• Restorative Dentistry and Endodontics
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• v.27 no.5
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• pp.502-514
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• 2002

The aim of this study was to evaluate the marginal adaptation of direct class II sandwich restoration with packable composites(P-60), resin modified glass ionomer cement(Fuji-II LC), flowable compomer(Dyract Flow), flowable composites(Filtek Flow) in comparison with total bond restorations. In addition, for sandwich restorations, influence of different sandwich techniques was also evaluated. Large butt-joint box typed class II cavites with cervical margins 1mm below the cemento-enamel junction were cut into 70 extracted human molars. The cavities(7 groups, n=10) were filled using a closed/open sandwich restoration or total bond restoration technique with materials according to the manufacturer's recommandation using the single-component bonding agent for each system. Teeth were thermocycled 500 times between 5$^{\circ}C$ and 55$^{\circ}C$ with 30-second dwell time. The teeth were then coated with nail polish 1mm short of the restoration, placed in a 2% methylene blue for 24 hours, and sectioned with diamond wheel. Sections were examined with a stereoscope to determine the extent of microleakage. Dentine /Cementum margins were analyzed for microleakage on scale of 0(no leakage) to 4(entire axial wall) and interface between materials, on scale of 0(no leakage) to 3(axial wall). Results were evaluated with Kruskal Wallis Test, corrected for ties, to determine whether there were statistically significant differences among the seven groups. Pairs of groups were analyzed using the Student-Newman-Keuls Method and Dunn s Method. The results were as follows : 1. All groups showed some micoleakage in cervical portion. But there were no microleakage in interface between materials. 2. Closed sandwich restorations with Fuji-II LC and Filtek Flow had significantly lower leakage rating than total restorations with only P-60. However, open sandwich restorations with Dyract Flow showed significantly higher (P<0.05) 3. Closed sandwich restorations had significantly lower leakage rating than total restorations. However open sandwich restoration s showed significantly higher (P<0.05). 4. Sandwich restorations with Fuji-II LC were iou$.$or leakage than only P-60. Filtek Flow, Dyract Flow. But there were no statistically differences among the materials. From the results above, it could be concluded, closed sandwich restorations was effective in reducing microleakage of class II restorations. The best results showing the least microleakage were for the closed sandwich technique with Fuji-II LC and Filtek Flow.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.6
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• pp.654-663
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• 2004

Statement of problem. According to the fracture pattern in several reports, fractures most frequently occur in the interface between the ceromer and the substructure. Purpose. The aim of this in vitro study was to compare the macro shear bond strength and microshear bond strength of a ceromer bonded to a fiber reinforced composite (FRC) as well as metal alloys. Material and methods. Ten of the following substructures, type II gold alloy, Co-Cr alloy, Ni-Cr alloy, and FRC (Vectris) substructures with a 12 mm in diameter, were imbedded in acrylic resin and ground with 400, and 1, 000-grit sandpaper. The metal primer and wetting agent were applied to the sandblasted bonding area of the metal specimens and the FRC specimens, respectively. The ceromer was placed onto a 6 mm diameter and 3 mm height mold in the macro-shear test and 1 mm diameter and 2 mm height mold in the micro-shear test, and then polymerized. The macro- and micro-shear bond strength were measured using a universal testing machine and a micro-shear tester, respectively. The macro- and micro-shear strength were analyzed with ANOVA and a post-hoc Scheffe adjustment ($\alpha$ = .05). The fracture surfaces of the crowns were then examined by scanning electron microscopy to determine the mode of failure. Chi-square test was used to identify the differences in the failure mode. Results. The macro-shear strength and the micro-shear strength differed significantly with the types of substructure (P<.001). Although the ceromer/FRC group showed the highest macroand micro-shear strength, the micro-shear strength was not significantly different from that of the base metal alloy groups. The base metal alloy substructure groups showed the lowest mean macro-shear strength. However, the gold alloy substructure group exhibited the least micro-shear strength. The micro-shear strength was higher than the macro-shear strength excluding the gold alloy substructure group. Adhesive failure was most frequent type of fracture in the ceromer specimens bonded to the gold alloys. Cohesive failure at the ceromer layer was more common in the base metals and FRC substructures. Conclusion. The Vectris substructure had higher shear strength than the other substructures. Although the shear strength of the ceromer bonded to the base metals was lower than that of the gold alloy, the micro-shear strength of the base metals were superior to that of the gold alloy.

