OBJECTIVE: The aim of this systematic multiscale analysis was to evaluate the effects of thermoforming on the physical and mechanical properties of thermoplastic materials used to fabricate transparent orthodontic aligners (TOAs). METHODS: Specimens were fabricated using four types of thermoplastic materials with different thicknesses under a thermal vacuum. Transparency, water absorption and solubility, surface hardness, and the results of three-point bending and tensile tests were evaluated before and after thermoforming. Data were analyzed using one-way analysis of variance and Student's t-test. RESULTS: After thermoforming, the transparency of Duran and Essix A+ decreased, while the water absorption ability of all materials; the water solubility of Duran, Essix A+, and Essix ACE; and the surface hardness of Duran and Essix A+ increased. The flexure modulus for the 0.5-mm-thick Duran, Essix A+, and eCligner specimens increased, whereas that for the 0.75-/1.0-mm-thick Duran and eClginer specimens decreased. In addition, the elastic modulus increased for the 0.5-mm-thick Essix A+ specimens and decreased for the 0.75-mm-thick Duran and Essix ACE and the 1.0-mm-thick Essix ACE specimens. CONCLUSIONS: Our findings suggest that the physical and mechanical properties of thermoplastic materials used for the fabrication of TOAs should be evaluated after thermoforming in order to characterize their properties for clinical application.
Elastic Modulus ; Hardness ; Solubility ; Vacuum ; Water

OBJECTIVE: This study was performed to investigate an appropriate degree of prestretch for orthodontic synthetic elastomeric chains focusing on time-dependent viscoelastic properties. METHODS: Orthodontic synthetic elastomeric chains of two brands were prestretched to 50, 100, 150, and 200% of the original length in one and three cycles, and the hysteresis areas of the obtained stress-strain curves were determined. Acrylic plates were employed to maintain constant strain during the experiment. A total of 180 samples were classified into nine groups according to brand, and their stresses and permanent deformations were measured immediately after prestretch (0 hour), after 1 hour and 24 hours, and after 1, 2, 3, 4, 5, 6, 7, and 8 weeks. The relationship between stress relaxation and permanent deformation was investigated for various degrees of prestretch, and the estimated stress resulting from tooth movement was calculated. RESULTS: The degree of prestretch and the stress relaxation ratio exhibited a strong negative correlation, whereas no correlation was found between the degree of prestretch and the average normalized permanent strain. The maximal estimated stress was observed when prestretch was performed in three cycles to 200% of the original length. CONCLUSIONS: Although prestretch benefited residual stress, it did not exhibit negative effects such as permanent deformation. The maximal estimated stress was observed at the maximal prestretch, but the difference between prestretch and control groups decreased with time. In general, higher residual stresses were observed for product B than for product A, but this difference was not clinically significant.
Elastomers* ; Relaxation* ; Tooth Movement

BACKGROUND: Suicide in young people is one of most common cause of death; and deliberate self-harm (DSH) is important indicator of suicide. It is currently unclear how old the rate begins to increase or when it reaches to the same level with adults. The purpose of this study was to find beginning age of DSH and compare their characteristics with adults. METHODS: This study retrospectively reviewed 5 years of nationwide prospective registry named Emergency Department-based Injury In-depth Surveillance (EDIIS) registry composed of all injured patients who were admitted to twenty tertiary university hospital emergency departments. Injured patients aged 29 years or younger from January 1, 2011 to December 31, 2015 were included. Incidence rate of DSH in all age was described. Patients were stratified by age: early teenage (11–15 years), late teenage (16–19 years), and early adulthood (20–29 years). Data of early teenage group were compared to those of other groups for examining their characteristics. RESULTS: Among 588,549 injury patients, 8,400 patients reported DSH. The rate began to rise at age 11 and reach at age 16 which was equivalent to that of age 20 to 29. Early teenage had significantly higher excess mortality ratio based injury severity score (EMR-ISS) and had almost same level without significant difference in operation incidence or mortality compared to late teenage and early adulthood. CONCLUSION: DSH rate began to rise at age 11, reaching adulthood level at age 16 in Korea.
Adult ; Cause of Death ; Emergencies ; Emergency Service, Hospital ; Humans ; Incidence ; Injury Severity Score ; Korea ; Mortality ; Prospective Studies ; Retrospective Studies ; Self-Injurious Behavior* ; Suicide

