• 구강회복응용과학지
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• 제23권3호
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• pp.259-268
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• 2007

purpose: This study was to evaluate the shear bond strength of Lithium Disilicate Glass-Ceramic by removable method of temporary cement on the abutment tooth. Material and Method: Sixty molar teeth of human with the occlusal surface up were mounted in acrylic resin blocks. The 45 specimens were prepared to exposure dentin by diamond bur and the eugenol-containing temporary cement($Cavitec^{TM}$ ($KERR^{(R)}$, U.S.A)was applied to the dentin surfaces. After initial removal of the cement with a dental explorer, the specimens were divided into 4 groups of 15 specimens each. The dentin surfaces of the specimens were treated by rotary instrument with as follow pastes: $Zircate^{(R)}$ prophy paste(Dentsply, U.S.A), Radent Prophy Paste(Pascal company,inc. U.S.A), and Dental pumice(Wip mix corporation,U.S.A). An adhesive resin luting agent(Variolink $II^{(R)}$, Ivoclar Vivadent, Leichtenstein) including Monobond-S and $Excite^{(R)}$ was applied to all specimens. The ceramic specimens were made with an A1 ingot of IPS Empress $II^{(R)}$ (Ivoclar Vivadent, Leichtenstein). After the specimens were stored in distilled water for 48hr, the shear bond strength(MPa) was measured by a Universal testing machine(Zwick 145641, Zwick, Germany) at a 1mm/min cross-head speed. The data were statistically analyzed by one-way ANOVA and Duncan's multiple range test. Results: In all group, there were no significant differences in comparison with the control group(p>0.05). The pattern of most failure showed the mixed type of cohesive and adhesive failure. Conclusion: Resin bond strength of IPS Empress $II^{(R)}$ was not affected by removal method of the temporary cement.

• 복합신소재구조학회 논문집
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• 제6권2호
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• pp.52-62
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• 2015

This study aims at developing a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were performed on one unreinforced beam-column specimen and two reinforced specimens with U-type precast wall panels. Top shear connection of the PC panel was required to show the composite strength of RC column and PC wall panel. However, the strength of the connection did not influence directly on the ultimate loading capacities of the specimens in the positive loading because the loaded RC column push the side of PC wall panel and it moved horizontally before the shear connector receive the concentrated shear force in the positive loading process. Under the positive loading sequence(push loading), the reinforced concrete column and PC panel showed flexural strength which is larger than 97% of the composite section because of the rigid binding at the top of precast panel. Similar load-deformation relationship and ultimated horizontal load capacities were shown in the test of PR1-LA and PR1-LP specimens because they have same section dimension and detail at the flexural critical section. An average of 4.7 times increase in the positive maximum loading(average 967kN) and 2.7 times increase in the negative maximum loading(average 592.5kN) had resulted from the test of seismic resistant specimens with anchored and welded steel plate connections than that of unreinforced beam-column specimen. The maximum drift ratios were also shown between 1.0% and 1.4%.

• Journal of the Korean Wood Science and Technology
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• 제34권5호
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• pp.11-18
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• 2006

This study was carried out to evaluate the mechano-sorptive deflection of shear creep of drift pin jointed solid wood. Specimens were the solid wood of Pinus densiflora. The joint was composed with steel plate and drift pin, 85mm in length and 10mm in diameter. The creep tests were conducted under the constant loads in an variable environment. Five different shearing loads were applied parallel to the grain of specimens. The shearing loads applied were 170, 340, 510, 680 and 850 kgf. The stress levels were 10, 20, and 30, 40 and 50% of the bearing strength obtained from the tension-type lateral strength test. The creep tests for specimens were carried out for 10300 hours. A few general conclusions could be drawn from this study: The mechano-sorptive deflection (${\delta}$ ms) is defined as ${\delta}\;ms={\delta}\;t-({\delta}\;c+{\delta}\;sh)-{\delta}\;o$, where ${\delta}$ t is the total deflection, ${\delta}$ c is the pure creep, ${\delta}$ sh is shrinkage-swelling behavior, and ${\delta}$ o is the initial deflection. Changes of relative humidity may cause more severe creep deflection than those of constant humidity, especially during the drying process. The mechano-sorptive behaviors of specimens, except the effects of shrinkage and swelling, gradually increased with increasing time. The deflection is increased in desorption process and recovered in adsorption process. The deflections of drift pin jointed solid wood under different loads showed almost same tendency in all specimens. Although the creep deflection tendencies of each series are very similar, the specimens subjected to a large shearing load exhibit large creep deflections in the desorption process than do those to the small shearing load specimens.