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.463-486
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• 1995

The effect of moistening and air-drying of acid-conditioned dentin before priming on the formation of resin-dentin hybrid zone was investigated, Freshly extracted human molars were used and divided at random into 5 groups, Groups 1 - 3 consisted of specimens conditioned with 10 % phosphoric acid for 20 seconds; Group 1 served as a control in which the conditioned dentin was simply blot-dried with a damp facial tissue; Group 2 was air dried for 30 seconds ; Group 3 was air dried for 30 seconds and immediately remoistened for 10 seconds with air-water syringe. and then the specimen was blot-dried with a damp facial tissue. Groups 4-5 were not acid conditioned ; In group 4, the smear layer on the dentin was blot dried before primer placement; Group 5 was air dried only for 30 seconds, The acetone-based primer and bonding agent of All Bond 2 (Bisco. Inc., USA) and composite resin (Z-100, 3M Dental products, USA) were applied for acid conditioned dentin and non-conditioned dentin. The morphologic ultrastructure of resin-dentin hybrid zone was examined by the use of SEM and TEM. and the existence of inorganic material and analysis of Ca/P weight-percent ratio in the resin-dentin hybrid zone were revealed by the EDAX, The results were as follows : 1. In the moistened specimens from acid-conditioned groups, the resin penetrated about 3-$4{\mu}m$ into dentin and the denatured collagen smear layer was not present at the surface. The resin tag was formed to a thickeness of 3-$4{\mu}m$ at the upper part of dentinal tubule and compactively connected to each other by means of many lateral branching. 2. In the air-dried specimens from acid-conditioned groups, the resin penetrated about 2.0-$2.5\;{\mu}m$ into dentin and an upper thin black layer to a thickness of 30-35nm was identified between adhesive resin and demineralized collagen layer. The resin tag to have a diameter of $2.5{\mu}m$ was formed at the upper part of dentinal tubule. However the funnel shape of the tag was not notable compared to the moistened specimens. 3. In the remoistened specimens from acid conditioned groups, the resin penetrated about 2.0-$2.5{\mu}m$ into dentin and an upper black layer was not present. The resin tag at the upper part of dentinal tubule was formed less than $2{\mu}m$ and was weakly connected to each other by means of few lateral branching. 4. In the non-conditioned groups, the smear layer was formed to a thickness of $0.5{\mu}m$ at dentin surface. However, the resin-dentin hybrid zone was not identified by TEM. The evidence of resin penetration into intertubular and intratubular dentin did not show. 5. All the acid-conditioned groups showed that the detected calcium and phosphorus weight percent ratios at the $2{\mu}m$ upper portion from the resin-dentin interface into the resin were much higher than that at the $2{\mu}m$ lower portion from the resin-dentin interface to dentin. (P<0.01).

• Restorative Dentistry and Endodontics
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• v.34 no.3
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• pp.184-191
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• 2009

