1.Study on Zr-xCu and Zr-xSi alloys with low elastic modulus for improving stress shield effect
Seung-Won KU ; Chung-Seok KIM ; Yeong-Mu KO
Korean Journal of Dental Materials 2021;48(3):175-190
The objective of this study was to fabricate Zr-xCu and Zr-xSi alloys with low elastic modulus for preventing bone resorption in dental biomaterials. Metallic materials are widely used for orthopedic and dental applications due to their superior characteristics of mechanical properties and biocompatibility. Many metals and alloys, such as stainless steel, Co-Cr alloys, and Ti-based alloys are commonly used. Among these dental metallic materials, pure Ti and Ti-6Al-4V alloy have become the most popular metals used for the endosseous parts of the implant, bone plates, and artificial joints due to their excellent specific corrosion resistance and high biocompatibility with natural bone. Stress shield effect results in the reduction in bone density as a result of the removal of typical stress from the bone by an implant. In general, the bone in a healthy person will remodel in response to the loads it is placed under. Therefore, if the loading on a bone decreases, the bone will become less dense and weaker because there is no stimulus for continued remodeling that is required to maintain bone mass. Although Ti-based alloys have been widely used as implant components and devices, its elastic modulus (110 GPa) is much higher than that of natural human bone (10–30 GPa). Serious damage may be easily caused in the human body when the modulus of implant materials does not match the natural bone due to the stress shield effects. Therefore, in recent, persistent efforts have been done to obtain biological hard tissue materials with low elastic modulus to transfer stress to the surrounding bones effectively. The Zr-xCu binary alloy exhibited moderate compressive strength (1291-1411 MPa), yield stress (517-552 MPa), favorable elongation (16.4–49.2%), elastic energy (6.76–7.43 MJ/m3 ) and low elastic modulus (18.5–23.1 GPa). The Zr-xSi binary alloy exhibited high compressive strength (1105-1623 MPa), yield stress (673-1514 MPa), favorable elongation (6.0–27.2%), high elastic energy (10.2–34.6 MJ/m3 ) and low elastic modulus (22.3–33.1 GPa). Consequently, Zr-xCu and Zr-xSi binary alloys have the potential to be used as biomaterials with nullifying stress shield effects for biological hard tissue materials.
2.Study on Zr-xCu and Zr-xSi alloys with low elastic modulus for improving stress shield effect
Seung-Won KU ; Chung-Seok KIM ; Yeong-Mu KO
Korean Journal of Dental Materials 2021;48(3):175-190
The objective of this study was to fabricate Zr-xCu and Zr-xSi alloys with low elastic modulus for preventing bone resorption in dental biomaterials. Metallic materials are widely used for orthopedic and dental applications due to their superior characteristics of mechanical properties and biocompatibility. Many metals and alloys, such as stainless steel, Co-Cr alloys, and Ti-based alloys are commonly used. Among these dental metallic materials, pure Ti and Ti-6Al-4V alloy have become the most popular metals used for the endosseous parts of the implant, bone plates, and artificial joints due to their excellent specific corrosion resistance and high biocompatibility with natural bone. Stress shield effect results in the reduction in bone density as a result of the removal of typical stress from the bone by an implant. In general, the bone in a healthy person will remodel in response to the loads it is placed under. Therefore, if the loading on a bone decreases, the bone will become less dense and weaker because there is no stimulus for continued remodeling that is required to maintain bone mass. Although Ti-based alloys have been widely used as implant components and devices, its elastic modulus (110 GPa) is much higher than that of natural human bone (10–30 GPa). Serious damage may be easily caused in the human body when the modulus of implant materials does not match the natural bone due to the stress shield effects. Therefore, in recent, persistent efforts have been done to obtain biological hard tissue materials with low elastic modulus to transfer stress to the surrounding bones effectively. The Zr-xCu binary alloy exhibited moderate compressive strength (1291-1411 MPa), yield stress (517-552 MPa), favorable elongation (16.4–49.2%), elastic energy (6.76–7.43 MJ/m3 ) and low elastic modulus (18.5–23.1 GPa). The Zr-xSi binary alloy exhibited high compressive strength (1105-1623 MPa), yield stress (673-1514 MPa), favorable elongation (6.0–27.2%), high elastic energy (10.2–34.6 MJ/m3 ) and low elastic modulus (22.3–33.1 GPa). Consequently, Zr-xCu and Zr-xSi binary alloys have the potential to be used as biomaterials with nullifying stress shield effects for biological hard tissue materials.
