• Restorative Dentistry and Endodontics
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• v.19 no.1
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• pp.124-134
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• 1994

The shade of restorative materials is very important for successful restoration esthetically harmonized with the natural tooth. The purpose of this study was to evaluate the color stability and the opacity change of conventional chemical setting and visible light curing glass-ionomer cements for restorative esthetic filling. Specimens of each brand (GC Fuji II and Fuji II LC) were uniformly prepared and divided into three groups: In group l(control group), the specimens received no surface treatment; in group 2, the specimens were coated with varnish and the excess gently blown off; and in group 3. the specimens were coated with light-cured bonding resin and irradiated by a visible light curing unit for 20 seconds on both sides. All specimens were stored in distilled water at $37^{\circ}C$ and checked after for 24 hours. 2 months. 4 months, 6 months. and 8 months. The color characteristics($L^*,\;a^*,\;b^*$) and the opacity(Y%) of all the samples were measured by a spectrocolorimeter and the total color differences(${\Delta}E^*$) and opacity changes(${\Delta}Y%$) were computed. The following results were obtained : 1. The total tolor differences in all groups increased with time. 2. The total color differences of the LC groups after immersion for 8 months in distilled water at $37^{\circ}C$ were lower than those of GC groups(p<0.01), and the total color differences of the varnish or the light-cured bonding resin coated groups were lower than those of the control group with glass-ionomer cements which had no surface treatment(p<0.01). 3. In all groups the translucency decreased with time. 4. In the control group and the varnish coating group. the opacity changes of the GC groups were lower than those of the LC groups(p<0.01) and in the light-cured bonding resin coated group, there was no significant difference between the GC group and the LC group. 5. The opacity changes of the varnish or the light-cured bonding resin coated groups were lower than those of the control group(p<0.01). These results suggest that color change and opacity of conventional chemical setting and light cured glass-ionomer cement were increased with time, and the color changes and the opacity changes of a control group after immersion for 8 months in distilled water at $37^{\circ}C$ were greater than those of the varnish or the light-cured bonding resin coated groups.

• Restorative Dentistry and Endodontics
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• v.38 no.4
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• pp.234-240
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• 2013

Objectives: This study evaluated the effects of intraradicular moisture on the pushout bond strength of a fibre post luted with several self-adhesive resin cements. Materials and Methods: Endodontically treated root canals were treated with one of three luting cements: (1) RelyX U100, (2) Clearfil SA, and (3) G-Cem. Roots were then divided into four subgroups according to the moisture condition tested: (I) dry: excess water removed with paper points followed by dehydration with 95% ethanol, (II) normal moisture: canals blot-dried with paper points until appearing dry, (III) moist: canals dried by low vacuum using a Luer adapter, and (IV) wet: canals remained totally flooded. Two 1-mm-thick slices were obtained from each root sample and bond strength was measured using a push-out test setup. The data were analysed using a two-way analysis of variance and the Bonferroni post hoc test with p = 0.05. Results: Statistical analysis demonstrated that moisture levels had a significant effect on the bond strength of luting cements (p < 0.05), with the exception of G-Cem. RelyX U100 displayed the highest bond strength under moist conditions (III). Clearfil SA had the highest bond strength under normal moisture conditions (II). Statistical ranking of bond strength values was as follows: RelyX U100 > Clearfil SA > G-Cem. Conclusions: The degree of residual moisture significantly affected the adhesion of luting cements to radicular dentine.

