• The Journal of Korean Academy of Prosthodontics
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• v.51 no.4
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• pp.284-291
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• 2013

Purpose: This study compared fracture strength and fracture modes between metal wire reinforcement and glass fiber reinforcement in repaired maxillary complete denture. Materials and methods: In this study, fracture was reproduced on center of maxillary complete dentures and the denture was repaired with auto-polymerizing resin. The experimental groups (n = 10) were subjected to the following condition: without reinforcing material (control group), reinforcing with metal wire (W group), reinforcing with glass fiber pre-impregnated with light-curing resin (SES MESH, INNO Dental Co., Yeoncheon, Korea, G group). The fracture strength and fracture modes of a maxillary complete denture were tested using Instron test machine (Instron Co., Canton, MA, USA) at a 5.0 mm/min crosshead speed. The flexure load was applied to center of denture with a 20 mm diameter ball attachment. When fracture occurred, the fracture mode was classified based on fracture lines. The Kruskal-wallis test and the Mann-whitney U test were performed to identify statistical differences at ${\alpha}=.05$. Results: W group showed the highest value of fracture strength, there was no significant difference (P>.05) between control group and G group. Control group and W group showed anteroposterior fracture mainly, group W showed adhesive fracture of denture base and reinforcing material. Conclusion: In limitation of this study, the glass fiber did not improve the fracture strength of repaired maxillary complete denture, and adhesive failure was occurred along the lines of glass fiber.

• Korean Journal of Digital Imaging in Medicine
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• v.15 no.2
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• pp.55-61
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• 2013

The purpose of this study is to evaluate image blurring according to variation of the ETL and propose the clinically appropriate ETL range. SIEMENS MAGNETOM Skyra 3.0T and 20 channel head coil were used for the study. MRI phantom was kept the lines horizontally to three direction(X,Y,Z) of the coil and T1, T2 weighted images that used the fast spin echo technique acquired. The ETL with increase of 10 was applied from 10 to 80. In addition, the ETL with increase of 1 was applied in the interval statistically significant differences occurred. And T1, T2 weighted images that used the conventional spin echo technique acquired to compare image blurring of the images that used the fast spin echo technique. The slope of lattice in the images was measured using Image J 1.47v program to evaluate image blurring. And image blurring was determined by the degree of the slope. The statistical significance of both techniques was evaluated by the Kruskal-Wallis test of the SPSS 17.0v. And the correlation of the ETL and image blurring was evaluated quantitatively by regression analysis. The slope of the T1, T2 weighted images that used fast spin echo technique decreased as contrasted with conventional spin echo technique. In the result of the Kruskal-Wallis test, the T1, T2 weighted images that used fast spin echo technique made a significant difference with conventional spin echo technique. Particularly, in the Tomhane' T2 test, the T1, T2 weighted images made a significant difference from ETL 22 and 31 respectively. In the result of the regression analysis, the R-squared of the T1, T2 weighted images are 0.762 and 0.793. It is difficult to apply the long ETL in the T1 weighted image caused by the short TR and multi-slices study. Therefore, clinical impact according to variation of the ETL is very slight in the T1 weighted images. But the application of the proper ETL is demanded in T2 weighted images using the fast spin echo technique in order to prevent image blurring.

• Journal of radiological science and technology
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• v.35 no.1
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• pp.35-44
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• 2012

The goal of this study is to awaken about risk occurred by CT examination. For radio-technologists working at 'S medical center' located in Seoul, we investigated a recognition about dose and risk CT and normal X-ray examination according by working experience in hospital, experience about CT examination and radiation source. For subjects of investigation, radio-technologists working at 'S medical center' located in Seoul helped us. We collected 131 questionnaires for a test of hypothesis. Cronbach @ coefficients of questionnaires were 0.825988 and 0.767161 and a rejection rate of p-value was below 0.05. SAS 9.1(SAS Institute Inc., Cary, NC, USA.) statistic package was used for hypothesis test. We used Mann-Whitney test, Kruskai-Wallis test, Two sample T-test, Two sample T-test with Bonferroni's Correction and One-way ANOVA methods. P-values of hypothesis about dose of CT and normal X-ray examination were 0.2291 ~ 0.9663. p-values of hypothesis about risk were 0.1924 ~ 1.0000. All of hypothesis is over rejection rate(<0.05). This study shows that radio-technologists of S medical center recognized that CT has higher dose and risk than general X-ray examination.

