• Restorative Dentistry and Endodontics
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• v.34 no.5
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• pp.397-405
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• 2009

This study compared the effect of an activator, intermediate bonding resin and low-viscosity flowable resin on the microtensile bond strength of a self-curing composite resin used with two-step total etching adhesives. Twenty extracted permanent molars were used. The teeth were assigned randomly to nine groups (n=10) according to the adhesive system and application of additional methods (activator, intermediate adhesive, flowable resin). The bonding agents and additional applications of each group were applied to the dentin surfaces. Self-curing composite resin buildups were made for each tooth to form a core, 5mm in height. The restored teeth were then stored in distilled water at room temperature for 24h before sectioning. The microtensile bond strength of all specimens was examined. The data was analyzed statistically by one-way ANOVA and a Scheffe's test. The application of an intermediate bonding resin (Optibond FL adhesive) and low-viscosity flowable resin (Tetric N-flow) produced higher bond strength than that with the activator in all groups. Regardless of the method selected, Optibond solo plus produced the lowest ${\mu}TBS$ to dentin. The failure modes of the tested dentin bonding agents were mostly adhesive failure but there were some cases showed cohesive failure in the resin.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.9-15
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• 2023

In this study, the lamination performance and strength characteristics of cement-based composite materials according to the laminated specimens manufacturing method were analyzed. As a result of evaluating the buildability according to the layer height, the highest dimensional stability was shown when the layer height was 10 mm in all parts. The mold casting specimen and the printing-Z specimen showed the same compressive strength performance at the age of 28 days. On the other hand, the compressive strength at 28 day of printing-X specimen was the lowest at 71.72 MPa, and 8% lower than that of the mold casting specimen and the printing-Z specimen. The split tensile strength of the laminated specimen may show similar performance to that of the mold casting specimen, but the strength performance may decrease by more than 10% depending on the direction of the layer and the number of layers in the specimen. As a result of the interface analysis of the laminated specimen through X-ray CT analysis, it was confirmed that pores of a certain size were distributed along the interface of the layer.

• Nutrition Research and Practice
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• v.7 no.3
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• pp.207-215
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• 2013

The objective of this study was to investigate the associations between the prevalence of overweight and obesity and the degree of adherence to the Korean Dietary Action Guides for Children (KDAGC). In a cross-sectional study based on a child care center-based survey in Seoul, Korea, we collected parental-reported questionnaires (n = 2,038) on children's weight and height, frequency of fruit and vegetable consumption, and the quality of dietary and activity behaviors based on the 2009 KDAGC Adherence Index (KDAGCAI) which was developed as a composite measure of adherence to the KDAGC. Overweight and obesity were determined according to age- and sex-specific BMI percentile from the 2007 Korean national growth chart. Associations were assessed with generalized linear models and polytomous logistic regression models. Approximately 17.6% of Korean preschool children were classified as overweight or obese. Obese preschoolers had lower adherence to the KDAGCAI compared to those with lean/normal weight. Preschoolers with a high quality of dietary and activity behaviors had a 51% decreased odds ratio (OR) of being obese (highest vs. lowest tertile of KDAGCAI-score, 95% CI 0.31, 0.78; P = 0.001); the associations were more pronounced among those who were older (P = 0.048) and lived in lower income households (P = 0.014). A greater frequency of vegetable consumption, but not fruit, was associated with a borderline significant reduction in the prevalence of obesity. Our findings support the association between obesity prevention and high compliance with the Korean national dietary and activity guideline among preschool children.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.4
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• pp.445-454
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• 2018

The aim of this study was to measure the shear bond strength (SBS) of different adhesive systems to calcium silicate-based materials (Biodentine and RetroMTA). Eighty cylindrical acrylic blocks, with a hole (5.0 mm diameter, 2.0 mm height) in each, were prepared. The holes were filled with Biodentine (BD) and RetroMTA (RMTA), and the specimens were divided into 2 groups. Each group was classified into 4 subgroups: Clearfil$^{TM}$ SE (CSE) ; AQ bond (AQ) ; All bond universal Self-etch (ABU-SE) ; and All bond universal Total-etch (ABU-TE). After the application of different adhesive systems, composite resin (Z350) was applied over BD and RMTA. The SBS was measured using a universal testing machine, and the data were compared using the Kruskal-Wallis test and the Mann-Whitney test. The highest and lowest values of SBS were observed for BD-ABU-SE and RMTA-AQ, respectively. No significant differences were found in the SBS between ABU-TE and ABU-SE and between ABU-TE and CSE to BD and RMTA. According to the data, BD showed a higher SBS than did RMTA when BD and RMTA are compared in the same adhesive agents. Further, among all groups, composite resin with ABU-SE showed better bond strength to BD and RMTA.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.5
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• pp.520-527
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• 2008

