• The Journal of Korean Academy of Prosthodontics
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• v.36 no.6
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• pp.858-866
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• 1998

Soldering is the usual method used to correct an unstable fixed partial denture framework at patient's try-in; However, presoldering base metal alloys is technique-sensitve and results are unstable because it is difficult to maintain uniform heat distribution and to prevent oxidation of an alloy. A cast-joining technique has been developed by Weiss and Munyon for repair, correction and addition to base metal framework. This joining technique eliminates the problem with presoldering of non-precious frameworks. The object of this study was to 1) compare the relative flexure strength and the joining effectiveness of Ni-Cr-Be cast in two pieces and 'pre-soldered' versus in two pieces and 'cast-joined'. 2) determine the effect of increasing the number of retentive grooves on the face of the cast and 3) determine the effect of the relative matched position of groove patterns on flexure strength. The joining effectiveness can be expressed by the ratio of the mean flexure stress of soldered or cast-joined specimens to that of one-piece cast. Resin rods 3mm in diameter were used as pattern of specimens for one-piece casted, presoldered, and cast-joined groups. Cast-joined specimens had two different patterns of retentive grooves on the joined faces. Type A had cross-shaped grooves 1mm in depth. 0.6mm in width. Type B was the same except for the addition of one more retentive groove. In the experiment connecting cast-joined specimens, half of specimens with type A pattern had their patterns on the faces of paired casts matched with each other as mirror image. With the rest pairs, it was proceeded that one of paired casts turned 45 degrees so that the patterns crossed. Half of specimens with type B pattern also had the patterns matched as mirror image; However, here, one of paired casts turned 90 degrees with the other pairs. Retentive groove in this study lacked the intentional undercuts, in contrast with the suggestion of Weiss and Munyon. The specimens were subjected to four-point flexural loading in an Instron testing machine. The midspan flexural stress was calculated at the point of initial plastic strain as determined from a strip-chart recorder or at the point of failure if this occured at a lower stress level. Within the scope of this study, the following results were obtained. 1. The presoldered group showed flexural strength at least 2 times higher than the cast-joined groups. Its joining effectiveness was 82%. 2. In cast-joined groups, the flexural strength of joints with type B patterns exhibited 1.5 times that of joints with type A patterns. Joining effectivenesses were 38% for type B patterns, 25-26% for type A patterns. 3. The relative matched position of groove patterns did not have any significant effect on flexural strength of the cast-joined specimens with either type A patterns or type B patterns(p>.05).

• Archives of Plastic Surgery
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• v.33 no.4
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• pp.407-412
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• 2006

Purpose: Various attempts of reconstruction for pharyngoesophageal defects after ablative surgery have been made to restore the function of the pharyngoesophagus. A fabricated tubed radial forearm free flap or free jejunal free flap was used when the width of remnant pharyngeal wall was less than 50% of the normal width. However there are many disadvantages such as stricture, saliva leakage and fistula formation on tubed radial forearm free flap. The jejunal free flap has the problem such as short pedicle, poor tolerance of ischemic time, wet voice and delayed transit of swallowed food due to the uncoordinated contraction. The authors studied the utility of patch-type radial forearm free flap using the remnant posterior pharyngeal wall of the hypopharynx. Methods: Retrospective reviews in Severance Hospital were made on 25 patients who underwent reconstruction surgery with patched radial forearm free flap because of the hypopharyngeal cancer between 1996 and 2005. The patients of Group I had the narrow posterior pharyngeal wall and its width was less than 3centimeters after the tumor was resected. Those of Group II had the partial pharyngectomy and the width of the remnant pharynx was larger than 3 centimeters. Results: Seven patients belonged to the group I and the flap of this group had 100% survival rate. One case of fistula and no swallowing discomfort due to stricture was reported. The Group II including 18 patients also had the 100% flap survival rate. Neither fistula nor stricture was seen but the lower diet grade was checked. Conclusion: The patch type radial forearm free flap using the remnant pharyngeal wall have the advantage of the radial forearm free flap, and furthermore this flap is the safe reconstructive method even if the width of the remnant pharyngeal wall is less than 30% of that of normal pharynx.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.384-390
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• 2018

Air and soil are being contaminated by the environmental pollution as a result of climate change and urbanization, resulting in water pollution reaching serious levels. In this studies, we investigated the use of antimicrobial copper for the removal of biological pollutants from water system. Specifically, we tested its effects against E. coli, B. subtilis, S. aureus, K. pneumoniae and P. aeruginosa. Made a sphere shape having a diameter of 2cm using a strip-shaped copper wire of 0.5g, 1g and 2g. And then, to confirm the antimicrobial activities, each copper ball was equipped in the broth which inoculated each pathogens. The results showed that bacterial growth of the five test bacteria was inhibited by more than 99% after reaction with a 0.5 g copper ball for at least 20 minutes. Based on the these results, if perform the further experiment such cytotoxicity, it is expected that will be enough to be used as a filter for water quality purification. The developed technique is expected to be widely applied in various industries.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.1
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• pp.19-26
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• 2007