• Restorative Dentistry and Endodontics
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• 제27권1호
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• pp.87-94
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• 2002

The purpose of this study was to evaluate the color changes of composite resin polymerized with three type of light curing units. Composite resin (Z100, shade A2) were applied in a cylindrical metal mold(2 mm thick, 7 mm diameter). Twenty specimens according to light curing units were made. Group 1 : the specimens were polymerized with Apollo 95E for 3seconds(1370 mW/$\textrm{cm}^2$). Group 2 : the specimens were polymerized with XL 3000 for 40seconds (480 mW/$\textrm{cm}^2$). Group 3 : the specimens were polymerized with Spectrum 800 for 10 seconds(250 mW/$\textrm{cm}^2$) and 30 seconds(700 mW/$\textrm{cm}^2$). The microhardness values(VHN) of upper and lower surfaces specimens after light polymerization were measured for the degree of polymerization. All specimens were stored in distilled water at 6$0^{\circ}C$ for 30 days. The color characteristics(L$^*$, a$^*$, b$^*$) of the specimens before and after immersion were measured by spectrophotometer and the total color difference ($\Delta$E$^*$) was computed. The results obtained were as follows : 1. The microhardness values of Group I showed significantly lower than those of Group II and III (p<0.05). 2. In all groups the $\Delta$E$^*$ values presented below 2.0. 3 Group I showed the highest $\Delta$E$^*$ values followed order from highest to lowest by Group II and III (p<0.05).

• Journal of Gastric Cancer
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• 제4권2호
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• pp.109-120
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• 2004

Purpose: Individual gastric cancers demonstrate complicated genetic alterations. The PCR-based analysis of polymorphic microsatellite sequences on cancer-related chromosomes has been used to detect chromosomal loss and microsatellite instability. For the purpose of preoperative usage, we analyzed the correspondance rate of the microsatellite genotype between endoscopic biopsy and surgical specimens. Materials and Methods: Seventy-three pairs of biopsy and surgical specimens were examined for loss of heterozygosity and microsatellite instability by using 40 microsatellite markers on eight chromosomes. Microsatellite alterations in tumor DNAs were classified into a high-risk group (baselinelevel loss of heterozygosity: 1 chromosomal loss in diffuse type and high-level loss of heterozygosity: 4 or more chromosomal losses) and a low-risk group (microsatellite instability and low-level loss of heterozygosity: 2 or 3 chromosomal losses in diffuse type or $1\∼3$ chromosomal losses in intestinal type) based on the extent of chromosomal loss and microsatellite instability. Results: The chromosomal losses of the biopsy and the surgical specimens were found to be different in 21 of the 73 cases, 19 cases of which were categorized into a genotype group of similar extent. In 100 surgical specimens, the high-risk genotype group showed a high incidence of nodal involvement (19 of 23 cases: $\leq$5 cm; 23 of 24 cases: >5 cm) irrespective of tumor size while the incidence of nodal involvement for the low-risk genotype group depended on tumor size (5 of 26 cases: $\leq$5 cm; 18 of 27 cases: >5 cm). Extraserosal invasion was more frequent in large-sized tumor in both the high-risk genotype group ($\leq$5 cm: 12 of 23 cases; >5 cm: 23 of 24 cases) and the low-risk genotype group ($\leq$5 cm: 7 of 26 cases; >5 cm: 16 of 27 cases). The preoperative prediction of tumor invasion and nodal involvement based on tumor size and genotype corresponded closely to the pathologic tumor stage (ROC area >0.7). Conclusion: An endoscopic biopsy specimen of gastric cancer can be used to make a preoperative genetic diagnosis that accurately reflect the genotype of the corresponding surgical specimen.

• 대한치과기공학회지
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• 제39권1호
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• pp.9-16
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• 2017

Purpose: The purpose of this study was to evaluate flexural strength, composite surface and fractured surface of three different indirect composite resins. Methods: Fifteen bar-shaped specimens ($25mm{\times}2mm{\times}2mm$) were fabricated for each FL group (Flow type and Light curing) and PLP group (Putty type and Light, Pressure curing) and PL group (Putty type and Light curing) according to manufacturer's instructions and ISO 10477. Fabricated specimens were stored in the distilled water for 24 hours at the temperature of $37^{\circ}C$. Three-point bending strength test was performed to measure flexural strength using universal testing machine at a crosshead speed of 1mm/min (ISO 10477). Surface and fractured surface of specimens were observed by digital microscope. Results were analyzed with Kruskal-wallis tests (${\alpha}=0.05$). Results: Mean (SD) of three different indirect composite resins were 83.38 (6.67) MPa for FL group, 139.90(16.53) MPa for PLP group and 171.72(16.74) MPa for PL group. Flexural strength were statistically significant (p<0.05). Differences were not observed at fractured surface among three groups. However, many pores over $100{\mu}m$ were observed at PL group in observing surface of specimen. Conclusion: Flexural strength of composite resins was affected by second polymerization method and content of inorganic filler.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제31권4호
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• pp.322-328
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• 2005

