• Restorative Dentistry and Endodontics
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• v.18 no.1
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• pp.197-204
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• 1993

This study was conducted to evaluate and compare the apical leakage in the following retrofilling techniques after apical resection; No apical cavity preparation and no retrofilling(control group), Amalgam(group I) or silver glass ionomer cement(group II) retrofilling after apical cavity preparation with mini contra-angle and bur, Amalgam(group III) or silver glass ionomer cement(group N) retrofilling after apical cavity preparation with ultrasonic micro endo tip. Extracted ninety upper anterior and lower canine teeth were fixed in skull simulators and root canals were prepared with step-back method and obturated with gutta-percha and zinc oxide eugenol sealer. Obturated roots were resected 2mm from apical ends and apical cavities of 1mm width and 2mm depth were prepared and retrofilled by above mentioned methods. After application of nail varnish on all surface except resected surface, apical 1/3 of the roots were placed in 1% methylene blue solution for 3 days. After longutudinal sectioning to expose central parts of filled materials, depths of penetrated dye were measured by measuring microscope and were analyzed statistically. The results were as follows. 1. Having no relation with instruments used in apical cavity preparation, amalgam retrofilling groups(group I and II) showed less apical leakage which was not significant statistically than no retrofilling group(control group) (P<0.05), but silver glass ionomer cement retrofilling gruoups(group II and IV) showed significantly less apical leakage than no retrofilling group(control group) (P<0.01). 2. In the groups retrofilled with the same material, the apical leakage in cavities prepared with ultrasonic micro endo tip (group III and IV) was less than that in cavities prepared with mini contra-angle and bur(group I and II), but not significant statistically(P>0.05). 3. When apical cavities were prepared with same instrument. the egroups retrofilled with silver glass ionomer cement(group II and IV) showed significantly less apical leakage than the groups retrofilled with amalgam(group I and III)(<0.01).

• Korean Journal of Materials Research
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• v.20 no.3
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• pp.117-124
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• 2010

Titanium dioxide ($TiO_2$) particles deposited on different quantitative Fe-treated carbon nanotube (CNT) composites with high photocatalytic activity of visible light were prepared by a modified sol-gel method using TNB as a titanium source. The composites were characterized by BET, XRD, SEM, TEM and EDX, which showed that the BET surface area was related to the adsorption capacity for each composite. From TEM images, surface and structural characterization of for the CNT surface had been carried out. The XRD results showed that the Fe-ACF/$TiO_2$ composite mostly contained an anatase structure with a Fe-mediated compound. EDX results showed the presence of C, O, and Ti with Fe peaks in the Fe-CNT/$TiO_2$ composites. The photocatalytic activity of the composites was examined by degradation of methylene blue (MB) in aqueous solution under visible light, which was found to depend on the amount of CNT. The highest photocatalytic activity among the different composites was related to the optimal content of CNT in the Fe-CNT/$TiO_2$ composites. In particular, the photocatalytic activity of the Fe-CNT/$TiO_2$ composites under visible light was better than that of the CNT/$TiO_2$ composites due to the introduction of Fe particles.

• Korean Journal of Chemical Engineering
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• v.35 no.12
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• pp.2384-2393
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• 2018

Porous alginate-based hydrogel beads (porous ABH) have been prepared through a facile and sustainable template-assisted method using nano-calcium carbonate and nano-$CaCO_3$ as pore-directing agent for the efficient capture of methylene blue (MB). The materials were characterized by various techniques. The sorption capacities of ABH towards MB were compared with pure sodium alginate (ABH-1:0) in batch and fixed-bed column adsorption studies. The obtained adsorbent (ABH-1:3) has a higher BET surface area and a smaller average pore diameter. The maximum adsorption capacity of ABH-1:3 obtained from Langmuir model was as high as $1,426.0mg\;g^{-1}$. The kinetics strictly followed pseudo-second order rate equation and the adsorption reaction was effectively facilitated, approximately 50 minutes to achieve adsorption equilibrium, which was significantly shorter than that of ABH-1:0. The thermodynamic parameters revealed that the adsorption was spontaneous and exothermic. Thomas model fitted well with the breakthrough curves and could describe the dynamic behavior of the column. More significantly, the uptake capacity of ABH-1:3 was still higher than 75% of the maximum adsorption capacity even after ten cycles, indicating that this novel adsorbent can be a promising adsorptive material for removal of MB from aqueous solution under batch and continuous systems.

