• The Journal of Korean Academy of Prosthodontics
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• v.38 no.4
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• pp.544-551
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• 2000

A fabrication method of inner and outer crown using CAD/CAM is presented. The information of abutment teeth is transferred to a computer through a 3-dimensional scanner. A Konus inner and outer crown is designed on a computer and a real crown is machined based on this design using CAM. This method can save laboratory time and reduce inaccuracies compare to conventional casting procedure. A stone model with six prepared abutment teeth from a patient was used in this study. Three dimensional information from the model was transferred to a computer using a contact type 3-dimensional scanner with a $25{\mu}m$ accuracy. All margins were identified on a computer image where there is a change in surface taper of a model. To provide a cement space, the image of a inner sur face of a Konus inner crown was duplicated $25{\mu}m$ apart from the surface of a prepared abutment teeth image. The cement space was $20{\mu}m$ at the cervical margin. All Konus crowns were machined with a $10{\mu}m$ accuracy. It was concluded that this method can reduce working-time for the laboratory process and increase accuracy. A further research is required to make a simplified process for a more complex prosthesis.

• Journal of Periodontal and Implant Science
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• v.34 no.3
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• pp.647-657
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• 2004

A non-carious cervical lesion(NCCL) is the loss of tooth structure at the cementoenamel junction level that is unrelated to dental caries. This study was to evaluate the occlusal and periodontal status of teeth with non-carious cervical lesions. We evaluated 105 teeth with non-carious cervical lesions in 35 subjects aged 38-75 years and characterized them based on the shape and dimension, plaque retention, bleeding on probing(BOP), probing pocket depth(PPD), occlusal status, brushing type, hypersensitivity and wear facet. The results of this study were as follows 1. No significant association was observed between cervical lesions and occlusal contact in lateral excursions. 2. No significant difference occurred in plaque retention, PPD, BOP between teeth with and without cervical lesions. 3. Test teeth had a significantly higher percentage of hypersensitivity and occlusal wear facet than teeth without cervical lesions. 4. Wedge shaped lesions had a significantly higher percentage of plaque than saucer shaped lesions. 5. Teeth with plaque were found to have significantly deeper PPD than teeth without plaque retention in cervical regions. 6. Teeth with occlusal contacts were found to have significantly deeper PPD than teeth without occlusal contacts. 7. No significant association was observed between cervical lesions and PPD independent of plaque retention and occlusal contacts Although more knowledge is necessary, our results suggest that occlusal contact and bacterial plaque may influence on periodontal tissue, but NCCL is not directly associated with periodontal health

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.6
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• pp.787-794
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• 2007

Statement of problem. Surface microgrooves on Ti substrata have been shown to alter the expression of genes responsible for various biological activities of cultured fibroblasts. However, their effect on enhancing cell proliferation is not yet clear. Purpose. The purpose of this study was to determine the dimension of surface microgrooves on Ti substrata that enhances proliferation and alters gene expression of cultured human gingival fibroblasts. Material and methods. Commercially pure Ti discs with surface microgrooves of monotonous $3.5{\mu}m$ in depth and respective 15 and $30{\mu}m$ in width were fabricated using photolithography and used as the culture substrata in the two experimental groups in this study (TiD15 and TiD30), whereas the smooth Ti was used as the control substrata (smooth Ti group). Human gingival fibroblasts were cultured on the three groups of titanium substrata and the proliferation, DNA synthesis, and gene expression of theses cells were analyzed and compared between all groups using XTT assay, BrdU assay, and reverse transcriptase-polymerase chain reaction (RT-PCR), respectively. Results. From the XTT assay at 48 h incubation, the proliferation of human gingival fibroblasts in TiD30 was significantly enhanced compared to that in smooth Ti and TiD15. The results from the BrdU assay showed that, at 24 h incubation, the DNA synthesis was significantly enhanced in TiD30 compared to that in smooth Ti. In RT-PCR, increase in the expression of PCR transcripts of fibronectin, CDK6, $p21^{cip1}$ genes was noted at 48h incubation. Conclusion. Surface microgrooves $30{\mu}m$ in width and $3.5{\mu}m$ in depth on Ti substrata enhance proliferation and alter gene expression of cultured human gingival fibroblasts.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.3
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• pp.635-648
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• 1998

