• Korean Journal of Agricultural Science
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• v.43 no.4
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• pp.656-664
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• 2016

Gear reducers are widely used for various agricultural machinery applications such as greenhouses, tractors, and agricultural vehicles. However, thermal deformation and surface pitting at gear tooth flank frequently occur in gear reducers due to high torque. Thus, surface heat treatment of gears is required to improve wear and fatigue resistance. The objective of this study was to simulate the load capacity of the agricultural gear reducer. The simulation was performed for the following three surface heat treatment methods: untreated gears, nitriding heat treatment, and induction hardening method, those mostly used for agricultural gear reducers. The load capacity of the gear reducer was simulated using the safety factor, limit bending stress, and limit contact stress of the gear. The simulation of the load capacity was conducted using KISSsoft commercial software for gear analysis. The main results of simulation test were as follows: first, the nitriding heat treatment resulted in the highest safety factor for bending stress, which was increased about 77% from those of the untreated gears. Second, the induction hardening was the highest safety factor for contact stress, which was increased about 150% from those of the untreated gears. The safety factor for contact stress of the induction hardening was increased about 64% from those of the nitriding heat treatment. The study result suggested that the surface heat treatments could enhance load capacity and that the method of surface heat treatment should be determined based on simulation results for appropriate use scenarios.

• Journal of Convergence Society for SMB
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• v.6 no.4
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• pp.107-114
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• 2016

The purpose of study was to obtain the data for development of oral health improvement programs for the high school students by investigation of oral health education experience. Excluding 19 inadequate answers, 279 questionnaire copies were analyzed. First, the analysis results is knowledge level of oral care, the students who smoking or drinking were found to be more than without experience groups (p=0.025). Second, in regard to the self perception of oral condition, the group with experience of proper tooth brushing techniques has statistically significant difference compared to the group without experience (p=0.000). And third, the question about oral health behavior was significantly higher than the group with no smoking experience. The importance of oral health care is closely related to oral health knowledge. It's necessary to provide oral health promotion program and smoking cessation programs in high school students.

• Biomedical Science Letters
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• v.23 no.2
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• pp.133-137
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• 2017

Periodontitis is the major causation of tooth loss in the elderly population. Multiple risk factors include oral microorganisms, smoking, metabolic syndrome, and genetic factors influence periodontitis development. In this study, we conducted a replication study of using previous Korean GWAS results by examining an independent population. The study population was recruited from Mir Dental Clinic, Daegu, Korea. In total, 93 samples were evaluated from July 2016 to January 2017. The sample groups include relatively older patients (>60 years) with no periodontitis (n = 31) and relatively younger patients (range 40~60 years) with severe periodontitis (n = 62). A total of seven markers which were previously reported to be associated with periodontitis were genotyped. Among the seven SNPs, rs16846206 and rs2392510 showed a significant association by logistic regression analysis and Chi square test, respectively. The former SNP showed significant association with severe periodontitis, whereas this study also showed same tendency in which individuals with the minor allele are significantly more frequent in cases than those in controls. The SNP is located on a coding gene (SLC9C2), where the alanine residue 505 is replaced by glycine (Ala505Gly). The later SNP was significant when differed between case and control groups, but there was no significance by logistic regression analysis when controlled for age and sex as covariant. Although the study population size examined in the current study was relatively smaller compared to previous studies, our results implicated that at least the two SNPs (rs16846206 and rs2392510) might be important candidates for the further genetic study.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.3
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• pp.305-310
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• 2017

Nowadays, the development of dental scanner and CAD/CAM technology can facilitate the fabrication of hybrid prosthesis. Double scanning technique, scanning a trial prosthesis and master model, made it possible to realize virtual design and simplify the laboratory work. Instead of using the metal or zirconia framework with composite, ceramic or denture tooth, the new high performance polymer Polyetherketoneketone (Pekkton, Cendres+$M{\acute{e}}taux$, Biel, Switzerland) as a framework with Polymethyl methacrylate (PMMA) veneering teeth (Visio-lign, Bredent, Senden, Germany) was used in this case. This case report showed an acceptable treatment outcome and satisfaction of patient using Pekkton and Visio-lign. However, long term clinical evaluation is needed.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.1
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• pp.70-76
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• 2000

Congenital biliary atresia with progressive sclerosis of the intra- and extra-hepatic duct system occurs in 1 : 10,000 live births, and has a poor prognosis with an expected survival of less than 5 years. Etiology of biliary atresia is unclear, however, it is believed a genetic or developmental cause. The clinical characteristics include pronounced jaundice, hepatosplenomegaly, pruritus, steatorrhea, xanthomas, growth retardation, portal hypertension, bleedings, ascites and respiratory infections. Oral manifestations have seldom been reported in patients with biliary atresia, but there may be enamel hypoplasia, delayed tooth eruption, and green teeth. Early diagnosis and surgical intervention have decreased morbidity. returned growth and development to normal and improved the prognosis for survival. Authors report the clinical and radiologic characteristics, proper managements about two cases with biliary atresia.