3.Prediction of Late Breast Cancer-Specific Mortality in Recurrence-Free Breast Cancer Survivors Treated for Five Years with Tamoxifen
Soo Yeon BAEK ; Ji Yeong KWON ; Young Joo LEE ; Sung chan GWARK ; Sae Byul LEE ; Jisun KIM ; Il Yong CHUNG ; Beom Seok KO ; Hee Jeong KIM ; Sung Bae KIM ; Seung Do AHN ; Gyungyub GONG ; Byung Ho SON ; Sei Hyun AHN ; Jong Won LEE
Journal of Breast Cancer 2019;22(3):387-398
PURPOSE: The extension of endocrine therapy beyond 5 years for recurrence-free survivors of breast cancer improves survival; however, the issue on how to clinically identify appropriate candidates remains controversial. This study aimed to identify prognostic factors for breast-cancer-specific mortality in patients who have had 5 years of tamoxifen treatment and categorize subgroups based on the risk of death using combinations of these prognostic factors to assist in the clinical decision to perform further endocrine therapy. METHODS: In total, 3,158 patients with breast cancer were enrolled. Breast cancer-specific survival rates after 5 years of tamoxifen treatment were calculated, and associated prognostic factors were analyzed using a Cox proportional-hazards model. RESULTS: An age extreme at diagnosis (i.e., < 40 or ≥ 60 years), tumor size > 2 cm, and positive lymphovascular invasion were robust independent prognostic factors for late breast cancer-specific death in tamoxifen-treated patients (hazard ratio [HR] = 2.162, 1.739, and 1.993; p = 0.001, 0.047, and 0.011, respectively). Lymph node metastasis and progesterone receptor negativity had borderline significance in this regard (HR = 1.741 and 1.638, p = 0.099 and 0.061). The study patients were classified into four groups according to the number of prognostic indicators, i.e., low, intermediate, high, and extremely high risk. The additional 5- and 10-year cumulative risks of breast cancer-specific death were 0.8% and 1.5% in the low-risk group, 0.9% and 3.9% in the intermediate-risk group, 1.3% and 7.3% in the high-risk group, and 4.8% and 13.8% in the extremely high-risk group, respectively. CONCLUSION: This new risk stratification system for late mortality in breast cancer can be used to identify the right candidates for extended endocrine therapy after 5 years of tamoxifen treatment.
Breast Neoplasms
;
Breast
;
Diagnosis
;
Humans
;
Lymph Nodes
;
Mortality
;
Neoplasm Metastasis
;
Prognosis
;
Receptors, Progesterone
;
Survival Rate
;
Survivors
;
Tamoxifen
4.Endobronchial Neurilemmoma Mimicking a Bronchial Polyp.
