• 한국지열·수열에너지학회논문집
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• 제8권2호
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• pp.1-8
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• 2012

The G-class cement is usually used for geothermal well grouting to protect a steel casing which is equipped in a geothermal well to transfer geothermal water from deep subsurface to ground surface. In geothermal grouting process, obtaining appropriate fluidity is extremely important in order to fill cement grout flawlessly. In this paper, a series of the V-funnel and Slump Flow test was performed on both of the Portland cement and the G-class cement in order to compare fluidity and filling ability of those kind of cements. In the result of V-funnel test, the fluidity of G-class cement was evaluated much better than the Portland cement at the water/cement ratio of 0.8. In the case of Slump Flow test, the fluidity of G- class cement was estimated slightly better than the Portland cement at both the water/cement ratio of 0.55 and 0.8. Even though the initial fluidity and filling ability of G-class cement were relatively higher than the Portland cement, the results could be considerably changed with time. The results show that the fluidity and filling ability for geothermal well cementation can be properly controlled with water content and additives for adverse geothermal well environment.

• Restorative Dentistry and Endodontics
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• 제22권2호
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• pp.596-608
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• 1997

The purpose of this study was to compare the apical leakage and adaptation to the dentinal wall of a glass ionomer root canal cement(Ketac-Endo) with those of AH-26 and Tubli-Seal. 102 single-rooted teeth were insrumented with step-back technique and randomly divided into four groups according to kinds of root canal cements: Ketac-Endo, AH-26, Tubli-Seal, and no root canal cement. Four experimental groups were as follows; Group 1 : Filling with gutta-percha and Ketac-Endo Group 2 : Filling with gutta-percha and AH-26 Group 3 : Filling with gutta-percha and Tubli-Seal Group 4 : Filling with gutta-percha without root canal cement All the specimens were obturated with lateral condensation technique, and stored in 100% humidity for 4 days. 20 teeth in each group were placed in centrifuge tube filled with India ink, and then centrifuged for 20 minutes at 3,000 rpm. And they were evaluated for linear dye leakage using a stereoscope and analyzed by one-way ANOVA. 22 teeth were split longitudinally and evaluated the adaptation to the dentinal wall using scanning electron microscope(4 teeth in each group) and stereoscope(2 teeth in 1, 2, 3 group). The obtained results were as follows ; 1. In case of not used root canal cement(Group 4), there was showed much degree of dye penetration comparerd with used root canal cements (Group 1, 2, 3)(P<0.01). 2. In the case of used root canal cements(Group 1, 2, 3), there was no significant difference in linear leakage in groups(P>0.01). 3. In the case of used root canal cements(Group 1, 2, 3), there was showed intimate adaptation to the dentinal wall independent on kinds of root canal cements. 4. Fractured surfaces indicated failure of cohesion in Ketac-Endo, and failure of adhesion to dentine in AH-26 and Tubli-Seal. 5. According to similar apical leakage and adaptability to the dentinal wall to another root canal cements, it is possible to be used glass-ionomer cement as root canal cement.

• Restorative Dentistry and Endodontics
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• 제19권2호
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• pp.409-428
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• 1994

Endodontic surgery is performed when conventional endodontic therapy fails or is contraindicated. In such cases, retrograde filling materials including amalgam, composite resin, and various cements have been used. Biocompatibilty and margin sealing ability of retrograde filling materials are important for the long term success of endodontic surgery. In vitro cell culture is frequently used as the method of measuring the biocompatibilty of dental materials. The purpose of this study was to evaluate the cytotoxicity of six kinds of retrograde filling materials including newly developed light curing glass ionomer cements. Each material was mixed according to. the manufacture's instruction and evaluated as : freshly mixed, 24-hour after mixing, and 168-hour after mixing respectively. The elution solution was extracted after 24-hour contact with materials using media. Cytotoxicity was evaluated by direct contact, or elution contact. Test results of radiochromium($^{51}Cr$) release, cell viability using tetrazolium dye (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl dimethyltetrazolium bromide(MTT) test and lactate dehydrogenase(LD) of damaged L929 cells were analyzed. In the $^{51}Cr$ release of direct contact, all experimental retrograde filling materials except amalgam and glass ionomer cement showed increased cytotoxicity compared to control. In the $^{51}Cr$ release of elution solution, the released $^{51}Cr$ was so minimal that it was impossible. to evlauate the cytotoxicity exactly. The elution solutions of glass ionomer cement and IRM showed marked cytotoxicity in MTT test. LD enzyme activity was highest in tests of direct contact with composite, light curing composite, and light curing glass ionomer cement and IRM. Amalgam revealed least cytotoxicity while IRM showed cytotoxicity using all three methods. Composite, light curing composite and light curing glass iomomer cement were cytotoxic in the tests of $^{51}Cr$ release and LD activity. Glass ionomer cement showed cytotoxic effect only in the MTT method. From these results it is suggested that the standardization and optimization of cytotoxicity testing, especially using elution solutions, should be strongly advised.

