• The korean journal of orthodontics
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• v.24 no.3 s.46
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• pp.535-546
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• 1994

The research work has been conducted in order to establish facts on posterior available space in patients with crowding. The relation between crowding and posterior available space was worked out through a cross sectinal study of fifty eight patients showing class I malocclusion. In addition, a longitudinal overlapping study was done by examing twenty patients who had their bicuspid extracted and forty nine patients who did not, at the orthodontic department of dental clinic affiliated in Chosun University. The patients had been examined for three years and eight months on a regular basis, and the study yielded the following conculusion. 1. There was a great difference in posterior available space between patients with serious crowding and those with slight crowding. The former marked 15.2mm of posterior available space and the latter 19.9mm. 2. Posterior crowding index was acquired by joint consideration of the diameter of posterior teeth and posterior available space, and manifested the highest relationship with crowding among measured items. 3. Patients who had their bicuspids extracted exhibited increase in posterior available space of 1.6mm/year and those who did not 1.8mm/year. 4. The absorption of anterior border of ramus turned out to be most deeply related with the increase of posterior available space. 5. Anterior border of ramus was absorbed at the average rate of 0.7mm/year during the period of observation. 6. The extraction of bicuspids had little influnce on the change in posterior available space.

• The korean journal of orthodontics
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• v.30 no.1 s.78
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• pp.67-82
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• 2000

The purpose of this study was to present the causes and their mechanisms of eruption failure of teeth and to investigate the treatment modalities. There are so many reports about eruption failure, but most of them are dealing with local mechanical interferences. But, we have patients suffered from eruption failure of another causes. Many developmental failures show eruption problems of teeth, although in some cases, the primary failure of eruption (failure of the eruption mechanism itself) can be the primary cause. We have to know about the causes, differences, and the treatment modalities for those abnormalities.

• The korean journal of orthodontics
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• v.47 no.6
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• pp.365-374
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• 2017

Objective: The objective of this study is to investigate the eruption pattern and root resorption of the bovine anterior dentition in relation to growth-related parameters based on dental maturity. Methods: A cross-sectional study was conducted on 110 bovine anterior mandibles by using standard radiography, cone-beam computed tomography (CBCT), and actual measurements. We determined the relationships between the stages of dental maturity by using a modification of Demirjian's method and various growth-related parameters, such as the activity of the root-resorbing tissue and mobility of the deciduous teeth. The correlation of growth-related parameters with interdental spacing and distal unusual root resorption (DRR) of the deciduous fourth incisor was assessed. The cause of mesial unusual root resorption (MRR) of the deciduous fourth incisor was determined on the basis of the arrangement of the permanent third incisor. Results: An independent t-test and chi-square test indicated significant differences in growth-related parameters associated with dental arch length discrepancy and factors related to the shedding of deciduous teeth between the low and high dental maturity groups. The samples with interdental spacing and DRR showed a larger sum of mesiodistal permanent crown widths and higher dental maturity than did the respective controls. Samples with MRR tended to show a lingually rotated distal tip of the adjacent tooth crown. Conclusions: Dental maturity has relevance to the interdental spaces and unusual root resorption of mixed dentition. The position of the adjacent tooth crown on CBCT may be correlated with the occurrence of unusual root resorption of the incisor.

• Journal of Korean society of Dental Hygiene
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• v.18 no.3
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• pp.281-293
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• 2018

Objectives: This study was conducted to identify the requirements for the clinical dental tasks in the dental hygienists using the frequency of dental hygienists' tasks in the Korean dental clinics, and to provide them with the core competencies for achieving these. Methods: This study was based on evaluation of a self-reported survey. The dental hygienists were investigated upon classification of their tasks into direct and assistant performances, and the dentists were investigated by the competency level of the dental hygienists. The data from 481 clinical dental hygienists and 67 dentists were used for final analysis in this study, excluding the subjects who provided incomplete or inappropriate responses to the survey. The collected data were analyzed by frequency analysis. Results: The clinical dental core competency tasks of the dental hygienists were divided into 4 tasks for common dentistry, 4 for periodontics, 5 for conservative dentistry, 5 for pediatric dentistry, 5 for dental prosthodontics, and 3 for dental orthodontics. Clinical dental core competency tasks of the dental hygienists were performed more frequently of tasks performance than 8.0, and dentists required competence level was similar to that of most dental hygienists clinical dental core competencies. Conclusions: It is necessary to check whether the curricula of the universities include the competencies for the students enough to perform the corresponding tasks and the core competencies need to be reflected in the curricula. The clinical dental core competencies need to be agreed by dental hygienists, and it is necessary to be organized as the evaluation guide of the institute of dental hygiene education and evaluation and utilized as the national examination.