The purpose of this study is to evaluate oral health status, caries-inducing bacterial activity of the mental retardation students, and developing motivation method for improving oral hygiene management by clarifying the relationship between caries-inducing bacterial activity and oral health status of mental retardation students. Caries experience indices, caries susceptibility test, gingival health evaluation, and oral hygiene management and oral health survey were performed. Results were as follows : 1. The DMFT index of disabled students(12 years) was 2.07. 2. The gingival inflammation was occurred more frequently in older ages. 3. There also was a high positive correlation between caries incidences and the results of caries-inducing bacterial activity test especially in deciduous teeth. This result suggested that the Dentocult SM mutans test as a caries activity test is a reliable method for measuring the status of dental caries in mental retardation students. Because it would motivate the mental retardation students to care more actively for their oral hygiene if they learn how much dental caries-inducing bacteria are living in their mouth by observing the bacterial colony on the cultured test strip, it can become a possibly efficient educational tool for the mental retardation students.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.3
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• pp.298-307
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• 2010

The purpose of this study was to assess the effect on oxygen inhibition layer(OIL) for the interfacial bonding between resin composite layers, including shear bond strength, fracture modes and degree of conversion. The first layer of specimen was filled with Z-250(shade A3) and was cured for 40s. The second layer of specimen was filled with same composite(shade A1) and was cured for 40s. The first layer of specimens for each group were prepared by methods as followings. Control(curing in atmospheric air), Group1(curing against Mylar strip), Group2(scrubbed with a acetone-soaked cotton), Group3(using Tescera light cup), Group4(using Tescera heat cup), Group5(stored in disti1led water for 30days at $37^{\circ}C$), Group6 (using bonding agent). The results were as follows: 1. There was no statistically significant different shear bond strength between control and group 1(p>0.05). 2. Group 2 showed significantly lower shear bond strength than control and group 1(p<0.05). 3. The observation of the fracture surface leads to the evidence that a major difference occurs in the case of control, group1 and group 3 samples which break mainly cohesively while the other groups break in majority adhesively. 4. The results of FTIR showed that the degree of conversion was the highest in group 2 and the lowest in control group(p<0.05). It can be concluded that an OIL is not necessary for bonding with composite resin. But if a reduced critical amount of the unreacted monomer is present, it was detrimental to bonding additional layers of composite. Further study, such as the quantitative analysis of the unreacted monomer are required.

• Management & Information Systems Review
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• v.3
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• pp.287-316
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• 1999

Cyberspace permits us to more beyond traditional face-to-face, mail and telephone surveys, yet still to examine basic issues regarding the quality of data collection: sampling, questionnaire design, survey distribution, means of response, and database creation. This article address each of these issues by contrasting and comparing traditional survey methods(Paper-and-Pencil) with Internet or Personal Computer networks-mediated (Screen-and-Keyboard) survey methods also introduces researchers to this revolutionary and innovative tool and outlines a variety of practical methods for using the Internet or Personal Computer Networks. The revolution in telecommunications technology has fostered the rapid growth of the Internet all over the world. The Internet is a massive global network and comprising many national and international networks of interconnected computers. The Internet or Personal Computer Networks could be the comprehensive interactive tool that will facilitate the development of the skills. The Internet or Personal Computer Networks provides a virtual frontier to expand our access to information and to increase our knowledge and understanding of public opinion, political behavior, social trends and lifestyles through survey research. Comparable to other technological advancements, the Internet or Personal Computer Networks presents opportunities that will impact significantly on the process and quality of survey research now and in the twenty-first century. There are trade-offs between traditional and the Internet or Personal Computer Networks survey. The Internet or Personal Computer Networks is an important channel for obtaining information for target participants. The cost savings in time, efforts, and material were substantial. The use of the Internet or Personal Computer Networks survey tool will increase the quality of research environment. There are several limitations to the Internet or Personal Computer Network survey approach. It requires the researcher to be familiar with Internet navigation and E-mail, it is essential for this process. The use of Listserv and Newsgroup result in a biased sample of the population of corporate trainers. However, it is this group that participates in technology and is in the fore front of shaping the new organizations of interest, and therefore it consists of appropriate participants. If this survey method becomes popular and is too frequently used, potential respondents may become as annoyed with E-mail as the sometimes are with mail survey and junk mail. Being a member of the Listserv of Newsgroup may moderate that reaction. There is a need to determine efficient, effective ways for the researcher to strip identifiers from E-mail, so that respondents remain anonymous, while simultaneously blocking a respondent from responding to a particular survey instrument more than once. The optimum process would be on that is initiated by the researcher : simple, fast and inexpensive to administer and has credibility with respondents. This would protect the legitimacy of the sample and anonymity. Creating attractive Internet or Personal Computer Networks survey formats that build on the strengths of standardized structures but also capitalize on the dynamic and interactive capability of the medium. Without such innovations in survey design, it is difficult to imagine why potential survey respondents would use their time to answer questions. More must be done to create diverse and exciting ways of building an credibility between respondents and researchers on the Internet or Personal Computer Networks. We believe that the future of much exciting research is based in the Electronic survey research. The ability to communicate across distance, time, and national boundaries offers great possibilities for studying the ways in which technology and technological discourse are shaped. used, and disseminated ; the many recent doctoral dissertations that treat some aspect of electronic survey research testify to the increase focus on the Internet or Personal Computer Networks. Thus, scholars should begin a serious conversation about the methodological issues of conducting research In cyberspace. Of all the disciplines, Internet or Personal Computer Networks, emphasis on the relationship between technology and human communication, should take the lead in considering research in the cyberspace.