• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.2
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• pp.61-68
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• 2004

Electric stimulation of teeth has been used for assessing pulp vitality. The principle is based upon the assumption that a subject feels the pain produced by electrical current stimulation of intradental nerve. Because of very high and wide range of impedance of the enamel, it is very difficult to determine stimulation levels regardless of teeth status. Most pulp testers adopt voltage stimulation method and thus, their stimulating threshold levels significantly depend on each individual. Therefore, a constant current stimulator is necessary to minimize the effect of wide variation due to different enamel thickness. And it is also necessary to test teeth vitality with a wide current range regardless of tooth impedance. In this study, we constructed a burst-wave type pulp tester to reduce the pain using a current stabilizing circuit with the maximum current of 150 uA.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.2
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• pp.345-350
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• 2008

In children with Class III malocclusion, it is important to identify whether the etiology is functional, dental, skeletal. FR-III developed by Rolf Frankel in 1970, has been used during deciduous, mixed, and early permanent dentition to correct class III malocclusion characterized by maxillary skeletal retrusion. According Frankel, the vestibular shields and upper labial pads act to counteract the forces of the surrounding musculature that restrict forward maxillary development and cause a retrusion in maxillary tooth position. This can achieve favorable developments with the basal bone, teeth and alveolar bone. We report FR-III that can be applicated in cases of early mixed dentition with mild maxillary deficiency and deepbite before the eruption of permanent maxillary incisor.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.3
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• pp.203-208
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• 2013

Although the first case of supernumerary teeth had been documented almost 20 centuries ago, the etiology of supernumerary teeth still remains unclear. The prevalence of supernumerary teeth in the general Asian population is between 2.7% and 3.4%. The pathogenesis of supernumerary teeth has been attributed to phylogenetic reversion(atavism), splitting of the tooth bud(dichotomy theory), locally induced hyperactivity of the dental lamina and a combination of genetic and environmental factors(unified etiologic explanation). This report describes 3 cases of monozygotic twins with mesiodens who visited the pediatric dental clinic of Kyungpook national university hospital, and this is significant to support genetic factors involoved in the development of supernumerary teeth.

• Journal of Korean society of Dental Hygiene
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• v.16 no.6
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• pp.931-941
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• 2016

Objectives: The purpose of this study was to examine the association between depression and poor oral health in Korean elderly using Korean version of the Patient Health Questionnaire-9 (PHQ-9) for assessment of depressive symptoms. Methods: This study used the data from Korean National Health and Nutrition Examination Survey (KNHANES VI-2). The study included 1,454 elderly Korean aged over 65. Variables included demographic characteristics (gender, age), socioeconomic factor (income, education), systemic diseases, oral health related factor (tooth brush, dental products), health related factor (alcohol drinking, smoking), and depression. Logistic regression analysis was used as sequential models. Effects were quantified as odds ratios (OR) and 95% confidence intervals (CI). Results: From frequency analysis, being female, primary school or less, non-alcohol drinking, poor oral health were significantly related to depression. In the multiple logistic regression model, depression was significantly associated with poor oral health (OR=1.96, CI=1.15-3.53) after adjustment for other covariates including demographic characteristics, socioeconomic factor, systemic diseases, oral health related factor, and health related factor (OR=1.91, CI=1.13-3.27). Conclusions: Depression had an influence on the poor oral health after adjustment as confounding variable in the elderly. It should be focused on the health promotion for the elderly vulnerable to depression and poor oral health. The development of the mental health and oral health should be established.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.112-119
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• 1993

A strength and durability estimation system of involute cylindrical gears which are commonly used as power transmission devices is developed on the personal computer, which analyzed and/or evaluates the gear design and the service performance at the point of view of strength and durability. The typical considerations are the bending strength and the sunface durability, and the strength and durability estimations are carried out using the reliable standards of AGMA&ISO. In addition, the finite element analysis (FEM) of tooth bending stress is conducted in order to compare the real maximum stress with the estimaed bending stress by the standard. Therefore, the system is built so that the variables or factors considered differently in those standards and the strength & durability are appraised seperately by each method, and a series of the estimation processes is integrated into the system can be used in the initial design at the view point of strength and durability. And it is useful to the purpose of the trouble-shooting of gear system and the purpose of introducing the methods for maintaining design strength in service, with appraising the strength and durability after design or with appraising the influencing factors, as a whole. Therefore, this strength and durability estimation system can help the aim of automatic design of cylindrical gears.

• International Journal of Industrial Entomology and Biomaterials
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• v.22 no.1
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• pp.17-20
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• 2011

The average life expectancy has continuously increased with the development of medical industry. As women get older, they experience the deficit of estrogen caused by decreased function of ovarian. Specifically, they suffer from temporary fever because of unstable vasomotion and, in the long term experience, degeneration of urogenital organs, tooth loss, arteriosclerosis, demantia, snores and so on. Because of these symptoms the estrogen medical supply is getting required. Along with this, many studies have conducted to find out substitutional medicals without any side effects. This research was carried out to find out such substitutable materials. For the purpose of study, we examined the change of estrogen using the rats fed with the pupa powder immediately before the eclosion, eclosed adult, the pupa extract immediately before the eclosion, and the silkworm powder prepared at $3^{rd}$ day of $5^{th}$ instar. The result showed no significant chance in weight, feeding and water intake quantity among variables. However, the estrogen hormone secretion effects was very high at 73 pg/ml in the rats fed with the freeze-dried powder of the Yeonnokjam male pupa prepared immediately before the eclosion, compared with the control at 59 pg/ml. The next was Yangwonjam male adult at 71 pg/ml.