• The korean journal of orthodontics
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• v.48 no.6
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• pp.405-411
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• 2018

Objective: This study was performed to investigate the rate of tooth movement and histological characteristics of extraction sockets those were subjected to corticotomy. Methods: A split-mouth randomized controlled trial experiment was designed. Thirty-two adult, male Wistar rats were divided into 2 groups: healing extraction socket (H) and recent extraction socket (R); these groups were randomly classified into 4 subgroups (0/7/21/60 days). The first maxillary molar was extracted on 1 side and 2 months were allowed for complete bone healing; then, the corresponding molar was extracted on the other side and surgical intervention was performed at the mid-alveolar point of the first maxillary molar. Ten grams of continuous force was applied. The outcomes measured were rate of tooth movement, percentage of periodontal space and histological evaluation. The rate of tooth movement was calculated as the measured distance divided by the duration of molar movement. Histomorphometric evaluations were performed on the second and third maxillary molars. The Wilcoxon signed rank test was used to compare differences between the two groups. Results: There were no significant differences in the rates of tooth movement between H and R groups at any of the 4 time points. The histological appearance and percentage of periodontal space between the R and H groups also demonstrated no significant differences. Conclusions: The rates of orthodontic tooth movement into recent and healed socket sites did not differ between the groups. Histological analysis of tooth movement revealed regional acceleration during every time period.

• Journal of radiological science and technology
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• v.38 no.3
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• pp.199-203
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• 2015

Panoramagraphy was the second most used intraoral radiography utilized in Korea, resulting in 17.8% in university dental hospitals, 24.8% in dental hospitals, and 31.4% in dental clinics. Depending on increased demand like orthodontics and implant, panoromagraphy tends to consistently increase. This study were used lead glasses and lead shielding to reduce unnecessary radiation to the eyeballs and thyroid. ESD was 41.4% when radiation was shielded with the lead glasses while reducing 47.3% of ESD by shielding the X-ray tube area with shielding lead. There was no statistically significant difference. The lead glasses is appropriated to reduce unnecessary radiation exposure to the eyeballs.

• The Journal of Advanced Prosthodontics
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• v.12 no.3
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• pp.157-166
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• 2020

PURPOSE. The aim of this study was to evaluate the clinical performance and reliability of plasma sprayed nanostructured zirconia (NSZ) coating. MATERIALS AND METHODS. This study consisted of three areas of analysis: (1) Mechanical property: surface roughness of NSZ coating and bond strength between NSZ coating and titanium specimens were measured, and the microstructure of bonding interface was also observed by scanning election microscope (SEM). (2) Biocompatibility: hemolysis tests, cell proliferation tests, and rat subcutaneous implant test were conducted to evaluate the biocompatibility of NSZ coating. (3) Mechanical compatibility: fracture and artificial aging tests were performed to measure the mechanical compatibility of NSZ-coated titanium abutments. RESULTS. In the mechanical study, 400 ㎛ thick NSZ coatings had the highest bond strength (71.22 ± 1.02 MPa), and a compact transition layer could be observed. In addition, NSZ coating showed excellent biocompatibility in both hemolysis tests and cell proliferation tests. In subcutaneous implant test, NSZ-coated plates showed similar inflammation elimination and fibrous tissue formation processes with that of titanium specimens. Regarding fatigue tests, all NSZ-coated abutments survived in the five-year fatigue test and showed sufficient fracture strength (407.65-663.7 N) for incisor teeth. CONCLUSION. In this study, the plasmasprayed NSZ-coated titanium abutments presented sufficient fracture strength and biocompatibility, and it was demonstrated that plasma spray was a reliable method to prepare high-quality zirconia coating.

• Journal of Microbiology and Biotechnology
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• v.30 no.3
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• pp.448-458
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• 2020

We investigated the therapeutic effects of microRNA-139-5p in relation to osteoporosis of bone marrow-derived mesenchymal stem cell (BMSCs) and its underlying mechanisms. In this study we used a dexamethasone-induced in vivo model of osteoporosis and BMSCs were used for the in vitro model. Real-time quantitative polymerase chain reaction (RT-PCR) and gene chip were used to analyze the expression of microRNA-139-5p. In an osteoporosis rat model, the expression of microRNA-139-5p was increased, compared with normal group. Down-regulation of microRNA-139-5p promotes cell proliferation and osteogenic differentiation in BMSCs. Especially, up-regulation of microRNA-139-5p reduced cell proliferation and osteogenic differentiation in BMSCs. Overexpression of miR-139-5p induced Wnt/β-catenin and down-regulated NOTCH1 signaling in BMSCs. Down-regulation of miR-139-5p suppressed Wnt/β-catenin and induced NOTCH1 signaling in BMSCs. The inhibition of NOTCH1 reduced the effects of anti-miR-139-5p on cell proliferation and osteogenic differentiation in BMSCs. Activation of Wnt/β-catenin also inhibited the effects of anti-miR-139-5p on cell proliferation and osteogenic differentiation in BMSCs. Taken together, our results suggested that the inhibition of microRNA-139-5p promotes osteogenic differentiation of BMSCs via targeting Wnt/β-catenin signaling pathway by NOTCH1.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.4
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• pp.506-515
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• 2015

