• Restorative Dentistry and Endodontics
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• v.15 no.1
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• pp.20-32
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• 1990

The plane strain fracture toughness of a material characterize the resistance to fracture in the presence of a sharp crack under severe tensile condition. Fracture toughness can be determined by indentation method. The purpose of this study was to investigate the fracture toughness of dental amalgams by measuring the plane strain fracture toughness and the fracture toughness from indentation method. Two conventional and four high copper amalgam alloys were employed for this study. The amalgams were prepared according to the A.D.A. spec. No. 1 and inserted into the specially designed mould with the single edge notch specimen to use in 3-point bending method. The specimens (20mm long, 4mm wide, 2mm thick) were stored at $37^{\circ}C$ for 1 week, and tested in 3-point bending by means of Instron at a cross-head speed of 1mm/min. In indentation method, the specimens were made in same manner as single edge notch specimens. The test was conducted with Vickers hardness tester at 10kg load. The following results were obtained. 1. The plane strain fracture toughness and the fracture toughness from indentation method were higher in the low copper amalgams than the high copper amalgams. 2. In high copper amalgams, the fracture toughness of amalgams decreases according as the copper contents increase. 3. In similar copper contents, the single composition amalgams have a higher fracture toughness than the admixed amalgams.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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• pp.27-30
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• 2001

Flow and transport at fracture intersections, and their effects on network scale transport, are investigated in three-dimensional random fracture networks. Fracture intersection mixing rules complete mixing and streamline routing are defined in terms of fluxes normal to the intersection line between two fractures. By analyzing flow statistics and particle transfer probabilities distributed along fracture intersections, it is shown that for various network structures with power law size distributions of fractures, the choice of intersection mixing rule makes comparatively little difference in the overall simulated solute migration patterns. The occurrence and effects of local flows around an intersection (local flow cells) are emphasized. Transport simulations at fracture intersections indicate that local flow circulations can arise from variability within the hydraulic head distribution along intersections, and from the internal no flow condition along fracture boundaries. These local flow cells act as an effective mechanism to enhance the nondiffusive breakthrough tailing often observed in discrete fracture networks. It is shown that such non-Fickian (anomalous) solute transport can be accounted for by considering only advective transport, in the framework of a continuous time random walk model. To clarify the effect of forest environmental changes (forest type difference and clearcut) on water storage capacity in soil and stream flow, watershed had been investigated.

• Journal of Korean Neurosurgical Society
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• v.29 no.3
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• pp.353-359
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• 2000

Objective : The fracture on the frontal bone in head-injured patients may be commonly encountered in the clinical situations. Biomechanical studies demonstrate that the anterior wall of the frontal sinus is intermediate in its ability to resist fracture on direct impact. If the frontal sinus is large and the anterior table is able to disperse the force of the impact over a greater area, the posterior table and intracranial contents usually can be spared. We analyzed the clinical features of the patients who presented with frontal skull fracture due to frontal blows. Patients and Methods : From January, 1992 to December, 1997, 172 patients with frontal skull fracture were selected among 1911 patients with head injury who were admitted to department of neurosurgery. Clinical records and radiological studies of all patients were reviewed and evaluated retrospectively. Results : The neurobehavioral changes was seen in 34 cases(19.8%) and showed statistical significances in case of facial bone fractures, acute subdural hematoma(SDH), and positive frontal lobe releasing sign(p<0.05). The good glasgow outcome score group(GOS, good recovery & moderate disability) at discharge was revealed in 77.3% of total patient population. The poor GOS group(severe disability & vegetative state & death) at discharge was revealed in 22.7%. The poor GOS group at discharge have statistical significances with acute epidural hematoma(EDH), traumatic intraventricular hemorrhage(t-IVH), traumatic intracranial lesion, poor initial glasgow coma scale(GCS) scores & Revised Trauma Score(RTS)(p<0.05). Conclusion : Because of their anatomical relationships and neurobehavioral patterns due to vulnerability of the frontal lobe, the frontal injury should be considered as complicated facial injuries. Therefore, these patients are more likely to have a cosmetic or neuropsychiatric problems.

• Advances in biomechanics and applications
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• v.1 no.2
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• pp.77-83
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• 2014

Creep phenomenon at the scale of bone tissue (small specimens) is known to be present and demonstrated for low strains. Here creep is demonstrated on a pair of fresh-frozen human femurs at the organ level at high strains. Under a constant displacement applied on femur's head, surface strains at the upper neck location increase with time until fracture, that occurs within 7-13 seconds. The monotonic increase in strains provides evidence on damage accumulation in the interior (probably damage to the trabeculae) prior to final fracture, a fact that hints on probable damage of the trabecular bone that occurs prior to the catastrophic fracture of the cortical surface layer.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.17 no.2
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• pp.163-170
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• 1995

The purpose of this study was to investigate the epidemiology of midface fractures. We observed clinically 71 patients with midface fracture who visited the Department of oral and maxillofacial-surgery, Chosun University, Dental Hospital, from 1991 to 1994. The results obtained were as follows. 1. There was the highest age incidence in the third decade(29.6%). 2. There was the highest incidence in the summer(36.6%). 3. The most etiologic factor of midface fracture was traffic accidents(43.6%) and next factor was fall down(38.0%). 4. The highest incidence fracture was zygomatic arch(38.7%) and next fracture was ZMC fracture(31.5%). 5. Most midface fracture was treated within 2 weeks(86.7%). 6. Midface fractures was most frequently combined with mandibular fracture(15.5%), head injuries(14.1%), orthhopedic injuries(8.5), thorax & abdomen(5.6%). 7. The highest complication was the nerve injury(8명), and next complications were infection(3명), epiphora(3명) etc.

