• Journal of Korean society of Dental Hygiene
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• v.1 no.2
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• pp.201-211
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• 2001

Dental caries causes the majority of tooth loss among Koreans. Korea is experiencing an increase in dental caries. And it shows a high prevalence of caries in preschool children, which contrasted with the much-improved situation in developed countries. So, it is important to control caries from preschool periods in Korea. Recently, inspections of the teeth of preschool children for evidence of dental disease became a legislative duty in Korea following Oral Health Act(2000). But, standardized oral health programs in preschool children is not yet proposed. Therefore, it is necessary to develop an community based oral health program in preschool children. The purpose of this study was to obtain basic data for the development of community based oral health program in preschool children of Sungnam city. Oral health status in primary dentition were surveyed in 862 2-6 year-old preschool children of Sungnam city by WHO criteria. From the data, df rate, percentage of preschool child ren with active caries, dft index, dt rate, percentage of preschool children with pit and fissure sealant of each age were calculated, and discussed. The obtained results were as follows : 1. The experience of dental caries in primary dentition showed a tendency to increase quickly between 2 and 3 year old children. So, the oral health program in preschool children should be developed to prevent dental caries and control their oral health under three years of age. 2. In 5 year-old children, the percentage with active caries was 60.8% and dft index was 5.06. The dt rate showed a tendency to decrease as proportion to age, but even though 6 year-old children, the dt rate was 47.7%. Therefore, the annual screening dental examination and oral health education programs at the institution for preschool children should be developed to detect and treat dental caries in primary dentition at early stage. 3. The percentage of preschool children with pit and fissure sealant at six years of age was 10.2%. So, pit and fissure sealant and professional fluoride application programs in Public Health Center should be developed to prevent dental caries. 4. Also, it is necessary to establish oral health goals in preschool children and develop water fluoridation program 10 improve and preserve oral health of preschool children in Seongnam city, effectively.

• Journal of dental hygiene science
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• v.12 no.5
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• pp.459-468
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• 2012

This study surveyed and analyzed on the relationship between obesity and oral health in early child hood and on the oral health realities targeting 90 young children at K Child Care Center where is located in Gangwon-do Province from 10 to 11, June, 2011. As a result, DMF rate accounted for 56.7%. D rate accounted for 42.2%. The young children with the higher age, height in 100~110cm, and weight in 25 kg were indicated to be higher in DF rate than other toddlers. The young children with height in 110~115 cm were indicated to be higher in prevalence of dental caries in deciduous teeth than other young children. It was indicated that the young children in the higher age and weight leads to the higher in DFT index and DFS index. It was indicated that the young children in the more overweight leads to the higher in the index of dental caries in primary teeth, the filling deciduous teeth index, DFT index, DMFS, and DFS index. Accordingly, the child care center needs to systematically perform the oral health education and oral health management for young children, to allow Young children to acquire right food habit, and to pay close attention even to selecting snack.

• Bulletin of the Korean Chemical Society
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• v.30 no.6
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• pp.1257-1261
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• 2009

We present the theoretical and experimental results of $^{31}P$ NMR and low energy CID MS/MS study of $Hg^{2+}$ binding to fenitrothion (FN). The calculated $^{31}P$ NMR chemical shifts order for FN with $Hg^{2+}$ complex is in good agreement with experimental $^{31}P$ NMR chemical shifts order. The experimental and theoretical $^{31}P$ NMR study of organophosphorus pesticide with $Hg^{2+}$ gives to important information for organophosphorus pesticide metal complexes. ESI-MS and low energy CID MS/MS experiments of $Hg^{2+}$-FN complexes combined with accurate mass measurements give insight into the metal localization and allow unambiguous identification of fragments and hydrolysis products.

• Journal of Korean society of Dental Hygiene
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• v.16 no.4
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• pp.525-530
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• 2016

Objectives: The purpose of the study is to investigate remineralization effect according to application cycle of fluoride varnish in preschool children. Methods: The study subjects were fifty six children (92 teeth) having one or more early dental caries lesion. Fluoride varnish was applied to the primary area of maxillary and anterior mandibular teeth with the interval of one month, three months, and six months. Results: Dft index was 3.54 in male and 3.44 in female. The fluorescence loss(${\Delta}F$) value due to early caries lesions showed a significant difference in experiment groups I and II after the application of fluoride varnish, but there was no significant difference in experiment group III. After fluoride varnish application, there was a significant change in experimental group I and III. The maximum fluorescence loss(${\Delta}Fmax$) from early caries lesions showed a significant difference after application of the fluoride varnish in all three experiment groups of I, II, and III(p<0.001). Conclusions: Fluoride varnish should be recommended and applied to the children of high risk caries group in every three months.

• Korean Journal of Materials Research
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• v.17 no.12
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• pp.637-641
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• 2007

The total energy and strength of Mg alloy doped with Al, Ca and Zn, were calculated using the density functional theory. The calculations was performed by two programs; the discrete variational $X{\alpha}\;(DV-X{\alpha})$ method, which is a sort of molecular orbital full potential method; Vienna Ab-initio Simulation Package (VASP), which is a sort of pseudo potential method. The fundamental mixed orbital structure in each energy level near the Fermi level was investigated with simple model using $DV-X{\alpha}$. The optimized crystal structures calculated by VASP were compared to the measured structure. The density of state and the energy levels of dopant elements was discussed in association with properties. When the lattice parameter obtained from this study was compared, it was slightly different from the theoretical value but it was similar to Mk, and we obtained the reliability of data. A parameter Mk obtained by the $DV-X{\alpha}$ method was proportional to electronegativity and inversely proportional to ionic radii. We can predict the mechanical properties because $\Delta{\overline{Mk}}$is proportional to hardness.