The clinical use of fluoride with a well known osteogenic action in osteoporotic patients is rational, because this condition is characterized by impaired bone formation. However, its anabolic effect has not been demonstrated well in vitro. The purpose of this study was to investigate the effects of sodium fluoride on the physiological role of osteoblastic cell. Osteoblastic cells were isolated from fetal rat calvaria. The results were as follows : 1. Mineralized nodules were shown in osteoblastic cell cultures, which had been maintained in the presence of ascorbic acid and ${\beta}-glycerophosphate$ up to 21 days. When cultures were treated with pulses of 48 hr duration before apparent mineralization was occurring, 2-fold increased in their number was detected. 2. Alkaline phosphatase activity of osteoblastic cells was inhibited by sodium fluoride in dose dependent manner. 3. The effect of sodium fluoride on the osteoblastic cell proliferation was measured by the incorporation of $[^3H]$-thymidine into DNA. As a result, sodium fluoride at $1{\sim}100{\mu}M$ increased the $[^3H]$-thymidine incorporation into DNA in a dose dependent manner. 4. The signaling mechanism activated by sodium fluoride dose-dependently enhanced the tyrosine phosphorylation of the adaptor molecule $Shc^{p66}$ and their association with Grb2, one of earlier events in a MAP kinase activation pathway cascade used by a significant subset of G protein-coupled receptors. 5. The phosphorylation of CREB(cAMP response element binding protein)was inhibited by the sodium fluoride in MC3T3E1 cells. In conclusion, the results of this study suggested that the mitogenic effect of the sodium fluoride in MC3T3E1 cell was stimulated in a dose-dependent manner and suggested "an important role for the interaction between She and Grb2" in controlling the proliferation of osteoblasts.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.4
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• pp.722-727
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• 2003

Xylitol is a 5-carbons carbohydrate, which can be replaced with sucrose for preventing caries. The effect of carbohydrates and their combinations with xylitol was studied for the replication of oral bacteria such as Streptococcus oralis and Streptococcus salivarius. The replication of Streptococcus oralis and Streptococcus salivarius was inhibited according to the increased concentration of xylitol. When Streptococcus oralis was incubated for 8 hours in the media added with lactose or sucrose, the optical density was 0.915 and 1.107, repectively. while being 0.127 and 0.104, respectively in the media combined with xylitol. When Streptococcus salivarius was incubated for 8 hours in the media added with lactose or fructose, the optical density was 1.550 and 0.420, repectively. while being 0.271 and 0.905, respectively in the media combined with xylitol. These results indicated that the replication of Streptococcus oralis and Streptococcus salivarius was changed according to kinds of carbohydrates and combined addition of xylitol.

• Child Health Nursing Research
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• v.5 no.2
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• pp.136-150
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• 1999

The subjects, under 18 old, 2,694 children who visited ER during 1998, were surveyed by the Triage and other statitical data. The results were as follows 1. The male to female ratio was 1.7 : 1, and the toddler(1-4 old) was the majority. 2. Triage ; critical 1.3%, acute 14.6%, urgent 29.5%, nonemergent 54.6%. 3. The reasons of visiting ER ; 1) The children had diseases(46.5%), injury (36.9%), TA(5.6%) and toxication(1.0%). 2) In diseases, male to female ratio was 1.5 : 1 and in injury, male to female was 2 : 1. 3) Among the children having in TA, 12-18 old groups was the majority(34.9%). 4. The time of visiting : the 20:00 - 22:00 was the majority(16.9%). 5. By monthly and seasonal distribution ; Jan. (9.7%), Mar. and May(9% respectively, Dec. and July(6.7%) respectively. The children who visted ER in spring and autumn showed higher portion than those of summer and winter. 6. Results ; admission(27.4%), discharge(68.4%), operations(2.8%), and DOA and DAA(0.4%), The mortality of the infancy and toddler groups was 83.3%. The infancy group showed the highest rate of admission. 7. The time of staying in ER ; 1-2 hrs was the major group(23.3%) and the average was 4.6 hours. 8. By clinical departments ; Ped. was 34.4%, PS was 20.8%, Dental Surgery was 10.3% and Dermatology was 0.9%. 9. The types of visting ; the group who visited by themselves was 80%, transfer from the primary and secondary clinic was 17% and OPD was 3.0%. 10. The traffic means . by the own cars and taxi were 87.6%, by hospital ambulance was 6.1% and by 119 ambulance was 4.3%.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.301-311
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• 2002