PURPOSE: In this study, we aimed to measure the effects of emergency department (ED) expansion at a tertiary hospital on overall ED length of stay (LOS). METHODS: This study was a before and after study using data from a tertiary medical center in Seoul, a large metropolis. We used electronic medical records and administrative databases obtained from the ED. The control period (before expansion) was defined as from January 1 to April 31, 2016. The study period (after expansion) was defined as from May 1 to August 31, 2016. The number of ED beds increased from 42 to 74 after the expansion. After adjusting individual characteristics and institutional characteristics, multivariate regression analysis was carried out to evaluate the effects of expansion on overall ED LOS. RESULTS: A total of 45,632 patients visited the emergency medical center: 20,592 patients before and 25,040 after the expansion. Although the absolute number of patients increased, the portion of medical patients, portion of non-referral patients, and ambulatory patients decreased during the study period (all p<0.001). Average visit number increased from 170.2 (standard deviation [SD], 27.3) to 203.6 (SD, 21.3) (p<0.001). The overall ED LOS increased from 332.2 (SD, 473.4) to 391.0 minutes (SD, 649.5). After adjusting for potential confounders, we found that ED expansion was associated with an increase in ED LOS by 75.8 minutes (95% confidence interval, 63.5 to 88.2). CONCLUSION: We found that the ED expansion was associated with a significant increase in ED LOS.
Crowding ; Electronic Health Records ; Emergencies* ; Emergency Medicine ; Emergency Service, Hospital* ; Hospital Administration ; Humans ; Length of Stay* ; Overall ; Seoul ; Tertiary Care Centers*

OBJECTIVE: The purpose of this study was to examine the effect of commercially available fluoride-containing oral rinses on the corrosion behavior of titanium alloys, which are the main components of orthodontic miniscrews. METHODS: Four commercially available oral rinses (solution A, pH 4.46/260 ppm fluoride; solution B, pH 4.41/178 ppm fluoride; solution C, pH 6.30/117 ppm fluoride; and solution D, pH 4.17/3.92 ppm fluoride) were tested on titanium alloy (Ti-6Al-4V) circular plates, and saline was used as the control. The open-circuit potential and potentiodynamic polarization of these materials were measured. Thereafter, all samples were evaluated under a field-emission scanning electron microscope. RESULTS: Among the tested oral rinses, except solution D, the more the fluoride content was, the greater was the corrosion potential downtrend; the corrosion resistance of the titanium alloy sample was also lowered significantly (p < 0.05). Field-emission scanning electron microscopic analysis of the surface morphology of the titanium alloy samples revealed that all samples had some defects, crevices, or pitting after exposure to the oral rinses than before treatment. In particular, the samples in solution A showed the most changes. CONCLUSIONS: Commercially available oral rinses having a high fluoride concentration and a low pH may reduce the corrosion resistance of titanium alloys used in dental appliances such as orthodontic titanium miniscrews and brackets.
Alloys* ; Corrosion* ; Fluorides ; Hydrogen-Ion Concentration ; Titanium*

OBJECTIVE: The aim of this study was to compare recycled and unused orthodontic miniscrews to determine the feasibility of reuse. The comparisons included both miniscrews with machined surfaces (MS), and those with etched surfaces (ES). METHODS: Retrieved MS and ES were further divided into three subgroups according to the assigned recycling procedure: group A, air-water spray; group B, mechanical cleaning; and group C, mechanical and chemical cleaning. Unused screws were used as controls. Scanning electron microscopy, energy-dispersive X-ray spectrometry, insertion time and maximum insertion torque measurements in artificial bone, and biological responses in the form of periotest values (PTV), bone–implant contact ratio (BIC), and bone volume ratio (BV) were assessed. RESULTS: Morphological changes after recycling mainly occurred at the screw tip, and the cortical bone penetration success rate of recycled screws was lower than that of unused screws. Retrieved ES needed more thorough cleaning than retrieved MS to produce a surface composition similar to that of unused screws. There were no significant differences in PTV or BIC between recycled and unused screws, while the BV of the former was significantly lower than that of the latter (p < 0.05). CONCLUSIONS: These results indicate that reuse of recycled orthodontic miniscrews may not be feasible from the biomechanical aspect.
Microscopy, Electron, Scanning ; Recycling* ; Spectrum Analysis ; Torque

BACKGROUND: Although several hospital-based stroke studies were published, there has not been any reliable data representing the clinical characteristics of stroke in Korea. We analyzed the clinical characteristics of patients with ischemic stroke registered in the Korean Stroke Registry (KSR), which is the largest prospective hospital-based nation-wide stroke registry in Korea. METHODS: The KSR provided standardized protocols for collecting data, which includes the data of demographics, subtypes of stroke, risk factors, and neurological outcome at discharge. The brain imaging studies, including CT or MRI, were performed in all cases. RESULTS: KSR registered 10,811 patients of acute ischemic stroke between Nov. 2002 and Jun. 2004. The large-artery atherosclerosis was the most common subtype (37.3%), followed by small vessel occlusion (30.8%). Hypertension (65.4%) was the most common risk factor, followed by smoking (34.5%) and diabetes (28.3%). Although most of the hypertensive and diabetic patients had been diagnosed before the stroke, less than 45.4% and 32.5% of them were under regular control. The steno-occlusive lesion of extracranial carotid artery was only 29.3% and the ratio of intra- to extracranial artery disease was more than 2 in KSR. Only 20.5% of patients were admitted within 3 hours after stroke onset and 2.1% were treated with intravenous thrombolysis. In-hospital case-fatality was 5.2%, which is relatively comparable to those of previous studies. CONCLUSIONS: The KSR provided informative data in understanding the clinical characteristics of ischemic stroke in Korea. Further analysis of KSR will facilitate clinical trials and development of guidelines for the management of stroke patients.
Arteries ; Atherosclerosis ; Carotid Arteries ; Cerebrovascular Disorders ; Demography ; Epidemiology ; Humans ; Hypertension ; Korea ; Magnetic Resonance Imaging ; Neuroimaging ; Prospective Studies* ; Registries ; Risk Factors ; Smoke ; Smoking ; Stroke*