• The korean journal of orthodontics
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• v.40 no.6
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• pp.432-443
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• 2010

Objective: The purpose of this prospective study was to evaluate the dentofacial effects of conventional and modified facemask therapies with rapid maxillary expansion, in a group of Class III patients; and compared with an untreated control group. Methods: The conventional facemask group (Group 1) comprised of 24 patients, 13 girls and 11 boys (mean age, $9.2{\pm}1.4$ years); the modified facemask treatment group (Group 2) comprised of 24 patients, 12 girls and 12 boys (mean age, $9.3{\pm}1.6$ years); and the control group (Group 3) comprised of 21 subjects, 11 girls and 10 boys (mean age, $9.8{\pm}1.9$ years). Treatment and control changes within the groups and the differences between the groups were analyzed statistically. Intra-group comparisons were evaluated using the non-parametric Wilcoxon's test and intergroup changes were analyzed using the Kruskal-Wallis test. The statistical significance of intergroup differences was further assessed with the Mann-Whitney test for independent samples and applying Bonferroni's correction (p < 0.016). Results: In group 1, SNB changes were less than the control. There were increases in SNA, ANB, SN-MP, A to N perp and Upper lip to E plane. In group 2, SNB, U1-NA (mm) U1-NA (${\circ}$) and Pog to N perp (mm) changes were less than the control. There were increases in SNA, ANB, SN-MP, A to N perp and Upper lip to E plane. Conclusions: Modified facemask appliance can be used effectively in Class III patients with a retrognathic maxilla. Facemask therapies with expansion resulted in an anterior advancement and translation of maxilla without rotation; and the mandible moved downward and backward ward in both treatment groups.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.3
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• pp.251-257
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• 2017

Purpose: The purpose of this study was to evaluate whether the internal abutment length affected screw stability in an internal connection implant. Materials and methods: Twenty long internal connection implants (Replus system, $4.7{\times}11.5mm$) were selected for this investigation. Abutments were assigned to four groups depending on the length of the internal connection (abutments with internal lengths of 1, 2, 3, and 4 mm, respectively). Each implant fixture specimen was embedded in resin medium and connected to an abutment with an abutment screw. A load of 100 N, applied at an angle of $30^{\circ}$ to the long axis of the implant, was repeated for $1.0{\times}10^6$ cycles. Reverse torque values (RTV) were recorded before and after loading, and the change in RTV was calculated. Data were analyzed with the Kruskal-Wallis test. Results: The change in RTV was not significantly different among the groups (P>.05). Screw loosening and fractures were not observed in any groups, and joint stability was maintained. Conclusion: The internal length of the abutment may not significantly affect the degree of screw loosening.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.210-217
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• 2016

Purpose: The aim of this study was to evaluate the marginal and internal adaptation of monolithic zirconia restoration made without physical model by digital intraoral scanner. Materials and methods: A prospective clinical trial was performed on 11 restorations as a pilot study. The monolithic zirconia restorations were fabricated after digital intraoral impression taking by intraoral scanner (TRIOS, 3shape, Copenhagen, Denmark), computer-aided designing, and milling manufacturing process. Completed zirconia crowns were tried in the patients' mouth and a replica technique was used to acquire the crown-abutment replica. The absolute marginal discrepancy, marginal gap, and internal gap of axial, line angle, and occlusal part were measured after sectioning the replica in the mesiodistal and buccolingual direction. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U test (${\alpha}=.05$). Results: From the adaptation analysis by replica, the statistically significant difference was not found between mesiodistal and buccolingual sections (P>.05), but there was significant difference among the measurement location (P<.01). The amount of absolute marginal discrepancy was larger than those of marginal gap and internal gap (P<.01). Conclusion: Within the limitations of this study, the adaptation accuracy of model-free monolithic zirconia restoration fabricated by intraoral scanner exhibited clinically acceptable result. However, the margin of zirconia crown showed tendency of overcontour and cautious clinical application and follow up is necessary.

