• Restorative Dentistry and Endodontics
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• v.10 no.1
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• pp.135-144
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• 1984

This study was undertaken to evaluate the degree of the marginal leakage of composite restoration with 3 brands of dental adhesives by means of the dye penetration at the enamel and dentinal margins. 150 cavities of class V were prepared on the buccal and lingual surfaces of 75 extracted anterior and premolar teeth, which were devided into 3 groups. The cavities were filled with composite resin, Silar$^{(R)}$ (3M) and Heliosit$^{(R)}$ (Vivadent) after application of the dental adhesives, specifically Scotchbond$^{(R)}$ (3M) which is essentially composed with halophosphorus ester of Bis-GMA, Dentin Adhesit$^{(R)}$ (Vivadent) which is polyurethane resin, and Enamel Bond$^{(R)}$ (3M) which is a product of Bis-GMA with low viscosity at internal surfaces and margins of the cavities. All specimens were immersed in $37^{\circ}C$, 0.5% methylene blue solution for 24 hours after thermocycling at $4^{\circ}C$ and $60^{\circ}C$, embedded in acrylic resin, and sectioned with diamond disk into two parts. The sectioned specimens observed with the light microscope. The following results were obtained: 1. The group filled with Scotchbond$^{(R)}$-Silar$^{(R)}$ the other two groups at the enamel margins. 2. No significant difference in the degree of the marginal leakage had appeared between Dentin Adhesit$^{(R)}$-Heliosit$^{(R)}$ group an d Enamel Bond$^{(R)}$-Silar$^{(R)}$ group at the enamel margins. 3. Severe marginal leakage with penetration of dye to the floor of cavity had appeared from the all three groups and no significant difference in the degree of marginal leakage existed between the three groups at the dentinal margins.

• Steel and Composite Structures
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• v.23 no.6
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• pp.633-646
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• 2017

The compressive behavior of special-shaped concrete filled tube (CFT) mega column coupled with multiple cavities is studied by testing six columns subjected to cyclically uniaxial compressive load. The six columns include three pentagonal specimens and three hexagonal specimens. The influence of cavity construction, arrangement of reinforcement, concrete strength on failure feature, bearing capacity, stiffness, and residual deformation is examined. Experimental results show that cavity construction and reinforcements make it possible to form a combined confinement effect to in-filled concrete, and the two groups of special-shaped CFT columns show good elastic-plastic compressive behavior. As there is no axial bearing capacity calculation method currently available in any Code of practice for special-shaped CFT columns, values predicted by normal CFT column formulas in GB50936, CECS254, ACI-318, EC4, AISCI-LRFD, CECS159, and AIJ are compared with tested values. The calculated values are lower than the tested values for most columns, thus the predicted bearing capacity is safe. A reasonable calculation method by dividing concrete into active and inactive confined regions is proposed. And high accuracy shows in estimating special-shaped CFT columns either coupled with multiple cavities or not. In addition, a finite element method (FEM) analysis is conducted and the simulated results match the test well.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.42-49
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• 2004

Electrical discharge machining (EDM) is one of the most extensively used non-conventional material removal process. The recent trend in reducing the size of product has given micro EDM a significant amount of research attention. Micro EDM is capable of machining not only micro holes and micro shafts as small as a few micrometers in diameter but also complex three dimensional micro cavities. But, longitudinal tool wear by electrical discharge is indispensable and this affects the machining accuracy in micro EDM process. Therefore, newly developed tool wear compensation strategy called round trip method is suggested and verified by experiment. In this method, machining depth of cut, overlap effect and critical travel length are also considered.

• Korean Journal of Veterinary Research
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• v.30 no.4
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• pp.395-400
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• 1990

A female Korean native calf with diprosopus was examined macroscopically and radiographically. Anterior head duplication (diprosopus) was observed and all structures caudal to it were normal. She had two complete mouths, four eyes and three ears. Single tongue was present in each oral cavity. The two tongues were joined at their base just posterior to the single epiglottis. Both oral cavities led jointly into a common pharynx and one esophagus. One laryngeal cavity communicated with one common trachea. The lower jaws were immobile because of overlapping mandibular rami. The atlas was complete, and two anterior articular cavities articulated with the lateral condyles of the occipital bones of each skull. The cerebrums were fused each other at their caudal portion, and the giri and sulci were underdeveloped. The cerebellums were also completely fused, and they had not characteristic appearance of the vermis. The spinal cord showed normal appearance.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.1
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• pp.53-61
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• 1999

Newley developed dentin bonding system which contains self-etching primer performed the removing of smear layer and etching procedure at once. So, it make possible more simple and shorter working time, the stronger bonding strength than conventional dentin bonding system. Cavities were prepared in the buccal and lingual surface of 30 extracted primary molars, and randomly assigned into three equal groups of 10 each. All cavities were filled with Z-100 composite resin following manufacturer's specifications after priming of three different dentin bonding system. Specimens stored for 7 days in 37 degree C water, thermocycled for 1000 cycles between 5 degree C and 55 degree C, immersed in 50% silvernitrate solution for 24 hours, and embedded in resin before being sectioned longitudinally. Data were analyzed by t-test and ANOVA. Mac-Bond II and Clearfil Linear-Bond II showed less microleakage at the occlusal and gingival margins compared to Scotchbond Multi Purpose. All dentin bonding systems showed significantly less microleakage at the occlusal margins compared to the gingival margins. But, there were no significantley difference between each group.