• Textile Coloration and Finishing
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• v.30 no.4
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• pp.245-255
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• 2018

In this study, cotton fabrics were coated with $TiO_2$ nanoparticles using 3-mercaptopropyltrimethoxysilane(3-MPTMS), which is highly reactive to cotton fabrics, as a medium, and the characteristics, antimicrobial properties, and photodegradation properties of the fibers were measured. The manufacturing process is as follows. (1) 3-MPTMS was added to isopropanol, and $TiO_2$ colloid was added to the mixture to prepare a solution. (2) Cellulose fibers were immersed in the prepared $3-MPTMS/TiO_2$ solution, stirred for 90 minutes at $45^{\circ}C$ in a constant temperature water bath, and dried thereafter. In order to identify the morphology of the cellulose fibers coated with $TiO_2$ nanoparticles, the surface was observed with a scanning electron microscope(SEM), and SEM-EDS was measured to identify the adhesion of $TiO_2$ nanoparticles. The SEM images showed $TiO_2$ nanoparticle and 3-MPTMS coated layers on the fibers and it was identified that $TiO_2$ nanoparticles were attached to the cellulose fibers. The antimicrobial activity of $3-MPTMS/TiO_2$-treated cotton fabrics was measured using a bacterial reduction method. $3-MPTMS/TiO_2$ cellulose fibers which was irradiated by ultra violet light, showed antimicrobial activity against Escherichia coli(ATCC 43895) and Staphylococcus aureus(ATCCBAA-1707) unlike unirradiated fibers. The cellulose fibers were stained with methylene blue and the photodegradation performance of the stained fabrics was analyzed. The stained fabrics showed high degradation performance with photolytic reactions of $TiO_2$ nanoparticles.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2283-2289
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• 2018

$TiO_2$ microspheres were successfully synthesised by simple solution phase method by using various amount of titanium butoxide as precursor. The prepared $TiO_2$ were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance absorption spectra (UV-DRS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XRD analysis revealed that the as-synthesized $TiO_2$ microsphere poses an anatase phase. The photocatalytic degradation experiments were carried out with three different dyes, such as methylene blue, brilliant black, reactive red-120 for four hours under UV light irradiation. The results show that $TiO_2$ morphology had great influence on photocatalytic degradation of organic dyes. The experimental results of dye mineralization indicated the concentration was reduced by a high portion of up to 99% within 4 hours. On the basis of various characterization of the photocatalysts, the reactions involved to explain the photocatalytic activity enhancement due to the concentration of titanium butoxide and morphology include a better separation of photogenerated charge carriers and improved oxygen reduction inducing a higher extent of degradation of aromatics.

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.780-788
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• 1995

The purpose of this study was to compare the apical seal following root canal shaping by different methods. From fourty extracted mandibular 1st and 2nd molars, fourty mesial roots whose canals have some degree of curvature were selected. The mesiobuccal root portion including mesiobuccal portion of a crown was sectioned in each molar. After access cavity preparation for the mesiobuccal canal, working length was determined with # 10 K-file. The sectioned roots were implanted in acrylic resin block and randomly divided into four groups. The canals of group I were shaped by step-down/balanced force, group II by stepdown/step-back, group III by step-back and group IV by conventional method. All of the shaped canals were obturated by Thermafil method and access cavities were filled with IRM. The roots were removed from acrylic resin block and placed in 100 % humidity for 7days. Except the root surfaces of apical 2mm, the root surfaces were nail-varnished 3 times. After the roots were placed in 700 torr vacuum pressure for 15 minutes, they were immersed in 2% methylene blue solution for 4 days. Nail varnishes were removed with acetone. After that, the roots were decalcified in 5 % nitric acid and dehydrated with alcohol series. Transparent specimens were made by methyl salicylate and the quality of apical seal was assessed by measuring the leakage linearly. The results were as follows. 1. The leakage in canals shaped by step-down/balanced force method was significantly less than that in canals shaped by step-back method(P<0.05) and was less but not statistically than that in canals shaped by step-down/step-back method (P>0.05). 2. The leakage in canals shaped by step-down/step-back method was less than that in canals shaped by step-back method, but there was no statistical significance(P>0.05). 3. The leakage in canals shaped by conventional method was significantly more than that in canals shaped by step-down/balanced force, step-down/step-back and step-back method (P<0.05).