The authors would like to amend a reference (Lee et al., 2003) that was cited in "Cell culture" section of "Materials and Methods". Instead of "(Lee et al., 2003)", we would like to change the reference to "(Kim et al., 2003)". In "References", it also needs to include the following reference. Kim YY, Seol HW, Ahn HJ. Temporal expression of differentiation markers in embryoid bodies from various human embryonic stem cell line. International Society for Stem Cell Research 1st Annual Meeting, Washington, DC. U.S.A. June 8-11, 2003, Abstract No. 35. The authors apologize for any inconvenience.

Complete or partial triplication of human chromosome 21 results in Down syndrome (DS). To analyze differential gene expressions in amniotic fluid (AF) cells of DS, we used a DNA microarray system to analyze 102 genes, which included 24 genes on chromosome 21, 28 genes related to the function of brain and muscle, 36 genes related to apoptosis, 4 genes related to extracellular matrix, 8 genes related to other molecular function and 2 house-keeping genes. AF cells were collected from 12 pregnancies at 16-18 weeks of gestation in DS (n=6) and normal (n=6) subjects. Our DNA microarray experiments showed that the expressions of 11 genes were altered by at least 2-folds in DS, as follows. Ten genes, COL6A1, CASP5, AKT2, JUN, PYGM, BNIP1, OSF-2, PRSS7, COL3A1, and MBLL were down-regulated and GSTT1 was only up-regulated. The differential expressions of GSTT1 and COL3A1 were further confirmed by semi-quantitative RT-PCR for each sample. The gene dosage hypothesis on chromosome 21 may explain the neurological and other symptoms of DS. However, our results showed that only two genes (COL6A1 and PRSS7), among 24 genes on chromosome 21, were down-regulated in the AF cells of DS. Our data may provide the basis for a more systematic identification of biological markers of fetal DS, thus leading to an improved understanding of pathogenesis for fetal DS.
Amniocentesis ; Amniotic Fluid/*cytology/*metabolism ; Apoptosis ; Cells, Cultured ; Chromosomes, Human, Pair 21 ; Collagen Type III/biosynthesis ; DNA, Complementary/metabolism ; Down Syndrome/*genetics/metabolism ; Down-Regulation ; Gene Dosage ; Gene Expression ; *Gene Expression Regulation ; Glutathione Transferase/biosynthesis ; Humans ; Models, Genetic ; *Oligonucleotide Array Sequence Analysis ; Research Support, Non-U.S. Gov't ; Reverse Transcriptase Polymerase Chain Reaction ; Time Factors ; Up-Regulation

Human embryonic stem (hES) cells are capable of differentiating into pluralistic cell types, however, spontaneous differentiation generally gives rise to a limited number of specific differentiated cell types and a large degree of cell heterogeneity. In an effort to increase the efficiency of specified hES cell differentiation, we performed a series of transient transfection of hES cells with EGFP expression vectors driven by different promoter systems, including human cellular polypeptide chain elongation factor 1 alpha (hEF1alpha), human cytomegalo-virus, and chicken beta-actin. All these promoters were found to lead reporter gene expression in undifferentiated hES cells, but very few drug-selectable transfectants were obtained and failed to maintain stable expression of the transgene with either chemical or electroporation methods. In an attempt to increase transfection efficiency and obtain stable transgene expression, differentiated hES cells expressing both mesodermal and ectodermal markers were derived using a defined medium. Differentiated hES cells were electroporated with a hEF1alpha promoter-driven EGFP or human noggin expression vector. Using RT-PCR, immunocytochemistry and fluorescence microscopy, the differentiated hES cells transfected with foreign genes were confirmed to retain stable gene and protein expression during prolonged culture. These results may provide a new tool for introducing exogenous genes readily into hES cells, thereby facilitating more directed differentiation into specific and homogenous cell populations.
Actins/genetics ; Animals ; Bone Morphogenetic Proteins/genetics ; *Cell Differentiation ; Chickens ; Cytomegalovirus/genetics ; Drug Delivery Systems ; Embryo/*cytology ; *Gene Therapy ; Green Fluorescent Proteins/genetics/*metabolism ; Humans ; Immunoenzyme Techniques ; Microscopy, Fluorescence ; Peptide Elongation Factor 1/genetics ; Pluripotent Stem Cells/*cytology ; Promoter Regions (Genetics)/*genetics ; Research Support, Non-U.S. Gov't ; Reverse Transcriptase Polymerase Chain Reaction ; Transcription, Genetic/genetics