• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.179-186
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• 2002

A molecular orbital analysis based on the extended Huckel calculations has been carried out to study the OH bond activation of water on the $TiO_2$(110) surface. $H_2O$ binds with its axis perpendicular to the surfac on top of the five-coordinate $Ti^{4+}$ atom via its $3a_1$ orbital. In this bonding situation, the two-coordinated bridging $O^{2-}$ atom ($O_b$, basic site) on $TiO_2$(110) is too distant from an H atom of water to form hydrogen-bondig interactions with water that facilitate O-H bond cleavage. It has been elucidated that the O-H bond is appreciably weakened when the water molecule is tilted to give a hydrogen bond with the $O_b$ atom. This mechanism includes mutual transfer of electron density from the $3a_1$ orbital of the water molecule to the $Ti^{4+} 3d_{z2}$ orbital and from the $O_b$ P orbitals to the $2b_1$ of the adsorbed water molecule This should result in lengthening of the O-H bond in the surface complex and the subsequent dissociation into the fragments OH and H.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.2
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• pp.157-170
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• 2001

The bond strength is the most important factor in establishing long-term success of resin-retained fixed prostheses. So, various surface treatment methods have been introduced to improve the bond strength of metal surface and bonding resin till now This study was performed to compare the effect of silicoating with that of metal primer and analyze the correlation between treatment time of sandblasting and the bond strength, so that meant to find more effective surface treatment method that could enhance the bond strength of resin-retained fixed prostheses. The surfaces of all specimens made of $Verabond^{(R)}$ alloys were air abraded with $250{\mu}m\;Al_2O_3$ according to treatment time of sandblasting and they were subdivided to be treated with only sandblasting(S group), silicoating following sandblasting(SS group) and metal primer application after sandblasting(SM group). Then pairs of metal specimens (${\phi}10mm{\times}h\;2mm,\;{\phi}6{\times}h\;2mm$) were bonded with Super bond $C&B^{(R)}$. The specimens were stored in $38^{\circ}C$ water for 48 hours and shear bond strength was measured using the universal testing machine. The results were as follows, 1. In the comparison of shear bond strength according to treatment time of sandblasting, bond strength was increased in the order of 0', 15', 30', 45', 60' group. 0' group had significantly lower value than any other, while 0', 15' group were significantly different with 30', 45', 60' group(p<0.05). 2. In the comparison of shear bond strength according surface treatment methods, bond strength was increased in the order of S group. SS group and SM group. S group was significantly different with SS group and SM group(p<0.05). 3. Observing the mode of bond failure. 0', 15' group showed only adhesive failure, and 30', 45', 60' group did mostly adhesive & cohesive failure in S group. In SS group and SM group, all other groups except 0', 15' group showed mostly cohesive failure. From the above results, it is considered that sandblasting should be treated for more than 30 seconds, and metal primer be more effective and available clinically than silicoater system which is complicate, technique-sensitive and time-consuming method, when nonprecious metal surface is planning be treated with in order enhance the bond strength of resin-retained fixed prostheses.

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.136-149
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• 1996

The effects of various All-Etching Agents (10% phosphoric acid, 10% maleic acid and 10 % citric acid) and 32 % phosphoric acid and varied etching time were evaluated by observing the morphology of the etched enamel surfaces using Scanning electron microscopy and by measuring the shear bond strength of a composite resin to human enamel. A total of 156 extracted premolar and molar teeth free of irregularities were employed in this study. Specimens for the observation of enamel morphology were divided into 12 groups of 3 teeth each, based on the type of etchant used and application time. After exposure to the etching agent specimens were washed air-dried and then glued to aluminum stubs and coated with a layer of gold for examination in the scanning electron microscope. Specimens for the evaluation of bond strength were divided into 12 groups of 10 teeth each also based on the type of etchant used and application time. After exposure to the etching agent the specimens were washed, air-dried and a thin layer of bonding agent was applied using a brush. Z 100 composite resin was light cured to the surface and stored at $37^{\circ}C$, 100% humidity for 7 days. An Instron Universal Testing Machine was used to apply a shearing force at $90^{\circ}$ angle from the enamel surface. It is concluded from this study that commercial All-etching agents can be used with a 15-second etching without adversely affecting retention of dental resin materials. At the same time, the acid concentration is probably a suitable compromise regarding the acid's function as a dentin demineralizing all-etch conditioning agent. The following results were obtained. 1. Specimens etched with 10 % citric acid showed a random superficial etching pattern which could not be related to prism morphology. 2. Specimens etched with 10 % and 32 % phosphoric acid and 10 % maleic acid showed a type I pattern in which core material was preferentially removed leaving the prism peripheries relatively intact or a type II pattern in which prism peripheries were preferentially removed. This delineation became more distinguished as etching time was increased. 3. All-Etching Agents and 32 % phosphoric acid showed a statistically significant higher shear bond strength at 15 seconds etching time.(p<0.05) 4. 10 % maleic acid and 32 % phosphoric acid exhibited a statistically significant higher shear bond strength than 10 % phosphoric and citric acid at 15 seconds etching time.(p<0.05).