The purpose of this study was to evaluate the physical properties of different self-adhesive resin cements and their shear bond strength on dentin and lithium disilicate ceramic and compare these result with that of conventional resin cement. For this study, four self-adhesive resin cements (Rely-X Unicem, Embrace Wetbond, Mexcem, BisCem), one conventional resin cement (Rely-X ARC) and one restorative resin composite (Z-350) were used. In order to evaluate the physical properties, compressive strength, diametral tensile strength and flexural strength were measured. To evaluate the shear bond strength on dentin, each cement was adhered to buccal dentinal surface of extracted human lower molars. Dentin bonding agent was applied after acid etching for groups of Rely-X ARC and Z-350. In order to evaluate the shear bond strength on ceramic, lithium disilicate glass ceramic (IPS Empress 2) disks were prepared. Only Rely-X ARC and Z-350 groups were pretreated with hydrofluoric acid and silane. And then each resin cement was adhered to ceramic surface in 2 mm diameter. Physical properties and shear bond strengths were measured using a universal testing machine. Results were as follows 1. BisCem showed the lowest compressive strength, diametral tensile strength and flexural strength. (P<0.05) 2. Self-adhesive resin cements showed significantly lower shear bond strength on the dentin and lithium disilicate ceramic than Rely-X ARC and Z-350 (P<0.05) In conclusion, self-adhesive resin cements represent the lower physical properties and shear bond strength than a conventional resin cement.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.183-196
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• 1998

The purpose of this study was to determine the effect of bleaching technique on the shear bond strength of esthetic restorative materials to bovine enamel. The bleaching agent was used 35% $H_2O_2$(Hi-Lite, Shofu, U.S.A.). Experimental groups were divided into two divisions as group A and B. Experimental A groups for the effect of number of bleaching were as follows ; Group Al : no bleaching Group A2 : bleaching 1 time ( for 5 minutes ) Group A3 : bleaching 3 times ( each for 5 minutes ) Group A4 : bleaching 6 times ( each for 5 minutes ) Group A5 : bleaching 9 times ( each for 5 minutes ) Experimental B groups for the effect of storage period in artificial saliva were as follows ; Group B1 : not stored in artificial saliva after bleaching Group B2 : stored in artificial saliva for 1 day after bleaching Group B3 : stored in artificial saliva for 1 week after bleaching Group B4 : stored in artificial saliva for 2 weeks after bleaching Group B5 : stored in artificial saliva for 4 weeks after bleaching Composite resin and glass ionomer cement were bonded to all specimens, and the shear bond strength between enamel and r~storative material were measured in Instron Universal Testing Machine(Instron, 4467, U.S.A,), Additionally, the bleached enamel specimens were examed after etching with 37.4% $H_3PO_4$ for 1 min under SEM(S-2300, Hitachi Co., Japan) to observe the effect of bleaching procedure on enamel surface morphology. The result were as follows ; 1. In SEM findings, bleached bovine enamel was found to be superficially rough. 2. In bleached bovine enamel, the effect of acid etching was reduced with the increase of number of bleaching. 3. The mean shear bond strength of composite resin and glass ionomer cement to bleached enamel surface tended to be lower than those to non-bleached enamel surface. 4. With the increase of number of bleaching, the shear bond strength of composite resin and glass ionomer cement to bleached enamel were progressively decreased. 5. Increasing the, storage period in artificial saliva after bleaching, the shear bond strength of composite resin and glass ionomer cement to bleached enamel were progressively increased. 6. The mean shear bond strength of glass ionomer cement to bleached bovine enamel tended to be clearly lower than that of composite resin.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.443-460
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• 1998

