 19 implants on anterior region and 145 implants on posterior region. 2. Most distribution of bone qaulity for implant site was type III(37.2%) and bone quantity was type C(61. 7%) 3. The majority of implants were those of 10, 12mm in length (85%) and regular diameter in width (48.8%). 4. 30 implants were installed with the advanced technique-GER, window opemng, osteotome technique. 5. Two implants were removed before prosthodontic treatment due to the osseointegraton failure. The success rate was 98.8% in 15.2 months follow up period and the marginal bone loss was 0.28mm. The results provided us with basic data on patient type, implant distribution, bone condition, and survival rate. Within the limit of present study, It was concluded that Implantium implant could be used satisfactorily in various clinical situations.

• Journal of Periodontal and Implant Science
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• 제49권5호
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• pp.287-298
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• 2019

Purpose: The aim of this retrospective study was to determine the prevalence of early implant failure using a single implant system and to identify the factors contributing to early implant failure. Methods: Patients who received implant treatment with a single implant system ($Luna^{(R)}$, Shinhung, Seoul, Korea) at Dankook University Dental Hospital from 2015 to 2017 were enrolled. The following data were collected for analysis: sex and age of the patient, seniority of the surgeon, diameter and length of the implant, position in the dental arch, access approach for sinus-floor elevation, and type of guided bone regeneration (GBR) procedure. The effect of each predictor was evaluated using the crude hazard ratio and the adjusted hazard ratio (aHR) in univariate and multivariate Cox regression analyses, respectively. Results: This study analyzed 1,031 implants in 409 patients, who comprised 169 females and 240 males with a median age of 54 years (interquartile range [IQR], 47-61 years) and were followed up for a median of 7.2 months (IQR, 5.6-9.9 months) after implant placement. Thirty-five implants were removed prior to final prosthesis delivery, and the cumulative survival rate in the early phase at the implant level was 95.6%. Multivariate regression analysis revealed that seniority of the surgeon (residents: aHR=2.86; 95% confidence interval [CI], 1.37-5.94) and the jaw in which the implant was placed (mandible: aHR=2.31; 95% CI, 1.12-4.76) exerted statistically significant effects on early implant failure after adjusting for sex, age, dimensions of the implant, and type of GBR procedure (preoperative and/or simultaneous) (P<0.05). Conclusions: Prospective studies are warranted to further elucidate the factors contributing to early implant failure. In the meantime, surgeons should receive appropriate training and carefully select the bone bed in order to minimize the risk of early implant failure.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제45권2호
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• pp.97-107
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• 2019

Objectives: Small animal maxillofacial models, such as non-segmental critical size defects (CSDs) in the rabbit mandible, need to be standardized for use as preclinical models of bone regeneration to mimic clinical conditions such as maxillofacial trauma. The objective of this study is the establishment of a mechanically competent CSD model in the rabbit mandible to allow standardized evaluation of bone regeneration therapies. Materials and Methods: Three sizes of bony defect were generated in the mandibular body of rabbit hemi-mandibles: $12mm{\times}5mm$, $12mm{\times}8mm$, and $15mm{\times}10mm$. The hemi-mandibles were tested to failure in 3-point flexure. The $12mm{\times}5mm$ defect was then chosen for the defect size created in the mandibles of 26 rabbits with or without cautery of the defect margins and bone regeneration was assessed after 6 and 12 weeks. Regenerated bone density and volume were evaluated using radiography, micro-computed tomography, and histology. Results: Flexural strength of the $12mm{\times}5mm$ defect was similar to its contralateral; whereas the $12mm{\times}8mm$ and $15mm{\times}10mm$ groups carried significantly less load than their respective contralaterals (P<0.05). This demonstrated that the $12mm{\times}5mm$ defect did not significantly compromise mandibular mechanical integrity. Significantly less (P<0.05) bone was regenerated at 6 weeks in cauterized defect margins compared to controls without cautery. After 12 weeks, the bone volume of the group with cautery increased to that of the control without cautery after 6 weeks. Conclusion: An empty defect size of $12mm{\times}5mm$ in the rabbit mandibular model maintains sufficient mechanical stability to not require additional stabilization. However, this defect size allows for bone regeneration across the defect. Cautery of the defect only delays regeneration by 6 weeks suggesting that the performance of bone graft materials in mandibular defects of this size should be considered with caution.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1419-1426
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• 2008