Ryoung Eun KO ; Seung Yong PARK ; Yeong Hun CHOE ; So Ri KIM ; Heung Bum LEE ; Yong Chul LEE ; Seoung Ju PARK
Soonchunhyang Medical Science 2015;21(2):176-179
Neurilemmomas are relatively uncommon, slowly growing tumors which originate from Schwann cells. Intrathoracic neurilemmomas often occur in the chest wall and posterior mediastinum, but endobronchial neurilemmomas are exceedingly rare. These tumors in trachea or bronchus are usually detected by radiologic examinations, mostly computed tomography scan of chest. An 88-year-old man was admitted for management of pneumonia in left lower lobe and parapneumonic effusion. On bronchoscopic examination, there was a small polypoid nodule less than 1 cm in diameter mimicking an endobronchial inflammatory polyp at the bifurcation of the right anterior segmental bronchus and lateral segmental bronchus and under auto-fluorescence imaging, the nodule showed reddish brown area with defined margin. The bronchoscopic biopsy revealed that the bronchial nodule was endobronchial neurilemmoma. This is an interesting case of endobronchial neurilemmoma mimicking a bronchial polyp that is detected incidentally via bronchoscopy.
Aged, 80 and over
;
Biopsy
;
Bronchi
;
Bronchoscopy
;
Humans
;
Mediastinum
;
Neurilemmoma*
;
Optical Imaging
;
Pneumonia
;
Polyps*
;
Schwann Cells
;
Thoracic Wall
;
Thorax
;
Trachea
5.Relationship between Locations of Facial Injury and the Use of Bicycle Helmets: A Systematic Review.
Kun HWANG ; Yun Moon JEON ; Yeong Seung KO ; Yeon Soo KIM
Archives of Plastic Surgery 2015;42(4):407-410
The aim of this study is to review the protective effect of a bicycle helmet on each facial location systematically. PubMed was searched for articles published before December 12, 2014. The data were summarized, and the odds ratio (OR) between the locations of facial injury was calculated. A statistical analysis was performed with Review Manager (The Nordic Cochrane Centre). Bicycle helmets protect the upper and middle face from serious facial injury but do not protect the lower face. Non-wearers had significantly increased risks of upper facial injury (OR, 2.07; P<0.001) and of middle facial injury (OR, 1.97; P<0.001) as compared to helmet users. In the case of lower facial injury, however, only a slightly increased risk (OR, 1.42; 95% confidence interval (CI), 0.67-3.00, P=0.36) was observed. The abovementioned results can be attributed to the fact that a helmet covers the head and forehead but cannot cover the lower face. However, helmets having a chin cap might decrease the risk of lower facial injury.
Bicycling
;
Chin
;
Facial Injuries*
;
Forehead
;
Head
;
Head Protective Devices*
;
Odds Ratio
6.Effect of Peritoneal Dialysis Modality on the 1-Year Rate of Decline of Residual Renal Function.
Chan Ho KIM ; Hyung Jung OH ; Mi Jung LEE ; Young Eun KWON ; Yung Ly KIM ; Ki Heon NAM ; Kyoung Sook PARK ; Seong Yeong AN ; Kwang Il KO ; Hyang Mo KOO ; Fa Mee DOH ; Seung Hyeok HAN ; Tae Hyun YOO ; Beom Seok KIM ; Shin Wook KANG ; Kyu Hun CHOI
Yonsei Medical Journal 2014;55(1):141-148
PURPOSE: The effect of different peritoneal dialysis (PD) modalities on the decline in residual renal function (RRF) is unclear due to inconsistencies among studies. In particular, the effect of automated peritoneal dialysis (APD) modalities [continuous cyclic peritoneal dialysis (CCPD) and nightly intermittent peritoneal dialysis (NIPD)] on RRF has not been examined in a large cohort. MATERIALS AND METHODS: We conducted a single-center retrospective study to investigate the association between PD modalities and decline in RRF in 142 incident PD patients [34 on CCPD, 36 on NIPD, and 72 on continuous ambulatory peritoneal dialysis (CAPD)]. RRF was measured within 2 months from PD start and at 1 year after PD initiation. RESULTS: The RRF at 1 year after PD initiation was 1.98+/-2.20 mL/min/1.73 m2 in CCPD patients and 3.63+/-3.67 mL/min/1.73 m2 in NIPD patients, which were moderately lower than 4.23+/-3.51 mL/min/1.73 m2 in CAPD patients (p=0.064). Moreover, there was no significant difference in the 1-year rate of decline of RRF between CCPD and NIPD patients, although APD patients had a faster 1-year RRF decline rate than CAPD patients (CCPD and NIPD vs. CAPD: -45.68 and -36.69 vs. 1.17%/year, p=0.045). APD was associated with a more rapid decline in RRF in patients with end-stage renal disease undergoing PD, although multivariate analysis attenuated the significance of this finding (beta=-31.50; 95% CI, -63.61 to 0.62; p=0.052). CONCLUSION: Our results suggest that CAPD might be more helpful than APD for preserving RRF during the first year of dialysis therapy, although there was no significant difference in the 1-year rate of decline of RRF between the two APD modalities.