The purpose of this study was to estimate the changes of tensile bond strength according to the difference in lining materials and lining area. Seventy non-carious extracted human molars were used in the present study, and they were randomly assigned into 2 experimental groups according to the difference in lining materials. Each experimental group was subdivided into 3 groups according to the difference in lining area. Circular cavities were prepared on the dentin surface to a diameter of 1.5mm, 2.0mm, 2.5mm and the prepared cavities were filled with Fuji II LC( Glass Ionomer Cement : GIC) or Dycal. Dentin specimens without circular cavity were used as control group. The primer and bonding agent of All-Bond 2 and composite resin (Z-100, 3M Dental Products, U. S. A.) were applied to the exposed dentin surface with or without lining. Tensile bond strengths for the experimental specimens were then measured. To examine the interface between dentin and liner & between liner and composite resin, two specimens from each group were fabricated and observed under the SEM. The results were as follows. 1. Tensile bond strength for the specimens lined with GIC was higher than that for specimens lined with Dycal. However, there was no significant difference between two groups(p>0.05). 2. Tensile bond strength for the specimens lined with GIC in a diameter of 1.5mm(GIC-1.5mm lining group) was statistically higher than that for the GIC-2.0mm lining group and GIC-2.5mm lining group(p<0.05). 3. Tensile bond strength for the specimens lined with Dycal in a diameter of 2.5mm (Dycal-2.5mm lining group)was statistically lower than that for Dycal-1.5mm lining group and Dycal-2.0mm lining group(p<0.05). 4. It was possible to observe the good adhesion of the resin composite to the GIC and the presence of a fissure between GIC and dentin all along the interface. Interfacial gaps of 7.2-$72.2{\mu}m$ between GIC and dentin were observed. The interfacial gap between GIC and dentin at the cavity base was greater. However, the gap was gradually decreased toward the occlusal portion. 5. It was possible to observe the poor adhesion of the resin composite to the Dycal. The detachment of Dycal was occurred all along the composite resin-Dycal interface, and the gaps of 2.0-$30.1{\mu}m$ were formed. In all the specimens, polymerization shrinkage of resin composite caused the detachment of Dycal from the body of Dycal. At a Dycal-dentin interface. it was possible to observe the good adhesion. but poor adhesion with interfacial gap of 2.9-$26.8{\mu}m$ was observed partially.

• Clean Technology
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• v.27 no.1
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• pp.24-32
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• 2021

Unburned carbon (UC) was successfully separated from fly ash by up to 85.8% in weight via froth flotation using soybean oil as a collector. An 18 wt% yield of microceramics (CM) could be achieved by employing a hydro cyclone separator located immediately after the flotation equipment. UC and CM were tested as alternatives to weight-adding material and polymer (especially polypropylene in this study) filler, respectively. Large particles of UC were broken down into smaller ones via ball milling to have an average particle diameter of 10.2 ㎛. When crushed UC was used as an alternative to clay as a rubber weight-adding material, a somewhat lower tensile strength and elongation rate than the allowed values were unfortunately obtained. In order to satisfy the standard limits, further treatment of UC is required to enhance surface energy for more intimate bonding with rubber. CM was observed in spherical forms with an average diameter of 5 ㎛. The surface of the CM particles was modified with phenol, polyol, stearic acid, and oleic acid so that the surface modified CM could be used as a polypropylene-filling agent. The flowability was good, but due to the lack of coupling forces with polypropylene, successful impact strength and flexural strength could not be obtained. However, when mixing the surface-modified CM with 1% silane by weight, a drastic increase in both the impact strength and flexural strength were obtained.

• Korean Journal of Heritage: History & Science
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• v.56 no.2
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• pp.124-133
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• 2023

Preservation processing for two combat boots was executed through application of 3-dimensional digital technology and with use of preservation materials providing outstanding reversibility and stability. The aim of this was to establish a method to preserve the relics of fallen Korean War soldiers that had been excavated by the soldiers remains excavation corps of the Ministry of National Defense. It was possible to estimate the foot size of the soldiers who would have worn the combat boots via 3-dimensional digital scanning and modeling of the boots. In this process, the original form of the combat boots was restored through the use of 3D-printed structures. The original form was restored through a process of removing contaminants from the excavated relics and performing a conditioning treatment, and through use of an antique-color treatment after bonding and filling in the sections that had been ripped or deteriorated. Following the aforementioned preservation processes, it was possible to confirm that both of the combat boots had soles and top sections made of rubber, and portions of the top section and ankle section of the boots were made of synthetic rubber. As such, it was confirmed that these were similar to the Shoe Pac(M-1944, 12-inch) winter boots that had been manufactured for the purposes of waterproofing and/or protection against cold, and introduced in 1944. Such results confirmed that it is possible to discover the manufacturing techniques, materials, and uses of relics excavated through application of preservation processing, thereby illustrating the importance of the convergent research of scientific preservation processing and 3-dimensional digital technology.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.3
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• pp.211-218
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• 2018

