• Restorative Dentistry and Endodontics
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• 제34권5호
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• pp.415-423
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• 2009

$\beta$-glycerophosphate는 치수의 상아모세포 분화를 촉진하는 물질이다. Portland cement는 수중에서 장기간에 걸쳐 용해되기 때문에 $\beta$-glycerophosphate을 혼합한 Portland cement는 수산화칼슘과 함께 $\beta$-glycerophosphate를 장기간 용출하게 된다. 본 실험에서는 $\beta$-glycerophosphate을 혼합한 Portland cament에 대한 인간치수세포의 반응을 알아보았다. 인간 치수 세포에 대한 $\beta$-glycerophosphate의 효과를 알아보기 위해 다양한 농도의 $\beta$-glycerophosphate와 dexamethasone에 대한 인간 치수 세포의 ALP activity을 측정하였고 alizarin red S로 염색하여 관찰하였다. $\beta$-glycerophosphate가 다양한 농도(10 mM, 100 mM, 1 M)로 혼합된 Portland cement에 대한 인간 치수 세포의 MTS assay, ALP activity를 측정하고 SEM으로 관찰하였다. 치수세포의 석회화 정도를 관찰한 연구에서 $\beta$-glycerophosphate와 dexamethasone 단독으로 적용하였을 때 거의 효과가 없었으나 5 mM $\beta$-glycerophosphate와 100 nM dexamethasone을 혼합 적용하였을 때 가장 높은 ALP acticity를 보였다. 분화제를 첨가하거나 첨가하지 않은 모든 실험군에서 치수세포에 대한 독성은 관찰되지 않았으며 Portland cement에 10 mM $\beta$-glycerophosphate을 혼합한 시편의 ALP activity가 대조군에 비교하여 가장 많이 증가하였다. 결론적으로 $\beta$-glycerophosphate이 혼합된 Portland cement는 세포 독성이 없으며 첨가물이 없는 Portland cement에 비해 치수 분화 및 석회화를 더 많이 일으키므로 임상적으로 $\beta$-glycerophosphate을 혼합한 Portland cement 적용은 재료 하방에 더 많은 상아질을 형성시킬 것으로 추측된다.

• 한국건축시공학회지
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• 제8권5호
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• pp.59-65
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• 2008

In the evaluation method of KS on the activity factor of fly ash, same amount of cement should be replaced with fly ash. Therefore, contradictory effects on concrete strength exist, i. e. strength decease due to low content of cement and strength increase of strength due to filling-pore-function of fly ash. European Committee for Standardization (CEN) specifies the method 1 to 4. adding fly ash without reducing the content of cement, for the evaluation method on activity factor of fly ash. This study investigates the applicability of the method 2 of CEN to mix design of concrete. The followings are derived ; There is a key ratio of f)y ash mixing which enhances the incremental ratio of mixing water to improve fluidity of mortar. The incremental ratio of mixing water is maximized about 11% ratio of fly ash mixing. Compressive strength most slightly increases at that ratio of fly ash mixing. Activity factor of fly ash increases as water-cement ratio becomes low and contents of fly ash becomes high. Moreover, quality of fly ash and condition of mix design affect the applicable amount of fly ash and available range of water-cement ratio. However, this method has some problems for practical purpose because activity factors of fly ash for some cases are over 1.0. Further research should be conducted to develop more useful method of evaluating activity factor of fly ash.

• 대한족부족관절학회지
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• 제22권1호
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• pp.38-43
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• 2018

