• Journal of Korean society of Dental Hygiene
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• v.12 no.3
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• pp.611-620
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• 2012

Objectives : This study evaluated the changes in surface roughness of denture base resin according to the types of denture cleansers. Methods : A denture base resin(Vertex RS, Dentimax, Netherland) was used. Two toothpaste(Antiplaque, Bukwang, Korea; 2080, Aekyung, Korea) and a kitchen detergent(Trio, Aekyung, Korea) were used as a denture cleanser. The specimens were put on the V8 crossbrushing machine(Sabri enterprises, Downers grove, IL, USA) to reproduce toothbrushing and the toothbrushes were flat, round end and soft type. The surfaces of denture base resin specimens were observed by profilometer(SJ-400, MITUTOYO, Japan) and SEM(S-3000N, Hitachi Co., Ibaraki, Japan). Results : 1. According to the result of measuring surface roughness, there was statistically significant difference in Ra, Rq, and Rz(p<0.05). 2. As for Ra, Rq and Rz, Antiplaque toothpaste showed the highest roughness, and there was significant difference from other groups(p<0.01). 2080 toothpaste, Trio, and distilled water were classified as the same group. 3. According to the result of observation with the SEM, the surfaces of the Antiplaque toothpaste group after toothbrushing showed the greatest roughness, and the surfaces of 2080 toothpaste, Trio, and distilled water groups were rough in order. Trio and distilled water had the surfaces similar to those before toothbrushing. Conclusions : Studies to compare the efficacy of denture management methods and examine the effects of denture cleansers on denture materials will be helpful for dental hygienists and dentists providing patients with proper information and education. And it will be also useful for denture users' oral health.

• Tribology and Lubricants
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• v.34 no.3
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• pp.84-92
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• 2018

Bearings are essential for reducing vibration and wear, in order to achieve high durability and increase longevity. White metal treatment of tilting pads via centrifugal casting method has the possibility of increasing durability. However, this manufacturing method has drawbacks such as long processing time, high defect rate, and harmful health effects. Laser cladding deposition technique is a powerful method that can address these issues by decreasing the processing time and providing good adhesion. In this study, we suggest optimum conditions for laser cladding deposition that can be used in industrial applications. We deposited a soft white metal layer on SCM440 that is primarily used in shafts to minimize wear of bearing pads. During the laser deposition process, we controlled factors such as laser power, powder feed rate, and laser head speed to determine the optimum conditions. In addition, we measured the hardness using micro Vickers, and performed field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and friction tests to investigate the mechanical properties and surface characteristics for different parameters. Based on the experimental results, we suggest that laser power, powder feed rate, and laser head speed of 1.3 kW, 2.5 rpm, and 10 mm/s, respectively, constitute the optimum conditions for producing white metals using laser cladding.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.438-452
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• 2005

Statement of problem: The use of Ceromer is increasing in dentistry. But, the research of Ceromer has not been conducted much. Purpose : This study was to evaluate the marginal fidelity and internal adaptation according to marginal position. Materials and Methods: In this study 60 resin crowns were fabricated. The measurements of the marginal fidelity were carried out using stereomicroscope $SZ-40^{(R)}$ (Olympus, Japan) and the measurements of fracture strength were done using Instron $8871^{(R)}$ (Instron Co., U.S.A.) at a cross head speed of 1mm/min. All of the measurements were statistically analyzed by ANOVA test, multiple range test and Weibull analysis. Statistical significance was set in advance at the probability level of less than 0.05. All of the measurements were analyzed with Window $SPSS^{(R)}$ Version 10.0 soft ware for the personal computer. Results : 1. There were no statistical differences of the marginal fidelity between $Targis^{(R)}$ and $Tescera^{(R)}$, but difference between these two and $BelleGlass^{(R)}$ according to materials. 2. There were no statistical differences of the marginal fidelity between no fiber group and fiber group. There were no interactions between each maerial and with/without fiber group in the marginal fidelity 3. There were statistical differences of the fracture strength between $Tescera^{(R)}$ and $BelleGlass^{(R)}$ but no statistical differences of the fracture strength between $Targis^{(R)}$ and $Tescera^{(R)}$, $Targis^{(R)}$ and $BelleGlass^{(R)}$ according to materials. 4 There were statistical differences of the fracture strength between no fiber group and fiber group. There were no interactions between each material and with/without fiber group in the fracture strength. 5. When comparing the fracture surface, no fiber group showed the resin which were fractured at the labial surface and separated from the adhesion surface. In fiber group, the fractures took a place in resin compartments. Conclusion. The marginal fidelity and the fracture strength were clinically acceptable. From these results, $Targis^{(R)}$ and $Tescera^{(R)}$ were superior than $BelleGlass^{(R)}$ in the marginal fidelity But, when applying these resin crowns in clinic, more careful consideration is needed and further study is recommended.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.3
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• pp.370-374
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• 2003

