OBJECTIVE: The aim of this study was to determine the relationship between the status of a unilateral palatally impacted maxillary canine (as seen on the panoramic radiograph) and the orthodontic treatment duration. METHODS: A total of 36 subjects were chosen (8 males and 28 females, 13.7 +/- 2.5 years). All patients had undergone orthodontic traction of the impacted canine after a closed flap surgery. The position of impacted canine on the panoramic radiograph was traced and calculated with regard to the treatment duration. RESULTS: The canine overlap over the lateral incisor (COGr) had significant statistical difference between the short-term and the long-term treatment duration groups (divided by average treatment time of 21 months) (p < 0.05). Multiple regression indicated that the variables of significance (with treatment duration as the dependent variable) were the canine vertical height from the occlusal plane (HCV, r(2) = 0.115; p < 0.05) and the mandibular anterior width (MnDW, r(2) = 0.142; p < 0.05). The treatment duration, the canine angle to the incisor midline (CA), and HCV decreased from primary dentition (under 12 yrs) to permanent dentition (15 yrs). Howerer, these increased again at the adolescent ages (over 16 yrs). CONCLUSION: These findings suggested that orthodontic treatment of a palatally impacted canine would show good prognosis at an age of early permanent dentition with the canine showing smaller CA and HCV.
Adolescent ; Dental Occlusion ; Dentition, Permanent ; Female ; Humans ; Incisor ; Male ; Prognosis ; Tooth, Deciduous ; Traction

OBJECTIVE: This study aimed to examine whether educational stressors and relational stressors are associated with burnout in medical students and to test social support as a moderator between stressors and burnout. METHODS: A total of 263 medical students attending Gyeongsang National University composed the study sample. A standardized questionnaire was used to investigate educational and relational stressors, three dimensions of burnout, and social support of medical students. RESULTS: The findings showed that overall burnout is very high among Korean medical students, with 9.9% totally burned out. Educational and relational stressors were significantly associated with the risk of burnout in medical students after controlling for socio-demographics and health behaviors. Social support moderated educational and relational stressors on personal accomplishment, but did not moderate stressors on emotional exhaustion and depersonalization. CONCLUSION: Burnout level is substantially high among Korean medical students. Educational and relational stressors are significantly associated with burnout risk in Korean medical students. Social support had moderated educational and relational stressors on personal accomplishment. The results suggest that more social support for medical students is needed to buffer stressors on and burnout.
Burns ; Depersonalization ; Health Behavior ; Humans ; Students, Medical*

PURPOSE: The purpose of this study was to establish optimal imaging acquisition conditions for the GE Advance(TM) PET imaging system by performing the acceptance tests designed by National Electrical Manufacturers Association (NEMA) protocol and General Electric Medical Systems (GEMS) test procedures. MATERIALS AND METHODS: Performance tests were carried out with 18FDG radioactivity source and phantoms by using a standard acquisition mode. Transaxial resolution and scatter fraction tests were performed with a line source and axial resolution with a point source, respectively. A cylindrical phantom made of polymethylmethacrylate (PMMA) was used to measure sensitivity, count rate losses and randoms, uniformity correction, and attenuation inserts were added to measure remaining tests. The test results were acquired in a diagnostic acquisition mode and analyzed mainly on high sensitivity mode. RESULTS: Transaxial resolution and axial resolution were measured as average of 4.65 mm and 3.98 mm at 0 cm, and 6.02 mm and 6.71 mm at 20 cm on high sensitivity mode, respectively. Average scatter fraction was 9.87%, and sensitivity was 225.8 kcps/micronCi/cc of trues. Activity at 50% deadtime was 4.6 Ci/cc, and the error of count rate correction at that activity was from 1.49% to 3.83%. Average nonuniformity for total slice was 8.37%. The accuracy of scatter correction was -0.95%. The accuracies of attenuation correction were 5.68% for air, 0.04% for water and -6.51% for polytetrafluoroethylene (PTFE). CONCLUSION: The results satisfied most acceptance criteria, indicating that the GE AdvanceTM PET system can be optimally used for clinical applications.
Electrons* ; Fluorodeoxyglucose F18 ; Polymethyl Methacrylate ; Polytetrafluoroethylene ; Positron-Emission Tomography* ; Radioactivity ; Water

