• Restorative Dentistry and Endodontics
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• v.30 no.3
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• pp.158-169
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• 2005

This study was done to evaluate the shear bond strength between light-cured glass ionomer cement (GIC) base and resin cement for luting indirect resin inlay and to observe bonding aspects which is produced at the interface between them by SEM. Two types of light cured GIC (Fuji II LC Improved, GC Co. Tokyo, Japan and Vitrebond$^{TM}$, 3M, Paul Minnesota U.S.A) were used in this study. For shear bond test, GIC specimens were made and immersed in 37$^{\circ}C$ distilled water for 1 hour, 24 hours, 1 week and 2 weeks. Eighty resin inlays were prepared with Artglass$^{(R)}$ (Heraeus Kultzer Germany) and luted with Variolink$^{(R)}$ II (Ivoclar Vivadent, Liechtenstein). Shear bond strength of each specimen was measured and fractured surface were examined. Statistical analysis was done with one-way ANOVA. Twenty four extracted human third molars were selected and Class II cavities were prepared and GIC based at axiopulpal lineangle. The specimens were immersed in 37$^{\circ}C$ distilled water for 1 hour, 24 hours, 1 week and 2 weeks. And then the resin inlays were luted to prepared teeth. The specimens were sectioned vertically with low speed saw. The bonding aspect of the specimens were observed by SEM (JSM-5400$^{(R)}$, Jeol, Tokyo, Japan) .There was no significant difference between the shear bond strength according to storage periods of light cured GIC base. And cohesive failure was mostly appeared in GIC On scanning electron micrograph, about 30 - 120 $\mu$m of the gaps were observed on the interface between GIC base and dentin. No gaps were observed on the interface between GTC and resin inlay.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.2
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• pp.272-277
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• 1998

Filtering rates of two farming ascidians Styela clava and S. plicata, and of a farming mussel Mytilus edulis were experimentally investigated with reference to effects of water temperature and size. Absorptiometric determinations of filtering rates were carried out in a closed system with experimental animals being decreased indicate dyes neutral red. Optical density (OD) of 440 nm in path length 22 mm cell used as the indication of food particles absorption was appeared directly in proportion with the concentration of neutral red dyes. The filtering rate F is calculated by Kim's equation $F\;=\;V(1-e^{-z})$, where V is the water volume ($\ell$) in the experimental jar, and Z is the decreasing coefficient of OD as meaning of instantaneous removal speed as In $C_t\;=\;In\;C_{o}-Z{\cdot}t$, in this formula $C_t$ is OD at the time t. Filtering rate of S. clava increased as exponential function with increasing temperature while not over critical limit, and the critical temperature for filtering rate was assumed to be between $28^{\circ}C$ and $29^{\circ}C$. In case of S. plicata, the critical temperature was to be below $13^{\circ}C$, and through the temperature range $15\~25^{\circ}C$ appeared a little difference in level even though with significant. M. edulis was not appear any significant effects by water temperature less than $29^{\circ}C$. The model formula derived from the results is as below, where F is filtering rate (${\ell}/hr/animal$), T is water temperature ($^{\circ}C$), and DW is dry meat weight (g) of experimental animal. $$S.\;Clava;\;F\;=\;e xp\;(0.119\;T-4.540)\;(DW)^{0.6745},\;T<29^{\circ}C$$) $$S.\;plicata;\;F\;=\;e xp\;(A_t)\;(DW)^{0.5675},\;(13^{\circ}C $$[A_t =-8.56+0.6805\;T-0.0153\;T^2]$$ $$M.\;edulis;\;F\;=\;0.3844\;(DW)^{0.4952},\;<29^{\circ}C$$)

• Restorative Dentistry and Endodontics
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• v.31 no.6
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• pp.477-484
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• 2006

