• Restorative Dentistry and Endodontics
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• v.31 no.4
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• pp.263-268
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• 2006

Recently, self-etching adhesive system has been introduced to simplify the clinical bonding proce- dures. It is less acidic compared to the phosphoric acid, thus there is doubt whether this system has enough bond strength to enamel. The purpose of this study was to investigate the influence of additional etching on the adhesion of resin composite to enamel. Ninety extracted bovine permanent anterior teeth were used. The labial surfaces of the crown were ground with 600-grit abrasive paper under wet condition. The teeth were randomly divided into six groups of 15 teeth each. Clearfil SE $Bond^{\circledR},\;Adper^{TM}$ Prompt L-Pop and Tyrian $SPE^{TM}$ were used as self-etching primers. Each self-etching primers were applied in both enamel specimens with and without additional etching. For additional etching groups, enamel surface was pretreated with 32% phosphoric acid (UNI-ETCH, Bisco, Inc., Schaumburg, IL. USA). Hybrid resin composite Clearfil AP-X, (Kuraray Co., Ltd., Osaka, Japan) was packed into the mold and light-cured for 40 seconds. Twenty-four hours after storage, the specimens were tested in shear bond strength. The data for each group were subjected to independent t - test at p < 0.01 to make comparisons among the groups. In Clearfil SE $Bond^{\circledR}$, shear bond strength of additional etching group was higher than no additional etching group (p < 0.01). In $Adper^{TM}$ Prompt L-Pop and Tyrian SPE, there were no significant difference between additional etching and non-etching groups (p > 0.01). In conclusion, self-etching adhesive system with weak acid seems to have higher bond strength to enamel with additional etching, while self-etching adhesive system with strong acid seems not.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.423-429
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• 2008

Currently, Ash-free clean coal producing process by solvent extraction is under development. The produced ash-free clean coal can be directly combusted in a gas turbine which results in substantial improvement of power generation efficiency. However, the clean coal produced by the solvent extraction still contain trace amount of alkali metal which may cause corrosion on turbine blades during the direct combustion. In present work ${\alpha},{\beta}$-metal (Zr and Ti) phosphates and H-Y zeolite were synthesized and their ion exchange characterizations were investigated for the application on alkali metal removal for clean coal production. $Na^+$ ion removal capacities of the metal phosphates and H-Y zeolite were measured and compared in both aqueous solution (100 ppmw, $Na^+$) and coal dissolved N-methyl-2-pyrrolidone (NMP, 12 ppmw $Na^+$) at elevated temperature. In aqueous solution, the ${\beta}$ form metal phosphates showed very high ion exchange capacities compared to ${\alpha}$ form. ${\beta}$ form metal phosphates also showed higher $Na^+$ removal capacities than H-Y zeolite. In ion exchange medium of NMP, all the ${\alpha}$ form metal phosphates showed over 90% of $Na^+$ ion removal efficiency in the temperature range of 200 to 400 while that of H-Y zeolite decreased as a half when the temperature was over 350. In addition, the regenerated metal phosphates by acid treatment showed no sign of degradation in $Na^+$ removal efficiency. Among the metal phosphates used, $Zr_{0.75}Ti_{0.25}(HPO_4)_2$ showed the best performance in $Na^+$ removal and is expected to be the most suitable inorganic ion exchanger for the alkali metal removal process.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.2
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• pp.112-118
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• 2012

Purpose: The purpose of this study was to evaluate the difference in shear bonding strength between resin cements to dental materials when a universal primer (Monobond plus) was applied in place of a conventional primer. Materials and methods: Four groups of testing materials: gold alloy (Argedent Euro, n = 16), non precious metal (T-4, n = 20), zirconia (Cercon, n = 20) and glass ceramic (IPS e.max press, n = 20), were fabricated into discs, which were embedded in an acrylic resin matrix. The gold alloy specimens were airborne-particle abraded, 8 of the specimens were coated with Metal primer II, while the remaining 8 specimens were coated with Monobond plus. The non precious and zirconia specimen were airborne-particle abraded then, the control group received Alloy primer coating, while the other was coated with Monobond plus. Glass ceramic specimens were etched. 10 specimens were coated with Monobond-S and the remaining specimens were coated using Monobond plus. On top of the surface, Multilink N was polymerized in a disc shape. All of the specimens were thermal cycled before the shear bonding strength was measured. Statistical analysis was done with Two sample $t$-test or Mann-Whitney U test (${\alpha}$=.05). Results: There were no significant differences in bonding strength depending on the type of primer used in the gold alloy and glass ceramic groups ($P$>.05), however, the bonding strengths of resin cements to non precious metal and zirconia groups, were significantly higher when the alloy primer was used ($P$<.05). Conclusion: Within the limitations of this study, improvement of universal primers which can be applied to all types of restorations is recommended to precious metals and zirconia ceramics. But, the bond strengths of non precious metals and zirconia ceramics were significantly lower when compared to a 10-MDP primer. More research is needed to apply universal primers to all types of restorations.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.2
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• pp.72-80
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• 2019

