• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.1093-1098
• /
• 2002

Dynamic behaviors of the Korean High-speed Train(KHST) have been analyzed to investigate the performance on the stability, the safety and the ride comfort. Multi-body dynamics analysis program using Recursive method, called RecurDyn, have been employed in the numerical simulation. To model the wheel-rail contact, the RecurDyn uses its built-in module which uses the square root creep law. The accuracy of the rail module in RecurDyn. however, decreases in the analysis of flange contact because it linearizes the shape of the wheel and rail. To solve this problem, a nonlinear contact theory have been developed that considers the profiles of the wheel and rail. The results show that the KHST still needs more stability. The problem should be solved by the examinations of module and modeling.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.16 no.6
• /
• pp.97-103
• /
• 2008

In general, the strength of gears is calculated using the formula of AGMA or JGMA. But these formula can not be applied directly to the strength calculation of the rack and pinion of steering gear assay, because of complex tooth and contact shapes. So Lewis bending stress and Hertzian contact stress formula are generally used for the design of rack and pinion of steering gear assay. But these formula do not also give the exact stress of rack and pinion. In this paper, comparing the finite element analysis results and the experimentally measured values, it is shown that the finite element modeling technique of the rack and pinion of steering assay is reasonable.

• Journal of dental hygiene science
• /
• v.21 no.4
• /
• pp.243-250
• /
• 2021

Background: Endodontic sealers or their toxic components may become inflamed and lead to delayed wound healing when in direct contact with periapical tissues over an extended period. Moreover, an overfilled sealer can directly interact with adjacent tissues and may cause immediate necrosis or further resorption. Therefore, the treatment outcome conceivably depends on the endodontic sealer's biocompatibility and osteogenic potential. This study aimed to evaluate the cell viability and osteogenic effects of four different sealers in osteoblastic cells. Methods: AH Plus (resin-based sealer), Pulp Canal Sealer EWT (zinc oxide-eugenol sealer), BioRoot RCS (calcium silicate-based sealer), and Well-Root ST (MTA-based calcium silicate sealer) were mixed strictly according to the manufacturer's instructions, and dilutions of sealer extracts (1/2, 1/5 and 1/10) were determined. Cell viability was measured using the water-soluble tetrazolium-8 (WST-8) assay. Differentiation was assessed by alkaline phosphatase (ALP) activity and mineralized nodule formation by Alizarin Red S staining. Results: The cell viability of the extracts derived from the sealers excluding Well-Root ST was concentration dependent, with sealer extracts having the least viability at a 1/2 dilution. At sealer extract dilution of 1/10, the test groups showed the same survival rate as that control group, with the exception of BioRoot RCS. Among all experimental groups, BioRoot RCS showed the highest cell viability after 48 hours. The ALP activity was significantly higher in a concentration-dependent manner. Furthemore, all four materials promoted ALP activity and mineralized nodule formation compared to the control at 1/10 dilutions. Conclusion: This is the first study to highlight the differences in biological activity of these four materials. These results suggest that the composition of root canal sealers appears to alter the form of biocompatibility and osteoblastic differentiation.

• Imaging Science in Dentistry
• /
• v.45 no.4
• /
• pp.233-240
• /
• 2015

Purpose: This study investigated maxillary third molars and their relation to the maxillary sinus using panoramic radiography and cone-beam computed tomography (CBCT) Materials and Methods: A total of 395 maxillary third molars in 234 patients were examined using panoramic radiographs and CBCT images. We examined the eruption level of the maxillary third molars, the available retromolar space, the angulation, the relationship to the second molars, the number of roots, and the relationship between the roots and the sinus. Results: Females had a higher frequency of maxillary third molars with occlusal planes apical to the cervical line of the second molar (Level C) than males. All third molars with insufficient retromolar space were Level C. The most common angulation was vertical, followed by buccoangular. Almost all of the Level C molars were in contact with the roots of the second molar. Erupted teeth most commonly had three roots, and completely impacted teeth most commonly had one root. The superimposition of one third of the root and the sinus floor was most commonly associated with the sinus floor being located on the buccal side of the root. Conclusion: Eruption levels were differently distributed according to gender. A statistically significant association was found between the eruption level and the available retromolar space. When panoramic radiographs showed a superimposition of the roots and the sinus floor, expansion of the sinus to the buccal side of the root was generally observed in CBCT images.