The purposes of this study were to compare the apical terminus width of simulated curved root canal prepared with three NiTi file systems used by undergraduates for evaluation the effects of flute angle and pitch or radial land on reducing screw-in effect and to determine more safe NiTi file system for inexperienced operators. Fifty inexperienced undergraduate students prepared 150 simulated curved root canals in resin blocks with three NiTi file systems ; ProFile$^{(R)}$, Hero Shaper$^{(R)}$, K3$^{TM}$. The electric motor set at a speed of 300 rpm and torque of 30 in a 16 : 1 reduction handpiece was used. The simulated root canal was prepared to ISO #25 sizes with each file system. The scanned images of pre- and post-instrumented canal of resin block were superimposed. To evaluate the screw-in effect of three NiTi file systems, apical terminus width of root canal was measured from superimposed images and statistical analysis was performed. There were significant differences in three NiTi flle systems. ProFile$^{(R)}$ had significantly smaller width than Hero Shaper$^{(R)}$ and K3$^{TM}$"" (P < 0.05), but no significant difference was observed between K3$^{TM}$ and Hero Shaper$^{(R)}$. Under the condition of this study, active file system (Hero SHaper$^{(R)}$, K3$^{TM}$) with variable pitch and helical angle had more screw-in effect than passive file system (ProFile$^{(R)}$) with constant pitch and helical angle. It seems that the radial lands play more important role in reducing screw-in effect.

• Restorative Dentistry and Endodontics
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• v.24 no.4
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• pp.647-656
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• 1999

The purpose of this study was to investigate the shear bond strength and marginal microleakage of composite to enamel and dentin according to different treatment methods when the applied bonding agent was contaminated by artificial saliva. For the shear bond strength test, the buccal and occlusal surfaces of one hundred twenty molar teeth were ground to expose enamel(n=60) and dentin surfaces(n=60). The specimens were randomly assigned into control and 5 experimental groups with 10 samples in each group. In control group, a bonding system(Scotchbond$^{TM}$ Multi-Purpose plus) and a composite resin(Z-100$^{TM}$) was bonded on the specimens according to manufacture's directions. Experimental groups were subdivided into 5 groups. After polymerization of an adhesive, they were contaminated with at artificial saliva on enamel and dentin surfaces: Experimental group 1 ; artificial saliva was dried with compressed air. Experimental group 2 ; artificial saliva was rinsed with air-water spray and dried. Experimental group 3 ; artificial saliva was rinsed, dried and applied an adhesive. Experimental group 4 ; artificial saliva was rinsed, dried, and then etched using phosphoric acid followed by an adhesive. Experimental group 5, artificial saliva was rinsed, dried, and then etched with phosphoric acid followed by consecutive application of both a primer and an adhesive. Composite resin(Z-100$^{TM}$) was bonded on saliva-treated enamel and dentin surfaces. The shear bond strengths were measured by universal testing machine(AGS-1000 4D, Shimaduzu Co. Japan) with a crosshead speed of 5mm/minute under 50kg load cell. Failure modes of fracture sites were examined under stereomicroscope. The data were analyzed by one-way ANOVA and Tukey's test. For the marginal microleakage test, Class V cavities were prepared on the buccal surfaces of sixty molars. The specimens were divided into control and experimental groups. Cavities in experimental group were contaminated with artificial saliva and those surfaces in each experimental groups received the same treatments as for the shear test. Cavities were filled with Z-100. Specimens were immersed in 0.5% basic fuchsin dye for 24 hours and embedded in transparent acrylic resin and sectioned buccolingually with diamond wheel saw. Four sections were obtained from the one specimen. Marginal microleakages of enamel and dentin were scored under streomicroscope and averaged from four sections. The data were analyzed by Kruskal-Wallis test and Fisher's LSD. The results of this study were as follows. 1. The shear bond strength to enamel showed lower value in experimental group 1(13.20${\pm}$2.94MPa) and experimental group 2(13.20${\pm}$2.94MPa) than in control(20.03${\pm}$4.47MPa), experimental group 4(20.96${\pm}$4.25MPa) and experimental group 5(21.25${\pm}$4.48MPa) (p<0.05). 2. The shear bond strength to dentin showed lower value in experimental group 1(9.35${\pm}$4.11MPa) and experimental group 2(9.83${\pm}$4.11MPa) than in control group(17.86${\pm}$4.03MPa), experimental group 4(15.04${\pm}$3.22MPa) and experimental group 5(14.33${\pm}$3.00MPa) (p<0.05). 3. Both on enamel and dentin surfaces, experimental group 1 and 2 showed many adhesive failures, but control and experimental group 3, 4 and 5 showed mixed and cohesive failures. 4. Enamel marginal microleakage was the highest in experimental group 1 and there was a significant difference in comparison with other groups (p<0.05). 5. Dentin marginal microleakages of experimental group 1 and 2 were higher than those of other groups (p<0.05). This result suggests that treatment methods, re-etching with 35% phosphoric acid followed by re-application of adhesive or repeating all adhesive procedures, will produce good effect on both shear bond strength and microleakage of composite to enamel and dentin if the polymerized bonding agent was contaminated by saliva.

