• Title/Summary/Keyword: AM materials

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A Study of Drag Reduction by Polymer-Surfactant Mixture System (고분자-계면활성제 혼합물에 의한 마찰저항 감소연구)

  • Kim, Jeong-Tae;Kim, Cheol-Am;Choe, Hyeong-Jin;Kim, Jong-Bo;Yun, Hyeong-Gi;Park, Seong-Ryong
    • Korean Journal of Materials Research
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    • v.8 no.2
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    • pp.135-140
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    • 1998
  • Drag reduction produced by dilute solution of water soluble ionic polymer-surfactant complex under turbulent flow in a rotating disk apparatus(RDA) was investigated in this study. Three different molecular weights of polyacrylic acid(PAA) were adopted as drag reducing additives, and distilled water was used as a solvent. Experiments were undertaken to observe the dependence of drag reduction on various factors such as polymer molecular weight, molecular expansions and flexibility, rotating speed of the disk and polymer concentration. Specific considerations were put on conformational difference between surfactant and polymer, and effect of pH on ionic polymer possessing various molecular conformation through pH. The complex of ionic polymer and surfactant(Sodium Dodecyl Sulfate) behaves like a large polyelectrolyte. Surfactant changes the polymer conformation and then increases the dimension of the polymer. The radius of gyration, hydrodynamic volume and relative viscosity of the polymer-surfactant system are observed to be greater than those of polymer itself. Such surfactant-polymer complex has enhanced drag reduction properties.

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The experiences of human body anatomy observations using the Cadaver Model in the nursing students (간호대학생의 카데바 모델을 이용한 인체해부 관찰경험)

  • Kang, Hyun-Lim;Lee, Yeong-Ran
    • Journal of Digital Convergence
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    • v.15 no.4
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    • pp.233-242
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    • 2017
  • It is to provide the basic materials for the development of a cadaver practice program, the anatomical, educational programs, etc. by confirming the experiences by the nursing college students of the human body anatomy observations using the Cadaver Model. It was intended to understand the meaning and the essence of the experiences by the nursing college students of the human body anatomy observations using the Cadaver Model by selecting the Colaizzi Analysis Method with the materials collected from the interviews with 2 focus group teams. Regarding the essential structure, 6 categories were arrived at, including 'The ambivalence regarding the cadaver practice', 'Running into the true reality', 'Learning a valuable thing', 'The mind for facing the human beings has become deep', 'The feeling that I am gradually becoming a person who tends the sick', and 'The deliberations regarding the sound giving. It was confirmed that, not only with the understanding of anatomy through the cadaver practices, but, also by experiencing and worrying about the understanding, the life and the respect, the death, the ethics regarding the job, etc. the nursing college students were gradually becoming the persons tending the sick.

A Study on Actual Conditions for Prevention of Infections by Dental Hygienists (치과위생사의 감염 예방 실태 조사)

