• The Journal of the Korean dental association
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• v.38 no.12 s.379
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• pp.1167-1171
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• 2000

• 한국전기화학회:학술대회논문집
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• 1999.04a
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• pp.80-80
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• 1999

• 한국전자현미경학회:학술대회논문집
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• 2001.11a
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• pp.66-69
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• 2001

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.812-817
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• 1995

Endodontically treated teeth are usually restored for crown protection, aesthetics, and prevention of root canal recontamination. Restoration of these teeth, however, often requires intracanal posts. Various depths and techniques have been recommended for the preparation of post space. Therefore the purpose of this study was to evaluate the effect that pst preparation has on the coronal seal by linear dye penetration of root canals obturated by lateral condensation, vertical condensation, and thermafil techniques. Forty canals of roots of incisors and canines were cleaned and shaped with the use of a step-back technique. Thirty canals were obturated, 10 each with lateral, vertical, and thermafil techhniques. Five root canals were obturated without a root canal sealer and served as positive controls. Another five root canals were obturated, and their coronal half was sealed with sticky wax and served as negative controls. The apical 5 to 6mm of the filling materials were exposed to india ink for 48 hours. The depth of dye penetration was measured in all groups and statistically analyzed (ANOVA). The results were as follows. 1. The apical plugs in the thermafil groups had the highest degree of coronal dye leakage. 2. The group filled by vertical condensation technique had the lowest degree of coronal dye leakage. 3. No significant statistical difference was found in the amount of coronal dye leakage in canals filled by lateral condensation versus those filled by the veritcal condensation technique. 4. Significant statistical differences in coronal dye penetration were found between the canals filled by thermafil and those filled by the lateral or vertical condensation techniques (p<0.05).

• Applied Microscopy
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• v.42 no.2
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• pp.111-114
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• 2012

The scanning electron microscopy is an ideal technique for examining plant surface at high resolution. Most hydrate samples, however, must be fix and dehydrate for observation in the scanning electron microscope. Because the microscopes operate under high vacuum, most specimens, especially biological samples, cannot withstand water removal by the vacuum system without morphological distortion. Cryo-techniques can observe in their original morphology and structure without various artifacts from conventional sample preparation. Rapid cooling is the method of choice for preparing plant samples for scanning electron microscopy in a defined physiological state. As one of cryo-technique, high-pressure freezing allows for fixation of native non-pretreated samples up to $200{\mu}M$ thick and 2 mm wide with minimal or no ice crystal damage for the freezing procedure. In this study, we could design to optimize structural preservation and imaging by comparing cryo-SEM and convention SEM preparation, and observe a fine, well preserved Arabidopsis stem's inner ultrastructure using HPF and cryo-SEM. These results would suggest a useful method of cryo-preparation and cryo-SEM for plant tissues, especially intratubule and vacuole rich structure.

• Mass Spectrometry Letters
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• v.11 no.2
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• pp.36-40
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• 2020

Untargeted metabolomics is a useful tool for drug development focusing on novel chemotherapeutic and chemopreventative agents against cancer cells. In recent years, quadrupole time of flight liquid chromatography-mass spectrometry (Q-TOF LC/MS)-based untargeted metabolomic approaches have gained importance to evaluate the effect of these agents at the molecular level. The researchers working on cell culture studies still do not apply standardized methodologies on sample preparation for untargeted metabolomics approaches. In this study, the rough and wet lysis techniques performed on MCF-7 breast cancer cells were compared with each other via the Q-TOF LC/MS-based metabolomic approach. The C18 and hydrophilic interaction liquid chromatography (HILIC) columns were used for the separation of the metabolites in MCF-7 cell lysates. 505 peaks were detected through the HILIC column and 551 peaks were found through the C18 column for the wet lysis technique. This situation supported by the base peak chromatograms showed that the wet lysis technique allowed us to extract higher number of non-polar metabolites. Almost equal number of metabolites was found for the C18 and HILIC columns (697 peaks for the HILIC column and 695 peaks for the C18 column) when the rough lysis technique was used. However, the intensities of polar metabolites were higher for the rough lysis technique on base peak chromatograms for both the HILIC and C18 columns. Although cell lysis technique, which is the first step in the sample preparation for cell culture studies, does not cause dramatic differences in the number of the detected metabolite peaks, it affects the polar and non-polar metabolite ratio significantly. Therefore, it must be considered carefully especially for in vitro drug development studies.

• 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.

• Journal of the Korean Ceramic Society
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• v.28 no.10
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• pp.831-837
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• 1991

Spherical TiO2 particles are prepared from TiCl4 aqueous solution by the spray pyrolysis method using ultrasonic atomization technique. The formation mechanism of TiO2 particles from atomized droplets it studied by varying the concentration of the source solution, reaction temperature, and the solvent. spherical TiO2 powders with almost the same normalized particle size distribution can be made reproducibly by changing the concentration of the source solution, and their mean sizes are in the range of 0.2~1.4${\mu}{\textrm}{m}$.

• Applied Microscopy
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• v.45 no.4
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• pp.203-207
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• 2015

Sample preparation is very important for crystal structure analysis of novel nanostructured materials in electron microscopy. Generally, a grid dispersion method has been used as transmission electron microscope (TEM) sampling method of nano-powder samples. However, it is difficult to obtain the cross-sectional information for the tabular-structured materials. In order to solve this problem, we have attempted a new sample preparation method using focused ion beam. Base on this approach, it was possible to successfully obtain the electron diffraction patterns and high-resolution TEM images of the cross-section of tabular structure. Finally, we were able to obtain three-dimensional crystallographic information of novel zeolite nano-crystal of the tabular morphology by applying the new sample preparation technique.

• Restorative Dentistry and Endodontics
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• v.13 no.1
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• pp.79-89
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• 1988

The purpose of this study was to evaluate the canal preparation time, deviation of the apex (Zipping), and debridement effect of the canal of three canal preparation techniques. Thirty extracted 1st and 2nd molars were divided into 3 groups and each group was enlarged by ultrasonic, sonic or hand instrument. The specimens were examined under scanning electron microscope and light microscope. The results were as follows: 1. In the canal preparation time, ultrasonic group was the shortest, followed by sonic, hand group. All pairs of groups were significantly different at the 0.05 level. (P < 0.05) 2. In the deviation of the canal, no two groups were significantly different at the 0.05 level. (P > 0.05) 3. In the evaluation of debris scores, ultrasonic and sonic groups were better debridement effect than hand group in the fine canals. In the large canals, ultrasonic group was the best results, followed by sonic, hand group. 4. In the evaluation of smear layer scores, ultrasonic group was the best and sonic and hand group were same effect in the fine canals. In the large canals, three groups were same effect. 5. In the effect of the removal of predentin and pulpal debris, in the regardless of canal size, three groups were same and pulpal debris was not completely removed by either technique.