• The Korean Journal of Air & Space Law and Policy
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• v.24 no.1
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• pp.91-118
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• 2009

In the Republic of Korea, Regional Airlines from Jeju Air and Hansung Airlines have recently entered the domestic market to compete with the existing Legacy Airlines. In addition many of newly established regional low cost carriers like Air Busan, JeanAir, Easter Airline, are preparing to enter the jungle market. These circumstantial changes have come about as transportation competitiveness are getting weak in the market due to simultaneous expansion of surface modes such as a new opening of high-speed rail and extension of highways. The jumbled market entry by regional low cost carriers makes an enormous influence not only in managing transport network of existing carriers but also for the domestic policy of aviation authorities. It is too early to judge whether they would succeed or not. It is necessary to analyze the network operation of these regional carriers launching domestic routes and preparing to launch short distance international routes under the rapid changing market circumstances such as introduction of KTX or decrease in domestic routes by Legacy Airlines. Many regional airlines are to launch the routes connecting Korea-China-Japan, if they could ensure long-haul international routes successfully, it would follow that the difference between Legacy Airlines and Regional Airlines would decrease more and more, which would result in appearance of the $3^{rd}$or $4^{th}$Legacy Airlines The purpose of this study is to analyze the introduction of low cost carriers by regions and economic regional carrier network for non-scheduled air transportation market by taking a look at the regional airlines transportation network in the early stage of the domestic air transport market. For this purpose, cost and profit structure and management effect of transportation cost will be analyzed by comparing the presently operated routes of regional airlines with those of Legacy Airlines. And also demonstrative analysis demanded by the actual market will be achieved through surveys from experts, the actual airlines and travel agencies to build up transportation network.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.310-321
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• 1999

