• Restorative Dentistry and Endodontics
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• v.33 no.4
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• pp.332-340
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• 2008

The purpose of this study was to evaluate the viability of periodontal ligament cell in rat teeth using slow cryopreservation method with magnetic field through MTT assay and TUNEL test. For each group, 12 teeth of 4 weeks old white female Sprague-Dawley rat were used for MTT assay, and 6 teeth in TUNEL test. The Maxillary left and right, first and second molars were extracted as atraumatically as possible under tiletamine anesthesia. The experimental groups were group1 (immediately extraction), group 2 (cold preservation at 4$^{\circ}C$ for 1 week), group 3 (rapid cryopreservation in liquid nitrogen), group 4 (slow cryopreservation with magnetic field of 1 G), and group 5 (slow cryopreservation). F medium was used as preservation medium and 10% DMSO as cryoprotectant. After preservation and thawing, the MTT assay and TUNEL test were processed. One way ANOVA and Scheffe method were performed at the 95% level of confidence. The value of optical density obtained after MTT analysis was divided by the value of eosin staining for tissue volume standardization. In both MTT assay and TUNEL test, it had showed no significant difference among group 3, 4, and 5. And group 3 had showed higher viability of periodontal ligament cell than group 2. From this study, slow cryopreservation method with magnetic field can be used as one of cryopreservation methods.

• Restorative Dentistry and Endodontics
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• v.34 no.2
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• pp.145-153
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• 2009

The purpose of this study was to evaluate the effect of instrument compliance on the polymerization shrinkage stress measurements of dental composites. The contraction strain and stress of composites during light curing were measured by a custom made stress-strain analyzer, which consisted of a displacement sensor, a cantilever load cell and a negative feedback mechanism. The instrument can measure the polymerization stress by two modes: with compliance mode in which the instrument compliance is allowed, or without compliance mode in which the instrument compliance is not allowed. A flowable (Filtek Flow: FF) and two universal hybrid (Z100: Z1 and Z250: Z2) composites were studied. A silane treated metal rod with a diameter of 3.0 mm was fixed at free end of the load cell, and other metal rod was fixed on the base plate. Composite of 1.0 mm thickness was placed between the two rods and light cured. The axial shrinkage strain and stress of the composite were recorded for 10 minutes during polymerization. and the tensile modulus of the materials was also determined with the instrument. The statistical analysis was conducted by ANOVA. paired t-test and Tukey's test (${\alpha}<0.05$). There were significant differences between the two measurement modes and among materials. With compliance mode, the contraction stress of FF was the highest: 3.11 (0.13). followed by Z1: 2.91 (0.10) and Z2: 1.94 (0.09) MPa. When the instrument compliance is not allowed, the contraction stress of Z1 was the highest: 17.08 (0.89), followed by FF: 10.11 (0.29) and Z2: 9.46 (1.63) MPa. The tensile modulus for Z1, Z2 and FF was 2.31 (0.18), 2.05 (0.20), 1.41 (0.11) GPa, respectively. With compliance mode. the measured stress correlated with the axial shrinkage strain of composite: while without compliance the elastic modulus of materials played a significant role in the stress measurement.

• Restorative Dentistry and Endodontics
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• v.34 no.5
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• pp.450-459
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• 2009

