수종의 세멘트가 근관 치료된 치아의 포스트 유지에 미치는 영향

김종원,이청희,조광헌 慶北大學校 齒科大學 1993 慶北齒大論文集 Vol.10 No.2

근관치료된 치아에 포스트를 할 경우 세멘트의종류와 포스트의 직경이 포스트의 유지력에 어떠한 영향을 주는지 알아보기 위하여, 하악절치 33개와 견치 17개를 이용하여 법랑-백악질 경계선상에서 치아장축에 수직되게 절단한 후 근관치료 및 근관충전을 하였다. 기성품의 parallel Para-post를 샌드브라스팅하여 깊이 7mm로 하여, Ⅰ에는 Z,P,C., Ⅱ에는 Panavia, Ⅲ군에는 All-Bond 및 복합레진으로 세멘트하였다. 1주일간의 레진 세멘트 경화시간을 준 후 인스트론 만능시험기에 치아를 거상하고 cross head speed 1mm/min로 인장력을 가하여 유지력을 측정하고, 치근 내부를 주사 전자 현미경으로 관찰하여 다음과 같은 결과를 얻었다. 1. 하악절치에서 평균 파단하중은 Ⅲ군에서 48.49±13.51Kg중, Ⅱ군에 서 21.47±9.32Kg중, Ⅰ군에서 21.34±7.85Kg중의 순서로 나타났으며 Ⅲ군이 Ⅰ군과 Ⅱ군에 비해 통계적으로 유의성있는 차이를 나타내었다(P<0.01). 2. 견치에서 평균 파단하중은 Ⅲ군에서 42.99±7.87Kg중,Ⅰ군에서 29.58±7.47Kg중, Ⅱ군에서 28.55±4.37Kg중으로 Ⅲ군이 Ⅰ군과 Ⅱ군에 비하여 통계적으로 유의성있는 차이를 나타내었다(P<0.05). 3. 포스트 직경의 크기에 따른 파단하중의 비교에 있어서, 각각의 실험군 내에서 Φ1mm의 하악절치와 Φ 1.25mm의 견치 사이에는 통계적 으로 유의성이 없었다(P>0.05). 4. 레진의 기계적 결합을 관찰하기 위한 주사전자 현미경 관찰에서 Ⅱ군에서는 상아질 세관내에 레진 tag가 관찰되지 않았으며, Ⅲ군 에서는 상아질 세관내에 레진tag가 상당히 관찰되었으나, 일부 치아에서는 관찰되지 않은 경우도 있었다. The prupose of this study was to evaluate the effect of various cements and the diameter of posts to retention of the post in endodontically treated teeth. Thirty three mandibular incisors and seventeen canines were used. The coronal portion of the teeth were removed at the cemento-enamel junction. Every tooth was made with a Para-post drill to the depth of 7mm(P-42-4 in mandibular incisors, P-42-5 in canines). The teeth were divided into three groups. Group Ⅰ was composed of 11 mandibular incisors & 6 canines, and posts were cemented with zinc phosphate cement. Group Ⅱ was composed of 11 mandibular incisors & 6 canines, and posts were cemented with Panavia cement. Group Ⅲ was composed of 11 mandibular incisors & 5 canines, and posts were cemented with All-Bond & composite luting cement. A special retention jig was made. After 1 week, teeth with cemeted posts were mounted on a retention jig and the failure loads of the specimens were measured by an Instron Universal Testinng Machine. Scanning electron microscopy examined the internal surface of the roots. The results were as follows; 1. There was a statistically significant difference between the failure loads of group Ⅲ and the others in the mandibular incisors(P<0.01). 2. There was a statistically significant difference between the failure loads of group Ⅲ and the others in canines(P<0.05). 3. There was no statistically significant difference between degrees of diameter of post in each experimental group(P>0.05). 4. In examination by scanning electron microscopy, group Ⅱ had no resin tags on the dentinal tubules. Group Ⅲ had resin tags on the dentinal tubules, though not present in some parts.