• Journal of Wetlands Research
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• v.17 no.1
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• pp.80-90
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• 2015

Variability of precipitation pattern and intensity are increasing due to the urbanization and industrialization which induce increasing impervious area and the climate change. Therefore, more severe urban inundation and flood damage will be occurred by localized heavy precipitation event in the future. In this study, we analyze the future frequency based precipitation under climate change based on the regional frequency analysis. The observed precipitation data from 58 stations provided by Korea Meteorological Administration(KMA) are collected and the data period is more than 30 years. Then the frequency based precipitation for the observed data by regional frequency analysis are estimated. In order to remove the bias from the simulated precipitation by RCP scenarios, the quantile mapping method and outlier test are used. The regional frequency analysis using L-moment method(Hosking and Wallis, 1997) is performed and the future frequency based precipitation for 80, 100, and 200 years of return period are estimated. As a result, future frequency based precipitation in South Korea will be increased by 25 to 27 percent. Especially the result for Jeju Island shows that the increasing rate will be higher than other areas. Severe heavy precipitation could be more and more frequently occurred in the future due to the climate change and the runoff characteristics will be also changed by urbanization, industrialization, and climate change. Therefore, we need prepare flood prevention measures for our flood safety in the future.

• Journal of Hospice and Palliative Care
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• v.18 no.1
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• pp.51-59
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• 2015

Purpose: Predicting life expectancy of terminally ill cancer patients is very important. In many studies, ferritin is detected at higher levels in the sera of cancer patients, and higher ferritin level correlates with aggressiveness of disease and poor outcomes of patients. This study evaluated a prognostic role of serum ferritin levels in terminally ill cancer patients. Methods: This study enrolled 65 terminally ill cancer patients from March through June 2012. We assessed routine laboratory findings including serum ferritin levels as well as demographic and clinical characteristics of the patients. To examine the association between serum ferritin levels and patient's characteristics, we used Spearman's correlation analysis, Wilcoxon's rank sum test or Kruskal-Wallis test, as appropriately. For multivariate analysis, Cox's proportional hazard regression model was used to evaluate significance of serum ferritin levels as a prognostic factor. Results: A negative correlation between serum ferritin levels and survival time was found. After adjusting for sex, age, performance status, creatinine levels and white blood cell counts, serum ferritin levels were significantly associated with survival time. Conclusion: Even at the very end of life of terminal cancer patients, serum ferritin levels were an independent prognostic factor for survival.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.4
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• pp.427-434
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• 2016

The aim of this study was to compare the mechanical properties of high viscosity bulk-fill resin composites, $Filtek^{TM}$ Bulk Fill Posterior Restorative (FBF) and $Tetric^{(R)}$ N-Ceram Bulk Fill (TBF), with conventional composite ($Filtek^{TM}$ Z-350 XT, Z-350). The Vickers hardness test which indicates the degree of conversion was performed and the dye penetration test was performed to measure the microleakage which indicates polymerization shrinkage amount. To minimize experimental error, the standardized 3D-printed molds and the bovine teeth were used. Obtained data were analyzed by the Kruskal-Wallis test and Mann-Whitney test with the confidence interval of 95%. In the microhardness test within 1 hour of polymerization, lower surface of FBF and TBF showed significantly lower value than that of Z-350 (p < 0.05). But after 24 hours, the microhardness of FBF had increased and showed no significant difference with Z-350 (p > 0.05). In top and 2 mm depth surface, mean microhardness values were in the following order: Z-350 > FBF > TBF (p < 0.05). The mean microleakage value of TBF was significantly lower than others (p < 0.05). For clinical application of bulk-fill resin composites, caution for applying masticatory forces during 24 hours after polymerization is advised and further studies to decrease microleakage should be conducted.

• Journal of Korea Water Resources Association
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• v.37 no.12
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• pp.1019-1032
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• 2004

Flood frequency estimate is an essential index for determining the scale of small and middle hydraulic structure. However, this flood quantity could not be estimated directly for practical design purpose due to the lack of available flood data, and indirect method like design rainfall-runoff method have been used for the estimation of design flood. To give the good explain for design flood estimates, regional flood frequency analysis was performed by flood index method in this study. First, annual maximum series were constructed by using the collected data which covers from Japanese imperialism period to 1999. Wakeby distribution recommended by WMO(1989) was used for regional flood frequency analysis and L-moment method by Hosking (1990) was used for parameter estimation. For the homogeneity of region, the discordance and heterogeneity test by Hosking and Wallis(1993) was carried for 4 major watersheds in Korea. Physical independent variable correlated with index flood was watershed area. The relationship between specific discharge and watershed area showed a type of power function, i.e. the specific discharge decreases as watershed area increases. So flood quantity according to watershed area and return period was presented for each watershed(Han rivet, Nakdong river, Geum river and Youngsan/Seomjin river) by using this relation type. This result was also compared with the result of point frequency analysis and its regionalization. It was shown that the dam construction couldn't largely affect the variation of peak flood. The property of this study was also examined by comparison with previous studies.