Adult
;
Female
;
Glomerular Filtration Rate/physiology
;
Humans
;
Kidney/pathology/physiopathology
;
Kidney Failure, Chronic/*therapy
;
Male
;
Middle Aged
;
Peritoneal Dialysis/*adverse effects
;
Retrospective Studies
7.The Role of Preoperative NT-proBNP in Elderly Orthopedic Patients with Normal Left Ventricular Systolic Function.
Eun Jung KO ; Jae Youn MOON ; Yeong Min LIM ; Won Jung HONG ; Suk Pyo SHIN ; Sang Hoon KIM ; Woo In YANG ; Jung Hoon SUNG ; In Jai KIM ; Sang Wook LIM ; Dong Hun CHA ; Seung Yun CHO
Korean Journal of Medicine 2014;87(3):302-310
BACKGROUND/AIMS: Preoperative N-terminal pro-brain natriuretic peptide (NT-proBNP) is a useful predictor of postoperative cardiovascular complications. The present study investigated whether blood NT-proBNP values are suitable for predicting postoperative cardiovascular complications after non-cardiac surgery in elderly patients showing normal left ventricular (LV) function on preoperative echocardiograms. METHODS: This study was performed by analyzing the medical records of elderly patients referred to the cardiology department for the purpose of assessing their cardiac function before orthopedic surgery. Of the patients who underwent echocardiography and NT-proBNP assessment simultaneously, 275 patients aged > or = 70 years and with an LV ejection fraction of > or = 55% were included in the study. RESULTS: Major adverse cardiac and cerebrovascular events (MACCEs) occurred in 33 (12%) of the 275 patients, and the NT-proBNP concentration was higher in patients with complications than in those without complications (1,904.20 +/- 2,300.23 vs. 530.58 +/- 882.27 pg/mL, p < 0.01). The ROC area under the curve was 0.756 (95% confidence interval 0.701-0.805, p < 0.001) with an optimal cutoff of 416.3 pg/mL (69.7% sensitivity, 67.36% specificity). A multivariate analysis showed that a preoperative age of > 80 years (odds ratio, 2.313; p = 0.047) and an increased blood NT-proBNP concentration (odds ratio, 3.189; p = 0.009) were independent risk factors for the prediction of MACCEs. CONCLUSIONS: Although elderly patients scheduled to undergo non-cardiac surgery may show normal LV systolic function on echocardiography, measurement of their preoperative blood NT-proBNP concentration is useful for predicting MACCEs occurring after non-cardiac surgery.
Aged*
;
Cardiology
;
Echocardiography
;
Humans
;
Medical Records
;
Multivariate Analysis
;
Natriuretic Peptides
;
Orthopedics*
;
Risk Factors
8.Left Atrium Compressed by a Traumatic Focal Aneurysm of the Thoracic Aorta.