  • Nam, Young-Shin;Yoo, Jung-Sook;Park, Myung-Suk
    • Journal of dental hygiene science
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    • v.7 no.1
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    • pp.1-7
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    • 2007
  • This study aimed to provide basic information on dental hygienists' practicing the prevention of infections by figuring out their actual conditions in dental clinics. The subjects of the study were the dental hygienists who participated in the continuing medical education of Incheon & Gyeonggi-do association and Seoul city association in October and November 2005 and the self-administered surveys were used for the prevention of infections. The results were as below. 1. In terms of education experiences of infection prevention, those who answered "there were" were 72 persons (42.9%) and those who followed the educational route for infection prevention were "through the in-house education from the hospital" and they were 42 persons (58%), which were highest. 2. In terms of the injury experiences, those who answered "there were" were 147 persons (87.5%) and the number of annual injury out of 147 persons with injury experiences was 7.7 time. For the tools that were damaged, 125 persons (75%) damaged the "explorer," which was highest. 3. For the experiences of being infected with contagious diseases, those who answered "there were" were 6 persons (3.6%) and there were four persons for "hepatitis B", one person for "rubella" and one person for "TB." 4. The questions with high practice scores were as in the following: "2. I wash my hands after conducting medical examinations (1.86 points)," "7. I always close the lid of a shot of Novocain after doing local anesthesia (1.86 points)" and "20. I separate and collect the wastes and give them to those who treat accumulated materials (1.85 points)". Meanwhile, the questions with low practice scores were as below: "16. I change my medical gowns (doctor wears) once a day (0.24 point)" and "I wash my medical gowns every time after examining patients with contagious diseases (0.52 points)." 5. The question with high knowledge was as below: "1. The contagion during the dental treatment is determined by source of infection, infection methods, infection routes and the host that is prone to infection (0.95 point)" and the question with the lowest knowledge was "5. HBV(hepatitis B) is destroyed after adding 95oC of heat for more than 5 minutes (0.27 points)." 6. The question with the highest organization-related factors was "I am always ready to use a mask, gloves, etc. if necessary" (0.89 points)" and the question with the lowest score was "There is a guideline that I can refer when I am exposed to dangerous situations related to the contagion in my workplace (0.33 point)." 7. In terms of the equipment conditions of protectors in medical environments, 168 persons for (disposable) mask (100%), 167 persons for disposable gloves (Latex) (99.4%), which meant that most of them were equipped with them. On the contrary, 108 persons (64.3%) are equipped with the protectors for frontal faces, which is the lowest and 165 persons (98.2%) said that they had autoclave in their disinfecting and sterilizing devices.

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A Study on the Knowledge and Attitude about Sex in One Commercial Girls' High school in Seoul (서울지역 일 여자 상업고등학교의 성에 대한 지식 및 태도에 관한 연구)

  • Kim, Eun Hee
    • Journal of the Korean Society of School Health
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    • v.4 no.2
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    • pp.100-118
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    • 1991
  • This study was conducted in order to grasp the condition of the student's knowledge and attitude about sex. And to offer the basic materials for sex education of school health service. The objects were comprised of 464 volunteered students who study in commercial girls' high school. The material of this study was the questionaire suited to the purposed of this research which has been made through studying references. All the questionaire written by students. The self reported questionaires were collected immediately without explanation on supervision of school nurse. The data was collected from 28th to 30th of June on 1990. Analysis of the data was done utilizing SPSS for percentage, mean, ANOVA and Pearson Correlation Coefficients. The Results are as follows; 1. General features of the objects of study School grade distribution was similar. Fathers of 41-50 years were the highest(58.3%), mothers of 41-50 years were the highest(64.3%), family of living together were the highest(87.5%), fathers of graduated high school were highest(60.7%), mothers of graduated middle school were the highest(43.0%) and neuclear families were highest(91.5%). 2. The Conditions of Knowledge about sex When 5 Point was given to "Well known" and 1 point was given to "Never known", the total average was 2.97, Especially the mean of Female physiology was shown 3.93, 73.4% of students have known. But the mean of male physiology was shown 2.23, 17.2% of students only. And Family planning item was 3.54, hymen item was 3.38, female genitalia item was 3.35, abortion item was 3.25, Intercourse and pregnancy item was 3.24, Ovulation item was 3.02, Contraception item was 2.97, Veneral disease and masturbation item was 2.82, maintenance of pregnancy item was 2.76, Anatomical differences between male and female item was 2.59, male genitalia item was 2.31, ejaculation item was 2.27. 3. The conditions of attitude about Sex When 5 point was given to "Very affirming" and 1 point was given to "Very deny" the total average was 3.20. Especially the mean of social intercourse between other sex was shown 3.92, 73.4% of students have affirmed. But the mean of psychic response on menstruation was shown 2.24, 8.8% of students only. And baby birth item was 3.72, the fact that I am a woman item was 3.53, marriage item was 3.49. Secondary body change item was 3.38, puberty item was 3.31, delivery and sexual intercourse item was 3.05, pregenancy item was 3.02, psychic condition on menarche item was 2.50. Also present counsellors about sex were teachers in charge (44.9%), friends(21.6%), mothers(20.6%), elder sisters (10.6%), mass-communications (1.5%), fathers (0.4%), school nurses and elder brother(0.2%). In addition to, future counsellors about sex were friends (37.7%), mothers(30.6%), elder sister (18.4%), school nurses (4.6%), mass communication (3.8%), teachers in charge (2.5%), elder brothers (1.4%) and fathers(1.0%). 4. Correlation between the general features and knowledge variables School grade and knowledge condition has relationship to female genitalia(P<0.05), female physiology (P<0.00), male physiology (P<0.05),ovulation (P<0.00), and femily planning (P<0.005). Fathers age and knowledge condition has relationship to male physiology(P<0.05), and abortion (P<0.05). Marrital status and knowledge condition has relationship to female physiology (P<0.01), masturbation (P<0.05). Fathers educational background and knowledge condition has relationship to masturbation (P<0.00). Mothers age and knowledge condition has relationship to family planning (P<0.05). 5. Correlation between the general futures and attituded variables Fathers age and attitude condition has relationship to psychic response on menstruation (P<0.05). Mothers age and attitude condition has relationship to fact that I am a woman (P<0.00). Mothers educational background and attitude condition has relationship to social intercourse between other sex (P<0.05). Type of family and attitude condition has relationship to puberty (P<0.01). 6. Correlation between knowledge condition and attitude condition Those who had more knowledge about sex have more affirmative response (P<0.001).