In this in vitro study, confocal laser scanning microscopic morphology of dentin-resin interface and its relationship to shear bond strength were investigated after the exposed dentin surfaces were treated with 3 different kinds of dentin adhesive systems[three-step; Scotchbond Multi-Purpose Plus(SMPP), self-priming bonding resin; Single Bond(SB), self-etching primer; Clearfil Liner Bond 2(LB2)]. 52 extracted human molar teeth without caries and/or restorations. The experimental teeth were randomly divided into three groups of seventeen teeth each. In five teeth of each group, class V cavities(depth: 1.5mm) with 900 cavosurface angles were prepared at the cementoenamel junction on buccal and lingual surfaces. Bonding resins of each dentin adhesive system were mixed with rhodamine B. Primer of SMPP was mixed with fluorescein. In group 1. the exposed dentin was conditioned with etchant, applied with above primer and bonding resin of SMPP. In group 2, with etchant and self-priming bonding agent of SB. In group 3, with self-etching primer and bonding agent of LB2. After treatment with dentin adhesive systems, composite resin were applied and photocured. The experimental teeth were cut longitudinally through the center line of restoration and grounded so that about $90{\mu}m$-thick wafers of buccolingually orientated dentin were obtained. And, $70{\sim}80{\mu}m$-thick wafers sectioned horizontally, thus presenting a dentinal tubules at 900 to the cut surface of a remaining tooth, were obtained. Primer of SMPP mixed with rhodamine B was applied to these wafers. Confocal laser scanning microscopic investigations of these wafers were done within of 24 hours after treatment. To measure shear bond strength, the remaining twelve teeth of each group were grounded horizontally below the dentinoenamel junction, so that no enamel remained. After applying dentin adhesive systems on the dentin surface, composite was applied in the shape of cylinder. The cylinder was 5mm in diameter, and 2mm in thickness. Shear bond strength was measured using Instron with a cross-head speed of 0.5mm/min. It was concluded as follows ; 1. Hybrid layer of SMPP(mean: $4.56{\mu}m$) was thicker than that of any other groups. This value was not statistically significant thicker than that of SB(mean: $3.41{\mu}m$, p>0.05), and significant thicker than that of LB2(mean: $1.56{\mu}m$, p<0.05). There was a statistical difference between SB and LB2(p<0.05). 2. Although there were variations in the length of resin tag even in a sample, and in a group, most samples in SMPP and SB showed resin tags extending above $20{\mu}m$. But samples in LB2 showed resin tags of $10{\mu}m$ at best. 3. Besides primer's infiltration into demineralized peritubular dentin and dentinal tubules, fluorophore of primer was detected in the lateral branches of dentinal tubules. 4. All groups demonstrated statistically significant differences from one another(p<0.05), with shear bond strengths given in descending order as follows: SMPP(18.3MPa), SB(16.0MPa) and LB2(12.4MPa). 5. LB2 having thinnest hybrid layer($1.56{\mu}m$) showed the lowest shear bond strength(12.4MPa).

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.265-285
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• 1999

The purposes of this investigation were to observe the reaction kinetics of five commercial dual cured resin cements (Bistite, Dual, Scotchbond, Duolink and Duo) when cured under varying thicknesses of porcelain inlays by chemical or light activation and to evaluate the effect of the porcelain disc on the rate of polymerization of dual cured resin cement during light exposure by using thermal analysis. Thermogravimetric analysis(TGA) was used to evaluate the weight change as a function of temperature during a thermal program from $25{\sim}800^{\circ}C$ at rate of $10^{\circ}C$/min and to measure inorganic filler weight %. Differential scanning calorimetry(DSC) was used to evaluate the heat of cure(${\Delta}H$), maximum rate of heat output and peak heat flow time in dual cured resin cement systems when the polymerization reaction occured by chemical cure only or by light exposure through 0mm, 1mm, 2mm and 4mm thickness of porcelain discs. In 4mm thickness of porcelain disc, the exposure time was varied from 40s to 60s to investigate the effect of the exposure time on polymerization reaction. To investigate the effect on the setting of dual cured resin cements of absorption of polymerizing light by porcelain materials used as inlays and onlays, the change of the intensity of the light attenuated by 1mm, 2mm and 4mm thickness of porcelain discs was measured using curing radiometer. The results were as follows 1. The heat of cure of resin cements was 34~60J/gm and significant differences were observed between brands (P<0.001). Inverse relationship was present between the heat of reaction and filler weight % the heat of cure decreased with increasing filler content (R=-0.967). The heat of reaction by light cure was greater than by chemical cure in Bistite, Scotchbond and Duolink(P<0.05), but there was no statistically significant difference in Dual and Duo(P>0.05). 2. The polymerization rate of chemical cure and light cure of five commercially available dual cured resin cements was found to vary greatly with brand. Setting time based on peak heat flow time was shortest in Duo during chemical cure, and shortest in Dual during light cure. Cure speed by light exposure was 5~20 times faster than by chemical cure in dual cured resin cements. The dual cured resin cements differed markedly in the ratio of light and chemical activated catalysts. 3. The peak heat flow time increased by 1.51, 1.87, and 3.24 times as light cure was done through 1mm, 2mm and 4mm thick porcelain discs. Exposure times recommended by the manufacturers were insufficient to compensate for the attenuation of light by the 4mm thick porcelain disc. 4. A strong inverse relationship was observed between peak heat flow and peak time in chemical cure(R=0.951), and a strong positive correlations hip was observed between peak heat flow and the heat of cure in light cure(R=0.928). There was no correlationship present between filler weight % or heat of cure and peak time. 5. The thermal decomposition of resin cements occured primarily between $300^{\circ}C$ and $480^{\circ}C$ with maximum decomposition rates at $335^{\circ}C$ and $440^{\circ}C$.