Instant face lifting cosmetics contain various film forming agents for stretching the wrinkles on the skin surface. But, most of the film-forming polymers have sticky feels. And they are easily scrubbed out when skin is rubbed on. In this study, we focused on the influence of sodium silicate that has rapid film forming effect on skin surface and immediate wrinkle reducing effect. Sodium silicate, also known as water glass or soluble glass, is a compound containing sodium oxide and silica. Sodium silicate is a white powder that is readily soluble in water, producing an alkaline solution. Sodium silicate is stable in neutral and alkaline solutions. The sodium silicate solution hardens by drying in air and rapidly forms a thin film. When the solution is applied to the skin, the fine membrane coating is formed by water evaporation and ionic bond re-formation. It also makes the strong siloxane (Si-O) bonding on the skin surface. When these fixation properties are applied to cosmetics, they can give remarkable skin tightening effect. The sodium silicate solution can provide the lifting effect by forming a film on skin at a proper concentration. But, skin irritation may be caused with too high concentration of sodium silicate. We studied a desirable range of the sodium silicate concentration and combination with other fixatives for skin care formulation that has no sticky feels and no scrubbing out phenomenon. Immediate lifting gel was developed by using sodium silicate and various thickening systems. Among of the various thickeners, aluminum magnesium silicate showed the best compatibility with sodium silicate for rapid lifting effect. This instant physical lifting gel was confirmed as a low stimulating formula by skin clinical test.

• Journal of Global Scholars of Marketing Science
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• v.18 no.4
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• pp.61-118
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• 2008