The aim of this study was to measure the initial dynamic modulus changes of light cured composites using a custom made rheometer. The custom made rheometer consisted of 3 parts: (1) a measurement unit of parallel plates made of glass rods, (2) an oscillating shear strain generator with a DC motor and a crank mechanism, (3) a stress measurement device using an electromagnetic torque sensor. This instrument could measure a maximum torque of 2Ncm, and the switch of the light-curing unit was synchronized with the rheometer. Six commercial composite resins [Z-100 (Z1), Z-250 (Z2), Z-350 (Z3), DenFil (DF), Tetric Ceram (TC), and Clearfil AP-X (CF)] were investigated. A dynamic oscillating shear test was undertaken with the rheometer. A certain volume ($14.2\;mm^3$) of composite was loaded between the parallel plates, which were made of glass rods (3 mm in diameter). An oscillating shear strain with a frequency of 6 Hz and amplitude of 0.00579 rad was applied to the specimen and the resultant stress was measured. Data acquisition started simultaneously with light curing, and the changes in visco-elasticity of composites were recorded for 10 seconds. The measurements were repeated 5 times for each composite at $25{\pm}0.5^{\circ}C$. Complex shear modulus G*, storage shear modulus G', loss shear modulus G" were calculated from the measured strain-stress curves. Time to reach the complex modulus G* of 10 MPa was determined. The G* and time to reach the G* of 10 MPa of composites were analyzed with One-way ANOVA and Tukey's test ($\alpha$ = 0.05). The results were as follows. 1. The custom made rheometer in this study reliably measured the initial visco-elastic modulus changes of composites during 10 seconds of light curing. 2. In all composites, the development of complex shear modulus G* had a latent period for $1{\sim}2$ seconds immediately after the start of light curing, and then increased rapidly during 10 seconds. 3. In all composites, the storage shear modulus G" increased steeper than the loss shear modulus G" during 10 seconds of light curing. 4. The complex shear modulus of Z1 was the highest, followed by CF, Z2, Z3, TC and DF the lowest. 5. Z1 was the fastest and DF was the slowest in the time to reach the complex shear modulus of 10 MPa.

• Restorative Dentistry and Endodontics
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• v.32 no.4
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• pp.385-396
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• 2007

The aims of this study were to compare the shaping effect and safety between single length technique recommended by manufacturer and crown-down technique using Mtwo rotary file and to present a modified method in use of Mtwo file. Sixty simulated root canal resin blocks were used. The canals were divided into three groups according to instrument and the manner of using methods. Each group had 20 specimens. Group MT was instrumented with single length technique of Mtwo, group MC was instrumented with crown-down technique of Mtwo and group PT was instrumented with crown-down technique of ProTaper. All of the rotary files used in this study were operated by an electric motor. The scanned canal images of before and after preparation were superimposed. These superimposed images were evaluated at apical 1 to 8 mm levels Angle changes were calculated. The preparation time, weight loss, instrument failure and binding, canal aberrations, and centering ratio were measured. Statistical analysis of the three experimental groups was performed with ANOVA and Duncan's multiple range tests for post-hoc comparison and Fisher's exact test was done for the frequency comparison. In total preparation time, group MT and group MC were less than group PT. In the aberrations, group MT had more elbows than those of group MC and group PT. The binding of group MC was least and group MT was less than group PT (P < 0.05). Under the condition of this study, crown-down technique using Mtwo rotary file is better and safer method than single length technique recommended by the manufacturer.

• Pediatric Infection and Vaccine
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• v.16 no.1
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• pp.40-46
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• 2009

Purpose : The purpose of this study was to identify useful predictors for diagnosing bacterial meningitis and performing CSF studies in febrile infants three months or younger. Methods : Six hundred and fifty two febrile infants with a rectal temperature ${\geq}38.0^{\circ}C$ presented from January 2003 to April 2008 and were retrospectively studied. The total white blood cell count (WBC), band count, absolute neutrophil count (ANC), quantitative C-reactive protein (CRP) and blood cultures were performed on admission. The clinical variables associated with bacterial meningitis were analyzed. Results : In patients with bacterial meningitis, the clinical variables including CRP (P=0.036), band count (P=0.037), ANC (P=0.036) and age (P=0.001) were significantly different. The area under the receiver-operating characteristic curve was 0.969 for CRP, 0.946 for the band count, 0.765 for the ANC and 0.235 for age. A CRP cutoff point of 8 mg/dL was determined to maximize both the sensitivity and specificity (sensitivity 83%, specificity 95%, likelihood ratio 16.6). A CRP concentration of <7 mg/dL "ruled-out" bacterial meningitis, with a likelihood ratio of 0.17, a posttest probability of <0.1% and negative predictive value 91%. A CRP concentration greater than 9 mg/dL had a much higher likelihood ratio (20.1) than the band count (16.6) and ANC (2.2). Conclusion : The CRP concentration was a useful laboratory test for the differential diagnosis of bacterial meningitis among febrile infants three months of age or younger. A CRP concentration of <7 mg/dL effectively ruled out bacterial meningitis; a value ${\geq}9mg/dL$ increased the clinical suspicion of bacterial meningitis and the need for CSF evaluation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2903-2913
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• 2014