• Korean Journal of Agricultural and Forest Meteorology
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• v.3 no.1
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• pp.22-29
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• 2001

In Korean high yielding varieties developed by crosses between indica and japonica rice, the most limiting factor for yield may be attributed to the less number of the tillers in the unit area. The goals of this study is to find out the effect of the temperature factors as well as cultural practices on the development and increase of tillers of Dasanbyeo, the high yielding indica crossed japonica cultivar. The effect of temperature was examined under controlled phytotron condition with 6 levels of temperature, 15, 17, 19, 22, 24 and 26$^{\circ}C$, respectively, For the experiment, the leading japonica variety in Korea, Hwaseongbyeo, was used for the check cultivar for the comparison with Dasanbyeo. The high temperature also accelerated the initiation and termination of tiller development. The cultivar difference in the speed of tiller development was observed, for example, more rapid development of tiller in Dasanbyeo than in Hwaseongbyeo was observed at the high temperature range of 24-26$^{\circ}C$, while the vice versa phenomena was observed at lower temperature range of 17-22$^{\circ}C$. The first secondary tiller of Dasanbyeo was observed on the 16, 17, 23, 27 and 38 days after transplanting (DAT) at 26$^{\circ}C$, 24$^{\circ}C$, 22$^{\circ}C$, 19$^{\circ}C$, and 17$^{\circ}C$, respectively. Those of Hwaseongbyeo was 19-22, and 26 DAT at 19-26$^{\circ}C$ and 17$^{\circ}C$, respectively. The last effective tiller of Dasanbyeo was observed on 27-33 DAT for the primary tiller, 20-41 DAT for the secondary tiller. Those of Hwaseongbyeo were 23-40 DAT for primary tiller, and 24-40 DAT for the secondary tiller, and 24-40 DAT for the secondary tiller.

• Restorative Dentistry and Endodontics
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• v.29 no.2
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• pp.177-184
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• 2004

Objectives : This study investigated the hypothesis that increasing light-curing time would leave the oxygen-inhibited layer (OIL) of the adhesive thinner, and in turn, result in lower shear bond strength (SBS) than those obtained by the routine curing procedures. Methods：120 human extracted posterior teeth were randomly divided into three groups for bonding with three adhesives：All Bond 2/sup (R)/, One Step/sup (R)/, and Adper Prompt/sup (R)/. They were subsequently divided into four subgourps with different light-curing time (10, 20, 30 and 60s). The assigned adhesives were applied on superficial occlusal dentin according to the manufacturer's instructions and cured with one of the four curing times. Composite resin cylinder, 2.35㎜ in diameter, were built on the cured adhesive and light-cured for 40s. SBS were measured after 24h from the bonding using a universal testing machine (crosshead speed 1.0 ㎜/min). The relative thickness of the OIL and the degree of conversion (DC) were determined from the adhesive on a slide glass using FT-NIR in an absorbance mode. Data were analysed with One-way ANOVA and Duncan's multiple test (p〈0.05), Results：With increasing cure time, although there were no significant difference in th SBS of One-step and Adper Prompt (p〉0.05), those of All Bond 2 decreased significantly (p〈0.05). The relative thicknesses of the OIL on each adhesive were not affected by the cure time (p〉0.05). Although the DC of All-Bond 2 were statistically not different with increasing cure time (p〉0.05), those of One-Step and Adper Prompt showed an increasing trends with increasing cure time (p〈0.05). Conclusions：Increasing light-curing time did not affect on the relative thickness of the OIL of the adhesives, and in turn, on the SBS to dentin.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.46-55
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• 2000