An Open Tubular CEC Column of Excellent Separation Efficiency for Proteomic Analysis

Cheong, Won Jo,Zaidi, Shabi Abbas,Kim, Yune Sung Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.10

Determination of Catechin Compounds in Korean Green Tea Infusions under Various Extraction Conditions by High Performance Liquid Chromatography

Cheong, Won-Jo,Park, Moon-Hee,Kang, Gyoung-Won,Ko, Joung-Ho,Seo, You-Jin Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.5

Liquid chromatographic methods with UV and fluorescence detection have been used to determine the levels of (+)-catechin, (-)-epicatechin, (-)-epicatechin gallate, and (-)-epigallocatechin gallate in Korean green tea infusions. The extracts of Korean green tea leaves or powders in water at various temperatures (100 ${^{\circ}C}$, 80 ${^{\circ}C}$, 60 ${^{\circ}C}$) and time, were washed with chloroform and re-extracted to ethyl acetate. The ethyl acetate phase was dried and re-dissolved in methanol and analyzed. Five catechin compounds were separated by gradient elution. The flavonoids were found decomposed on prolonged extraction, thus exhaustive extraction by a Soxhlet apparatus was found useless for green tea. Some unknown components were found in the extracts at 100 ${^{\circ}C}$. When the green tea was filtered and re-extracted with new fresh water, still some flavonoids were extracted. However, the contents of flavonoids in the third extract were found negligible. The flavonoid extraction rate of green tea powders was higher than that of green tea leaves, but flavonoid decomposition of green tea powders was also faster than that of green tea leaves. The traditional way of drinking green tea was found appropriate in view of flavonoids intake.

A Modified Adsorption Model for Retention of Nonpolar Solutes in Reversed Phase Liquid Chromatography

Cheong Won Jo Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.1

The adsorption model in reversed phase liquid chromatography has been critically examined. It has been found that use of the Everett type surface activity coefficient for the solute in the stationary phase is not useful to study the retention characteristics of a nonpolar solute. We suggest a modified model. In this model it is assumed that the displaced modifier molecules from the surface monolayer do not transfer into the bulk mobile phase but stick to the nonpolar solute which has displaced them. In addition, we prefer to use an apparent stationary phase activity coefficient of the soluie instead of the Everett type activity coefficient. This modified adsorption model well explains the mobile and stationary phase effects on the solute retention upon variation of mobile phase composition.

Limitations of the Linear Solvation Energy Relationships in Reversed Phase Liquid Chromatography

Cheong, Won-Jo,Choi, Jang-Duck Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.10

We have re-examined the linear solvation energy relationships in reversed phase liquid chromatography by considering various solutes including quite a number of compounds of strong hydrogen bond capability. We observed that solutes of strong hydrogen bond ability should be excluded in order to obtain resonable correlations between In k' and solute polarity parameters and that inclusion of one or two such solutes causes severe distortions of correlation results. This anomaly may be due to existence of residual silanol groups in the stationary phase, that is, their specific interactions with solutes.

The Hydroxyl Group-Solvent and Carbonyl Group-Solvent Specific Interactions for Some Selected Solutes Including Positional Isomers in Acetonitrile/Water Mixed Solvents Monitored by HPLC

Cheong, Won-Jo,Keum, Young-Ik,Ko, Joung-Ho Korean Chemical Society 2002 Bulletin of the Korean Chemical Society Vol.23 No.1

We have evaluated the specific hydroxyl group-solvent and carbonyl group-solvent interactions by using an Alltima C18 stationary phase and by measuring the retention data of carefully selected solutes in 60/40, 70/30, and 80/20(v/v%) acetonitrile/water eluents at 25, 30, 35, 40, 45, and 50 oC. The selected solutes are phenol, acetophenone, alkylbenznes(benzene to hexylbenznene), 4 positional isomers of phenylbutanol, 5-phenyl-1-pentanol, 3 positional isomers of alkylarylketone derived from butylbenzene, and 1-phenyl-2-hexanone. The magnitudes of hydroxyl group-acetonitrile/water specific interaction enthalpies are larger than those of carbonyl group-acetonitrile/water specific interaction enthalpies in general while the magnitudes of carbonyl group-methanol/water specific interaction enthalpies are larger than those of hydroxyl group-methanol/water specific interactions. We observed clear discrepancies in functional group-solvent specific interaction among positional isomers. The variation trends of solute transfer enthalpies and entropies with mobile phase composition in the acetonitrile/water system are much different from those in the methanol/water system. The well-known pocket formation of acetonitrile in aqueous acetonitrile mixtures has proven to be useful to explain such phenomena.