• The Journal of the Korea Contents Association
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• v.9 no.10
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• pp.451-463
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• 2009

The purpose of this research is to develop thin film materials and fabrication process for efficient $TiO_2$/CdTe solar cells. In this work photocatalyst titanium dioxide was prepared by sol-gel procedure according to reaction condition, the mole ratio of $H_2O$/TTIP, pH of solution and aging condition of powder. The prepared titanium dioxide was thermally treated from 300 to $750^{\circ}C$. Maximum intensity of anatase phase of titanium dioxide was achieved by calcination at $600^{\circ}C$ for 2 hr. And it was mixture of anatase and rutile phase when temperature of calcination was $750^{\circ}C$. It has been known that the properties of synthesized titanium dioxide according to aging time and calcination temperature was converted to anatase phase crystal on increasing of aging time. Also the current density has been increased with aging time and temperature, the efficiency has been increased with because of reason on above results. The formation of chemical bonding on oxygen and cadmium telluride under oxygen circumstances had been observed, and oxygen of thin film surface on cadmium telluride had been decreased with the treatment of chromate and hydrazine. As results had been shown that the energy conversion efficiency of cadmium telluride use by rapidly treatmented heat at the condition of $550^{\circ}C$ under air circumstance got 12.0%, 6.0% values according to $0.07cm^2$, $1.0cm^2$ surface area, respectively.

• The Korean Journal of Pesticide Science
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• v.14 no.3
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• pp.183-190
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• 2010

To search the new potent herbicidal agents by receptor-based approach, the interactions between receptor and substrate molecules from molecular docking to acetyl-CoA carboxylase(PDB code: 3K8X) of 2-(4-(6-chloro-2-benzoxazolyl)oxy)phenoxy-N-phenylpropionamide analogues (1-38) as substrate molecules were performed and discussed quantitatively. The most of the substrate molecules were formated 2 H-bonds between carbonyl oxygen atom of the substrate molecules and the amino acid residues (Ala1627 and Ile1735) in binding site of acetyl-CoA carboxylase (ACCase). But, the substrate molecules such as $R_l$=Acetyl substituents (6 & P9) were formated 3 H-bonds between H-bond acceptors in the substrate molecules and the H-bond donors in three amino acid residues including the rest residue (Gly 1998). Therefore, the inhibitory activity factors of the substrate molecules against ACCase are due to the H-bonding characters that will be able to apply to the optimization of herbicidal agents.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.3
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• pp.253-264
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• 2010

The purpose of this study is to know whether Yttrium-stabilized-tetragonal -zirconia-polycrystal(Y-TZP ceramic) gets enough shear bond strength for clinical uses by applying veneering composite resin through surface treatment on it and finally to compare it with the case of applying veneering porcelain. LavaTM zirconia frameworks(3M ESPE, Seefeld, Germany) were prepared. Group P was manufactured with LavaTM Ceram(3M ESPE, Seefeld, Germany) in cylindrical shape which has 4mm diameter, 5mm height. Group ZSR disposed sandblasting and applied silane, bonding agent and after that indirect composite resin was applied. Group ZRR got tribochemical coating by RocatecTM system(3M ESPE. Seefeld, Germany) and treated silane. Finally Group ZPR took the same treatment and applied LavaTM Ceram in the size of 0.3-0.5mm height. After burning out, sandblasting, HF and silane was applied. And then, indirect composite resin was applied. 1000 cycle thermocycling was performed in $5-55^{\circ}C$ and shear bond strength was measured. There were no significant differences between combining veneering porcelain to Y-TZP ceramic group and combining veneering resin to Y-TZP ceramic group in the aspect of shear bond strength (p>.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.41-46
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• 2003

