• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.3
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• pp.491-498
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• 2005

Occlusal fissures and pits are ideal places for the development of caries. Pit and fissure sealants are now considered as a very effective means to prevent dental caries. The purpose of this investigation was to examine the effect on the sealant penetration of the elapse of time from the application of sealant until exposure to visible light, and to examine the effect of the filler content and tooth position on the sealant penetration. 192 extracted human premolars were used to this experiment. Following enamel conditioning, a light-polymerized sealant was applied and 4 different periods of time(3, 5, 10, 20 seconds) were allowed until exposure to the light source. The results obtained were as follows; 1. According to time, in both unfilled sealant and filled sealant penetration increases deeply through mindfulness. 2. Sealant that apply to mandiblar premolar penetrated deeply through than to maxillay teeth. 3. Penetration difference according to filler content, unfilled sealant penetrated deeply through than filled sealant. The result from this study indicated that unfilled sealant penetrated most deeply in mandible when at least 20s time elapsed.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.3
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• pp.310-321
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• 2019

Objectives: The purpose of this study was to investigate types and characteristics of chemical substances used in LCD(Liquid crystal display) panel manufacturing process. Methods: The LCD panel manufacturing process is divided into the fabrication(fab) process and module process. The use of chemical substances by process was investigated at four fab processes and two module processes at two domestic TFT-LCD(Thin film transistor-Liquid crystal display) panel manufacturing sites. Results: LCD panels are manufactured through various unit processes such as sputtering, chemical vapor deposition(CVD), etching, and photolithography, and a range of chemicals are used in each process. Metal target materials including copper, aluminum, and indium tin oxide are used in the sputtering process, and gaseous materials such as phosphine, silane, and chlorine are used in CVD and dry etching processes. Inorganic acids such as hydrofluoric acid, nitric acid and sulfuric acid are used in wet etching process, and photoresist and developer are used in photolithography process. Chemical substances for the alignment of liquid crystal, such as polyimides, liquid crystals, and sealants are used in a liquid crystal process. Adhesives and hardeners for adhesion of driver IC and printed circuit board(PCB) to the LCD panel are used in the module process. Conclusions: LCD panels are produced through dozens of unit processes using various types of chemical substances in clean room facilities. Hazardous substances such as organic solvents, reactive gases, irritants, and toxic substances are used in the manufacturing processes, but periodic workplace monitoring applies only to certain chemical substances by law. Therefore, efforts should be made to minimize worker exposure to chemical substances used in LCD panel manufacturing process.

• The korean journal of orthodontics
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• v.49 no.4
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• pp.246-253
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• 2019

Objective: To evaluate the effectiveness of three different caries-preventing agents on artificial caries in a Streptococcus mutans-based caries model. Methods: Sixty-five caries-free human molar enamel blocks were treated with a demineralization solution and a remineralization solution. The specimens were assigned to the following groups according to the caries-protective product applied: group A, chlorhexidine varnish; group B, fluoride-releasing chemically cured sealant; group C, fluoride-releasing lightcured sealant; group D, positive control (specimens that were subjected to de- and remineralization cycles without treatment with any caries-protective agents); and group E, negative control (specimens that were not subjected to de- and remineralization cycles). Samples in groups A-D were stored in demineralization solution with S. mutans and thereafter in artificial saliva. This procedure was performed for 30 days. Average fluorescence loss (${\Delta}F$) and surface size of the lesions were measured using quantitative light-induced fluorescence at baseline and on the 7th, 14th, and 30th days. Results: After 30 days, group A demonstrated a significant increase in ΔF and the surface size of the lesions, no significant difference in comparison with the positive control group, and a significant difference in comparison with the negative control group. Group B showed no significant changes in both parameters at any of the measurement points. While group C showed increased ${\Delta}F$ after 14 days, no significant fluorescence change was observed after 30 days. Conclusions: Both fluoride-releasing sealants (chemically or light-cured) show anti-cariogenic effects, but the use of chlorhexidine varnish for the purpose of caries protection needs to be reconsidered.