During bonding procedure of composite resin, the prepared cavity can be contaminated by saliva. In this study, marginal microleakage and shear bond strength of a composite resin to primed enamel and dentin treated with artificial saliva(Taliva$^{(R)}$) were evaluated. For the marginal microleakage test, Class V cavities were prepared in the buccal surfaces of fifty molars. The samples were randomly assigned into 5 groups with 10 samples in each group. Control group was applied with a bonding system (Scotchbond$^{TM}$ Multi-Purpose plus) according to manufacture's directions without saliva contamination. Experimental groups were divided into 4 groups and contaminated with artificial saliva for 30 seconds after priming: Experimental 1 group ; artificial saliva was dried with compressed air only, Experimental 2 group ; artificial saliva was rinsed and dried. Experimental 3 group ; cavities were etched with 35% phosphoric acid for 15 seconds after rinsing and drying artificial saliva. Experimental 4 group ; cavities were etched with 35% phosphoric acid for 15 seconds and primer was reapplied after rinsing and drying artificial saliva. All the cavities were applied a bonding agent and filled with a composite resin (Z-100$^{TM}$). Specimens were immersed in 0.5% basic fuschin dye for 24 hours and embedded in transparent acrylic resin and sectioned buccolingually with diamond wheel saw. Four sections were obtained from one specimen. Degree of marginal leakage was scored under stereomicroscope and their scores were averaged from four sections. The data were analyzed by Kruscal-Wallis test and Fisher's LSD. For the shear bond strength test, the buccal or occlusal surfaces of one hundred molar teeth were ground to expose enamel(n=50) or dentin(n=50) using diamond wheel saw and its surface was smoothed with Lapping and Polishing Machine(South Bay Technology Co., U.S.A.). Samples were divided into 5 groups. Treatment of saliva-contaminated enamel and dentin surfaces was same as the marginal microleakage test and composite resin was bonded via a gelatin capsule. All specimens were stored in distilled water for 48 hours. The shear bond strengths were measured by universal testing machine (AGS-1000 4D, Shimaduzu Co., Japan) with a crosshead speed of 5 mm/minute. Failure mode of fracture sites was examined under stereomicroscope. The data were analyzed by ANOVA and Tukey's studentized range test. The results of this study were as follows : 1. Enamel marginal microleakage showed no significant difference among groups. 2. Dentinal marginal microleakages of control, experimental 2 and 4 groups were lower than those of experimental 1 and 3 groups (p<0.05). 3. The shear bond strength to enamel was the highest value in control group (20.03${\pm}$4.47MPa) and the lowest value in experimental 1 group (13.28${\pm}$6.52MPa). There were significant differences between experimental 1 group and other groups (p<0.05). 4. The shear bond strength to dentin was higher in control group (17.87${\pm}$4.02MPa) and experimental 4 group (16.38${\pm}$3.23MPa) than in other groups, its value was low in experimental 1 group (3.95${\pm}$2.51 MPa) and experimental 2 group (6.72${\pm}$2.26MPa)(p<0.05). 5. Failure mode of fractured site on the enamel showed mostly adhesive failures in experimental 1 and 3 groups. 6. Failure mode of fractured site on the dentin did not show adhesive failures in control group, but showed mostly adhesive failure in experimental groups. As a summary of above results, if the primed tooth surface was contaminated with artificial saliva, primer should be reapplied after re-etching it.