Purpose: This study was conducted to evaluate the shear bond strength of composite resin to dentin when etched with laser instead of phosphoric acid. Material and methods: Recently extracted forty molars, completely free of dental caries, were embedded into acrylic resin. After exposing dentin with diamond saw, teeth surface were polished with a series of SiC paper. The teeth were divided into four groups composed of 10 specimens each; 1) no surface treated group as a control 2) acid-etched with 35%-phosphoric acid 3) Er:YAG laser treated 4) Er,Cr:YSGG laser treated. A dentin bonding agent (Adapter Single Bond2, 3M/ESPE) was applied to the specimens and then transparent plastic tubes (3 mm of height and diameter) were placed on each dentin. The composite resin was inserted into the tubes and cured. All the specimens were stored in distilled water at $37^{\circ}C$ for 24 hours and the shear bond strength was measured using a universal testing machine (Z020, Zwick, Germany). The data of tensile bond strength were statistically analyzed by one-way ANOVA and Duncan's test at ${\alpha}$= 0.05. Results: The bond strengths of Er:YAG laser-treated group was $3.98{\pm}0.88$ MPa and Er,Cr:YSGG laser-treated group showed $3.70{\pm}1.55$ MPa. There were no significant differences between two laser groups. The control group showed the lowest bond strength, $1.52{\pm}0.42$ MPa and the highest shear bond strength was presented in acid-etched group, $7.10{\pm}1.86$ MPa (P < .05). Conclusion: Laser-etched group exhibited significantly higer bond strength than that of control group, while still weaker than that of the phosphoric acid-etched group.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.2 no.1
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• pp.1-9
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• 1999

To find pertinent soil type and maintenance method for artificial planting ground, the effects of soil compositions{sandy loam(S), vermiculite(V), sandy loam+vermiculite+sand(SVS), sandy loam+ carbonized rice husk+sand(SCS), sandy loam+humus sawdust+sand(SHS)}, and fertilizers (organic, chemical) on plant(kentuckyblue grass) growth were measured and compared from the field experiment. The results are summarized as follows 1. the highest germination rate is found from "vermiculite(V)" and the lowest from "sandy loam(S)" among tested 5 soil compositions. 2. "sandy loam+vermiculite+sand(SVS)" composition shows the highest plant height growth effect (5cm growth during tested 3 months) comparing to other 4 compositions. 3. "sandy loam+vermiculite+sand(SYS)" composition shows the highest ground covering rate after first two months, but it concede its order to "sandy loam+humus sawdust+sand(SHS)" composition after next one month growing. 4. the effects of fertilizers are follows 1) Among the blocks where no fertilizer was tried, the predominant height growth was obvious in "sandy loam+carbonized rice husk+sand(SCS)" and "sandy loam+humus sawdust+sand(SHS)" composition. 2) Among the blocks where chemical fertilizer was tried, relatively positive results were found from "vermiculite(V)" and "sandy loam+vermiculite+sand(SYS)" blocks on germination and growth rate. But on the ground coverage ratio, the effect of "sandy loam+carbonized rice husk+sand(SCS)" composite precede that of those 2 composites. 3) Among the blocks where organic fertilizer was tried, "sandy loam+humus sawdust+sand(SHS)" and "vermiculite(V)" blocks show relatively high ground coverage rate, growth rate than others. 4) When compositional differences were not considered, the block where organic fertilizer was tried shows most positive effects on all 3 measurements-germination ratio, height growth and ground covering.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.357-367
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• 1993

The purpose of this study was to evaluate the fracture strength of class II restored premolars with amalgam, posterior composite, amalgam - Ketac silver, resin - Ketac silver restorations at marginal ridge. Fifty extacted maxillary and mandibular premolar teeth that were caries free, fracture free, and restoration free were selected and randomly divided into five groups : Group 1 : 10 intact teeth, Group 2 : 10 teeth with class II cavities and restored with, amalgam, Group 3: 10 teeth with class II cavities and restored with posterior resin, Group 4 : 10 teeth with class II cavities and restored with amalgam - ketac silver, Group 5 : 10 teeth with class II cavities and restored with resin - Ketac silver. All teeth were mounted in base of dental stone within metal rings of 2cm diameter, exposing only the crown portion. Class II mesio - occlusal or disto - occlusal cavities were prepared into specimens of Group 2 through 5 by using a No. 710 fissure bur. The occlusal portion was prepared to a faciolingual width of 1.5mm and a pulpal depth of 1.5mm. The proximal protion was prepared to a faciolingual width of 4mm, a occlusogingival height of 4mm, and a gingival floor of 1.5mm. The teeth in Group 2 and 3 were resotored with silver amalgam apd posterior resin respectively. In Group 4 and 5, proximal portions were first filled with Ketac silver 1.5mm gingivally and remaining cavities were restored with amalgam and posterior resin respectively. All specimens were stored in 100 % relative humidity at $37^{\circ}C$ for 48 hours before testing. All teeth were subjected to a compressive load in a Universal Instron Testing Machine at marginal ridges. The loads required to fracture the restorations were recorded in killograms and the data obtained were subjected to statisticall analysis. The results were all follows : 1. The fracture strength of Group 1 which were unprepared were $100{\pm}10.1\;kg$ and the higher values than Group 2, 3, 4, 5 which were prepared and resotred. 2. In restored groups, Group 2 had the higher fracture strength($81.8{\pm}12.4\;kg$) than other groups and Group 4 had the lowest fracture strength($66.8{\pm}9.2kg$). 3. There were significant differences between fracture strength of between Group 1 and Group 3, 4, 5(P<0.05), but not significant difference between fracture strength of Group 2, 3, 4, 5(P>0.05).