• Journal of Korean society of Dental Hygiene
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• v.15 no.5
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• pp.907-915
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• 2015

Objective: The purpose of the study is to investigate the curriculum development and operation based on national competency standard (NCS). Methods: The duty of the dental hygienist was analyzed based on DACUM by ten experts in January, 2011. The duty model of the dental hygienist was inspected after duty analysis. The subjects of choice were preventive dentistry and practice. The satisfaction with the subjects were carried out from March to June, 2015. Results: The duty analysis of dental hygienist by DACUM produced preventive dental treatment(11 tasks), oral health education(3 tasks), comprehensive dental hygiene treatment(6 tasks) and 12 categories(156 tasks). Preventive dental treatment was divided into preventive dentistry and practice, oral health education was changed into oral health education and practice, and comprehensive dental hygiene treatment was replace by comprehensive dental hygiene and practice. The contents of preventive dentistry and practice included outline, learning objective, related knowledge and self evaluation. Professional evaluation required mutual experience and evaluation of the students. The mutual evaluation of the students was $4.61{\pm}0.506$(dental plaque control) and $1.80{\pm}0.316$(tooth brushing). The professional evaluation was $1.73{\pm}0.274$(dental plaque control) and $1.60{\pm}0.322$(tooth brushing)(p<0.01). The satisfaction with preventive dentistry and practice was $4.61{\pm}0.506$(improvement in practical work ability), $4.58{\pm}0.511$(knowledge improvement) and $4.55{\pm}0.572$(NCS educational environment) in order. Conclusions: The operation of NCS curriculum is considered to improve practical work ability and to solve skill mismatch between dental industries and educational training institutions.

• Journal of Technologic Dentistry
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• v.15 no.1
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• pp.89-94
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• 1993

The tooth size and shape of the permanent incisor teeth have been studied and analyzed about the mean size, S.D, S.E, etcs and percentage from stone model of 100 Korean male and 74 Korean female. The results were as follows. 1. The crown length of permanent incisor teeth were longer in males than in females statistical differences of males and female were not found. 2. the mesio-distal diameters of permanent incisor teeth were larger in males than in females and statistical differences of males and females were found in mandibular lateral incisor and the bigest were max. central incisor, 2nd max. lateral incisor, 3rd man. lateral incisor and the smallest were man. central incisor. 3. The square form in max. central incisor was the greatest percentage and the tapering form in max. lateral incisor and man, incisor was the greatest percentage but tapering form and ovoid form and other shape were found in max. lateral at the same ratio. 4. Concerning the labial developmental groove "midium" was the greatest percentage in the max. central incisor and "low" was the greatest percentage in the man incisor. Concerning the incisal line, straight line was the greatest percentage in the max, incisor and man, incisor and concerning the lingual tubercle "none" was the greatest percentage in the max. incisor. 5. In comparison between left side and right side of incisor, the ratio of same shape ware 22.4%-36.2% but similar or dissimilar cases were more frequently found.

• The korean journal of orthodontics
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• v.45 no.5
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• pp.217-225
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• 2015

Objective: Three-dimensional (3D) printing is a recent technological development that may play a significant role in orthodontic diagnosis and treatment. It can be used to fabricate skull models or study models, as well as to make replica teeth in autotransplantation or tooth impaction cases. The aim of this study was to evaluate the accuracy of fabrication of replica teeth made by two types of 3D printing technologies. Methods: Fifty extracted molar teeth were selected as samples. They were scanned to generate high-resolution 3D surface model stereolithography files. These files were converted into physical models using two types of 3D printing technologies: Fused deposition modeling (FDM) and PolyJet technology. All replica teeth were scanned and 3D images generated. Computer software compared the replica teeth to the original teeth with linear measurements, volumetric measurements, and mean deviation measurements with best-fit alignment. Paired t-tests were used to statistically analyze the measurements. Results: Most measurements of teeth formed using FDM tended to be slightly smaller, while those of the PolyJet replicas tended to be slightly larger, than those of the extracted teeth. Mean deviation measurements with best-fit alignment of FDM and PolyJet group were 0.047 mm and 0.038 mm, respectively. Although there were statistically significant differences, they were regarded as clinically insignificant. Conclusions: This study confirms that FDM and PolyJet technologies are accurate enough to be usable in orthodontic diagnosis and treatment.