Cell cracking method using a non-collision was evaluated for the possibility of new red ginseng grinding technique. Based on particle size distribution analysis by 1size shaker, the ratios of 100 mesh penetrated particles were 94.9% for hammer mill (group A) and 95.6% for cell crack (group B). The ratio of 120 mesh penetrated particle of group A was higher than that in group B. The particle size distributions for 100 mesh non-penetrated Powder between 2 groups were not significantly different, and particle size distribution analysis by laser scattering analyzer showed that the particle size ranges were 0.77~128.07 ${\mu}{\textrm}{m}$ for group A and 4.24~180.07 ${\mu}{\textrm}{m}$ for group B. The Particle size distribution in group A was more broad than that in group B. The mean particle size in group B was larger than that in group A, while the standard deviation of particle size distribution in group B was less than that in group A. Structural surface characteristics, in group A, particle size distribution was broad and the distribution curve was amorphous. The structure of individual particles was similar to unequal stone which was roughly grinded and had soft cotton-like surface. In the contrary, in group B, particle size distribution was relatively narrow and also individual size particles were ubiquitously distributed. The structure of individual particles was unequal cut stone shape.

• Journal of Korean Foot and Ankle Society
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• v.16 no.4
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• pp.247-256
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• 2012

Purpose: This study was performed to evaluate the clinical outcomes of operative treatment using mini-open sinus tarsi approach for displaced intraarticular calcaneal fractures. Materials and Methods: We studied 18 cases (16 patients) of intraarticular calcaneal fractures who were treated with sinus tarsi approach by same surgeon. The mean age of patients was 44.8 years, and mean follow-up period was 17.2 months. The measurement of B$\ddot{o}$hler angle, Gissane angle, the degree of articular surface depression, and the period to union were performed through preoperative and postoperative radiographs. The clinical evaluation was performed according to hindfoot score of the American Orthopaedic Foot and Ankle Society (AOFAS) and scale of the Creighton-Nebraska health foundation (CNHF). Results: B$\ddot{o}$hler angle and Gissane angle had improved significantly from preoperative average $9.8^{\circ}$, $117.6^{\circ}$to average $22.4^{\circ}$, $113.4^{\circ}$ immediate postoperatively, and had maintained to average $21.8^{\circ}$and $114.2^{\circ}$ at the last follow-up. The degree of articular surface depression had improved significantly from preoperative average 5.2 mm to 1.2 mm at the last follow-up. All cases achieved bone union, and the period to union was average 10.5 weeks. AOFAS score was average 86.2 points at the last follow-up. There were 7 excellent, 9 good, and 2 fair results according to the CNHF scale. Therefore, 16 cases (88.8%) achieved satisfactory results. Conclusion: The minimally invasive sinus tarsi approach using headless compression screw seems to be an effective surgical method for displaced intraarticular calcaneal fractures, because of the possibility of accurate restoration of articular surface and the low risk of postoperative soft tissue complications.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.4
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• pp.405-415
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• 2019

Excessive tooth wear can cause irreversible damage to the occlusal surface and can alter the anterior occlusal relationship by destroying the structure of the anterior teeth needed for esthetics and proper anterior guidance. The anterior deep bite is not a morbid occlusion by itself, but it may cause problems such as soft tissue trauma, opposing tooth eruption, tooth wear, and occlusal trauma if there are no stable occlusal contacts between the lower incisal edge against its upper lingual surface. The most important goal of treatment is to form stable occlusal contact in centric relation. In this case report, patients with decrease in vertical dimension and anterior deep bite due to maxillary posterior tooth loss and excessive tooth wear were treated full mouth rehabilitation with increased vertical dimension to regain the space for restoration and improve anterior occlusal relationship and esthetics. The functional and aesthetic problems of the patient could be solved by the equal intensity contact of all the teeth in centic relation (CR), anterior guidance in harmony with the functional movement, and restoration of the wear surface beyond the enamel range.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.269-275
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• 2019