• Journal of the Mineralogical Society of Korea
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• v.16 no.2
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• pp.135-149
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• 2003

Domestic zeolite ores are mostly composed of Ca-type clinoptilolite, accompanying a little amounts of mordenite. However, other types of zeolite ores rich in ferrierite, heulandite, or mordenite are less commonly found. Based on the quantitative XRD analysis, zeolite contents are determined to be nearly 50∼90 wt%. Impurities (mostly ＞ 10 wt%) in the zeolite ores chiefly consist of quartz, feldspar, smectite, and opal-CT. The determined CEC values ($CEC_{AA}$ ) of powdery samples (grain size: < 125 $\mu\textrm{m}$) of zeolite ores by the Ammonium Acetate method are mostly higher than 100 meq/100 g. Some zeolites from the Guryongpo area, corresponding to the clinoptilolite ore, are measured to be dominantly high in CEC values ranging 170∼190 meq/100 g. Cation exchange property of the zeolite ores varies greatly depending on the types or zeolite species present in the ores. Despite of the lower grade in zeolite content, the $CEC_{AA}$ of ferrierite ore is comparatively high. Compared to this, the $CEC_{AA }$ of heulandite ore is very low, though the zeolite ore exhibits the highest grade ranging up to about 90 wt%. In addition, the CEC values calculated theoretically from the framework composition of clinoptilolite-heulandite series are not consistent with those determined by the cation exchage experiment. The measured $CEC_{AA}$ of clinoptilolite ores are generally higher than those of heulandite ores. This may be due to the higher Ca abundance in exchangeable cation composition and the presence of probable stacking faults in heulandite. The variation of $CEC_{CEC}$ is roughly proportional, though not strictly compatible, to the zeolite contents in clinoptilolite ores. It seems to be caused by the fact that the $CEC_{AA}$ of clinoptilolite locally varies depending on crystal-chemical diversity, i. e., the variation in framework composition (Si/Al) and exchangeable cation composition (especially, the contents of Ca and K). In addition, the determined CEC values ($CEC_{MB}$ ) of zeolite ores by the Methylene Blue method are much higher than those calculated from smectite contents. It suggests a probable reaction of Methylene Blue ion ($C_{16}$ $H_{18}$ $N_3$S+) with larger-pore zeolites than clinoptlolite-heulandite series, i.e., ferrierite and mordenite as well as with smectite. This can be supported by the fact that the ferrierite ore accompanying little amount of smectite has the highest value in CE $C_{MB}$ .

• Restorative Dentistry and Endodontics
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• v.27 no.4
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• pp.432-440
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• 2002

The purpose of this study is to identificate root canal system including ideal access placement, root curvature, canal configuration, incidence of isthmus in mandibular incisors for success of endodontic treatment. 200 mandibular incisors were selected. The ideal access placement was determimed as follows. The teeth there radiographed from mesiodistal and buccolingual views using intraoral dental film. The image was divided into coronal, middle and apical third using the proximal film. Straight line access was determined by measuring the faciolingual canal width and placing points at midway point between the buccal and lingual wall at the junction of the middle and apical third and at the juntion of coronal and middle third of the root canal. A line was drawn connecting these two points extending through the crown of the tooth. The point at which the line crossed the external crown surface was recorded as facial, incisal, lingual. Degree of root curvature was determined by Schneider Protractor Method. Both section method and clearing method were used in this study. By section method, 100 mandibular incisors were embedded in clear resin and transeverse serial sectioned at 0.5, 1.0, 2.0, 3.0, 4.0, 5.0mm level from root apex. The resected surfaces were stained by methylene blue and examined under $\times$40 magnification with a stereomicroscope. By clearing method, 100 mandibular incisors were cleared in methysalicylate after decalcification with 10% nitric acid and evaluated under $\times$18 magnification with a stereomicroscope. The results were as follows ; 1. 29% had the center of the plotted straight-line access facial to incisal edge, whereas 71% had straight-line access at the incisal edge. When incisal wear classified as extensive, the straight-line access was plotted on the incisal edge 95.5%. When incisal wear classified as slight/none, the straight-line access was plotted on the facial 65.9%. 2. Degree of curvature of main canal was straight or almost straight, and only 10% in buccolingual direction had a degree of curvature greater than 20 degrees and 5.5% in mesiodistal direction had. 3. In section method, canal configuration analysis showed that 51% of the specimen classified as type I, 27% as type II, 12% as type III, 10% as type IV. For theses setions with two canals, the incidence of an isthmus was 36.7%, 64.3%, 79.2%, 96.3%, 97.4%, 97.6% at each level and highest in 3~5mm sections. 4. In clearing method, canal configuration analysis showed that 74% of the specimen classified as type I, 11% as type II, 6% as type III, 9% as type IV. These results suggested that traditional access from lingual should be moved as far toward the incisal as possible to locate and debride the lingual canal and root canal system should be cleaned, shaped completely and obturated three dimensionally for successful endodontic treatment.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.67 no.3
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• pp.137-146
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• 2022