PURPOSE: Abutted scatter energy windows used for a triple energy window (TEW) method may provide wrong estimation of scatter. This study is to propose an extended TEW (ETEW) method, which doesn't require abutted scatter energy windows and overcomes the shortcomings of TEW method. MATERIALS AND METHODS: The ETEW is a modification of the TEW which corrects for scatter by using abutted scatter rejection windows, which can overestimate or underestimate scatter. The ETEW is compared to the TEW using Monte Carlo simulated data for point sources as well as hot and cold spheres in a cylindrical water phantom. Various main energy window widths (10 %, 15 % and 20 %) were simulated. Both TEW and ETEW improved image contrast, % recovery coefficients and normalized standard deviation. RESULTS: Both of TEW and ETEW improved image contrast and % recovery coefficients. Estimated scatter components by the TEW were not proportional to the true scatter components over the main energy windows when ones of 10 %, 15 %, and 20 % were simulated. The ETEW linearly estimated scatter components over the width of the main energy windows. CONCLUSION: We extended the TEW method into the method which could linearly estimate scatter components over the main energy windows.
Tomography, Emission-Computed, Single-Photon* ; Water

OBJECTIVES: This study sought to evaluate trabecular changes in the mandible using fractal analysis and to explain the transient osteopenia related to rapid orthodontic tooth movement after orthognathic surgery. MATERIALS AND METHODS: Panoramic radiographs were taken of 26 patients who underwent bilateral sagittal split ramus osteotomy. Radiographs taken before the surgery and 1 month after surgery were overlapped, and 40x40 pixel square regions of interest were selected near the mandibular canines and 1st molars. After the image processing procedure, the fractal dimension was calculated using the box-counting method. RESULTS: Fractal dimension after orthognathic surgery decreased in a statistically significant manner (P<0.05). The change in fractal dimension on the canine side had greater statistical significance as compared to that seen on the 1st molar side. CONCLUSION: This study found that bone density decreases after orthognathic surgery due to transient osteopenia related to the regional acceleratory phenomenon. This result can provide a guide to evaluating orthodontic tooth movement after orthognathic surgery.
Bone Density ; Bone Diseases, Metabolic ; Fractals ; Humans ; Mandible ; Molar ; Orthognathic Surgery ; Osteotomy, Sagittal Split Ramus ; Tooth Movement

Genome-wide association studies (GWASs) facilitated the discovery of countless disease-associated variants. However, GWASs have mostly been conducted in European ancestry samples. Recent studies have reported that these European-based association results may reduce disease prediction accuracy when applied in non-Europeans. Therefore, previously reported variants should be validated in non-European populations to establish reliable scientific evidence for precision medicine. In this study, we validated known associations with type 2 diabetes (T2D) and related metabolic traits in 125,850 samples from a Korean population genotyped by the Korea Biobank Array (KBA). At the end of December 2020, there were 8,823 variants associated with glycemic traits, lipids, liver enzymes, and T2D in the GWAS catalog. Considering the availability of imputed datasets in the KBA genome data, publicly available East-Asian T2D summary statistics, and the linkage disequilibrium among the variants (r2 < 0.2), 2,900 independent variants were selected for further analysis. Among these, 1,837 variants (63.3%) were statistically significant (p < 0.05). Most of the non-replicated variants (n = 1,063) showed insufficient statistical power and decreased minor allele frequencies compared with the replicated variants. Moreover, known variants showed <10% genetic heritability. These results could provide valuable scientific evidence for future study designs, the current power of GWASs, and future applications in precision medicine in the Korean population.

OBJECTIVE: The purpose of this study was to evaluate the correlation between menton deviation and dental compensation in facial asymmetry. METHODS: Tooth axis and distance of first molar and canine to the reference plane were investigated by cone-beam computerized tomography. The subjects consisted of 50 patients with asymmetric mandibles (male 21, female 29, mean age 24.3 years). Control groups were also assessed (male 11, female 9, mean age 25.6 years). Nine measurements (5 linear measurements and 4 angular measurements) were measured in order to evaluate the correlation between menton deviation and the linear and angular difference of first molar and canine in the deviated and none-deviated sides using the defined MPR images. The differences between deviated and non-deviated side, according to menton deviation, were statistically analyzed using stepwise multiple regression analysis. RESULTS: From the result, Menton deviation was negatively correlated with mandibular first molar's angular measurement (Delta Angle LM6-Mn plane (dev.-ndev.)) and positively with maxillary fist molar's angular measurement (Delta Angle UM6-FH plane (dev.-ndev.)) (p<0.01). Two angular measurements (Delta Angle LM6-Mn plane (dev.-ndev.), Delta Angle UM6-FH plane (dev.-ndev.)) explained the variability in menton deviation with a significant r2 value of 0.589. CONCLUSIONS: This study suggests that the tooth axis of upper and lower first molars leans towards the deviated side of Menton when there is mandibular asymmetry with Menton deviation.
Axis, Cervical Vertebra ; Compensation and Redress ; Cone-Beam Computed Tomography ; Dental Occlusion ; Facial Asymmetry ; Female ; Humans ; Mandible ; Molar ; Tooth