Fulminant hepatic failure is a clinical syndrome associated with a high mortality rate. Orthotopic liver transplantation is the only clinically proven effective treatment for patients with end-stage liver disease who do not respond to medical management. A major limitation of this treatment modality is the scarcity of donor organs available, resulting in patients dying while waiting for a donor liver. An extracorporeal bioartificial liver (BAL) device containing viable hepatocytes has the potential to provide temporary hepatic support to liver failure patients, serving as a bridge to transplantation while awaiting a suitable donor. In some patients, providing temporary hepatic support may be sufficient to allow adequate regeneration of the host liver, thereby eliminating the need for a liver transplant. Although the BAL device is a promising technology for the treatment of liver failure, there are several technical challenges that must be overcome in order to develop systems with sufficient processing capacity and of manageable size. In this overview, the authors describe the critical issues involved in developing a BAL device. They also discuss their experiences in hepatocyte culture optimization within the context of a microchannel flat-plate BAL device.

• 한국전자파학회논문지
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• 제29권8호
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• pp.624-631
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• 2018

위성 탑재체 합성 개구면 레이다(synthetic aperture radar: SAR) 시스템에서는 다양한 SAR 성능 변수의 제약조건을 충족하기 위해 안테나의 요구되는 특성을 분석하여야 한다. 본 논문에서는 결함 안테나 소자 존재 시 위성 SAR 안테나 빔 패턴을 최적화함으로써 SAR 시스템 성능변수를 최적화를 수행한다. SAR 시스템 성능변수 제약조건에 맞는 마스크 패턴을 설계한 후, 입자 군집 최적화(particle swarm optimization: PSO) 기법을 통해 마스크 패턴에 들어맞는 안테나 패턴 최적화 재합성을 수행한다. 시뮬레이션에서는 실제 위성 SAR 시스템 성능변수를 기반으로 안테나 빔 패턴 재합성을 수행하여 제안한 알고리즘의 성능을 확인한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1161_1162
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• 2009

The recent environmental protection trend requires more strict energy saving, therefore every transportation system should reduce energy consumption to the minimum value. High-efficiency operation system, energy saving and $CO_2$ emissions shall be addressed as important issue in railway system. These issues are the most essential factors of railway, compared to major public transportation system. Recently, saving energy in the electric railway system has been studied. For such new energy saving, the energy storage system is considered for saving energy. Energy saving is possible by efficient use of regenerated energy. Regenerated energy is recycled amongst vehicles by mean of charge and discharge corresponding to powering and braking of electric vehicle operations. This energy saving contributes to cut $CO_2$ to reduce greenhouse gas emissions. Recycling regenerated energy demonstrate significant effect on peak cut of consumption energy in railway substation. Absorption of excess energy avoids regeneration failure due to high traction voltage. Therefore, the energy storage system is needed to be adopted to use regeneration energy when the vehicle is braking.

• Molecular & Cellular Toxicology
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• 제3권3호
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• pp.151-158
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• 2007

The failure of injured axons to regenerate in the mature central nervous system (CNS) has devastating consequences for victims of spinal cord injury (SCI). Traditional strategies to treat spinal cord injured people by using drug therapy and assisting devices that can not help them to recover fully various vital functions of the spinal cord. Many researches have been focused on accomplishing re-growth and reconnection of the severed axons in the injured region. Using cell transplantation to promote neural survival or growth has had modest success in allowing injured neurons to re-grow through the area of the lesion. Strategies for successful regeneration will require tissue engineering approach. In order to persuade sufficient axons to regenerate across the lesion to bring back substantial neurological function, it is necessary to construct an efficient biocompatible bridge (cell-free or implanted with different cell lines as hybrid implant) through the injured area over which axons can grow. Therefore, in this paper, spinal cord and its injury, different strategies to help regeneration of an injured spinal cord are reviewed. In addition, different aspects of designing a biocompatible bridge and its applications and challenges surrounding these issues are also addressed. This knowledge is very important for the development and optimalization of therapies to repair the injured spinal cord.