• The Journal of the Korea Contents Association
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• v.22 no.3
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• pp.586-592
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• 2022

In this study cerium nano particles(CNPs) with 0-4.0 wt% was incorporated to the conventional dental pit and fissure sealant(ConciseTM) to produce new pit and fissure sealant the physical properties and cytotoxicity. The physical properties were measured for polymerizing depth the degree of water absorption and solubility. The cytotoxicity of cell viability was analyzed by MTT assay using immortalized human oral keratinocyte(IHOK). As a result of this preceding study the polymerizing depth was decreased by the increasing of the amount of CNPs. The solubility degree of the sealant added CNPs with 2.0 wt% showed was the lower and the water absorption showed no significantly difference with the control groups(p>0.05). The cytotoxicity test results showed high survival rates in all experimental groups. Therefore, pit and fissure sealant by the addition of CNPs excellent cell viability be produced without weaken the physical property of the cell viability fissure sealant containing CNPs does not weaken physical properties and has no cytotoxic effects biocompatibility. Considering its properties effect of CNPs, further studies are required for distribution technology application.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4D
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• pp.587-592
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• 2006

The joint sealants used in the airside should resist the high temperature of the jet blast and the jet fuel oil spilled when the aircraft is maintained and filled. The material of joint sealant for the airside should be different from that for the road due to these characteristics. Three different kinds of the joint sealant materials were tested in this paper. The materials include the polysulfide, the polyurethane and the silicon. The test results show that the physical properties and the performance of the polysulfide show the high resistance to the jet blast and the jet fuel oil. When the characteristics of the airside considered, the polysulfide may apply in the both of the runway and the apron area, the polyuretane can be applied the taxiway. The use of the silicon sealant is not recommended for the airside.

• Wind and Structures
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• v.37 no.4
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• pp.289-302
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• 2023

Insulating glass units (IGUs) have been widely used in buildings in recent years due to their superior thermal insulation performance. However, because of the panel reciprocating motion and fatigue deterioration of sealants under long-term wind loads, many IGUs have the problem of early failure of watertight properties in real usage. This study aimed to propose a statistical method for wind-induced deflection of IGU panels during the whole life service period, for further precise analysis of the accumulated fatigue damage at the sealed part of the edge bond. By the estimation of the wind occurrence regularity based on wind pressure return period, the events of each wind speed interval during the whole life were obtained for the IGUs at 50m height in Beijing, which are in good agreement with the measured data. Also, the wind-induced deflection analysis method of IGUs based on the formula of airspace coefficient was proposed and verified as an improvement of the original stiffness distribution method with the average relative error compared to the test being about 3% or less. Combining the two methods above, the deformation of the outer and inner panes under wind loads during 30 years was precisely calculated, and the deflection and stress state at selected locations were obtained finally. The results show that the compression displacement at the secondary sealant under the maximum wind pressure is close to 0.3mm (strain 2.5%), and the IGUs are in tens of thousands of times the low amplitude tensile-compression cycle and several times to dozens of times the relatively high amplitude tensile-compression cycle environment. The approach proposed in this paper provides a basis for subsequent studies on the durability of IGUs and the wind-resistant behaviors of curtain wall structures.

• Journal of Environmental Health Sciences
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• v.50 no.1
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• pp.43-53
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• 2024

Background: Exposure assessment is an important part of risk assessment for consumer products. Exposure models are used when estimating consumer exposures by considering exposure routes, subjects, and circumstances. These models differ based on their tiers, types, and target populations. Consequently, exposure estimates may vary between models. Objectives: This study aimed to compare the results of different exposure models using identical exposure factors. Methods: Chemical exposure from consumer products was calculated using four consumer exposure assessment models: Targeted Risk Assessment 3.1, Consumer Exposure Model 2.1 (CEM), ConsExpo web 1.1.1, and the Korean Exposure Algorithm (primary and detailed) issued by the Ministry of Environment, No. 972 (MOE). The same exposure factors were used in each model to calculate inhalation and dermal exposures to acetaldehyde, d-limonene, and naphthalene in all-purpose cleaners, leather coating sprays, and sealants. Results: In the results, TRA provided the highest estimate. Generally, MOE (detailed), CEM and ConsExpo showed lower exposures. The inhalation exposure for leather coating spray showed the largest differences between models, with differences reaching up to 1.2×10⁷ times. Since identical inputs were used for the calculations, it is likely that the models significantly influenced the estimated results. Conclusions: Despite using the same exposure factors to calculate dermal and inhalation exposures, the results varied substantially based on the model's exposure algorithm. Therefore, selecting an exposure model for assessing consumer products should be done with careful consideration.