Purpose: The purpose of this study is to compare and analyze the shear bond strength and fracture pattern in different enamel tooth surface treatments for resin splinting materials. Materials and Methods: G-FIX and LightFix were used as tooth splinting materials. Twenty bovine mandibular incisors were used for the preparation of the specimens. The exposed enamel surface was separated into four parts. Each tooth was treated with 37% phosphoric acid, 37% phosphoric acid + adhesive resin, 37% phosphoric acid + G-premio bond, and G-premio bond for each fraction. Shear bond strength was measured using a universal testing machine. After measuring the shear bond strength, the fractured surface of the specimen was magnified with a microscope to observe the fracture pattern. Two-way ANOVA was used to verify the interaction between the material and the surface treatment method. One-way ANOVA was used for comparison between the surface treatment methods of each material and post-hoc test was conducted with Scheffe's test. An independent t-test was conducted to compare shear bond strengths between materials in each surface treatment method. All statistics were conducted at 95% significance level. Results: G-FIX, a tooth splinting resin, showed similar shear bonding strength when additional adhesive resins were used when material was applied after only acid etching, and LightFix showed the highest shear bonding strength when additional adhesive resins were used after the acid etching. In addition, both G-FIX and LightFix showed the lowest shear bond strength when only self-etching adhesive was applied without additional acid etching. Verification of interactions observed interconnection between resins and surface treatment methods. Most of the mixed failure was observed in all counties. Conclusion: When using G-FIX and LightFix, which are tooth-splinting materials, it is considered that sufficient adhesion will be achieved even after applying only acid etching as instructed by the manufacturer.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.3
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• pp.437-445
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• 2008

The presence of a "prismless" layer on the enamel surface particularly on deciduous teeth has been reported by a number of workers. This structure, which appears to lack the normal prism delineations, could interfere with tag formation and hence, reduce bonding to such surfaces. The purpose of this study was to investigate the relationship of etching times on the effect of acid etching on primary enamel with respect to the quality of etching patterns. Labial surfaces of 32 extracted or exfoliated caries-free primary anterior teeth were used. 35% phosphoric acid gel was used only cervical regions of labial surfaces for each etching time group, 15, 30, 45 and 60 seconds. The surfaces were then washed with water for 20 seconds and dried with air spray for 20 seconds. 1. The Type 3 is 75% when the 15 seconds acid etching time was used. 2. The Type 1 is 38% and Type 2 is 75% when the 30 and 45 seconds acid etching time was used. 3. The Type 1 is 25% and Type 2 is 75% when the 60 seconds acid etching time was used. 4. An etching time of 60 seconds produced a constant and regular etching pattern. 5. There is a significant difference between the groups with respect to the patterns of etch achieved(p<0.05). 6. We confirmed that the acid induced patterns(type 1, 2) became more pronounced when the application time increased(p<0.05). $45{\sim}60$ seconds was the optimal time for etching on the primary enamel.

• Korean Journal of Soil Science and Fertilizer
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• v.6 no.4
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• pp.205-211
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• 1973

General physical and chemical characteristics of eleven apple orchard soils derived from granite, granodiorite, diorite, arkose sandstone and shale were investigated in relation to soil profile. The results are summerized as follows: 1. Soils were mostly sandy and showed pH 4.35 to 6.75, 1.14 to 5.58 of organic matter, 0.065 to 0.209% of nitrogen. All properties decreased with depth. 2. Total exchangeable bases of surface soils were comparablly low (4.89 to 17.81me/100g, Ca>Mg>K>Na). Cation exchange capacity ranged from 7.74 to 21.72 mg/100g and base saturation percentage from 22.52 to 94.62%. 3. Phosphorus content of surface soil was very low (less than 35.5 mg/100g). The contents of potassium (7.2-79.2 mg/100g), available copper (1.0-16.9 ppm) and water soluble boron (0.18-0.72 ppm) were high in surface soil but low with depth. The content of manganese showed clear difference with pH, that is, at pH 4 to 6 water soluble manganese ranged from 0.42 to 17.8 ppm and exchangeable manganese from 9.82 to 66.38 ppm but above pH 6 the water soluble was less than 0.70 ppm and the exchangeable less than 22.25 ppm.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.57-64
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• 2006