• Journal of the korean academy of Pediatric Dentistry
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• v.42 no.1
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• pp.62-68
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• 2015

Supernumerary teeth (SNTs) refer to extra teeth over normal numbers. SNTs can influence adjacent teeth and structure. Therefore, it is important to find SNTs before they cause problems and to decide when to extract them. Etiology of SNTs has not exactly been found, but it has been proposed that genetic and environmental factors are associated. SNT appears as a single unit in most cases and multiple SNTs usually occur as a part of a syndrome. Non-syndromic multiple SNTs are rarely seen. This report is to document the occurrence of multiple supernumerary premolars in a father and his three sons. Heritage is an important factor in SNT development so familial history is important for early detection of SNT.

• Journal of the Korea Convergence Society
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• v.2 no.4
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• pp.47-52
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• 2011

Periodontal disease is a common inflammatory disorder that is being considered as a risk factor for atherosclerotic complication. Recent epidemiological evidence also supports that its potential association with increased blood pressure levels and hypertensive prevalence. Data from cross-sectional studies suggest that in hypertensive patients periodontal disease may enhance the risk and degree of target organ damage. So dental infections have been associated with cardiovascular diseases. There are potential pathophysiologic links between hypertension and periodontits. The role of the inflammatory pathway include C-reactive protein(CRP). CRP is an inflammatory mediator that has been shown to predict the development of hypertension independently of baseline BP and traditional risk factors, has been consistently reported as at least mildly elevated in patients with periodontal disease. Reactive oxygen species produced by locally infiltrating neutrophils participate in periodontal tissue destruction. Periodontits can lead to inflammatory responses in the atrial myocardium, which disturbs the structural and electrophysiologic properties of the atrium and facilitates atrial fibrillation in the animal experiment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.8
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• pp.3850-3857
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• 2013

This study aims to examine the effect of the program by identifying changes in oral health behaviors, oral health knowledge, the Patient Hygiene Performance(PHP) index and others after performing oral health promotion program on children in community children's centers to develop persistent and more effective program. The final analysis subjects were 27 children. According to the examination results of dental plaque score, the PHP index score was reduced from 3.42 to 2.43 before and six month after the tooth brushing education, respectively, indicating the effect of oral health promotion program(p<0.001). The data of this paper can be used oral health promotion programs development based on the social ecological model.

• The Journal of the Korea Contents Association
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• v.14 no.3
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• pp.259-268
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• 2014

The purpose of this study is to investigate correlation between experience of visiting the dentist and oral symptoms with 10,701 high school seniors in the research data of the 8th juvenile online health behavior carried out in 2012. The results of this research showed that the lower academic grades, the more tooth crack they experienced, and the lower economic conditions, the more toothache they tended to experience. The main reasons they visited the dentist were because their teeth ached, tingled or throbbed with pain. Scores of oral symptoms, sex, economic conditions and the number of experience of visiting the dentist were found to have a significant correlation. In order to improve high school students' dental health continually, we need to install the school dental health room and need to systemize continuous dental health care system for high school students, along with development of various school dental health education programs, by vitalizing prevention based school dental health education.

• The korean journal of orthodontics
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• v.17 no.1
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• pp.135-148
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• 1987

To investigate the relationship between craniofacial growth and bone maturity of the hand wrist in normal occlusion, the author took cephalogram and handwrist radiogram of 391 students (male 192, female 199) and assessed the measurements of cephalogram according to skeletal maturity stages of the hand and wrist. In this study, four skeketal stages and 36 linear, angular measurements of the cephalometrics were selected. In hand-wrist X-ray the bones used to determine skeletal maturity were the middle phalanges of the third finger, and distal epiphysis of the radius. In cephalogram, the landmark used to measure the angle and length were N, S, Po., Ar., Go., Me., Gn., Pog., Point B, Point A, ANS, PNS, Or., U1, L1, U6, L6 etc.. The results were as follows, 1. The table of mean, standard deviation, p-value from measurements were made in each group and both sex. 2. The increased measurements according to skeletal maturity were anterior cranial bese length, posterior cranial base length, ramus height, anterior facial height, posterior facial height, L1 to mandibular plane (mm), facial plane angle. In contrast to, decreased measurements were genial angle, facial cnvexity and facial plane angle. 3. Denture pattern measurements (IMPA, FMIA, occlusal plane to Go-Gn, interincisal angle, U1 to SN plane, U1 to SN plane, U1 to facial plane, L1 to facial plane etc.) .had nothing to do with skeletal maturity. 4. Skeletal maturity had close relationship with craniofacial growth, but had little to do with tooth development.