Purpose: Treatment of diabetic foot infection due to methicillin-resistant Staphylococcus aureus (MRSA) remains challenging. Applying vancomycin-impregnated cement is one of the best methods of treatment. Vancomycin-impregnated cement has been used worldwide; however, to date, there is a limited number of studies regarding its use. We evaluated the duration of antimicrobial activity of vancomycin-impregnated cement stored at room temperature after manufacturing. Materials and Methods: The vancomycin-impregnated cement was manufactured by mixing 1 g of vancomycin with 40 g of polymer and adding 17.90 g of liquid monomer. The cement dough was shaped into flat cylinders with diameter and height of 6 mm and 2 mm, respectively. Another cement of the same shape without mixing vancomycin was prepared as the negative control. All manufactured cements were sterilized with ethylene oxide gas and stored at room temperature. Each cement was placed on Mueller Hinton agar plate lawned with standard MRSA strain. Standard vancomycin disk and gentamicin disk were placed together. After 24 hours, the diameter of inhibition zone was measured, and if the diameter was less than 15 mm, vancomycin-impregnated cement was regarded as a loss of antimicrobial activity. The study was repeated every 2 weeks until vancomycin-impregnated cements lost their antimicrobial activity. Results: Vancomycin-impregnated cement stored for a duration of 16 weeks created a 14 mm inhibition zone, while vancomycin disk created a 15 mm inhibition zone. Vancomycin-impregnated cement stored for a duration of 17 weeks created 7 mm and 9 mm inhibition zones, while vancomycin disk created 16 mm and 15 mm inhibition zones, respectively. Conclusion: We found a decrease of antimicrobial activity in vancomycin-impregnated cements after 16 weeks. After 17 weeks, they showed definite loss of antimicrobial activity. Therefore, we recommend not using vancomycin-impregnated cement spacers that has been stored for more than 16 weeks at room temperature.

• Restorative Dentistry and Endodontics
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• 제12권1호
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• pp.77-84
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• 1986

This study was designed to compare the antimicrobial effect of the several root canal cements and to determine the duration of their activity. After Strep. sanguis 9811 was streaked on the surface of BHI agar and Plain agar, PVC tubes filled with root canal cements were applied and cultured for 48 hours, aerobically. Following results were obtained, 1. All of the examined root canal cements had antimicrobial activity with varying degree. 2. The antimicrobial activity of N2 was larger than any other root canal cements. Nogenol and Tubliseal showed the lowest activity. ZOE, AH26, Procosol and PCA cement showed the moderate antimicrobial activity. (P>0.05) 3. At one day after mixing the root canal cements, all of the root canal cements except N2 and PCA cement showed greatly reduced antimicrobial activity. 4. At three days after mixing, PCA cement showed the reduced antimicrobial activity. N2 showed the reduced activity at 7 days after mixing.

• Computers and Concrete
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• 제11권2호
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• pp.93-104
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• 2013

The use of rock wool waste, an industrial by-product, in cement-based composites has positive effects on the environment because it reduces the problems associated rock wool disposal. The experiments in this study tested cement-based composites using various rock wool waste contents (10, 20, 30 and 40% by weight of cement) as a partial replacement for Portland cement in mortars. The pozzolanic strength activity test, flow test, compressive strength test, dry shrinkage test, absorption test, initial surface absorption test and scanning electron microscope observations were conducted to evaluate the properties of cement-based composites. Test results demonstrate that the pozzolanic strength activity index for rock wool waste specimens is 103% after 91 days. The inclusion of rock wool waste in cement-based composites decreases its dry shrinkage and initial surface absorption, and increases its compressive strength. These improved properties are the result of the dense structure achieved by the filling effect and pozzolanic reactions of the rock wool waste. The addition of 30% and 10% rock wool wastes to cement is the optimal amount based on the results of compressive strength and initial surface absorption for a w/cm of 0.35 and 0.55, respectively. Therefore, it is feasible to utilize rock wool waste as a partial replacement of cement in cement-based composites.

• Restorative Dentistry and Endodontics
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• 제18권2호
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• pp.261-276
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• 1993