The purpose of this study was to compare the distributing pattern of stress on the finite element models with the different vertical bone level of implant fixture. The two kinds of finite element models were designed according to vertical bone level around fixture ($4.0mm{\times}11.5mm$). The cemented crowns for mandibular first and second molars were made. Three- dimensional finite element model was created with the components of the implant and surrounding bone. Vertical loads were applied with force of 200N distributed within 0.5mm radius circle from the center of central fossa and distance 2mm and 4 mm apart from the center of central fossa. Von-Mises stresses were recorded and compared in the supporting bone, fixtures, abutment screws, and crown. The results were as following : (1) In vertical loading at the center circle of central fossa on model 1 and 2, the difference from vertical bone in implant placement did not affect the stress pattern on all components of implant except for crown. (2) With offset distance incerasing and the bone level of implant decreasing, the concentration of stress occured in the buccal side of long crown, around the buccal crestal bone, and on the fixture- abutment interface. As a conclusion, the research showed a tendency to increase the stress on the supporting bone, fixture and screw under the offset loads when the vertical level of bone around fixture was different. Since the same vertical bone bed has more benefits than the different bone bed around fixtures, it is important to prepare a same vertical level of bone bed for the success of implants under occlusal loads.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.251-276
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• 2002

The purpose of this study was to compare and analyze the stress distribution and displacement of the fully bone anchored bridge and implant-supported overdenture in edentulous mandible on certain conditions such as number of implants, different design of superstructure. Three dimensional analysis was used and nine kinds of models designed for this study. FEM models were created using commercial software[$Rhinoceros^{(R)}$ (Ver. 1.0 Robert McNeel & Associates, USA)], and analyze using commercial software [Cosmos/$Works^{TM}$(Ver. 4.0 Structural Research & Analysis Corp., US A)]. A vertical load and $45^{\circ}$ oblique load of 17kgf were applied at the left 1st. molar. The results were as follows : (1) In the group of OVD, the displacement was reduced as increasing the number of fixture under vertical loading but there was no specific difference in Von Mises stress. Under oblique loading, the displacement was same at the vertical loading but Von Mises stress was reduced in order of OVD-3, OVD-4, OVD-2. But, bending moment reduced according to increasing the number of fixture. (2) In the group of FBAB, under vertical and oblique loading, the magnitude of Von Mises stress and displacement reduced according to increasing the number of fixtures. FBAB-4 and FBAB-5 showed similar score and distribution, but FBAB-6 showed lower value relatively. (3) In cantilever design, the maximum displacement reduced under vertical loading but increased under oblique loading. However, von mises stresses on fixtures increased under vertical and oblique loading. (4) In comparing OVD-group with FBAB-group, FBAB showed low magnitude of displacement in respect of oblique loading. However OVD-group was more stable in respect of stress distribution.

• Korean Journal of Occupational Health Nursing
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• v.18 no.1
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• pp.5-13
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• 2009

Purpose: The purpose of the study is to investigate health problems of migrant workers in Korea. Methods: The data were collected from the records of the medical history of 2,233 migrant workers who visited the community health clinic in Ansan city, Gyeonggi province from Jan. 2005 to Jan. 2007. The data were analyzed by SPSS. Results: Men accounted for 56.4% of the total who participated in the study. Most of them were Chinese, Russian, and Bangladesh people. The 590 people out of all the migrant workers were employed in manufacturing industries and they comprised the largest percentage. The most commonly complained health problems were musculoskeletal (31.7%), digestive (20.7%), respiratory (12.5%), dermatologic (6.5%), cardiovascular (5.5%) and dental disorder (5.2%). The 1,853 (36.0%) workers were assumed to have hypertensive disorder and 1310 (11.1%) workers, some diseases due to high cholesterol level. Conclusions: It is necessary to establish a public health care system to improve health and welfare of migrant workers. Furthermore, the communities need to draw their attention to this matter. And it is also necessary to make accurate research on their health and medical service.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.781-785
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• 2011

In this work, a nano-sized samaria-doped ceria(SDC) was prepared by a urea-based hydrothermal method and characterized by XRD, FESEM and TEM. It was observed that the increase in synthesis time and temperature gave rise to crystallity and particles size. Moreover, the synthesised powders had a excellent ion-conductivity(0.1 S/cm at 600~$800^{\circ}C$) which is suitable for electrolyte of intermediate temperature-solid oxide fuel cell(IT-SOFC). Subsequently for use as electrolyte for anode-supported IT-SOFC, we tried to deposit the SDC powder on a porous NiO-SDC substrate by electrophoretic deposition(EPD) method. From the FESEM observation, a compact