• The korean journal of orthodontics
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• v.46 no.5
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• pp.310-322
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• 2016

Objective: The aim of this study was to determine the optimal loading conditions for pure intrusion of the six maxillary anterior teeth with miniscrews according to alveolar bone loss. Methods: A three-dimensional finite element model was created for a segment of the six anterior teeth, and the positions of the miniscrews and hooks were varied after setting the alveolar bone loss to 0, 2, or 4 mm. Under 100 g of intrusive force, initial displacement of the individual teeth in three directions and the degree of labial tilting were measured. Results: The degree of labial tilting increased with reduced alveolar bone height under the same load. When a miniscrew was inserted between the two central incisors, the amounts of medial-lateral and anterior-posterior displacement of the central incisor were significantly greater than in the other conditions. When the miniscrews were inserted distally to the canines and an intrusion force was applied distal to the lateral incisors, the degree of labial tilting and the amounts of displacement of the six anterior teeth were the lowest, and the maximum von Mises stress was distributed evenly across all the teeth, regardless of the bone loss. Conclusions: Initial tooth displacement similar to pure intrusion of the six maxillary anterior teeth was induced when miniscrews were inserted distal to the maxillary canines and an intrusion force was applied distal to the lateral incisors. In this condition, the maximum von Mises stresses were relatively evenly distributed across all the teeth, regardless of the bone loss.

• Imaging Science in Dentistry
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• v.43 no.1
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• pp.1-6
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• 2013

Purpose: This study investigated the possible correlation between the mineralization of the second molars and the chronological age of a sample population of the state of Paraiba, Brazil. Materials and Methods: One thousand eight hundred fifty-four digitized panoramic images using a scanner of a private dental radiology service were obtained in six months. Of these, 457 were selected from patients aged 4.6 to 16 years who met certain criteria. The images were assessed twice by a radiologist with 5 years experience. A minimum interval of 30 days between the evaluations of the same patient was established. To analyze the relationship between chronological age, calcification level proposed by Demirjian et al in 1973, gender, and tooth, a multiple linear regression model was adjusted, taking age as the response variable (p<0.05). Results: The gender and calcification level were significantly correlated with the age of the patients (p<0.05). There was a significant difference between the average age of the patients' upper teeth compared to the lower ones in both genders (p<0.05). The dental development occurred earlier in female individuals than in male ones, and there was no significant difference between the right and left second permanent molars. Conclusion: It was observed that ethnic variables are related to certain parameters of age and sex identification in the Brazilian population, providing important information for forensic evaluations.

• Journal of Magnetics
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• v.22 no.2
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• pp.299-305
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• 2017

Magnetic fluid, a new type of magnetic material, is a colloidal liquid constituted of nano-scale ferromagnetic particles suspended in carrier fluid. Magnetic fluid sealing is one of the most successful applications of magnetic fluid. As a new type of seal offering the advantages of no leakage, long life and high reliability, the magnetic fluid seal has been widely utilized under vacuum- and low-pressure-differential conditions. In practical applications, for improved pressure capacity, a multistage sealing structure is always used. However, in engineering applications, a uniform distribution of magnetic fluid under each tooth often cannot be achieved, which problem weakens the overall pressure capacity of the seals. In order to improve the pressure capacity of magnetic fluid seals and broaden their applications, the present study theoretically and experimentally analyzed the degree of non-uniform distribution of multistage magnetic fluid seals. A mathematical model reflecting the relationship between the pressure capacity and the distribution of magnetic fluid under a single tooth was constructed, and a formula showing the relationship between the volume of magnetic fluid and its contact width with the shaft was derived. Furthermore, the relationship of magnetic fluid volume to capacity was analyzed. Thereby, the causes of non-uniform distribution could be verified: injection of magnetic fluid; the assembly of magnetic fluid seals; the change of magnetic fluid silhouette under pressure loading; the magnetic fluid sealing mechanism of pressure transmission, and seal failure. In consideration of these causes, methods to improve the pressure capacity of magnetic fluid seals was devised (and is herein proposed).