The purpose of this study was to evaluate for the cytotoxicity of glass-ionomer cement liners(GC liningcement, Ketac-bond, Vitrebond and Fuji lining LC) on the fibroblasts cultured from human pulp. The fibroblasts were cultured in DMEM-10% FBS medium. The measurement of pH, succinate dehydrogenase (SDH) activity test and $^{51}Chromium$ release test were performed. Viable cell count and $^{14}C$-leucine incorporation rate were evaluated following culture time of 2, 4 and 6 days. The results of this study were as follows : 1. The pH in all cements was to be neutralized as time elapsed, and Fuji lining LC was the lowest pH value among them. 2. SDH activity was more inhibited in GC lining cement and Vitrebond than Ketac-bond and Fuji lining LC with the setting process, and GC lining cement and Ketac-bond were reduced after 5 minute's setting and then elevated as time elapsed. 3. In SDH activity test following exposure time, the activity in Vitrebond, GC lining cement and Fuji lining LC was inhibited with increased exposure time, but it was fairly constant in Ketac-bond. 4. Overall the liquid component was more inhibited than the powder component of glass-ionomer cement in SDH activity test. 5. In $^{51}Cr$-release test, Fuji lining LC was the most released of all the cements tested and followed by : Vitrebond, Ketac-bond, GC lining cement. 6. In viable cell count, the number of cells increased as the culture day proceeded in Ketac-bond, but they decreased in GC lining cement. Fuji lining LC was only observed after 2 days culture and there was not observed the whole culture days in Vitrebond. 7. In $^{14}C$-leucine incorporation rate test, protein synthesis was decreased with the number of culture days in GC lining cement, Vitrebond and Fuji lining LC, but it was followed that of control in Ketacbond.

• 한국세라믹학회지
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• 제37권5호
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• pp.410-417
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• 2000

In this study the effects of specifics surface area of cement, addition amount of gypsum and substitution ratio of gypsum anhydrite ont he physical properties of cement mortars were investigated by measruements of setting time, flow, compressive strength and hydration heat evolution rate. The results showed that fluidity of mortars was increased by 40 wt.% of maximum flow change with the decreasing specific surface area of cement from 3,500$\textrm{cm}^2$/g to 3,300${\pm}$50$\textrm{cm}^2$/g and affected by the relationship between the cement and balancing between the chemical activityof cement and solubility of calcium sulfate are desirable to prevent the fluidity of concrete from decreasing by high temperature in summer season.

• Advances in environmental research
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• 제6권4호
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• pp.255-264
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• 2017

This work investigated the use of sugarcane bagasse ash (SCBA) generated by an energy cogeneration process in sugarcane mill as an alternative raw material in soil-cement brick. The SCBA obtained from a sugarcane mill located in southeastern Brazil was characterized with respect to its chemical composition, organic matter content, X-ray diffraction, plasticity, and pozzolonic activity. Soil-cement bricks were prepared by pressing and curing. Later, they were tested to determine technical properties (e.g., volumetric shrinkage, apparent density, water absorption, and compressive strength), present crystalline phases, and microstructural evolution. It was found that the SCBA contains appreciable amounts of silica ($SiO_2$) and organic matter. The results showed that the SCBA could be used in soil-cement bricks, in the range up to 30 wt.%, as a partial replacement for Portland cement. These results suggest that the SCBA could be valorized for manufacturing low-cost soil-cement bricks.

• 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.

• 한국재료학회지
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• 제22권11호
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• pp.598-603
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• 2012

MgO based cement for the low-temperature calcination of magnesite required less energy and emitted less $CO_2$ than the manufacturing of Portland cements. Furthermore, adding reactive MgO to Portland-pozzolan cement can improve their performance and also increase their capacity to absorb atmospheric $CO_2$. In this study, the basic research for magnesia cement using $MgCO_3$ and magnesium silicate ore (serpentine) as starting materials was carried out. In order to increase the hydration activity, $MgCO_3$ and serpentinite were fired at a temperature higher than $600^{\circ}C$. In the case of $MgCO_3$ as starting material, hydration activity was highest at $700^{\circ}C$ firing temperature; this $MgCO_3$ was completely transformed to MgO after firing. After the hydration reaction with water, MgO was totally transformed to $Mg(OH)_2$ as hydration product. In the case of using only $MgCO_3$, compressive strength was 35 $kgf/cm^2$ after 28 days. The addition of silica fume and $Mg(OH)_2$ led to an enhancements of the compressive strength to 55 $kgf/cm^2$ and 50 $kgf/cm^2$, respectively. Serpentine led to an up to 20% increase in the compressive strength; however, addition of this material beyond 20% led to a decrease of the compressive strength. When we added $MgCl_2$, the compressive strength tends to increase.