• The korean journal of orthodontics
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• v.25 no.2 s.49
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• pp.223-233
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• 1995

The purpose of this study was to evaluate the effects of surface conditioning with $10\%$ polyacrylic acid, etching with $38\%$ phosphoric acid, and polishing with a slurry of pumice on shear bond strengths of light-cured glass ionomer cement, chemically cured glass ionomer cement, and a composite resin to enamel, and to observe the failure patterns of bracket bondings. Shear bond strengths of glass ionomer cements were compared with that of a composite resin. Metal brackets were bonded on the extracted human bicuspids after enamel surface treatments, and samples were immersed in the $37^{\circ}C$ distilled water bath, and shear bond strengths of glass ionomer cements and a composite resin were measured on the Instron machine after 24hrs passed, and the deboned samples were measured in respect of adhesive remnant index. Scanning electron micrographs were taken of enamel surfaces after various treatments. The data were evaluated and tested by ANOVA and Duncan's multiple range test, and those results were as follows. 1. Shear bond strength of light-cured glass ionomer cement showed statistically higher than that of chemically cured glass ionomer cement. 2. Shear bond strengths of light-cured and chemically cured glass ionomer cements to enamel treated with $10\%$ polyacrylic acid and $38\%$ phosphoric acid showed statistically higher than those with a slurry of pumice. 3. According to scanning electron micrographs, enamel surface conditioned with $10\%$ polyacrylic acid is slightly etched and cleaned, that etched with $38\%$ phosphoric acid is severely etched, and that polished with a slurry of pumice is irregulary scretched and not completely cleaned. 4. After debonding, light-cured glass ionomer cement to enamel treated with $10\%$ polyacrylic acid showed less residual materials on the enamel solace than composite resin to enamel etched with $38\%$ phosphoric acid. 5. There was no significant difference in the shear bond strength of light-cured glass ionomer cement to enamel treated with $10\%$ polyacrylic acid and that of composite resin to enamel etched with $38\%$ Phosphoric acid.

• Journal of dental hygiene science
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• v.11 no.5
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• pp.445-453
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• 2011

Objectives : The purpose of this study was to determine of fluoride-releasing of orthodontic resin cements containing fluoride and compare decalcification of tooth attached fluoride and non-fluoride resin cements. Methods : Total eighty premolar tooth were used in this study. Forty tooth were used for fluoride releasing measurement and forty tooth were used for decalcification measurement. Each forty tooth were randomly divided into four groups, and brackets were attached on tooth surface with Blugloo, Light Bond, Orthofolw(experimental groups) and Transbond cement(control group). After brackets were attached on tooth surface, forty tooth were immersed in artificial salival and then the quantity of fluoride releasing was measured ever day for 8days and then three-days intervals for 3 weeks. Forty tooth were immersed in decalcification solution for 48hours and then degree of decalcification was measured as lesion area, ${\Delta}F$, and ${\Delta}Q$ using QLF. The data were analysed by one-way ANOVA and Pearson's correlation coefficient using SPSS 12.0 program. Results : Fluoride release of experimental groups was higher than control group(p<0.05). Cumulative fluoride release of experimental groups was also higher than control group(p<0.05). There were the highest release during first day. ${\Delta}F$, and ${\Delta}Q$ was high TB > BG > OF > LB (p<0.05). Change of ${\Delta}F$, and ${\Delta}Q$ was also high TB > BG > OF > LB (p<0.05). As for correlation between fluoride release and lesion area, ${\Delta}F$, and ${\Delta}Q$ showed negative correlation but there was no significant difference. Conclusions : This study shows that orthodontic reins cements containing fluoride release fluoride and prevent initial enamel decalcification caused by orthodontic treatment.

• Restorative Dentistry and Endodontics
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• v.33 no.4
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• pp.369-376
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• 2008

The aim of this study was to compare the compositions and cytotoxicity of white ProRoot MTA (white mineral trioxide aggregate) and 3 kinds of Portland cements. The elements, simple oxides and phase compositions of white MTA (WMTA), gray Portland cement (GPC), white Portland cement (WPC) and fast setting cement (FSC) were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray fluorescence spectrometry (XRF) and X-ray diffractometry (XRD). Agar diffusion test was carried out to evaluate the cytotoxicity of WMTA and 3 kinds of Portland cements. The results showed that WMTA and WPC contained far less magnesium (Mg), iron (Fe), manganese (Mn), and zinc (Zn) than GPC and FSC. FSC contained far more aluminum oxide ($Al_2O_3$) than WMTA, GPC, and WPC. WMTA, GPC, WPC and FSC were composed of main phases. such as tricalcicium silicate ($3CaO{\cdot}SiO_2$), dicalcium silicate ($2CaO{\cdot}SiO_2$), tricalcium aluminate ($3CaO{\cdot}Al_2O_3$), and tetracalcium aluminoferrite ($4CaO{\cdot}Al_2O_3{\cdot}Fe_2O_3$). The significance of the differences in cellular response between WMTA, GPC, WPC and FSC was statistically analyzed by Kruskal-Wallis Exact test with Bonferroni' s correction. The result showed no statistically significant difference (p > 0.05). WMTA, GPC, WPC and FSC showed similar compositions. However there were notable differences in the content of minor elements. such as aluminum (Al), magnesium, iron, manganese, and zinc. These differences might influence the physical properties of cements.