• Journal of Chest Surgery
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• v.28 no.6
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• pp.601-605
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• 1995

Clinical evaluations were performed on 54 cases of the traumatic sternal fracture, those were admitted and treated at the department of Thoracic and Cardiovascular Surgery in Chosun University Hospital during the past 5 years period from January 1990 to December 1994. The frequency was about 7.8% of the nonpenetrating chest trauma. The ratio of male to female was 2 : 1 in male predominance. Average age was 45.7 years old and age distribution was from 18 to 80 years old. The most common cause in the sternal fracture were high decelerating injury[ 38 cases . The most common fracture site was sternal body. Associated intrathoracic organ injuries were cardiac contusion[11cases , hemopneumothorax and pulmonary contusion. Added, thoracic cage and extrathoracic organ injuries were rib fracture, head injuries, thoracic spinal fracture and long bone fracture. Abnormal ECG findings were sinus bradycardia[4 cases , sinus tachycardia[3 cases , bundle branch block, atrial fibrillaton, left ventricular hypertrophy and myocardial ischemia. The average days of admission was 19.1 days. All patients were treated with conservative treatment. The complications after treatment were atelectasis[2 cases ,empyema[1 cases , ARDS[1 cases .

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.1
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• pp.1-8
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• 2020

The aim of this retrospective study was to investigate etiology, clinical features, and treatment modalities of the mandibular condyle fracture in children and young adolescents. This study was conducted based on medical records and radiographic examinations of 44 pediatric patients. Patients received treatment under diagnosis of mandibular condylar fracture. They were divided into 4 groups according to their age. The involvement of condyle in the mandible fracture occurred in higher percentage in younger age groups. Falling was the most common etiologic factor in all age group, especially in children with age under 7. Condyle head was the most frequent site of fracture in age group of 4 - 7 whereas fracture tends to occur in lower condylar areas in older groups. In 54.5% of the mandibular condyle fracture, symphysis fracture was accompanied. Teeth injury occurred in higher incidency when condyle fracture accompanied symphysis fracture. Conservative treatments were applied to 43 out of 44 patients.

• Journal of Korean Foot and Ankle Society
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• v.11 no.1
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• pp.111-114
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• 2007

Open calcaneal fracture with more than lateral half of bone loss and soft tissue defect occurred in 17 year-old male patient due to motor vehicle accident. Soft tissue defect included heel pad, peroneal tendon. Bone loss involved mainly most part of inferior tuberosity but not subtalar joint. Open dressing and debridement were done daily in operating room and antibiotics administration was started. After granulation tissue formed, femoral head allograft was performed and fixed with 6.0 mm screws to replace bone defect. Soft tissue defect was covered with latissimus dorsi musculocutaneous free flap. No sign of infection nor major osteolysis was observed in 15 months follow up period. Soft tissue defect was covered with latissimus dorsi musculocutaneous free flap.

• Clinics in Shoulder and Elbow
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• v.23 no.1
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• pp.27-30
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• 2020

Osborne-Cotterill lesion is an osteochondral fracture located in the posterolateral margin of the humeral capitellum, which may be associated with a defect of the radial head after an elbow dislocation. This lesion causes instability by affecting the lateral ulnar collateral ligament over its capitellar insertion, which is associated with a residual capsular laxity, thereby leading to poor coverage of the radial head, and hence resulting in frequent dislocations. We present a 54-year-old patient, a physician who underwent trauma of the left elbow after falling from a bike and suffered a posterior dislocation fracture of the elbow. The patient subsequently presented episodes of instability, and additional work-up studies diagnosed the occurrence of Osborne-Cotterill lesion. An open reduction and internal fixation of the bony lesion was performed, with reinsertion of the lateral ligamentous complex. Three months after surgery, the patient was asymptomatic, having a flexion of 130° and extension of 0°, and resumed his daily activities without any limitation. Currently, the patient remains asymptomatic 2 years after the procedure. Elbow instability includes a large spectrum of pathological conditions that affect the biomechanics of the joint. The Osborne-Cotterill lesion is one among these conditions. It is a pathology that is often forgotten and easily overlooked. Undoubtedly, this lesion requires surgical intervention.

• Journal of Yeungnam Medical Science
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• v.40 no.2
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• pp.212-217
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• 2023

We report a case of transient osteoporosis of the hip with a femoral neck fracture found during follow-up. A 53-year-old man presented with left hip pain without trauma. The pain did not improve after 2 weeks and he was brought to our hospital by ambulance. Magnetic resonance imaging (MRI) of the left hip joint showed diffuse edema in the bone marrow, which was identified by low signal intensity on T1-weighted images, high signal intensity on T2-weighted images, and increased signal intensity on short tau inversion recovery. This edema extended from the femoral head and neck to the intertrochanteric area. He was diagnosed with transient osteoporosis of the left hip. Rest gradually improved his pain; however, 3 weeks later, his left hip pain worsened without trauma. X-ray, computed tomography, and MRI results of the hip joint demonstrated a left femoral neck fracture, and osteosynthesis was performed. Differential diagnoses included avascular necrosis of the femoral head, infection, complex regional pain syndrome, rheumatoid arthritis, leukemia, and other cancers. Transient osteoporosis of the hip generally has a good prognosis with spontaneous remission within a few months to 1 year. However, a sufficient length of follow-up from condition onset to full recovery is necessary to avoid all probable complications such as fractures.