• Imaging Science in Dentistry
• /
• v.53 no.3
• /
• pp.199-207
• /
• 2023

Purpose: The objective of this study was to evaluate the accuracy and effectiveness of an artificial intelligence (AI) program in identifying dental conditions using panoramic radiographs(PRs), as well as to assess the appropriateness of its treatment recommendations. Materials and Methods: PRs from 100 patients(representing 4497 teeth) with known clinical examination findings were randomly selected from a university database. Three dentomaxillofacial radiologists and the Diagnocat AI software evaluated these PRs. The evaluations were focused on various dental conditions and treatments, including canal filling, caries, cast post and core, dental calculus, fillings, furcation lesions, implants, lack of interproximal tooth contact, open margins, overhangs, periapical lesions, periodontal bone loss, short fillings, voids in root fillings, overfillings, pontics, root fragments, impacted teeth, artificial crowns, missing teeth, and healthy teeth. Results: The AI demonstrated almost perfect agreement (exceeding 0.81) in most of the assessments when compared to the ground truth. The sensitivity was very high (above 0.8) for the evaluation of healthy teeth, artificial crowns, dental calculus, missing teeth, fillings, lack of interproximal contact, periodontal bone loss, and implants. However, the sensitivity was low for the assessment of caries, periapical lesions, pontic voids in the root canal, and overhangs. Conclusion: Despite the limitations of this study, the synthesized data suggest that AI-based decision support systems can serve as a valuable tool in detecting dental conditions, when used with PR for clinical dental applications.

• The korean journal of orthodontics
• /
• v.51 no.4
• /
• pp.231-240
• /
• 2021

Objective: This outcome analysis study evaluated the actual positions of the orthodontic miniplate and miniplate anchoring screws (MPASs) and the risk factors affecting adjacent anatomic structures after miniplate placement in the mandibular incisal area. Methods: Cone-beam computed tomographic images of 97 orthodontic miniplates and their 194 MPASs (diameter, 1.5 mm; length, 4 mm) in patients whose miniplates provided sufficient clinical stability for orthodontic treatment were retrospectively reviewed. For evaluating the actual positions of the miniplates and analyzing the risk factors, including the effects on adjacent roots, MPAS placement height (PH), placement depth (PD), plate angle (PA), mental fossa angle (MA), and root proximity were assessed using the paired t-test, analysis of variance, and generalized linear model and regression analyses. Results: The mean PDs of MPASs at positions 1 (P1) and 2 (P2) were 2.01 mm and 2.23 mm, respectively. PA was significantly higher in the Class III malocclusion group than in the other groups. PH was positively correlated with MA and PD at P1. Of the 97 MPASs at P1, 49 were in the no-root area and 48 in the dentulous area; moreover, 19 showed a degree of root contact (19.6%) without root perforation. All MPASs at P2 were in the no-root area. Conclusions: Positioning the miniplate head approximately 1 mm lower than the mucogingival junction is highly likely to provide sufficient PH for the P1-MPASs to be placed in the no-root area.

• Restorative Dentistry and Endodontics
• /
• v.20 no.2
• /
• pp.789-801
• /
• 1995

Canals with artificially made internal resorption were filled with 4 techniques(Lateral condensation, Ultrafil, Obtura II, Thermafil) to compare the efficacy of canal filling according to the filling techniques. After canal filling, radiographic examination, dye penetration through the apical portion and percentage of G-P filled area on the internal resorption area were evaluated. To examine the degree of crystal-like structure and the interface between filled G-P and canal wall, SM and SEM images were taken too. The results were as follows : 1. There was no statistically significant difference in apical microleakage among the 4 root canal filling techniques. 2. As a result of radiographic examination, Ultrafil was the best and Obtura II was acceptable but Lateral condensation and Thermafil showed unfavorable canal filling pattern similarly. 3. Ultrafil filled most of artificially made internal resorption area and Obtura II, Lateral condensation, Thermafil in that order filled unfavorably. 4. Degree of crystal like structure was the highest in the group filled with Ultrafil and those of Obtura II and Thermafil were similar and that of gutta percha used in Lateral condensation showed the lowest value. 5. Penetration of gutta percha into the dentinal tubules couldn't be seen in all groups. In the contact surface between the filled G-P and the canal wall, Lateral condensation showed relatively close sealing, Obtura II and Thermafil had irregular contact surface and Ultrafil showed regular filling pattern. 6. Contact surface between the core of Thermafil and the gutta percha showed close relationship without gap formation.