Objectives: This study was conducted to evaluate the status of hazard communication regarding dental materials among dental hygienists in the Daegu Metropolitan City and the North Gyeongsang-do Province area. Materials: A total of 310 dental hygienists were surveyed using self-administered questionnaires to investigate the status of hazard communication on dental materials and information needs. We collected instructions for use and material safety data sheets(MSDSs) for 67 dental materials frequently used at dental hospitals located in the Daegu Metropolitan City and the North Gyeongsang-do Province area. Results: The questionnaire surveys showed that only 11% of the 310 dental hygienists had knowledge of MSDS and 46.8% of respondents never read instructions for use before using materials. Just 7.4% of dental hygienists have undergone training on hazard information for dental materials. In particular, dental hygienists working at dental clinics had significantly lower response rates on knowledge of MSDS(p<0.001), reading of instructions for use(p=0.042) and training on the hazard information of dental materials(p=0.004) than those in dental hospitals or general hospitals. The essential information most desired by dental hygienists was hazard identification(82.3%) followed by first-aid measures(53.9%), handling and storage(51%), disposal considerations (49%) and toxicological information(47.1%). All dental materials were on foreign products which came from Japan(59.7%), the USA(26.9%) and Liechtenstein(13.7%). In terms of usage, 56.7% of dental materials were prosthetic, followed by conservation(31.3%), orthodontics(9%), and prevention(3%). We found that dental hygienists had accessed MSDSs for only five dental products among the 67 dental materials. The instructions for the use of the 67 dental materials provided hazard identification(64.2%), first-aid measures(83.6%), handling and storage(97%), disposal considerations(20.9%) and toxicological information(26.9%). Conclusions: Based on the results of this study, the hazard communication system for dental hygienists working at dental clinics should be improved.

• The korean journal of orthodontics
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• v.21 no.2 s.34
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• pp.325-340
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• 1991

There are evidences that occlusal splint therapy is critical to diagnose hidden akeleto-occlusal disharmonies in malocclusion patients and capable of enhancing stability after orthodontic treatment. In addition, evidences have implicated occlusal splint therapy in condylar positional changes during TMJ disorder treatment. In view of these evidences, this study was performed to investigate the effect of occlusal splint therapy on condylar positional changes in malocclusion patients and the possible clinical application of the occlusal splint as an additional orthodontic tool. For this study, 8 Angle's Class I malocclusion patients, who had centric occlusion-centric relation discrepancy within 1.0 mm and had no clinical symptoms of TMJ disorder, were selected as control group. And 22 malocclusion patients who had centric occlusion-centric relation discrepancy over 1.0 mm were selected and subdivided as Class I Malocclusion group, Class II div. 1 malocclusion group, Class II div. 2 malocclusion group, Open bite group, and Mandibular asymmetry group. For each subject the occlusal splint with mutually protected type of occlusal scheme was applied for 3 months. Condylar positions in centric relation and centric occlusion were measured using Panadent articulators and Panadent condylar position indicator (CPI) before and after occlusal splint therapy. On the basis of this study, the following conclusions might be drawn: 1, In control group, Class II div. 2 malocclusion group, and mandibular assymetry group, there were no significant differences in condylar positions before and after occlusal splint therapy. 2. In Class I malocclusion group, condyles were moved $0.27{\pm}0.45mm$ forward (p < 0.05) and $0.98{\pm}0.25mm$ upward (p < 0.01) after occlusal splint therapy. 3. In Class I malocclusion group, condyles were moved $0.24{\pm}0.21mm$ backward (p < 0.05) and $1.01{\pm}0.33mm$ upward (p < 0.01) after occlusal splint therapy. 4. In open bite group, condyles were moved $1.24{\pm}0.30mm$ upward (p < 0.01) after occlusal splint therapy. 5. In both control and experimental groups, there were no significant differences in lateral condylar positions before and after occlusal splint therapy.