• Journal of Gastric Cancer
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• v.24 no.1
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• pp.108-121
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• 2024

Anastomotic leaks and fistulas are significant complications of gastric surgery that potentially lead to increased postoperative morbidity and mortality. Surgical intervention is reserved for cases with severe symptoms or hemodynamic instability; however, surgery carries a higher risk of complications. With advancements in endoscopic treatment options, endoscopic approaches have emerged as the primary choice for managing these complications. Endoscopic clipping is a traditional method comprising 2 main categories: through-the-scope clips and over-the-scope clips. Through-the-scope clips are user friendly and adaptable to various clinical scenarios, whereas over-the-scope clips can close larger defects. Another promising approach is endoscopic stent insertion, which has shown a high success rate for leak closure, although vigilant monitoring is required to monitor stent migration. Infection control is essential in post-surgical leakage cases, and endoscopic internal drainage provides a relatively safe and noninvasive means to manage fluids, contributing to infection control and wound healing promotion. Endoscopic suturing offers full-thickness wound closure, but requires additional training and endoscopic versatility. As a promising tool, endoscopic vacuum therapy potentially surpasses stent therapy by draining inflammatory materials and closing defects. Furthermore, the use of tissue sealants, such as fibrin glue and cyanoacrylate, has been reported to be effective in selected situations. The choice of endoscopic device should be tailored to individual cases and specific patient conditions, with careful consideration of the nature of the defect. Further extensive studies involving larger patient populations are required to provide more robust evidence on the efficacy of endoscopic approach in managing post-gastric anastomotic leaks.

• Journal of Dental Anesthesia and Pain Medicine
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• v.24 no.1
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• pp.57-65
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• 2024

Background: The objective of behavioral guidance is to establish effective communication that aligns with a child's requirements to manage disruptive behavior. This study aimed to evaluate the effectiveness of the Tell-Show-Do and Ask-Tell-Ask techniques in managing dental anxiety in children during their initial appointment. Methods: The study included 50 children (28 boys and 22 girls) without any prior experience between the ages of 7 and 11 at their first dental visit. The children were randomly categorized into two groups: Group 1, Tell Shows Do, and Group 2, Ask-Tell-Ask. Subsequently, all children underwent noninvasive treatment procedures such as restorations, sealants, and oral prophylaxis. Furthermore, behavioral management techniques were employed based on the allocated group. Finally, anxiety levels for all children were assessed using the Raghavendra, Madhuri, and Sujata Pictorial Scale (RMS-PS) and heart rate at three different intervals (before, during, and after). The obtained data were entered into Microsoft Excel, and statistical analysis was performed using SPSS software. A paired t-test and Mann-Whitney U-test were used to compare the mean and median values of the two groups and determine their effectiveness. Results: Children in the TSD group exhibited statistically significant heart rates and RMS-PS scores in intra-group comparisons. However, children in the ask-tell-ask group showed a significant reduction only in the RMS-PS scores (P < 0.001) but not in the measures used to assess heart rate (P < 0.001). Conclusion: Tell-Show-Do was more effective than ask-tell-ask in alleviating dental anxiety in children. The simultaneous application of these two strategies can synergistically alleviate dental anxiety during a child's initial dentist appointment.

• The korean journal of orthodontics
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• v.29 no.5 s.76
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• pp.589-597
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• 1999

The purpose of this study was to evaluate the effects of fluoride releasing orthodontic sealants, light-cured (Group L1&L2) and self-cured (Group S1&S2) $FluoroBond^{\circledR}$, on enamel microhardness under artificial carious solution in vitro.112 extracted human premolar teeth were collected for experiments and divided into seven groups. A Tukon microhardness tester equipped with a Knoop diamond indenter was employed to determine microhardness. Tukon 23 program converted the number of microhardness into KHN (Knoop hardness number). The results were as follows: 1. The microhardness of enamel depth of all groups were the least at the depth of $50{\mu}m$ and that of all groups except L2 group, the greatest at the depth of $200{\mu}m$, were the greatest at the depth of $300{\mu}m$. And as the enamel depth of all groups except L2 and S2 group increased, the microhardness value also increased. 2. There was a little preventive effect in enamel decalcification both light-and self-cured orthodontic sealant groups, but had no statistical significance between the groups(p>0.05). 3. Light-cured orthodontic sealant groups had a progressive inhibiting effect in enamel decalcification at the depth of $100{\mu}m,150{\mu}m,\;and\;200{\mu}m$ (p<0.05). 4. Self-cured orthodontic sealant groups had a progressive inhibiting effect in enamel decalcification at the depth of $150{\mu}m$ (p<0.05). 5. There was no difference of the anti-enamel demineralization effect between light- and self-cured orthodontic sealant groups (p>0.05).