Seed disinfection is a necessary process to decrease Bakanae disease in rice and is carried out at 30℃ to increase disinfection efficiency. However, the length of sprout after seed disinfection is not suitable for sowing, so additional processes such as seed soaking is needed. For this reason, this study was conducted to develop the efficient and effective seed disinfection method. When the seed disinfection finished after soaking seeds in cold water for 2 days, length of sprout was about 1.0 mm and sowing can be done without additional processes. In addition, the incidence of Bakanae disease was greatly reduced by 64% compared to conventional method. In order to find out why the newly developed method (disinfection after soaking) is more efficient than conventional method, soaked and not soaked seeds were stained using methylene blue staining. It was found that soaked seeds were more easily stained with about 50% of internal and external endosperm stained. Therefore, pesticide can be absorbed easily into internal endosperm of soaked seeds and efficiently destroy the spore of pathogen. As a results of this study, newly developed method will be useful as it can improve efficiency of agricultural work and also effectively decrease Bakanae disease compared to conventional method.

• Restorative Dentistry and Endodontics
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• v.27 no.5
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• pp.521-529
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• 2002

The purpose of this study was to compare the shaping time of two shaping methods and the leakage of three different obturation techniques. Ninty three canaled human molar teeth were used, which were randomly divided into two groups of forty teeth each and ten control teeth. After working length determination, the one group was prepared crown-down technique using rotary root canal instruments of GT rotary files .12/20, .10/20, .08/20 and .06/20 taper(Maillefer Instrument SA. Switzerland). The other group was instrumented with Gates Glidden burs(#1, #2, and #3) to coronal preparation and GT rotary files .08/20 and .06/30 taper to apical preparation. Shaping time was measured. After root canals were instrumented, they were divided to three subgroups and obturated as follows : Subgroup 1, obturated with single cone method Subgroup 2, obturated with lateral condensation : Subgroup 3, obturated with continuous wave technique. Three subgroups were obturated using non-standardized gutta-percha cone(Diadent, Korea, .06 or .08 taper) and AH-26(Dentsply DeTrey, Germany) as a root canal cement. Ten unobturated teeth served as positive and negative controls. After immersion in 2% methylene blue solution for 1 month, the teeth were washed during 24h. The teeth were demineralized in 10% nitric acid and dehydrated by immersion in 80, 90 and 100% ethyl alcohol. The teeth were finally cleared and stored in 100% methylsalicylate, and apical dye penetration was evaluated under stereomicroscope(Leica M420, LC, U.S.A)at $\times$8.75 magnification. Liner measurement of dye penetration was assessed with the use of digitalized image analysing system (analySIS, GmbH, Germany) The data were analysed statistically using independent T-test and Two-way ANOVA and Tukey test. The result were as follows 1. In canal prepared with GT$^{TM}$ rotary file, shaphing time taked more than the group of using Gates Glidden drill to coronal preparation without statistical significance (p>0.05) 2. The group of single cone obturation using canal preparation of GT$^{TM}$ rotary files showed significantly more apical leakage than those of lateral condensation and continuous wave technique regardless of shaping method (p<0.05). 3 The group of single cone obturation using canal preparation of GT$^{TM}$ rotary files and Gates Glidden drill showed significantly more apical leakage than those of continuous wave technique regardless of shaping method (p<0.05). 4. Regardless of shaping method, The group of continuous wave obturation showed less apical leakage than those of lateral condensation without statistical significance (p>0.05). 5. The group of single cone obturation using canal preparation of GT$^{TM}$ rotary files and Gates Glidden drill showed more apical leakage than the group of lateral condensation using same shaping method with-out statistical significance (p＞0.05).