In order to evaluate the sufficient etching time for successful bonding and also minimizing unnecessary mineral loss, the enamel surface roughness analysis was performed using confocal laser scanning microscopy. Sixty extracted sound human molar teeth were imbedded in the center of acrylic cylinder using self-curing clear resin exposing buccal surface, and then polished with series of SiC paper(220, 500, 800, 1000, 2000, 4000 grit). Each specimen was randomly assigned to six groups(N=10). 37% phosphoric acid was applied to the polished tooth surface for 10, 20, 30, 40, 50, 60 seconds respectively and washed with copious water. After the surface roughness analysis, five roughness parameters(Sa, Sq, Sz, Sdr, Ra) were statistically analysed by ANOVA and Duncan post hoc test. We found that the all five parameters had higher roughness value in 30 seconds etching time, especially parameter Sz showed the lowest value in 10 seconds etching time and the highest value in 30 seconds etching time compared with the other etching times(p<0.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.3
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• pp.341-349
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• 2017

Blood decontamination is an important factor in success of the orthodontic bracket. The purpose of this study is to evaluate the shear bond strength affected by blood decontamination. The shear bond strength was measured on blood decontamination before and after primer photopolymerization. And the adhesive remnants type and surface patterns was evaluated under scanning electron microscopy. A total of 50 human premolars were prepared. Group I was attached using conventional resin-acid etching method as control group. Group II and III were blood contaminated before curing primer and groups IV and V were blood contaminated after curing primer. Group II and IV were treated only with cotton pellet and Groups III and V were treated with cotton pellet after water washing. The mean shear bond strengths were in the order of groups I, V, III, II, and IV. In scanning electron micrographs group III and V showed more uniform surface than group II and IV. The ARI was significantly different between the control group and the experimental groups (p <0.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.374-382
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• 2001

The purpose of this study was to investigate the surface morphology and measure shear bond strength of Er : YAG lased enamel. To determine the most effective energy density of laser for improving bonding strength of human enamel, 24 specimen were lased from 30mJ to 150mJ at 1Hz used focused, defocused beam. After irradiation, the lased specimen were observed scanning electron microscope. To determine the resin shear bond strength of Er : YAG lased enamel, the 90 specimen were divided into 3 groups. The Control group was etched with 37% phosphoric acid for 15seconds and rinsed. Group 1 was only laser irradiaton(60mJ, 10Hz), Group 2 was irradiated as Group 1 regimen, followed 37% phosphoric acid etching. The following results were obtained: 1. In both focused and defocused Er : YAG lased enamel surface are similar to acid-etched enamel more than 60mJ in SEM evaluation. 2. The more increased laser energy, the more observed fissuring surface. 3. The highest mean shear bond strength value was observed in control group with the statistical significance(p<0.05) between all the other groups and the shear bond strength in group 1 was the lowest with significant difference among the other groups.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.238-244
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• 2003

With the purpose of evaluating the effect of ailing amount of pit and assure sealants on the microleakage, 6 groups of specimens with different filling amount, filling materials and surface pretreatment were investigated. Sixty permanent third molars were divided into three groups. The occlusal surface of each tooth was divided into two parts; the filing width of one part was below 1mm (group1, 3, 5), and in the other part more than 2mm (group 2, 4, 6) Group 1 and 2: Helioseal F was applied directly to etched enamel; Group 3 and 4: Helioseal F was applied to etched and scotchbond Multi-purpose plus pre-treated enamel; Group 5 and 6: Tetric Flow was applied. After 500 times thermocycling and dye infiltration, we evaulated the microleakage. The results were as follows; 1. The mean microleakage score at each width were increased in the following order;group 5<3<1, and group 6<4<2. 2. In comparing the groups with same material and surface pretreatment but with different filling width (group 1 versus 2, 3 versus 4, 5 versus 6), the microleakage scores were significantly different. 3 The microleage was affected by filling amount of pit and assure sealants than Oiling materials and dentin bonding agent pretreatment.