• The Korea Journal of Herbology
• /
• v.28 no.6
• /
• pp.25-29
• /
• 2013

Objectives : The dried root of Sophora flavescens Aiton have been used to treat patient with skin diseases such as eczema in Eastern countries. S. flavescens can clear away heat and dry dampness and purge sthenic-fire from the liver and gallbladder. Recently, anti-allergic effect of S. flavescens has been reported. However, the effect on skin condition of contact dermatitis still remains unknown. Thus, the purpose of this study is to evaluate the efficacy of S. flavescens on contact dermatitis. Methods : In order to investigate the effects of S. flavescens (methanol extract of S. flavescens, MESR) on skin condition, the contact dermatitis was induced in mice skin by using 1-fluoro-2,4-dinitrofluorobenzene (DNFB). As the effective endpoints, skin thickness, skin weight, histopathological change were checked. In addition, effects on skin lesion, body weight and spleen/body weight ratio were also investigated. Results : Topical application of MESR ($500{\mu}g/day$) lowered skin thickness (P < 0.05) and skin weight (P < 0.05), respectively. MESR-treated group showed diminished spongiosis and immune cell infiltration in skin tissues compared to those of non-treated control group. The inhibition of skin lesions was also observed in MESR-treated group. In addition, MESR did not affect body weight gain and spleen/body weight ratio in contrast with those in dexamethasone-treated group. Conclusion : These data suggest that Sophorae Radix could improve skin lesion of contact dermatitis. This indicates the possibility for Sophorae Radix to be used to patients with skin diseases such as contact dermatitis.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.39 no.10
• /
• pp.25-34
• /
• 2002

In this paper, silicidation induced Schottky contact area was obtained using the current voltage(I-V) characteristics of shallow cobalt silicided p+-n and n+-p junctions. In reverse bias region, Poole-Frenkel barrier lowering influenced predominantly the reverse leakage current, masking thereby the effect of Schottky contact formation. However, Schottky contact was conclusively shown to be the root cause of the modified I-V behavior of n+-p junction in the forward bias region. The increase of leakage current in silicided n+-p diodes is consistent with the formation of Schottky contact via cobalt slicide penetrating into the p-substrate or near to the junction area and generating trap sites. The increase of reverse leakage current is proven to be attributed to the penetration of silicide into depletion region in case of the perimeter intensive n+-p junction. In case of the area intensive n+-p junction, the silicide penetrated near to the depletion region. There is no formation of Schottky contact in case of the p+-n junction where no increase in the leakage current is monitored. The Schottky contact amounting to less than 0.01% of the total junction was extracted by simultaneous characterization of forward and reverse characteristics of silicided n+-p diode.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.23 no.1
• /
• pp.95-104
• /
• 2007

I. Objective The primary requirement of an endodontic root canal sealer is the biologic compatibility, because they remain in close contact with living periapical tissues over a long period of time. The aim of this study was the evaluation of cytotoxicity and genotoxicity of resin-based root canal sealers, AH 26 and ADSEAL. II. Material & Methods In this study, human periodontal ligament cells, human oral cancer cells (KB) and mouse osteoblasts (MC-3T3-E1) were used. Specimens of AH26, ADSEAL were eluted with culture medium for 1, 3, 5 and 7 days. Cytotoxicity was evaluated by using tetrazolium bromide reduction assay (MTT assay) for mitochondrial enzyme activity and cell viability. Genotoxicity was evaluated by using alkaline single cell gel electrophoresis assay (Comet assay). Also cell apoptosis induced by AH 26 was detected by Hoechst33258 staining. III. Results AH 26 and ADSEAL exhibited cytotoxic effects in all investigated cell groups. Genotoxicity was also noted for both sealers in mouse osteoblasts (MC-3T3-E1). But, ADSEAL presented significantly low cytotoxicity and genotoxicity compared with AH 26. Cytotoxicity and genotoxicity induced by AH 26 resulted in apopotosis. IV. Conclusion Our results clearly indicate that the recently invented ADSEAL has better biocompatibility than another resin based root canal sealer, AH 26. However ideal root canal sealer should have not only biocompatibility but also satisfactory physico-chemical properties such as sealing ability and stability. Thus continuous studies and developments should follow.