The crack presented in concrete structures causes a structural defect, the durability decrease, and external damages etc. Therefore, it is necessary to improve durability through the effort to control the crack. Fluosilicic acid($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicates prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. Mix proportions for experiment were modulated at 0.45 of water to cement ratio and $0.0{\sim}2.0%$ of adding ratio of fluosilicate salt based inorganic compound. To evaluate correlation of concrete strength and adding ratio of fluosilicate salt based inorganic compound, the tests were performed about design strength(21, 24, 27 MPa) with 0.5% of adding ratio of fluosilicate salt based inorganic compound. Applications of fluosilicate salt based inorganic compound to reduce cracks resulted from plastic and drying shrinkage, to improve durability are presented in this paper. Durability was evaluated as neutralization, chloride ion penetration depth, freezing thawing resistant tests and weight loss according reinforcement corrosion. It is ascertained that the concrete added fluosilicate salt based inorganic compound showed m ability to reduce the total area and maximum crack width significantly as compared non-added concrete. In addition, the durability of concrete improved because of resistance to crack and watertightness by packing role of fluosilicate salt based inorganic compound obtained and pozzolanic reaction of soluble $SiO_2$ than non-added concrete.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3748-3754
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• 2009

An integral head loss test in a test apparatus was conducted to simulate chemical effects on a head loss across a strainer in a pressurized water reactor (PWR) containment water pool after a loss of coolant accident (LOCA). The test was conducted during 30 days in the condition of a short spray, a long spray, and no materials with chemical effects. The result exhibited that the head loss was affected on amounts of the exposed materials according to spray conditions. XRD analysis of the collected precipitates showed that the precipitates were phosphate compounds. Comparison of the head loss with dissolved species concentration showed that high increase rate of the head loss resulted from the corrosion of aluminum and zinc but slow increase rate of the head loss resulted from the precipitates induced by Si, Mg, and Ca from leaching reaction at NUKON and concrete after passivation of metal specimens.

• Applied Biological Chemistry
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• v.15 no.3
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• pp.229-240
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• 1972

Not only in order to determine reasonable application amounts of PCP in terms of soil texture, but also to get basic data for fish-toxicity-free treatment by estimating fish toxicity, some aspects of PCP adsorption were observed taking various paddy soils with different physico-chemical characteristics in the Choongbook Area as samples. The results obtained are summarized as follows: 1. There was a positive correlation between PCP adsorption and clay contents, total nitrogen, organic matter, cation exchange capacity, exchangeable bases, and phosphorus absorption coefficients, respectively; whereas there was a negative one between PCP adsorption and pH. Although they were not significant, it was remarkable that there was a relatively large amount of correlation between PCP adsorption and clay contents, $H^+,\;Mg^{++}$, and CEC, respectively. 2. PCP adsorption in terms of soil texture was in the order of Clay>Loam>Sandy loam. 3. Although PCP adsorption in the $H_2O_2-treated$ soils decreased remarkably, it was not proportional to the humus contents. 4. The order of PCP adsorption in the exchangeable base-treated soils was H^+-exchanged soil>$K^+-soil$>$Na^+-soil$>$Ca^{++}-soil$>Mg^{++}-soil. 5. Langmuir's and Freundlich's adsorption isotherms were applicable to the PCP adsorption, and thereby were able to be calculated maximum adsortion amounts of PCP, bond energy, and the depths of adsorption layers. 6. Maximum adsorbed amounts of PCP were 212.14 mg/100gr in Clayey loam, 97.28 to 121.59mg/100gr in Loam, and 32.92 to 91.74mg/100gr in Sandy loam, respectively. 7. The depths of mixed layers of limiting application for fish-toxicity-free treatment were 0.88cm of the Jinchun soil, the shallowest and 4.29 cm of the Naesan-ri Sandy loam, the deepest.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.2
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• pp.195-204
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• 2008

Orthodontic brackets often need to be bonded to porcelain such as porcelain fused to metal crowns and porcelain jacket crowns. The purpose of this study was to evaluate the clinical usability of direct bonding system on porcelain teeth by measuring shear bond strength according to various conditions and observing adhesive failure patterns. The specimens, 20 maxillary premolars and 80 porcelain teeth that were produced by duplication of the labial surface of a maxillary first premolar were used and randomly divided into four groups of twenty teeth each. The 5 different preparation procedures tested: (1) application of 37% phosphoric acid on natural teeth, (2) sandblasting on porcelain surfaces, (3) sandblasting and application of 9.6% hydrofluoric acid on porcelain surfaces, (4) sandblasting and application of silane on porcelain surface, (5) sandblasting and application of 9.6% hydrofluoric acid and silane on porcelain surfaces. The metal brackets were bonded with Transbond $XT^{(R)}$ bonding material. The shear bond strength was tested by the micro universal testing machine(Kyung-Sung, Korea) and the amount of residual adhesive on the tooth surface after debonding was examined by stereoscope and assessed with an adhesive remnant index. The results of this study suggest that the direct bonding system on porcelain teeth with sandblasting, HF and porcelain primer is clinically useful.