As the national industry is developing gradually due to the expansion of the economic scale, the construction of large and super high-rise structures for building social infrastructure has been increasing, and studies have been conducted actively to transmit the large loads at the upper portion to the lower bedrock. In this study, the PHC was extended to an ultra-high strength PHC, which increased the concrete compressive strength of the PHC from the conventional 80 MPa to 110 MPa, and the PHC, which extended the tip of the pile. After construction with the driving method and injected pile method, the tendency of the bearing capacity was tested through a load test. Measurements of the bearing capacity of the extended PHC using the pile driving method revealed the main surface friction force to be smaller than that of the general PHC, and the stet-up effect was also insignificant. On the other hand, the effect of the friction force on the ground surface when the injected pile method was applied is expected to increase the bearing capacity when the gap between the main surface and the ground is wide and the cement paste is filled tightly. In addition, the ultrahigh strength PHC showed higher bearing capacity than the conventional PHC, and the permissible pile stress was less than 60%. Therefore, it is possible to reduce the number of piles and reduce the construction cost and effect of shortening the length of the pile by designing the tip of the pile on the ground with the intensity of soft rock as a method for utilizing the increased strength of the ultra-high strength PHC.

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.1
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• pp.24-31
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• 2016

Purpose: Many studies have shown that airborne-particle abrasion of fiber post can improve the bonding strength to resin cement. But, airborne-particle abrasion may influence the property of fiber post. The purpose of this study is to evaluate the influence of airborne-particle abrasion on flexural strength of fiber post. Materials and Methods: Two fiber-reinforced posts; DT Light Post Size 2 (1.8 mm diameter, Bisco Inc) and RelyX Fiber Post Size 3 (1.9 mm diameter, 3M ESPE); were used in this study. Each group was divided into 3 subgroups according to different surface treatments; without pretreatment: $50{\mu}m$ aluminum oxide (Cobra$^{(R)}$, Renfert): and $30{\mu}m$ aluminum oxide modified with silica (Rocatec Soft$^{(R)}$, 3M ESPE). After airborne-particle abrasion procedure, three-point bending test was done to determine the flexural strength and flexural modulus. The diameter of each posts was measured to an accuracy of 0.01 mm using a digital micrometer. There was no diameter change before and after airborneparticle abrasion. The mean flexural moduli and flexural strengths calculated using the appropriate equations. The results were statistically analyzed using One-way ANOVA and Scheffe's post-hoc test at 95% confidencial level. Results: There was no significant difference on flexural strength between groups. Conclusion: In the limitation of this study, flexural strength and flexural modulus of fiber post are not affected by airborne-particle abrasion.

• Clean Technology
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• v.25 no.4
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• pp.283-288
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• 2019

Monodisperse microparticles has been particularly enabling for various applications in the encapsulation and delivery of pharmaceutical agents. The microfluidic devices are attractive candidates to produce highly uniform droplets that serve as templates to form monodisperse microparticles. The microfluidic devices that have micro-scale channel allow precise control of the balance between surface tension and viscous forces in two-phase flows. One of its essential abilities is to generate highly monodisperse droplets. In this paper, a microfluidic approach for preparing monodisperse polycaprolactone (PCL) microparticles is presented. The microfluidic devices that have a flow-focusing generator are manufactured by soft-lithography using polydimethylsiloxane (PDMS). The crucial factors in the droplet generation are the controllability of size and monodispersity of the microdroplets. For this, the volumetric flow rates of the dispersed phase of oil solution and the continuous phase of water to generate monodisperse droplets are optimized. As a result, the optimal flow condition for droplet dripping region that is able to generate uniform droplet is found. Furthermore, the droplets containing PCL polymer by solvent evaporation after collection of droplet from device is solidified to generate the microparticle. The particle size can be controlled by tuning the flow rate and the size of the microchannel. The monodispersity of the PCL particles is measured by a coefficient of variation (CV) below 5%.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.285-296
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• 1999

Preloading method is used to prevent the settling of a foundation and to increase the strength of ground by consolidation settlement in advance. But, the embankment used in preloading method brings large deformation and sliding failure in the soft ground. Recently, reinforcement method is often used in embankment in order to prevent sliding failure. But, until now, the research on the stability analysis considering both the rate of strength increase of clay by embankment load and increase of resistance force by the geosynthetics in the embankment body is not found. In this study, the stability analysis program(REAP) for embankment including these two points is developed. By this program(REAP), the stability analysis can be done about during the gradual increase of embankment and the stability counterplan can be established when the safety factor is lower than allowable safety factor of design. After calculating the position of sliding failure surface, the force of geosynthetics which is selected by either the effective tensile strength or tensile force caused by the displacement of soil mass in this position is applied to stability analysis. And the increase of resisting moment can be calculated by this force. Also, the construction period can be estimated and the time for the appropriate counterplan can be decided in order to maintain the stability of embankment. And then, safe and economical embankment design can be performed.