Gun PARK ; Seung Yeong KO ; Ju Yeong KIM ; Sang Don NA ; Dong Han KIM ; Jang Hyun CHO
Korean Journal of Medicine 2014;86(3):329-333
A 78-year-old woman presented to our hospital with progressive dyspnea (NYHA class I-II) and epigastric discomfort that had developed after a traffic accident. She had a history of hypertension and cerebral infarction, but no history of cardiovascular disease. Her blood pressure was 130/70 mmHg and her heart rate was 66 beats/min and regular. The electrocardiogram showed normal sinus rhythm. The chest X-ray revealed bilateral pleural effusions. Transthoracic echocardiography (TTE) demonstrated an aneurysm of the descending thoracic aorta compressing the left atrium (LA). Left and right ventricular systolic function was preserved. Whole-body computed tomography (CT) angiography revealed that a focal 40-mm-diameter saccular aneurysm in the descending aorta at the level of T7-8, with an intramural hematoma, was compressing the LA and left pulmonary vein. After surgical management, follow-up TTE and CT showed decompression of the LA and left pulmonary vein.
Accidents, Traffic
;
Aged
;
Aneurysm*
;
Angiography
;
Aorta, Thoracic*
;
Aortic Aneurysm
;
Blood Pressure
;
Cardiovascular Diseases
;
Cerebral Infarction
;
Decompression
;
Dyspnea
;
Echocardiography
;
Electrocardiography
;
Female
;
Follow-Up Studies
;
Heart Atria*
;
Heart Rate
;
Hematoma
;
Humans
;
Hypertension
;
Pleural Effusion
;
Pulmonary Veins
;
Thorax
9.A Case of Kerion Celsi Caused by Microsporum gypseum.
Dong Yeob KO ; Seung Min HA ; Su Young JEON ; Kwang Sook WOO ; Jin Yeong HAN ; Ki Hoon SONG ; Ki Ho KIM
Korean Journal of Dermatology 2013;51(5):375-376
No abstract available.
Microsporum
;
Tinea Capitis
10.Corrected QT Interval Prolongation during Severe Hypoglycemia without Hypokalemia in Patients with Type 2 Diabetes.
Jae Won BEOM ; Jung Min KIM ; Eun Joo CHUNG ; Ju Yeong KIM ; Seung Yeong KO ; Sang Don NA ; Cheol Hwan KIM ; Gun PARK ; Mi Yeon KANG
Diabetes & Metabolism Journal 2013;37(3):190-195
BACKGROUND: To evaluate the effects of severe hypoglycemia without hypokalemia on the electrocardiogram in patients with type 2 diabetes in real-life conditions. METHODS: Electrocardiograms of adult type 2 diabetic patients during the episodes of severe hypoglycemia and the recovered stage were obtained and analysed between October 1, 2011 and May 31, 2012. Patients who maintained the normal serum sodium and potassium levels during the episodes of severe hypoglycemia were only selected as the subjects of this study. Severe hypoglycemia was defined, in this study, as the condition requiring active medical assistance such as administering carbohydrate when serum glucose level was less than 60 mg/dL. RESULTS: Nine type 2 diabetes patients (seven men, two women) were included in the study. The mean subject age was 73.2+/-7.7 years. The mean hemoglobin A1c level was 6.07%+/-1.19%. The median duration of diabetes was 10 years (range, 3.5 to 30 years). Corrected QT (QTc) intervals were significantly increased during the episodes of severe hypoglycemia compared to the recovered stage (447.6+/-18.2 ms vs. 417.2+/-30.6 ms; P<0.05). However, the morphology and the amplitude of the T waves were not changed and ST-segment elevation and/or depression were not found during the episodes of severe hypoglycemia. CONCLUSION: In this study, QTc interval prolongation during the episodes of severe hypoglycemia was observed without hypokalemia. Therefore, the distinct alterations in cardiac repolarization during the episodes of severe hypoglycemia may not be associated with hypokalemia.
Adult
;
Depression
;
Diabetes Mellitus, Type 2
;
Electrocardiography
;
Glucose
;
Hemoglobins
;
Humans
;
Hypoglycemia
;
Hypokalemia
;
Male
;
Medical Assistance
;
Potassium
;
Sodium

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