The purpose of this study was to examine the effects of aroma inhalation method with roll-on in occupation stress, depression and sleep in female manufacture shift workers. The study was a nonequivalent control group pre-post test design. The subjects in this study were female manufacture shift workers who were from K-do area; 26 in the experiment group and 26 in the control group. Data was collected from April 1 to May 25. The questionnaires about pre and post occupation stress, depression and sleep were used to identify the effect of aroma inhalation method with roll-on. The data was analyzed using SPSS Win 18.0 version program. The homogeneity between two groups of general characteristics was analyzed by Chi-square test and independent t-test. The homogeneity of occupation stress, depression and sleep were analyzed by independent t-test. The difference of pre-post occupation stress, depression and sleep were analyzed by independent t-test. The finding of this study were as follows: The first research hypothesis that the occupation stress of the experimental group might get less than the control group was rejected(t=-0.37, p=.717). The second research hypothesis that depression of the experimental group might get less than the control group was accepted(t=-6.11, p<.001). The third research hypothesis that sleep of the experimental group might get less than the control group was accepted(t=3.15, p=.003). Based on the above-mentioned findings, Aroma inhalation method with roll-on can be utilized as an effective intervention for depression and sleep in female shift workers in the manufacturing industry. and The multiple nursing intervention should be needed to decrease on occupation stress in female manufacture shift workers.

• Restorative Dentistry and Endodontics
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• v.34 no.4
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• pp.356-363
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• 2009

The purpose of this study was to evaluate the viability of periodontal ligament cells in rat teeth using slow cryo-preservation method under pressure by means of MTT assay and WST-1 assay. Eighteen teeth of Sprague-Dawley white female rats of 4 week-old were used for each group. Both sides of the first and second maxillary molars were extracted as atraumatically as possible under Tiletamine anesthesia. The experimental groups were group 1 (Immediate control), group 2 (Cold preservation at $4^{\circ}C$for 1 week), group 3 (Slow freezing), group 4 (Slow freezing under pressure of 3 MPa). F-medium and 10% DMSO were used as preservation medium and cryo-protectant. For cryo-preservation groups, thawing was performed in $37^{\circ}C$water bath, then MTT assay and WST-1 assay were processed. One way ANOVA and Tukey method were performed at the 95% level of confidence. The values of optical density obtained by MTT assay and WST-1 were divided by the values of eosin staining for tissue volume standardization. In both MTT and WST-1 assay, group 4 showed significantly higher viability of periodontal ligament cells than group 2 and 3 (p < 0.05), but showed lower viability than immediate control group. By the results of this study, slow cryo-preservation method under pressure suggests the possibility for long term cryo-preservation of the teeth.

• Restorative Dentistry and Endodontics
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• v.35 no.6
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• pp.445-452
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• 2010

Objectives: The aim of this study was to compare apical sealing ability and physical properties of MTA, MTA - AH-plus mixture (AMTA) and experimental Portland cement - Epoxy resin mixture (EPPC) for a development of a novel retro-filling material. Materials and Methods: Forty-nine extracted roots were instrumented and filled with gutta-percha. Apical root was resected at 3 mm and the retro-filling cavity was prepared for 3 mm depth. Roots were randomly divided into 3 groups of 15 roots each. The retro-filling was done using MTA, AMTA, and EPPC as the groups divided. Four roots were used as control groups. After setting in humid condition for 24 hours, the roots were immersed in 1% methylene blue dye solution for 72 hours to test the apical leakage. After immersion, the roots were vertically sectioned and photos were taken to evaluate microleakage. Setting times were measured with Vicat apparatus and digital radiographs were taken to evaluate aluminum equivalent thickness using aluminum step wedge. The results of microleakage and setting time were compared between groups using one-way ANOVA and Scheffe's post-hoc comparison at the significance level of 95%. Results: AMTA and EPPC showed less microleakage than MTA group (p < 0.05). AMTA showed the highest radio-opacity than other groups and the novel EPPC showed 5 mm aluminum thickness radio-opacity. EPPC showed the shortest initial and final setting times than other groups while the MTA showed the longest (p < 0.05). Conclusions: Under the condition of this study, the novel composite using Portland cement-Epoxy resin mixture may useful for retro-filling with the properties of favorable leakage resistance, radio-opacity and short setting time.