• The Korean Journal of Ceramics
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• v.2 no.3
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• pp.147-151
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• 1996

By adding borax into the raw mix, Modified Belite Cement clinker and cements were prepared. Clinkerization and hydration reactions were investigated in order to better understand. Borax-bearing MBC clinker sintered at 1300℃ for 1 hour showed excellent burnability. Borax stabilized α'and β-C2S at room temperature. In the hydration of the cement prepared with the borax-bearing clinker, ettringite, monosulphate, C-S-H hydrates and CH were formed. The hydration of calcium sulphoaluminate was less reactive than the cement prepared with the controlled clinker at early hydration time. But, as hydration time elapsed, this cement showed more active hydraulicity and higher compressive strength development.

• The Journal of the Korean dental association
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• v.50 no.7
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• pp.368-376
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• 2012

The demand for tooth-colored restorations has grown considerably during the last decade. Posterior composite restorations have risen in popularity as a result of the development of improved resin composites, bonding systems and operating techniques. A major limitation of direct composite restoration is the difficulty of controlling the polymerization shrinkage. To overcome this limitation, the indirect fabrication of a composite restoration and cementation with resin cement has been advocated. Unfortunately, the current available resin cements with indirect restorations do not always bond to dentin as strongly as dentin adhesive systems bond with direct resin composite restorations. Several procedural strategies have been proposed for indirect composite restoration. In this regard, the rationale for the indication, characteristics and clinical application is described in this paper. As a result, we will try to suggest the evidence-based guidelines for indirect composite restorations by reviewing each available indirect composite products, technical procedure and pronosis.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.245-250
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• 1998

The Elastic modulus depends on the elastic property of composition materials, the gravity of aggregate, the bond strength of binder, the usage and quantity of admixture, curing and measuring method, etc. Accordingly, the aim of this study, by manufacturing concrete of practical high strength range(600~ 1000kg/$\textrm{cm}^2$) with the specific cement and mineral admixtures, is to compare elastic modulus with the existing equations and also to estimate elastic property of use materials. As a result, it could be confirmed that the existing equations which were proposed by the ACI 363, CEB-FIP Code, and New-RC have a tendency to the overestimation in general. However, it could be confirmed that the KCI-96 and Norwegian NS 3473 equations are closed to measuring results, and that the elastic modulus property have a different tendency due to types of cements.

• Journal of the Korean Ceramic Society
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• v.16 no.3
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• pp.164-168
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• 1979

In the previous paper, it was reported that formation of desirable calcium alunimate(CA) in clinker was considerably affected by sulfur-contaminated alumina which was prone to form a disadvantageous mineral, $C_4A_3S$. In this study, however, sulphate-free alumina cement was made from sulfur-free alumina refined from alunite and corresponding materials. The major minerals in the clinker were identified by X-ray diffraction patterns as calcium aluminate (CA), calcium dialuminate $(CA_2)$ and dicalcium alumino silicate $(C_2AS)$. The formation of CA was more effective with decreasing contents of silica to 2 per cent or less and sulfur in the refined alumina. Physical properties of prepared alumina cement such as setting time, stability and compressive strength were measured. The values were similar to those of commercial alumina cements.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.683-688
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• 2001

In case of constructing the concrete structures under seawater environment, the concrete suffers from deterioration due to penetration of various ions such as chloride, sulfate and magnesium in seawater. Tn the present study, Immersion tests with artificial seawater were carried out to investigate the resistance to seawater attack of antiwashout underwater concrete. From the results of compressive strength, it was found that blended cement concrete due to mineral admixtures such as fly ash(FA) and ground granulated blast-furnace slag(SGC), were superior to ordinary portland cement concrete with respect to the resistance to seawater attack. Moreover, XRD analysis indicated that the formed reactants of ordinary portland cement paste by sulfate and magnesium ions led to the deterioration of concrete. As expected, however, the blended cements with FA or SGC have a good resistance to seawater attack. This paper would discuss the mechanism of seawater deterioration and benefical effects of antiwashout underwater concretes with mineral admixtures.

• Journal of the Korea Concrete Institute
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• v.16 no.3 s.81
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• pp.433-440
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• 2004

In order to improve the performance of concrete, generally, modern cements often incorporate several mineral admixtures. In this study, the experimental included the flow value, air content of mortar containing limestone powder and length change and compressive strength of mortar specimen immersed in sulfate solutions. From the experimental results, the limestone powder cement matrices improved the physical properties and sulfate resistance of cement matrices at $10\%$ replacement ratio of limestone powder. The $30\%$ replacement ratio of limestone powder was significantly deteriorated in sodium sulfate solution. Irrespective of fineness levels of limestone powder, length change and SDF of mortar specimens with only $10\%$ replacement was much superior to the other replacements.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10c
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• pp.66-71
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• 1998

Recently, it has been increased to construct massive concrete structures, like under-ground structure, offshore structure etc., ie. concrete construction have become larger and higher and are demanding lower heat concrete to prevent thermal cracking. It has been progressed to replace cements with fly-ash and slag to lower heat of hydration, but it is hard to control quality of the mineral admixtures in stage of adjusting of real construction. Application of low heat portland(Belite Rich) cement for the mass concrete is the best solution to satisfied those requirements. Here are explained the basic properties of fresh concrete as well as hardened concrete of using low heat portland cement(LHPC). Also, we compare the results of adiabatic temperature rise test using LHPC and OPC.