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Grazing Effects of Freshwater Bivalve Unio douglasiae on the Hibernal Diatom Bloom in the Eutrophic Lake and Stream (저온기 부영양 수계의 규조 발생에 대한 말조개의 섭식특성)

  • Lee, Song-Hee;Hwang, Soon-Jin;Kim, Baik-Ho
    • Korean Journal of Ecology and Environment
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    • v.41 no.2
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    • pp.237-246
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    • 2008
  • Filtration rates and fecal production of freshwater bivalve, Unio douglasiae on two kinds of hibernal diatom communities were measured simultaneously in a laboratory. One community is the Han River (HAN), which dominated by Asterionella Formosa. Stephanodiscus hantzschii (ca. 98% of total phytoplankton). The other community is the Ilgam Lake (IL), which dominated by Synedra ulna, Scenedesmus sp. Microcystis aeruginosa (ca. 82%). The HAN water has higher concentrations of nutrient (TN and TP) and chlorophyll $\alpha$ (Chl-$\alpha$), lower turbidity and conductivity than the IL water. Water sampling for the feeding experiment was conducted in the same day (Jan 15, 2008) and similar time (AM 10:00 for HAN, AM 11:00 for IL). Mussels with the similar size ($0.0{\pm}0.5\;cm$) were collected from the Gunsan and Okgu district (Jeonbuk), and starved in a laboratory for 2 days before the experiment. The experiment comprised CON (no addition of mussel), LOW (addition of mussel at 0.3 indiv. $L^{-1}$), MID (1.0 indiv. $L^{-1}$) and HIGH (2.0 indiv. $L^{-1}$), respectively. With the increment of mussel density and time, the concentration of Chl-$\alpha$ in two diatom communities were clearly decreased; Chl-$\alpha$ of HAN gradually decreased after 1 hour of mussel treatment, while that of IL decreased as soon as mussel introduction. In 7 hours of treatment, the former was removed finally up to about 90% of control, while the later was remained as about 50%. Under the presence of mussel, total phytoplankton density was shifted as the similar patterns to that of Chl-$\alpha$ (r=0.705, P<0.0001), however, there showed the drastic differences following a species. Based on the concentration of Chl-$\alpha$, filtration rate of U. douglasiae averaged 0.266 $L\;g^{-1}\;h^{-1}$ (0.115 to 0.442) on HAN and $0.577\;L\;g^{-1}\;h^{-1}$ (0.146 to 1.428) on IL water, respectively. There were no differences in feces production among the mussel density in the HAH water (ANOVA, P>0.5), while in IL water, including lots of seston, the HIGH mussel produced the higher fecal materials, over one hundred times of LOW. These results suggest that freshwater bivalve Unio douglasiae have the alternative potential, as a filter-feeder of seston in turbid lake, and a biological controller of diatom bloom in cold stream.

