• Journal of the Korean Society of Radiology
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• v.10 no.5
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• pp.291-298
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• 2016

Recently, the interest in the orthodontic treatment for children is increased by a rise in national income level. The number of cephalometric radiography that could diagnose a malocclusion and malposition between teeth and jawbone increased. It required attention to radiation exposure, because the subject of dental examination is children which are more sensitive to radiation and the head and neck, the object of that include radiation sensitive organ such as the thyroid, bone marrow, eyes, salivary gland, and so on. In this study, we measured two-dimensional dose distribution in cephalometric radiography system (VATEC Pax-400C) using Agfa CP-G Plus film and MagicMax Dosimeter, and calculated radiation organ dose of head and neck through MCNPX simulation. And then we designed a radiation protective device to decrease radiation dose. The dose distribution of the cephalometric radiography system irradiated the head and neck overall as well as the oral and maxillofacial parts. The radiation organ dose calculated that thyroid, oesophagus and eyes are irradiated high, and the radiation organ dose decreased about 70 ~ 80% by the application of the radiation protective device. The results of this study will be used construction of database for dental radiation exposure and research of reducing radiation dose.

• The korean journal of orthodontics
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• v.27 no.5 s.64
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• pp.761-770
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• 1997

71 Class I malocclusion samples were selected and they were divided into premolar-extraction and non-extraction groups. Vertical and horizontal cephalometric evaluations on dental and soft tissue measurements were done before and after treatment. Also, treatment results in adolescent patients and adult patients were compared. The following conclusions were obtained: 1. In comparison of extraction and non-extraction groups, all the dental and soft tissue measurements, with exception of SN-MP angle, upper lip to E-line, vertical movement of upper first molar, md horizontal movement of lower first molar, showed statistically significant differences. 2. In comparison of extraction and non-extraction groups of adolescent samples, there were statistically significant differences in upper and lower incisor inclinations, horizontal dental movements from vertical reference line, positional changes in upper and lower lips, and mesial movements of upper first molar. 3. In comparison of extraction and non-extraction groups of adult samples, there were statistically significant differences in upper and lower incisor inclinations, horizontal dental movements from vertical reference line, positional changes in upper and lower lips from I-line and vertical reference line, vertical height of upper first molar, and mesial movement of lower first molar. 4. There was no statistically significant difference in SN-MP angle between extraction and non-extraction groups of both adolescent and adult samples.

• Journal of Oral Medicine and Pain
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• v.38 no.3
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• pp.267-274
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• 2013

This study was performed to investigate the skeletal factors related to open lock of the temporomandibular joint(TMJ). We compared the skeletal measurements on the cephalogram and transcranial radiograph among 3 groups, open lock group consisting of consecutively filed 50 patients with at least one open lock episode within recent 1 year, temporomandibular disorder(TMD) group of 50 TMD patients without open lock diagnosed by Research Diagnostic Criteria for TMD (RDC/TMD) Axis I, and normal group of 50 patients without TMD or open lock. The patients of TMD and normal group were randomly selected in an age-and-gender-matched way with ones of open lock group. Open lock group showed smaller saddle angle than normal group on cephalograms and steeper inclination of the articular eminence than TMD and normal groups on transcranial radiographs. These results imply that the patients with the joint located more anterior and the articular eminence with steeper inclination might be riskier to TMJ open lock.

• Journal of Yeungnam Medical Science
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• v.5 no.2
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• pp.71-77
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• 1988

This study was made to investigate the influence of mouth breathing to tongue, mandible and hyoid bone position. It has been clinically suggested that the mouth breathing is induced by the respiratory dysfunction of nasopharyngeal airway causing by the Adenoids. The author used the 50 children, who were the nasal breathes with normal occlusion as the control group, and 50 children, who were mouth breathers with Adenoid as the experimental group. Results were as following: 1. In experimental group, the tongue was positioned more anterior and lower than that of the normal children. 2. In experimental group, the mandible was positioned more lower than that of the normal children. 3. In experimental group, the hyoid bone was positioned more anterior and lower than that of the normal children.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.1
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• pp.109-118
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• 2005

In the field of pediatric dentistry, comparison and analysis of cephalogram values of children are important fir evaluation of growth and development, and are essential to evaluate the craniofacial form and growth pattern for early diagnosis of malocclusion. For this, cephalographic norm values are important, but not many studies on the primary dentition exist. To compare the past norm values of normal occlusion in the primary dentition with current norms, preschool children, 4 to 5 years of age, with normal occlusion in the primary dentition who visited our hospital were examined. Among these children, 46 children with normal facial form and developmental status were chosen for evaluation of cephalogram values. The following results were as follows: 1. For skeletal values, the angular values showed no significant differences between males and females, and the linear values were generally greater in males than females. 2. SNA was $81.3^{\circ}$, SNB was $76.6^{\circ}$ and ANB difference was $4.7^{\circ}$. 3. The ratio for Mandibular body length to Anterior cranial base length was 0.9 : 1 for both male and female and the ratio for posterior facial height to anterior facial height was 61.4 % for male, 62.0 % for female. 4. For dental values, IMPA was $84.2^{\circ}$ and UA to SN was $90.8^{\circ}$. 5. The upper lip to Ricketts esthetic line was positioned 2.6 mm anteriorly, and the lower lip to Ricketts esthetic line was positioned 2.5 mm anteriorly.