• Restorative Dentistry and Endodontics
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• 제8권1호
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• pp.155-159
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• 1982

The author has studied comparatively the sealing quality of conventional Z.O.E. cement, chloropercha and FR cement by means of penetration of 2% methylene blue solution through the apex of human teeth in 112 cases as the time elapsed. The results were as follows; 1. All the specimen, of which dye immersion time is three days, showed dye penetration of low degree unrelated to the kinds of root canal cement and the degree of dye penetration was increased as the time elapsed. 2. Of all the experimental group, the Z.O.E. cement group showed the lowest degree of dye penetration and the FR filling group showed the highest degree of dye penetration. 3. The degree of dye penetration of FR cement group was higher than that of the Z.O.E. cement group but lower than that of the chloropercha group.

• 대한치과보철학회지
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• 제25권1호
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• pp.227-242
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• 1987

This study was designed to investigate the pulpal effects of the glass ionomer cement. (Lining cement, G-C Co. Japan) For this purpose, 10 cats were selected, and Class V cavities were prepared on canines of the cats. One experimental group was filled with glass ionomer cement and the other group was filled with zinc phosphate cement . (G-C Co, Japan) The animals of the experimental and control group were sacrificed at 1,2,3,4,6, weeks after the experiment. For comparison of reparative dentin formation pattern in direction of the pulpal and fractured lateral surface, each of them was observed with scanning electron microscope. The findings led to the following conclusions; 1. Reparative dentin of the glass ionomer cement and zinc phosphate cement filling groups were formed on the internal surface of dentin as the shape of hemispherical and spherical with a rough surface. 2. Some of reparative dentin of the glass ionomer cement filling group was started to form at 1 week after experiment, and at 6 weeks after experiment, it had been increased gradually in number and size. 3. Reparative dentin of zinc phosphate cement filling group was formed vigorously, however, gradually was decreased in number and size, and disappeared at 6 weeks after experiment. 4. During the formation of reparative dentin, peritubular dentins were indistinguishable. 5. The diameter of dentinal tubules of reparative dentin has been decreased, during the reparative dentin formed, and it became very irregularly at 6 weeks after experiment.

• Restorative Dentistry and Endodontics
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• 제19권2호
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• pp.499-512
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• 1994

The purpose of this study was to evaluate the microleakage electrochemically using different retrograde filling materials, different root resection angle, and different cavity preparation instruments. 104 extracted single-rooted teeth were selected for this study. 100 teeth were used as experimental groups and four was used as controls. Anatomical crowns were resected, root canals were prepared, and the apical 2 mm of roots were removed. The experimental roots were randomly divided into five equal groups. Experimental groups : Group 1. no bevel, cavity preparation with ultrasonic instruments, amalgam filling Group 2. no bevel, cavity preparation with ultrasonic instruments, SuperEBA cement filling Group 3. no bevel, cavity preparation with ultrasonic instruments, desiccated ZOE filling Group 4. $45^{\circ}$ bevel, cavity preparation with ultrasonic instruments, amalgam filling Group 5. no bevel, cavity preparation with conventional bur, amalgam filling Microleakage was measured once a day for 30 days using electrochemical method and were analyzed statistically. The results were as follows : 1. The group with Super EBA cement filling showed the least marginal leakage from second to fourth day(p<0.05), there was no significant difference between the group with amalgam filling during eighth to eighteenth day(p>0.05), but after the nineteenth day here was a higher marginal leakage than the group with amalgam filling(p<0.05). 2. The group with desiccated ZOE filling demostrated that the highest marginal leakage, started on the eighth day(p<0.05). 3. The group using ultrasonic instrument showed lower marginal leakage than the group using bur until the nineteenth day(p<0.05), but there was no significant differnce with the group using bur after twentythird day(p>0.05). 4. The group without bevel showed lower marginal leakage than the group with bevel (p<0.05). 5. Whether bevel or nor had much more effect on marginal leakage than with cavity perparation instrument when the cavity was retrogrdefilled with amalgam(stepwise regression).