Morphological Characteristics and Classification Criteria for Azalea Cultivars for Landscaping in Korea (조경용 철쭉재배품종의 형태적 특성 및 분류기준)

  • Choi, Jae-Jin;Park, Seok-Gon
    • Journal of the Korean Institute of Landscape Architecture
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    • v.42 no.2
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    • pp.77-85
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    • 2014
  • This study was conducted to examine the morphological characteristics of those Azalea Cultivars(hereinafter, Azalea Cultivars) that are mainly used for landscaping in Korea in order to prepare classification criteria. As testing materials, major Azalea Cultivars cultivated in large quantities by its producing companies were collected. Thereafter, the qualitative and quantitative characteristics of the traits of Azalea Cultivars were investigated in the way of characteristic investigation for new cultivars of azalea used by the Korea Seed and Variety Service in order to classify them and prepare the classification criteria. Since cultivar names have not been established for Azalea Cultivars for landscaping thus far, the data were compiled using the names used by cultivating companies. According to the results, Azalea Cultivars cultivated in Suncheon, Jeonnam mainly for landscaping were 10 in number; Beni, Daewang, Three, Zasanhong, Hancheol, Sancheoljuk, Gyeobsancheoljuk, Baekcheoljuk, Akado, and Seok-am. Among them, the cultivars Beni, Daewang, and Three could not be easily distinguished from each other because they are commonly called Yeongsanhong by cultivating companies and the shapes of their leaves and flowers are similar to each other. In particular, the flower color of Beni was 'bright red', that of Daewang was 'vivid purple', and that of Three was 'bright purple'. In addition, Zasanhong and Hancheol were similar to each other in shape the degree of expression of spots on the flowers and the gloss on the front side of the leaves of Hancheol were higher and stronger compared to that of Zasanhong. Sancheoljuk flowered in early April, earlier compared to other Azalea Cultivars. Gyeobsancheoljuk is an elementary species of Sancheoljuk and it had double flowers although all other traits were similar to those of Sancheoljuk. Although Baekcheoljuk was easily distinguished because it had white flowers, its leaves were similar to those of Akado the reason why these two cultivars could not be easily distinguished from each other. The cultivar Akado flowered early May later compared to other Azalea Cultivars and its flowers were relatively large in diameter as with Baekcheoljuk and Sancheoljuk. Finally, the cultivar Seok-am was easily distinguished because it had smaller leaves compared to other cultivars and it flowered late as with the cultivar Akado.

A problem of authenticity in the chapter 'Confucius became aged, and liked "The Book of Changes"' of yao 要, "essentials," seen throughout 『帛書周易』 the Mawangdui Boshu Zhouyi Manuscript. -in relation to Confucius and 『易』"The Changes"- (『백서주역(帛書周易)』 「요(要)」의 '부자노이호역(夫子老而好易)'장의 진위(眞僞) 문제 -공자와 『역』의 관계를 중심으로-)