• Korean Journal of Construction Engineering and Management
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• v.19 no.2
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• pp.117-125
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• 2018

The primary objectives of this study are to develop a detail design of automated PHC pile head cutting machine and structural stability analysis of detail design that improves the conventional head cutting work in safety, quality, and productivity. For this, the following research works are conducted sequentially; 1)literature review and field study, 2)expert survey and interview, 3)selection of core technology using AHP analysis, 4)deduction of detail design 5) verification of structural stability. As an outcome, it is analyzed that gripper and gripper bearing shaft are structurally stable. Their maximum stresses are shown as 15.93%, 10.58% compared to their yield strength respectively. The results of detail design and structural stability analysis in this study will be utilized for the actual development of the automated PHC pile cutting machine prototype.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.1
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• pp.65-74
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• 2018

The aim of this study was to obtain the traceability of the software used to analyze lateral cephalometry and to calculate the uncertainty of the measurements. Furthermore, this study aimed to provide a basis for obtaining standard references for measurement values for orthodontic treatment in children. Cephalometric data were collected from 100 children diagnosed with class I malocclusion between the ages 6 to 13 years who visited the pediatric dentist at Seoul National University Dental Hospital. To ensure traceability, a phantom device was created. Correction values were calculated by measuring the length and angle of the phantom device using the software. Type A uncertainty was calculated by obtaining the standard deviation of cephalometric measurements of 100 persons and the standard error of repeated measurements. Determination of the type B uncertainty was induced by minimum resolution and the position of the head. Using these, the combined standard uncertainty was obtained and the expanded uncertainty was calculated. The results of this study confirm that the currently used software has high accuracy and reliability. Furthermore, the uncertainty of orthodontic measurements in Korean children aged 6 to 13 years was calculated, and distribution range for class I malocclusion with 95% confidence interval was suggested.

• The korean journal of orthodontics
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• v.30 no.1 s.78
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• pp.53-66
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• 2000

This study was performed to find out the effect of projection errors on cephalometric linear and angular measurements according to head rotation during taking lateral cephalometric radiographs. Seventeen skulls with permanent dentition and no gross asymmetry were obtained from the Department of Anatomy, Medical School, Chosun University. Total 527 x-ray films were taken with $1^{\circ}$ interval from the reference position($0^{\circ}$) to ${\pm}15^{\circ}$ around the vertical axis (Z axis) which is perpendicular to the midpoint of the line connecting the center of two ear rods in submento-vertex direction. Statistical analysis was performed by paired t-test if there were statistically significant differences between the mean of the reference position($0^{\circ}$) and that of each rotation angle. The following results were obtained. 1. The projection errors of angular measurements were smaller than those of linear measurements. 2. The projection errors of angular measurements including midline landmarks were smaller than those including bilateral landmarks. 3. The horizontal linear measurements were gradually decreased when the stroll was rotated toward the film, but slightly increased and then decreased when the skull was rotated toward the focal spot. However, the changes were smaller in focal direction. 4. The projection errors of horizontal linear measurements were larger than those of vertical linear measurements. 5. The projection errors of vertical linear measurements were increased with increased distance from the rotation axis to vertical measurements. It is concluded that the use of angular measurements rather than linear measurements is recommended to minimize the projection errors.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.1
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• pp.73-81
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• 1991

The purpose of this study was to analyze the position of mandibular condyle on the submentovertex radiograph, thereafter to evaluate the usefulness of submentovertex radiograph in diagnosis of temporomandibular joint dysfunction, and to check the best method of tomographic techniques. Submentovertex radiographs which were taken in 75 temporomandibular joint dysfunction patients and 75 normal persons were used as the sample for this study. The obtained results were as follows: The submentovertex radiograph was a improper method in diagnosis of temporomandibular joint dysfunction and discrimination of affected side. The selective tomography was a better method than any other tomographic techniques in diagnosis of temporomandibular joint dysfunction.

• Applied Microscopy
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• v.34 no.3
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• pp.179-184
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• 2004

Normal and abnormal morphology of the epididymal spermatozoa in the big white-toothed shrew, Crocidura lasiura were studied with the light and electron microscopy. Normal spematozoa were observed with a few abnormal spermatozoa. This indicates that abnormal morphology is no absolute indicator of infertility. However, the existence of the abnormal spermatozoa is related to infertility. Especially abnormal morphology of the sperm head is definitely associated with infertility. The following types of abnormal head morphology of the epididymal spermatozoa in the wild healthy adults of the C. lasiura were described: 1) Nucleus with lack of condensation of the nucleoplasm 2) Destructed acrosome 3) Folded acrosome and plasma membrane 4) Separation of the acrosome from the nucleus 5) Acrosome with irregular condensation 6) Wrongly located granules of the apical body.