• Journal of the Semiconductor & Display Technology
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• v.7 no.3
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• pp.35-39
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• 2008

We study the interaction of acetone molecule $[(CH_3)_2CO]$ on Si(001) surface using density functional theory. An acetone molecule is adsorbed on a Si atom of the Si dimer of the Si(001) surface. The adsorption of the acetone molecule on the Si atom at lower height between the two Si atoms of the dimer is more favorable than that on the Si atoms at upper height. Then we calculate an energy variation of dissociation and four-membered ring structures of the acetone molecule adsorbed on the Si surface. Total energy difference between the two structures is about 0.05 eV, indicating that the two structures are almost equally stable. Energy barrier exists when a hydrogen atom is dissociated and adsorbed on the other Si atom of the dimer, while energy barrier does not exist when the adsorbed acetone molecule changes to four-membered ring structure, except for the rotation of the acetone molecule along z-direction. Therefore, four-membered ring structure is kinetically more favorable than the dissociation structure when the acetone molecule is adsorbed on the Si(001) surface.

• Journal of Electrochemical Science and Technology
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• v.8 no.3
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• pp.222-235
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• 2017

First, in this study, the inhibition efficiencies of metal complexes with Cu(II), Ni(II) and Zn(II) of STSC ligand for corrosion control of mild steel in oilfield formation water were investigated. The IEs for a mixture of 500 ppm STSC and 5 ppm metal ion ($Cu^{+2}$, $Ni^{+2}$, $Zn^{+2}$) were found to be 88.77, 87.96 and 85.13 %, respectively. The results were obtained from the electrochemical techniques such as open circuit potential, linear and tafel polarization methods. The polarization studies have showed that all used Schiff base metal complexes are anodic inhibitors. The protective film has been analyzed by FTIR technique. Also, to detect the presence of the iron-inhibitor complex, UV-Visible spectral analysis technique was used. The inhibitive effect was attributed to the formation of insoluble complex adsorbed on the mild steel surface and the adsorption process follows Langmuir adsorption isotherm. The surface morphology has been analyzed by SEM. Secondly, the computational studies of the ligand and its metal complexes were performed using DFT (B3LYP) method with the $6-311G^{{\ast}{\ast}}$ basis set. Finally, it is found that the experimental results were closely related to theoretical ones.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4199-4204
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• 2011

Using models simulating the environment of two distinct adsorption sites of $H_2$ in metal-organic framework-5 (MOF-5), binding energies of $H_2$ to MOF-5 were evaluated at the MP2 and CCSD(T) level. For organic linker section modeled as dilithium 1,4-benzenedicarboxylate ($C_6H_4(COO)_2Li_2$), the MP2 and CCSD(T) basis set limit binding energies are estimated to be 5.1 and 4.4 kJ/mol, respectively. For metal oxide cluster section modeled as $Zn_4O(CO_2H)_6$, while the MP2 basis set limit binding energy estimate amounts to 5.4 kJ/mol, CCSD(T) correction to the MP2 results is shown to be insignificant with basis sets of small size. Substitution of benzene ring with pyrazine ring in the model for the organic linker section in MOF-5 is shown to decrease the $H_2$ binding energy noticeably at both the MP2 and CCSD(T) level, in contrast to the previous study based on DFT calculation results which manifested substantial increase of $H_2$ binding energies upon substitution of benzene ring with pyrazine ring in the similar model.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.2
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• pp.421-429
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• 1998

The purpose of this study was to investigate the effects of syrup medication for asthmatic children on the salivary invertase activity and caries experience. 26 ashmatic children for the study group and 30 healthy children for the control group were selected, respectively. Caries experience was examined and salivary reductase activity was tested. The parents of asthmatic children were asked to fill in the questionaire about syrup intake period and home dental behavior, and the parents of healthy children were asked to fill in the same questionaire without syrup intake period. The results were as follows : 1. The ds index of asthmatic children were higher than that of healthy children(P < 0.05). 2. There was significant difference in dt index between the intake period of 'shorter than 10 months' and 'longer than 20 months'. The ds, dft and dfs indices had a tendency to increase as the intake period increased. 3. The salivary reductase activity had a tendency to increase as the intake period of syrup increased.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.423-428
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• 2009

The comparative study of three calix[4]heterocycles (calix[4]pyrrole, calix[4]furan, and calix[4]thiophene) has been theoretically performed by using high-level density functional theory (DFT) at the MPWB1K/6-311G$^{**}$//B3LYP/6- 311G$^{**}$ level. The effect of different hetero-atoms (nitrogen, oxygen, and sulfur) placed in the heterocycles on the conformational flexibility, thermodynamic stability order, cavity sizes, charge distributions, and binding propensities are examined. The thermodynamic stability differences between the conformers are found to be much greater in calix[4]pyrrole compared to those in calix[4]furan and calix[4]thiophene. Relatively larger NH group and higher dipole of a pyrrole ring in calix[4]pyrrole contribute to the higher energy barrier for the conformational conversions and relatively rigid potential energy surface compared to the case of calix[4]furan and calix[4]thiophene. The computational results herein provide theoretical understanding of the conformational flexibility and the thermodynamic nature which can be applied to understand the complexation behavior of the three calix[4]heterocycles.