  • Kim, Sang-sup
    • Journal of Korean Philosophical Society
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    • v.129
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    • pp.1-22
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    • 2014
  • Columns 12-18 record a conversation between an aged Confucius and his disciple Zi Gong concerning the Changes and especially the role of divination in its use. The last section, from the bottom of column 24, concerns the hexagrams Sun損, "Decrease," and Yi益, "Increase," which Confucius is here made to regard as the culmination of wisdom in the Zhouyi. The conversation between Confucius and Zi Gong, and especially Zi Gong's apparent misunderstanding of Confucius's interest in the text, has already attracted considerable scholarly interest. Zi Gong criticizes Confucius for changing his teaching about the importance of the Zhouyi and for performing divinations. Confucius responds that while he does indeed perform divinations. there is a major difference between his use of the text and that of others: he regards the I Ching as a repository of an ancient wisdom. This would seem to signal recognition of a dramatic change in the function and status of the text. Zi Gong said: "Does the Master also believe in milfoil divination?" The Master said: "I am right in only seventy out of one hundred prognostications. Even with the prognostications of Liangshan of Zhou one necessarily follows it most of the time and no more." The Master said: "As for the Changes, I do indeed put its prayers and divinations last, only observing its virtue and property. Intuiting the commendations to reach the number, and understanding the number to reach virtue, is to have humaneness and to put it into motion properly. If the commendation do not lead to the number, then merely acts as a magician; if the number does not lead to virtue, then one merely acts as a scribe. The divinations of scribes and magicians tend toward it but are not yet there; delight in it but are not correct. Perhaps it will be because of the Changes that sires of later generations will doubt me. I seek its virtue and nothing more. I am on the same road as the scribes and magicians but end up differently. The conduct of the gentleman's virtue is to seek blessings; that is why he sacrifices, but little; the righteousness of his humaneness is to seek auspiciousness; that is why he divines, but rarely. Do not the divinations of priest and magicians come last!" Although Confucius says two ways of the symbolic numbers and virtue-property, he emphasizes his way of virtue and property more important. In fact he who wrote in Yao 要, "essentials," Confucius's saying describes his own viewpoints of the Changes throughout the conversations between Confucius and his disciple Zi Gong, and is only to borrow the name of Confucius. Furthermore, quoting the original text in Yao 要, "essentials," in sequence, also comparing the materials of "the Analects of Confucius論語," with "the Shih chi史記," this thesis will be centered to a great extent on the relative similarity and differences between the Mawangdui Boshu Zhouyi Manuscript and the received text, and discussed the authencity of Yao 要, "essentials," of the contents shown in the chapter of 'Confucius became aged, and liked "The Book of Changes."' the relation of Confucius and the Changes will be clarified naturally through this progress.

Synthesis and Photovoltaic Properties of New π-conjugated Polymers Based on 2,3-dimethyl-5,8-dithiophen-2-yl-quinoxaline (2,3-Dimethyl-5,8-dithiophen-2-yl-quinoxaline을 기본 골격으로 한 새로운 고분자 물질의 합성 및 광전변환특성)

  • Shin, Woong;Park, Jeong Bae;Park, Sang Jun;Jo, Mi Young;Suh, Hongsuk;Kim, Joo Hyun
    • Applied Chemistry for Engineering
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    • v.22 no.1
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    • pp.15-20
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    • 2011
  • Poly[2,3-dimethyl-5,8-dithiophene-2-yl-quinoxaline-alt-9,9-dihexyl-9H-fluorene] (PFTQT) and poly[2,3-dimethyl-5,8-dithiophen-2-yl-quinoxaline-alt-10-hexyl-10H-phenothiazine (PPTTQT) based on 2,3-dimethyl-5,8-dithiophen-2-yl-quinoxaline weresynthesized by Suzuki coupling reaction. All polymers were soluble in common organic solvents such as chloroform, chlorobenzene, o-dichlorobenzene, tetrahydrofuran (THF) and toluene. The maximum absorption wavelength and band gap of PFTQT were 440 nm and 2.30 eV, and PPTTQT were 445 nm and 2.23 eV, respectively. The HOMO and LUMO energy level of PFTQT were -6.05 and -3.75 eV, and PPTTQT were -5,89 and -3.66 eV, respectively. The organic photovoltaic devices based on the blend of polymer and PCBM (1 : 2 by weight ratio) were fabricated. Efficiencies of devices were 0.24% (PFTQT) and 0.16% (PPTTQT), respectively. The short circuit current density ($J_{sc}$), fill factor (FF), and open circuit voltage ($V_{oc}$) of the device with PFTQT were $0.97mA/cm^2$, 29% and 0.86 V, and the device based on PPTTQT were $0.80mA/cm^2$, 28% and 0.71 V, 31% and 0.71 V, respectively, under air mass (AM) 1.5 G and 1 sun condition ($100mA/cm^2$).