• Journal of Science and Technology Studies
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• v.16 no.2
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• pp.99-147
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• 2016

This paper critically reviews the previous discussion over public engagement with science and technology by Science and Technology Studies literatures with a focus on justification and acceptance. Recent studies pointed out that the "participatory turn" after the late 1990s was followed by confusion and disagreement over the meaning and agency of public engagement. Their discussion over the reproduction of the ever-present boundary between science and society along with so-called late modernity and post-normal science and sometimes through the very processes of public engagement draws fresh attention to the old problem: how can lay participation in decision-making be justified, even if we agree that privileging the position of experts in governance of science and technology is no longer justified? So far STS have focused on two conditions for participatory turn-1) uncertainties inherent in experts' ways of knowing and 2) practicability of lay knowledge. This paper first explicated why such discussion has not been logically sufficient nor successful in promoting a wide and well-thought-out acceptance of public engagement. Then the paper made a preliminary attempt to explain what new types of expertise can support the construction and sustainment of participatory governance in science and technology by focusing on one case of lay participation. The particular case discussed by the paper revolves around the actions of a civil organization and an activist who led legal and regulatory changes in wind power development in Jeju Special Self-governing Province. The paper analyzed the types of expertise constructed to be effective and legitimate during the constitution of participatory energy governance and the local society's support for it. The arguments of this paper can be summarized as follows. First, an appropriate basis of the normative claim that science and technology governance should make participatory turn cannot be drawn from the essential characteristics of lay publics-as little as of experts. Second, the type of 'expertise' which can justify participatory governance can only be constructed a posteriori as a result of the practices to re-construct the boundaries between factual statements and value judgment. Third, an intermediary expertise, which this paper defines as a type of expertise in forming human-nonhuman associations and their new pathways for circulations, made significant contribution in laying out the legal and regulatory foundation for revenue sharing in Jeju wind power development. Fourth, experts' conventional ways of knowing need to be supplemented, not supplanted, by lay expertise. Ultimately, the paper calls for the necessity to extend STS discussion over governance toward following the actors. What needs more thorough analysis is such actors' narratives and practices to re-construct the boundaries between the past and present, facts and values, science and society. STS needs a renewed focus on the actual sites of conflicts and decision-making in discussing participatory governance.

• Journal of The Korean Association For Science Education
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• v.41 no.5
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• pp.371-390
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• 2021

The purpose of this study is to develop a neuropsychological model for the spatial ability factor and to divide the brain active area involved in the light & shadow problem solving process into the domain-general ability and the domain-specific ability based on the neuropsychological model. Twenty-four male college students participated in the study to measure the synchronized eye movement and electroencephalograms (EEG) while they performed the spatial ability test and the light & shadow tasks. Neuropsychological model for the spatial ability factor and light & shadow problem solving process was developed by integrating the measurements of the participants' eye movements, brain activity areas, and the interview findings regarding their thoughts and strategies. The results of this study are as follows; first, the spatial visualization and mental rotation factors mainly required activation of the parietal lobe, and the spatial orientation factor required activation of the frontal lobe. Second, in the light & shadow problem solving process, participants use both their spatial ability as a domain-general thought, and the application of scientific principles as a domain-specific thought. The brain activity patterns resulting from a participants' inferring the shadow by parallel light source and inferring the shadow when the direction of the light changed were similar to the neuropsychological model for the spatial visualization factor. The brain activity pattern from inferring an object from its shadow by light from multiple directions was similar to the neuropsychological model for the spatial orientation factor. The brain activity pattern from inferring a shadow with a point source of light was similar to the neuropsychological model for the spatial visualization factor. In addition, when solving the light & shadow tasks, the brain's middle temporal gyrus, precentral gyrus, inferior frontal gyrus, middle frontal gyrus were additionally activated, which are responsible for deductive reasoning, working memory, and planning for action.