Porous Silica Particles As Chromatographic Separation Media: A Review

Cheong, Won Jo Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.12

Porous silica particles are the most prevailing raw material for stationary phases of liquid chromatography. During a long period of time, various methodologies for production of porous silica particles have been proposed, such as crashing and sieving of xerogel, traditional dry or wet process preparation of conventional spherical particles, preparation of hierarchical mesoporous particles by template-mediated pore formation, repeated formation of a thin layer of porous silica upon nonporous silica core (core-shell particles), and formation of specific silica monolith followed by grinding and calcination. Recent developments and applications of useful porous silica particles will be covered in this review. Discussion on sub-$3{\mu}m$ silica particles including nonporous silica particles, carbon or metal oxide clad silica particles, and molecularly imprinted silica particles, will also be included. Next, the individual preparation methods and their feasibilities will be collectively and critically compared and evaluated, being followed by conclusive remarks and future perspectives.

The Positional Effect of Solute Functional Group among Positional Isomers of Phenylpropanol in Hydroxyl Group-Solvent Specific Interactions in Methanol/Water Mixed Solvents Monitored by HPLC

Cheong, Won-Jo,Ko, Joung-Ho,Kang, Gyoung-Won Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.8

We have evaluated the hydroxyl group-solvent specific interactions by using a Lichrosorb RP18 stationary phase and by measuring the retention data of carefully selected solutes in 50/50, 60/40, 70/30, 80/20, and 90/10(v/v%) methanol/water eluents at 25, 30, 35, 40, 45, and 50 ${^{\circ}C}$. The selected solutes are 3 positional isomers of phenylpropanol, that is, 1-phenyl-1-propanol, 1-phenyl-2-propanol, and 3-phenyl-1-propanol. There exist clear discrepancies in ${\Delta}H^o$ (solute transfer enthalpy from the mobile to the stationary phase) and $T{\Delta}S^o$ (solute transfer entropy) among positional isomers. The difference in ${\Delta}H^o$ and $T{\Delta}S^o$ between secondary alcohols (1-phenyl-1-propanol and 1-phenyl-2-propanol)is negligible compared to the difference between the primary alcohol (1-phenyl-3-propanol) and secondary alcohols. The $T{\Delta}S^o$ values of 3-phenyl-1-propanol are close to those of butylbenzene while the $T{\Delta}S^o$ values of secondary alcohols are close to those of propylbenzene. The difference in ${\Delta}{\Delta}H^o$ (specific solute-mobile phase interaction enthalpy) between the primary alcohol and the secondary alcohol decreases with increase of methanol content in the mobile phase. A unique observation is an extremum for 1-phenyl-3-propanol in the plot of $T{\Delta}{\Delta}S^o$ vs. methanol volume %. The positive sign of $T{\Delta}{\Delta}S^o$ of 3-phenyl-1-propanol implies that the entropy of 3-phenyl-1-propanol is greater than that of the hypothetical alkylbenzene (the same size and shape as phenylpropanol) in the mobile phase.

An Open Tubular CEC Column of Excellent Separation Efficiency for Proteomic Analysis

Won Jo Cheong,샤비,Yune Sung Kim 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.10

Preparation of Cucurbituril Anchored Silica Gel by Cross Polymerization and Its Chromatographic Applications

Cheong, Won-Jo,Go, Joung-Ho,Baik, Yoon-Suk,Kim, Sung-Soon,Nagarajan, Erumaipatty R,Selvapalam, Narayanan,Ko, Young-Ho,Kim, Ki-Moon Korean Chemical Society 2008 Bulletin of the Korean Chemical Society Vol.29 No.10

A new chromatographic stationary phase has been prepared by cross polymerization between allylsilica and perallyloxycucurbit[6]uril and characterized by elemental analysis and FT-IR spectroscopy. The double endcapping has been proven to improve the separation efficiency of the cucurbituril-based stationary phase material. The first end-capping was carried out when allylsilica was made. The second end-capping was done as the final step of the whole process, and the use of a mixture of hexamethyldisilazane (HMDS) and trimethylchlorosilane (TMCS) as an end-capping reagent was found better than the use of only HMDS or TMCS. Our stationary phase has shown generally good results in separation of nonpolar and polar analytes. This phase showed even better separation performance than the commercial C18 phase for the case where hostguest chemistry was properly incorporated in solute retention.