• Advances in concrete construction
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• v.8 no.1
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• pp.65-76
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• 2019

This paper investigates the effect of recycled glass powder (RGP) on flowing properties of self-compacting mortars (SCMs) containing different ratios of fillers and superplasticizer dosages. Fly ash (FA), nano-silica (NS), micro-silica (MS), metakaolin (MK) and rice husk ash (RHA) are used as fillers and their synergistic effect with RFP is studied. The effects of fillers and high-range water reducer (HRWR) on flowing ability of mortars are primarily determined by slump flow and V-funnel flow time tests. The results showed that for composites with a higher RGP content, the mortar flowing ability increased but tended to decrease when the composites containing 10% MK or 5% RHA. However, the flowing ability of samples incorporating 5% RGP and 10% SF or 25% FA showed an opposite result that their slump flow spread decreased and then increased with increasing RGP content. For specimens with 3% NS, the influence of RGP content on flowing properties was not significant. Except RHA and MS, the fillers studied in this paper could reduce the dosage of HRWR required for achieving the same followability. Also, the mixture parameters were determined and indicated that the flowability of mixtures was also affected by the content of sand and specific surface area of cement materials. It is believed that excess fine particles provided ball-bearing effect, which could facilitate the movement of coarse particles and alleviate the interlocking action among particles. Also, it can be concluded that using fillers in conjunction with RGP as cementitious materials can reduce the material costs of SCM significantly.

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.67-78
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• 2008

In this study, artificial cemented sand made of a few portland cement and Nak-Dong river sand was researched closely to investigate cementing effect quantitatively through unconfined tests and triaxial tests. The peak strength and elastic modulus increased and dilation of cemented sand was restricted by the cementation, but after breakage of the cementation, dilation and negative excess pore water pressure increased. In stress-strain curve, strain-softening behavior appeared in drained condition but strain-hardening behavior was appeared in undrained condition as a result of the increase of effective stress. The test was quantitatively analyzed by multiple regression models, correlating each response variable with input variable. The equations are valid only over the range investigated. Its adjusted coefficient of determination was $0.81{\sim}0.91$, and dry density is important factor for estimating strength of cemented sand.

• The Journal of Korean Academy of Prosthodontics
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• v.59 no.3
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• pp.319-332
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• 2021

With the rapid development of aesthetic ceramic materials and resin adhesives, the transition from metal ceramic crown to all-ceramic restoration is being actively carried out. When making porcelain restorations, the advantages can be maximized only when appropriate forms and techniques are used. Recently, an esthetic partial-coverage restoration method with supra-gingival margins was introduced by applying a minimally invasive tooth removal method that preserves enamel as much as possible and enhances adhesion efficiency. Through this, various advantages such as minimization of tooth structure removal and ease of excess cement removal can be obtained. In addition, since this manufacturing method does not require cord packing, it is possible to save time for impression taking and reduce patient discomfort. Furthermore, the margins can be clearly obtained without the intervention of gingival fluid or blood, making it possible to manufacture more accurate restorations. In the following cases of patients with partial tooth defects, esthetic ceramic partial-coverage restorations with supra-gingival margin was applied using minimally invasive tooth preparation method according to the concept of adhesive dentistry. Therefore, unnecessary tooth abutment preparation was prevented and residual tooth structure could be preserved as much as possible. After delivery of the ceramic partial-coverage restorations, favorable outcome was obtained.

• Journal of the Korean Geotechnical Society
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• v.22 no.8
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• pp.43-54
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• 2006

The scope of this paper covers the applications of bender element tests in consolidation, tomography, and liquefaction. Loading and unloading time during consolidation are evaluated based on shear wave velocity. As S-wave velocity is dependent on effective stress, the loading step may be determined. However, cautions are required due to the different mechanism between the settlement and effective stress criteria. The stress history may be evaluated because the S-wave shows the cement controlled regime and stress controlled regimes. A fixed frame complemented with bender elements permits S-wave tomography The tomography system is tested at low confinement within a true triaxial cell. Results show that shear wave velocity tomography permits monitoring changes in the velocity field which is related to the average effective stress. To monitor the liquefaction phenomenon, S-wave trans-illumination is implemented with a high repetition rate to provide detailed information on the evolution of shear stiffness during liquefaction. The evolution of shear wave propagation velocity and attenuation parallel the time-history of excess pore pressure during liquefaction. Applications discussed in this paper show that bender elements can be a very effective tool for the detection of shear waves in the laboratory.