Clinical Results of Footprint Restoration Anterior Cruciate Ligament Reconstruction with Remnant Preservation (잔여부 보존술식을 이용한 고유부착부 재현 전방십자인대 재건술의 임상결과)

  • Chung, Hyun-Min;Seo, Young-Jin;Song, Si Young;Cha, Myoungsoo
    • Journal of the Korean Orthopaedic Association
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    • v.54 no.6
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    • pp.537-546
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    • 2019
  • Purpose: Anteromedial (AM), posterolateral (PL), anterior, and posterior remnant preserving anterior cruciate ligament (ACL) reconstructions were conducted on patients with partial ACL tears based on the arthroscopic findings. The clinical results of the four groups were compared. Materials and Methods: This study included 98 patients who underwent a remnant preserving ACL reconstruction from January 2013 to June 2016 and could be followed-up for at least two years. The subjects were categorized into four groups according to the selective bundles reconstructed: group A, anteromedial selective bundle reconstruction; group B, posterolateral selective bundle reconstruction; group C, anterior bundle reconstruction; and group D, posterior bundle reconstruction. The preoperative and postoperative anterior translation from the stress X-ray, International Knee Documentation Committee Subjective Knee Form (IKDC SKF) score, Lysholm score, and hospital for special surgery (HSS) score were compared. Results: All four groups showed significant improvement in anterior translation on the stress X-ray conducted with knees at 15° flexion, IKDC SKF score, Lysholm score, and HSS score postoperatively (in all groups, p<0.001). No intergroup differences were observed in terms of the functional outcomes except that preoperative IKDC SKF score was higher in the C group than in the A group (p=0.021), and the preoperative Lysholm score was higher in the B group than in the A group (p=0.03). Conclusion: After the AM, PL, anterior, and posterior remnant preserving ACL reconstructions, all four groups showed satisfactory results in terms of the anteroposterior stability and functional knee scores with no significant intergroup differences.

Flexural strength of various kinds of the resin bridges fabricated with 3D printing (3D 프린팅으로 제작된 여러 종류의 레진브릿지의 굴곡강도에 대한 연구)

  • Park, Sang-Mo;Kim, Seong-Kyun;Park, Ji-Man;Kim, Jang-Hyun;Jeon, Yoon-Tae;Koak, Jai-Young
    • Journal of Dental Rehabilitation and Applied Science
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    • v.33 no.4
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    • pp.260-268
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    • 2017
  • Purpose: Manufacturing with AM (Additive manufacturing) technique has many advantages; but, due to insufficient study in the area, it is not being widely used in the general clinic. In this study, differences of flexural strength among various materials of 3 unit fixed dental prosthesis were analyzed. Materials and Methods: A metal jig for specimens that had a 3-unit-fixed dental prosthesis figure were fabricated. The jigs were made appropriately to the specifications of the specimens. Three different kinds of materials of specimens which were NC (mathacrylic esther based), DP-1 (Bisphenol A epoxy acrylate type oligomer based), and DT-1 (urethane acrylate based) were printed with DLP machine. Five specimens for each kind of material were printed with an angle of $30^{\circ}$ from the horizontal surface. The specimens were placed on the jig and the flexural strength was measured and recorded using Universal testing machine. The recorded data was analyzed in SPSS using One-way ANOVA and Tukey HSD to determine the significance of the differences of flexural strength among the groups. Results: The flexural strengths of each group were the followings: NC, $1119{\pm}305$ N; DP-1, $619{\pm}150$ N; DT-1, $413{\pm}65N$. Using One-way ANOVA and Tukey Honestly Significant Difference test, significant difference was found between NC and the other groups (P < 0.05), but there was no significant difference between DP-1 and DT-1 (P > 0.05). Conclusion: Higher flexural strength was shown in 3-unit-fixed dental prosthesis that were 3D printed using a DLP machine with NC material.