• Transactions of Materials Processing
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• v.17 no.2
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• pp.124-129
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• 2008

Net shape forging technologies give many effects into the costs and qualities for the finished products. So, the studies to reduce the additional machining amount are very important in forging industry. Specially, there are two main topics in cold forging industry, such as, tool life and precision forging. In this study, new forging technique was proposed to eliminate the machining process for fixing up the length and improve the lead accuracy of gear. The luck-up hub is manufactured through many processes, such as upsetting, piercing and direct extrusion. The gear is formed in direct extrusion process; however, lead accuracy of the gear is over allowance limit. Therefore, the additional sizing process must be added. In this study, process design for closed-die forging of a lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• Journal of Korean society of Dental Hygiene
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• v.12 no.1
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• pp.103-111
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• 2012

Objectives : The purpose of this study was to survey the recognition of college-preparatory students who interested and prevented themselves in oral health diseases for dental hygienist in Yeungnam South Korea. Methods : The subjects in this study were 328 students who was seriously worried for career and entrance into a school. The survey period was from August 16th 2011 to November 26th 2011, and the data was collected from the high school students in Yeungnam and the preparatory students who visited S college in Gyeongju. This study was conducted by using the self-reported questionnaire. Results : The result of this study are as follows. 87.2% of the subjects have recognized about the name of dental hygienist, 51.5% have distinguished dental hygienist in the clinic, and 67.4% have recognized about education of dental hygienist that was more than a college graduate. The received services from dental hygienist was scalling(15.6%), assistant of treatment(14.7%), tooth brushing instrument(11.5%), Reception & receipt(11.0%), and etc. The majority of the subjects have recognized that dental hygienist was the professional(4.82 points), the important role in oral health(4.88 points), and the intermediary between patients and dentists(4.60 points). And they were friendly(4.64 points), responsible(4.81 points), and worthwhile job(5.01 points). However their appellation has not been established yet(4.00 points), they was difficult to distinguish from nursing assistants(4.37 points), and their task did not differs from AN(4.53 points). Also they compared to other job was not stressful job(3.58 points). Conclusions : Refer to these results, those will be the basis for professional development and status establish of clinical dental hygienists and for the upright role as a professional medical personnel of dental hygiene students. In addition, those will help to patients in the future, and become an effective instrument to learn knowledge, skill, and service that needed to conduct business.

• Journal of Korean society of Dental Hygiene
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• v.12 no.4
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• pp.801-815
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• 2012

Objectives : To obtain necessary fundamental data for the development of oral health improvement programs for senior citizens in the manner of investigating the Status of their oral health. Methods : Data were collected from 346 senior citizens aged 65 years or older who had lived in Seoul and Gyeonggido province, Republic of Korea. This study was conducted for 3 months from April 2011 to June 2011. Excluding those obtained from 34 respondents who gave inadequate responses to given questions, the data from 312 respondents were analyzed. Results : 1. The number of senior citizens who chose 'Sometimes' to as an answer to the question about the self-perception of their own oral conditions such as mastication, swallowing, gingiva hemorrhage, dry mouth, and/or oral malodor was the largest. As an answer to the question about the presence of interpersonal avoidance, 'No' accounted for the largest proportion. The number of respondents choosing gingiva treatment regarding the perception of the necessity for medical interventions was the largest. 2. In regard to the knowledge of oral health care, the percentage of correct answers was the highest for 'I brush my tooth before each meal' ($0.69{\pm}0.156$), while the lowest percentage of correct answers was seen for 'Gingival diseases can be improved by medications' ($0.33{\pm}0.472$). Conclusions : Based upon the above mentioned results, the author conclude that developing relevant national programs and support policies at a national level as well as implementing proactive and systematic home-visiting oral health programs at the levels of local autonomous entities or communities will lead to significant improvements in senior citizens' oral health and QoL (quality of life).

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.4
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• pp.477-487
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• 2006

Purpose : this study was to evaluate the fitness of adjustable dental impression trays on the Koreans : the trays used in the previous study by Kim et al. as part of the dental adjustable tray development project were improved and modified. Material and method: The patterns of tray were made through CAD-CAM process, and a simple silicone-base molds were made from them. The trial products were reproduced by pouring polyurethane into these molds. 30 male students(Wonkwang University, Dental College) and 30 female students (Wonkwang Health Science College, Department of Dental Hygiene) were selected and Reversible hydrocolloid impression materials were used for this study. The fitness of the trays was evaluated by measuring the width and length of impression materials of each measurement sites. Results and conclusion : 1. In adapting the trays inside the mouth, a uniform width of impression material(3 $\sim$ 6mm) was obtained in most sites due to the tooth stops and the inclined planes accommodating the width of the tray 2. The thickness of impression material in the central part of the palate was a mean 9.8mm, which turned out to be somewhat thick. 3. In the mandible. the thickness of the impression material in the lingual side inferior to the contact point of the 1st and 2nd molars was 2.7mm, and the thickness of the material in the lingual side of the rearmost margin was 2.5 mm. The thickness of the impression material of these areas was relatively thin.