Oral and maxillofacial infections are most commonly odontogenic in origin. The present study was implemented for patients with oral and maxillofacial infections in order to determine what differences were present in cultured bacteria, depending upon the different types of infection. For the present study, the epidemiological characteristics, the state of infection, and the results of the pus culture and antibiotic susceptibility tests were analyzed for the 159 cases where pus culture tests were performed. The patients were treated at the Oral and Maxillofacial Surgical Department of Chonnam National University Hospital during an 18-months period from March 2003 to August 2004. Among the total 159 pus culture specimens, bacteria were cultured in 111 cases (69.8%). In the 111 pus culture specimens, Streptococcus species, Neisseria species, and Staphylococcus species were cultured from 69 cases (51.1%), 21 cases (15.6%), and 15 cases (11.1%), respectively and were determined to be bacterial strains the predominant bacteria responsible for oral and maxillofacial infectious diseases. Twenty four cases (15.1%) among the 159 specimens showed mixed infections. The mostly isolated bacteria from each of the space abscess, dentoalveolar abscess, inflammatory cyst, and pericoronitis cases were the Viridans streptococci. There was little relevance between the type of infection and the type of cultured bacteria. Antibiotic susceptibility tests showed a high level of susceptibility to teicoplanin(100%), vancomycin(100%), chloramphenicol(96.4%), ofloxacin(88.3%), imipenem(83.3%), erythromycin(82.5%) and a low susceptibility to cefazolin(40.0%), oxacillin(44.7%), ampicillin(49.4%), penicillin(51.1%). These results indicate that there was no significant difference among the cultured bacteria depending on the type of infections and their susceptibility to cephalosporin and penicillin G was low.

• Steel and Composite Structures
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• 제27권6호
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• pp.675-689
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• 2018

Buckling-restrained braces (BRBs) have received considerable attention in seismic design of various types of structures. Conventional BRBs are composed of steel core and surrounding steel tube filled with concrete. Eliminating the steel tube can be advantageous to BRB. In this study the idea of replacing the steel tube by CFRP layers in BRBs is proposed. The advantages of this type of BRB are mentioned, and its design criteria are introduced. The construction procedure of two BRB specimens is described. The specimens are uniaxially tested based on moderate, and severe earthquake levels and the performance of the specimens is investigated. The backbone curves resulted from the hysteresis curve are presented for the design proposes. The results of this study show that CFRP layers can effectively provide the expected performance of the encasing, and the proposed BRB can be considered a viable alternative to the conventional BRBs.

• 대한치과의사협회지
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• 제22권5호통권180호
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• pp.423-427
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• 1984

A total of 114 extracted human mandibular first molars were used to study the configuration of the floor of the chamber. The specimens were ground and the pulp chamber was examined with a magnifier and explored with sharp explorer. The study showed the shape of the pulp chamber, number of root canals, and the type of canal orifice. The results were as follows; 1. In so far as observing the shape of the pulp chamber of the teeth, 58.8% of the teeth were square, 34.2% were triangle and 7.0% were ovoid shape. 2. 58.8% of the specimens have 4 root canal orifices, 34.2% have 3 root canal orifices, 7.0% have 2 root canal orifices. 3. 41.2% of the specimens show 'H' shape, 17.6% show 'Square' shape, 31.6% show 'T' shape, 2.0% show 'reverse-T' shape and 7.0% show 'I' shape.

• Restorative Dentistry and Endodontics
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• 제6권1호
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• pp.105-107
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• 1980

A total of 125 extracted maxillary first molars were used to study the configuration of the floor of the pulp chamber. The specimens were ground and the pulp chamber was examined with a magnifying glass and explored with sharp explorer. The study showed the shape of the pulp chamber, number of root canals, and type of canal orifice. The results were as follows; 1. In so far as observing the shape of the pulp chamber of the teeth, 50.4% of the teeth were trapezoid, 20.8% were inverted trapezoid, 18.4% were rectangle and 10.4% were triangle shape. 2. 71.2% of the specimens have 3 root canal orifices, and 28.8% have 4 root canal orifices. 3. 71.2% of the specimens have 1 mesiobuccal canal orifice, 23.2% have 2 mesio-buccal canal orifices joined by a groove, and 5.6% have 2 mesio-buccal canal orifices seperated each other.