The purpose of this research is to construct research framework for international franchising based on existing literature and to identify research components in the framework. Franchise can be defined as management styles that allow franchisee use various management assets of franchisor in order to make or sell product or service. It can be divided into product distribution franchise that is designed to sell products and business format franchise that is designed for running it as business whatever its form is. International franchising can be defined as a way of internationalization of franchisor to foreign country by providing its business format or package to franchisee of host country. International franchising is growing fast for last four decades but academic research on this is quite limited. Especially in Korea, research about international franchising is carried out on by case study format with single case or empirical study format with survey based on domestic franchise theory. Therefore, this paper tries to review existing literature on international franchising research, providing research framework, and then stimulating new research on this field. International franchising research components include motives and environmental factors for decision of expanding to international franchising, entrance modes and development plan for international franchising, contracts and management strategy of international franchising, and various performance measures from different perspectives. First, motives of international franchising are fee collection from franchisee. Also it provides easier way to expanding to foreign country. The other motives including increase total sales volume, occupying better strategic position, getting quality resources, and improving efficiency. Environmental factors that facilitating international franchising encompasses economic condition, trend, and legal or political factors in host and/or home countries. In addition, control power and risk management capability of franchisor plays critical role in successful franchising contract. Final decision to enter foreign country via franchising is determined by numerous factors like history, size, growth, competitiveness, management system, bonding capability, industry characteristics of franchisor. After deciding to enter into foreign country, franchisor needs to set entrance modes of international franchising. Within contractual mode, there are master franchising and area developing franchising, licensing, direct franchising, and joint venture. Theories about entrance mode selection contain concepts of efficiency, knowledge-based approach, competence-based approach, agent theory, and governance cost. The next step after entrance decision is operation strategy. Operation strategy starts with selecting a target city and a target country for franchising. In order to finding, screening targets, franchisor needs to collect information about candidates. Critical information includes brand patent, commercial laws, regulations, market conditions, country risk, and industry analysis. After selecting a target city in target country, franchisor needs to select franchisee, in other word, partner. The first important criteria for selecting partners are financial credibility and capability, possession of real estate. And cultural similarity and knowledge about franchisor and/or home country are also recognized as critical criteria. The most important element in operating strategy is legal document between franchisor and franchisee with home and host countries. Terms and conditions in legal documents give objective information about characteristics of franchising agreement for academic research. Legal documents have definitions of terminology, territory and exclusivity, agreement of term, initial fee, continuing fees, clearing currency, and rights about sub-franchising. Also, legal documents could have terms about softer elements like training program and operation manual. And harder elements like law competent court and terms of expiration. Next element in operating strategy is about product and service. Especially for business format franchising, product/service deliverable, benefit communicators, system identifiers (architectural features), and format facilitators are listed for product/service strategic elements. Another important decision on product/service is standardization vs. customization. The rationale behind standardization is cost reduction, efficiency, consistency, image congruence, brand awareness, and competitiveness on price. Also standardization enables large scale R&D and innovative change in management style. Another element in operating strategy is control management. The simple way to control franchise contract is relying on legal terms, contractual control system. There are other control systems, administrative control system and ethical control system. Contractual control system is a coercive source of power, but franchisor usually doesn't want to use legal power since it doesn't help to build up positive relationship. Instead, self-regulation is widely used. Administrative control system uses control mechanism from ordinary work relationship. Its main component is supporting activities to franchisee and communication method. For example, franchisor provides advertising, training, manual, and delivery, then franchisee follows franchisor's direction. Another component is building franchisor's brand power. The last research element is performance factor of international franchising. Performance elements can be divided into franchisor's performance and franchisee's performance. The conceptual performance measures of franchisor are simple but not easy to obtain objectively. They are profit, sale, cost, experience, and brand power. The performance measures of franchisee are mostly about benefits of host country. They contain small business development, promotion of employment, introduction of new business model, and level up technology status. There are indirect benefits, like increase of tax, refinement of corporate citizenship, regional economic clustering, and improvement of international balance. In addition to those, host country gets socio-cultural change other than economic effects. It includes demographic change, social trend, customer value change, social communication, and social globalization. Sometimes it is called as westernization or McDonaldization of society. In addition, the paper reviews on theories that have been frequently applied to international franchising research, such as agent theory, resource-based view, transaction cost theory, organizational learning theory, and international expansion theories. Resource based theory is used in strategic decision based on resources, like decision about entrance and cooperation depending on resources of franchisee and franchisor. Transaction cost theory can be applied in determination of mutual trust or satisfaction of franchising players. Agent theory tries to explain strategic decision for reducing problem caused by utilizing agent, for example research on control system in franchising agreements. Organizational Learning theory is relatively new in franchising research. It assumes organization tries to maximize performance and learning of organization. In addition, Internalization theory advocates strategic decision of direct investment for removing inefficiency of market transaction and is applied in research on terms of contract. And oligopolistic competition theory is used to explain various entry modes for international expansion. Competency theory support strategic decision of utilizing key competitive advantage. Furthermore, research methodologies including qualitative and quantitative methodologies are suggested for more rigorous international franchising research. Quantitative research needs more real data other than survey data which is usually respondent's judgment. In order to verify theory more rigorously, research based on real data is essential. However, real quantitative data is quite hard to get. The qualitative research other than single case study is also highly recommended. Since international franchising has limited number of applications, scientific research based on grounded theory and ethnography study can be used. Scientific case study is differentiated with single case study on its data collection method and analysis method. The key concept is triangulation in measurement, logical coding and comparison. Finally, it provides overall research direction for international franchising after summarizing research trend in Korea. International franchising research in Korea has two different types, one is for studying Korean franchisor going overseas and the other is for Korean franchisee of foreign franchisor. Among research on Korean franchisor, two common patterns are observed. First of all, they usually deal with success story of one franchisor. The other common pattern is that they focus on same industry and country. Therefore, international franchise research needs to extend their focus to broader subjects with scientific research methodology as well as development of new theory.