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.90-91
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• 2020

Utilization of upgraded fine fly ash in cement-based materials has been proved by many researchers as an effective method to improve compressive strength of cement based materials at early ages. The addition of fine fly ash has introduced dilution effect, enhanced pozzolanic reaction effect, nucleation effect and physical filling effect into cement-fly ash system. In this study, an integrated reaction model is adpoted to quantify the contributions from cement hydration and pozzolanic reaction to compressive strength. A modified model related to the physical filling effect is utilized to calculate the compressive strength increment considering the gradual dissolution of fly ash particles. Via combination of these two parts, a numerical model has been proposed to predict the compressive strength development of fine fly ash mortar considering fly ash fineness. The reliability of the model is validated through good agreement with the experimental results from previous articles.

• 한국농촌건축학회논문집
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• 제23권3호
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• pp.1-8
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• 2021

Rural multi-purpose buildings needs to ensure their safety against various disasters. Therefore, a pile foundation, which is a foundation type that can transmit the load of the structure to the bedrock layer, has been designed. The pile foundation method is largely divided into driving piles method and pre-bored pile method. Recently, in order to respond to the Noise and Vibration Control Act and related environmental complaints, construction of pile foundation adopts pre-bored pile method. The bearing capacity of the pre-bored pile method is calculated through a load test in situ. However, a disadvantage stems in that it is difficult to measure the ultimate bearing capacity due to field conditions. Therefore, in this study, the skin frictional force of pre-bored pile was measured through a model test in laboratory for each pile filling material. In result, the pile filling material with using circulating resources shows superior skin frictional force than ordinary portland cement. This study also judged that the result can be applied in place of ordinary Portland cement in the field.

• Advances in concrete construction
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• 제14권2호
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• pp.139-151
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• 2022

Filling materials poured into precast member joint are subjected to restraint stress by the precast member and joint reinforcement. The induced stress will likely cause cracks at early ages and performance degradation of the entire structure. To prevent these issues and design reasonable joints, it is very important to analyze and evaluate the restrained shrinkage cracks of filling materials at various restraint conditions. In this study, a new time zero-that defines the shrinkage development time of a filling material-is proposed to calculate the accurate amount of shrinkage. The tensile stresses and strengths at different ages were compared through the ring test (AASHTO PP34) to evaluate the crack potential of the restrained filling materials at various restraint conditions. The mixture which contained an expansive additive and a shrinkage reducing agent exhibited high resistance to shrinkage cracking owing to the high-drying shrinkage compensation effect. The high-performance, fiber-reinforced cement composite, and ultra-high-performance, fiber-reinforced cement composite yielded very high resistance to shrinkage and cracking owing to the pull-out property of steel fibers. To this end, multiple nonlinear regression analyses were conducted based on the test results. Accordingly, a modified tensile stress equation that considered both the geometric shape of the specimen and the intrinsic properties of the material is proposed.

• Restorative Dentistry and Endodontics
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• 제13권1호
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• pp.53-67
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• 1988

An investigation was carried out to compare the pulp responses against a few type of composite and streptococcus mutans contamination under the zinc oxide eugenol cement, and also confirmed pulpal responses of various composites with or without base. Seventy eight teeth from 6 dogs were employed and divided into 6 groups. Class V cavities were prepared on each tooth routinely with low speed dental engine. Paper disc about 0.3mm thick was immersed in the BHI broth in which streptococcus mutans had been enriched and the disc was inserted on the cavity floor prior to filling. Scotch bond puls Silux as Bis-GMA system composite resin and Helimolar as urethane system composite resin were adopted. Control group: Zinc-Oxide Eugenol cement filling Experimental groups: Group 1. Scotch bond + Silux filling with Dycal base Group 2. Heliomolar filling with Dycal base Group 3. Scotch bond + Silux filling without base Group 4. Heliomolar filling without base Group 5. Streptococcus mutans application. All cavities were sealed with thick ZOE cement to avoid marginal leakage. Postoperative intervals of 1, 2, 3, 4, 5 and 6 weeks teeth were carefully extracted, processed and stained with Hematoxylin and Eosin. The results were as follows: 1. S. mutans application group and composites without any base showed more severe pupal response than control group and dyca based groups. 2. The experimental group of S. mutans application showed severe response in the early stage compared to the two groups of composite resin without base, but no significant difference was found following periods. 3. The difference of pulpal response is not significant between Bis-GMA system and urethane system. 4. Streptococcus mutans application group and composites without base groups showed the evidence of histologic recovery at the six week cases and the large amount of reparative dentin was the prominent feature. 5. Pulp responses against every material were inclined to normal according to the time elapsed.