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.63-68
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• 1990

The chemical ingredients such as $SiO_2,\;Al_2O_3,\;MgO,\;Fe_2O_3,\;CaO$ and $TiO_2$in silica minerals were determined by X-ray fluorescence spectrometry using a matrix correction method. The synthesized standards mixed with reagent grade oxides and the sample were diluted by fusing with 16 times $Li_2B_4O_7$. The matrix effects correlated among the ingredients were corrected by the empirical coefficient method based on the Lucas-Tooth and Pyne model. The analytical results showed relatively good agreement between the different sets of coefficients but were improved with increasing the number of standard. The accuracy of this method was also examined with the standard reference material of NIST.

• Journal of the Korean Society for Precision Engineering
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• v.1 no.3
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• pp.85-94
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• 1984

The WILDHABER-NOVIKOV gear, one of the circular arc gears, has the large contact area between the convex and concave profiled mating teeth, moves from one end of the tooth to the other axially making a face contact. Hence it provides a large load capacity than the Involute gear and still satisfying the law of gearing. In order to analyze the gear stress, a photoelastic investigation was carried out. Photo elastic model of the WILDHABER-NOVIKOV gears were made of Araldite CT200 in this investigation. For both the many teeth gear and the few teeth gear segments, External gears of all addendum type WILDHABER-NOVIKOV gear and the involute gear were tested. Included were the models with various profile raddi at the same pressure angle 20 .deg. and module 13.5. The flank stresses and fillet stresses of these gears were observed in each case and compared with those of gears. From this investigation, the following results were obtained. A. In the case of having many teeth gear: As the profile radius is increased, the fillet stresses of the WILDHABER-NOVIKOV gear become the same or less than that of the INVOLUTE gea, and the flank stress becomes smaller than that of the INVOLUTE gear. Therefore the better design condition is satisfied with a large profile radius. B. IN the case of having a few teeth gear: As the profile radius is increased the flank stress of WILDHABER-NOVIKOV gear becomes smaller than that of the INVOLUTE gear, but the fillet stresses become larger than that of the INVOLUTE gear. Therefore the larger design condition is satisfied with small profile radius.

• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.379-384
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• 2018

The purpose of this study was to investigate the effect of diabetes on periodontal disease according to oral health behavior. The date from the 2013-2015 Korean National Health and Nutrition Survey were used, and 14,282 subjects were included in the analysis. Periodontal disease was assessed using the Community Periodontal Index and using logistic regression. When all of the oral health behaviors were included in the model, tooth brushing frequency, flossing, and interdental brushing were significantly associated with periodontal disease, and periodontal disease risk was significantly higher with diabetes, but there was little difference in periodontal disease risk by input factors. Oral health behaviors were associated with periodontal disease in the normal blood glucose group but not in the presence of diabetes mellitus. If there is diabetes, it is difficult to manage periodontal disease by only the health behavior, so it is necessary to control blood sugar.

• Journal of dental hygiene science
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• v.20 no.4
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• pp.187-199
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• 2020

Background: Korean dental hygienists perform various tasks under the supervision of dentists in addition to the tasks listed in the law. Many meaningful studies have been conducted to determine the actual tasks of dental hygienists, but these studies did not show common results due to the differences in research methods or designs. Hence, this study aimed to review the reported data on the tasks of dental hygienists in Korea and to clarify them based on a systematic literature review. Methods: For the literature search, the COre, Standard, and Ideal model presented by the National Library of Medicine was referenced. Seven databases were searched for literatures published in Korea, including PubMed, and Google Scholar. Of the 352 studies found using key words, titles, and abstracts, 46 were finally extracted based on the first and second exclusion criteria. After confirming the tasks of Korean dental hygienists in 46 literatures, 136 tasks were listed and calculated as appearance rate in the literature. Results: The most common tasks in 46 studies were fluoride application (67.2%), radiography (65.4%), scaling (65.4%), sealant (60.7%), patient management and counseling (56.7%), tooth-brushing education (52.2%), impression taking with alginate (50.1%), and making temporary crowns (47.9%). The most mentioned tasks of dental hygienists in public health centers were fluoride application (100%), sealant (100%), oral health education (71.4%), public oral health program evaluation (71.4%), school fluoride mouth-rinsing program (71.4%), water fluoridation (57.1%), tooth-brushing education (57.1%), school oral health programs (57.1%), and public elderly oral health programs (57.1%). Conclusion: This study showed that Korean dental hygienists had 136 tasks by reviewing 46 related studies and that the main job of Korean dental hygienists was oral disease prevention including scaling, sealant, and fluoride application.