OBJECTIVES: The relationship of depressive symptoms to lower extremity function and balance, especially in older adults without a depression diagnosis, remains unclear. Therefore, our study analyzed this relationship using a large sample of Korean older adults. METHODS: We used data from the Korean National Health Insurance Service’s Health Screening Program database. Individuals aged 66 years who had undergone the National Screening Program for Transitional Ages in Korea and were without a diagnosis of depressive disorder were included. The lower extremity function and balance were evaluated using 2 physical tests, while depressive symptoms were assessed using a 3-question survey. Multivariable-adjusted logistic regression analysis was used to examine the association between depressive symptoms and lower extremity function and balance. RESULTS: Among 66,041 individuals, those with depressive symptoms showed significantly higher rates of abnormal lower extremity function and abnormal balance. The adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for the association of depressive symptoms to abnormal lower extremity function and abnormal balance were (aOR, 1.34; 95% CI, 1.25 to 1.44) and (aOR, 1.38; 95% CI, 1.29 to 1.48), respectively. Assessment of the relationship based on depressive symptom scores revealed that higher scores were associated with higher aORs (p for trend <0.001). Subgroup analyses further confirmed this relationship, especially among patients with cerebrovascular disease or dementia. CONCLUSIONS This study revealed an association between depressive symptoms and the abnormal lower extremity function and balance of 66-year-old individuals without a diagnosis of depressive disorder.

PURPOSE: Women with dense breast are known to be at high risk for breast cancer, but their prevalence and number of Korean women are unknown. The current study was to investigate the distribution of mammographic breast density by age of women undergoing screening mammography, and to estimate the prevalence of Korean women with dense breasts, quantitatively. MATERIALS AND METHODS: For obtaining a nationwide representative sample, 6,481 mammograms were collected from 86 screening units participated in the National Cancer Screening Program for breast cancer. Based on the American College of Radiology Breast Imaging Reporting and Data System classification, breast density was evaluated by six breast radiologists, qualitatively. We applied these breast density distributions to age-specific counts of the Korean women population derived to mid-year 2017 to estimate the number of Korean women with dense breasts. RESULTS: Overall, 54.4% (95% confidence interval [CI], 52.9% to 55.8%) of women 40 to 69 years of age had heterogeneously or extremely dense breasts, and this proportion was inversely associated with age. Based on the age distribution of Korean women, we estimated that 6,083,000 women (95% CI, 5,919,600 to 6,245,600) age 40-69 years in Korean have dense breasts. Women aged 40-49 years (n=3,450,000) accounted for 56.7% of this group. CONCLUSION: More than half of Korean women aged 40 and over have dense breasts. To prevent breast cancer effectively and efficiently, it is necessary to develop a new personalized prevention strategy considering her status of breast density.
Age Distribution ; Breast Neoplasms ; Breast ; Classification ; Cross-Sectional Studies ; Early Detection of Cancer ; Female ; Humans ; Information Systems ; Korea ; Mammography ; Mass Screening ; Prevalence

Central pontine myelinolysis (CPM) by complicating rapid correction of severe hyponatremia has been widely reported. Additionally, CPM was occasionally reported among patients with post-liver transplantation, burns, chronic renal failure with dialysis, or other diseases associated with or not associated with other electrolyte changes or hyperosmolarity. However, there have been a few reports of CPM occurring in diabetic patients without documented electrolyte changes. This report is, to the best of our knowledge, the first report of CPM in type 2 diabetic patients without electrolyte changes in Korea. A 40-year-old man with type 2 diabetes mellitus with abruptly developed dysarthria and ataxia was admitted to our facility. He suffered from poor glucose control and multiple diabetic complications. Brain magnetic resonance imaging (MRI) revealed a well-defined bilateral symmetric hyperintense lesion in the central portion of the pons on T2- and diffusion-weighted images, which was consistent with CPM. After the patient's blood glucose and blood pressure normalized, his dysarthria and ataxia improved. Six months after discharge, follow-up MRI showed a persistent, but greatly reduced symmetric lesion in the central pons. It is certainly possible for CPM to be overlooked clinically in diabetic patients, but more cases could be diagnosed if careful attention was paid to this syndrome.
Adult ; Ataxia ; Blood Glucose ; Blood Pressure ; Brain ; Burns ; Diabetes Complications ; Diabetes Mellitus, Type 2 ; Dialysis ; Dysarthria ; Follow-Up Studies ; Glucose ; Humans ; Hyponatremia ; Kidney Failure, Chronic ; Korea ; Magnetic Resonance Imaging ; Myelinolysis, Central Pontine ; Pons ; Transplants