• Design & Manufacturing
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• v.15 no.1
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• pp.32-40
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• 2021

Mold design for in-mold coating was carried out to achieve simultaneous injection molding and two-color coating for car gas cap cover. The developed mold includes one core and three cavities which are composed of a substrate cavity and two coating cavities. To provide a sealing edge for complete seal during the second coating, the first coated material was used at the boundary between the first coating and the second one, and injection molded substrate was used at the parting line. The materials used were PC/ABS for substrate and 2-component Polyurea for coating. Through experiments, it was found that the suggested sealing edges were effective for complete seal during the second coating. In cavity pressure traces, there were three peaks caused by mold closing, coating-material injection and cleaning-piston advancement inside the mixing head. The cavity pressure increased with decreasing coating thickness.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.4
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• pp.419-424
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• 2012

In addition to respiration, the nose performs three other major physiological functions-air-conditioning, filtering, and smelling. On the basis of our experience in experimental investigations of nasal airflows in normal and abnormal nasal cavity models, airflows in the normal model and three artificially deformed models, which simulate the results of surgical treatments (inferior turbinectomy), are investigated by PIV and CFD. The left cavities of all three models are normal, and the right cavities are modified as follows: (1) excision of the head of the inferior turbinate, (2) resection of the lower fifth of the inferior turbinate, and (3) resection of almost the entire inferior turbinate. The use of high-resolution CT data and careful surface rendering of three-dimensional computer models with the help of an ENT doctor provide more sophisticated nasal cavity models. Nasal airflows for both normal and deformed cases are also compared.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.395-411
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• 1993

The purpose of this study was to examine the clear concept of the designs for cavity preparations. Among the several parameters in cavity designs, profound understanding of isthmus width factor would facilitate selection of the appropriate cavity preparation for a specific clinical situation. In this study, the cavities were prepared on maxillary first premolar and filled with gold inaly. A two - dimensional model was composed of 1037 - node triangle elements. In this model, isthmus was varied in width at 1/4, 1/3 and 1/2 of intercuspal width and material properties were given for four element groups, i.e., enamel, dentin, pulp and gold. The 500N occlusal load varied in direction and it was examined using three types of load : concentrated load, divided load and distributed load. The models were also examined with empty cavities using the devided load and distributed load. These models were analyzed the displacement and strees distribution by the two - dimensional Finite Element Method. The results were as follows : 1. All experimental models which filled with gold inlay after cavity preparation were similar direction of displacement with control model under same load type. But in the models with empty cavities, as isthmus width was wider, the degree of displacement was increased at same load type. 2. Among the experimental models which were filled with gold inaly after cavity preparation, the model II showed the least stress concentration under concentrated load and divided load. But in the models with empty cavities, the model III showed the largest stress concentration and tooth fracture is expected regardless isthmus width. 3. All experimental models showed similar displacement pattern beneath restorative material under a concentrated load. In the models with empty cavities, a divided load resulted in a lingual displacement of the lingual cusp, but a distributed load resulted in a buccal displacement of the lingual cusp. In regard to the above results, the restored models were stronger than empty models in respect to the bending moment and tensile stress. The empty models are expected to fracture regardless isthmus width. The safest isthmus width was 1/3 of intercuspal distance, which showed the least stress concentration in respect to the effect of stress distribution.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.680-692
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• 1997

New bonding agent systems have been supplied which operators can simply apply to conditioned tooth surfaces. The purpose of this study was to evaluate the shear bond strengths and the microleakages of three bonding agents and composite resins to dentin. Seventy-five extracted human maxillary and mandibular molar teeth were used in this study. For the shear bond strength test, the entire occlusal dentin surfaces of thirty teeth were exposed with Diamond Wheel Saw and smoothed with Lapping and Polishing Machine (South Bay Technology Co., U.S.A). For the microleakage test, Class V cavities were prepared in the buccal surfaces of fourtyfive teeth. They were randomly assigned into 3 groups according to dentin bonding agents ($Scotchbond^{TM}$ Multi-Purpose plus, ONE-$STEP^{TM}$ and Prime & $Bond^{TM}$)and composite resins (Z-100, $Aelitefil^{TM}$ and TPH $Spectrum^{TM}$) to be used. Bonding agents and composite resins were bonded to exposed dentin surfaces of the tooth crown and to Class V cavities on the buccal surfaces respectively according to manufacturer's directions. The shear bond strengths were measured by universal testing machine($U^{TM}$ AGS-100, Japan). In addition, the degree of micro leakage at the occlusal and gingival margin was examined by 2 % methylene blue and stereomicroscope(Olymous SZH 10, Japan). The results were as follows: 1. The shear bond strength to dentin was the highest value in SBMP-Plus group($16.68{\pm}7.38$ MPa) and the lowest value in Prime & Bond group($11.61{\pm}5.82$ MPa), but there was no significant difference of shear bond strength among three groups. 2. The degree of microleakage at both occlusal and gingival margin was showed the lowest in SBMP-Plus group and the highest in ONE-STEP group. 3. At both occlusal and gingival margin, there was significant difference of microleakage between SBMP-Plus and ONE-STEP/ Prime & Bond groups(p<0.05), but no significant difference of microleakage between ONE-STEP and Prime & Bond group(p>0.05).

• Restorative Dentistry and Endodontics
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• v.41 no.2
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• pp.83-90
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• 2016

Objectives: This study was evaluated the marginal microleakage of two different adhesive systems before and after aging with two different dye penetration techniques. Materials and Methods: Class V cavities were prepared on the buccal and lingual surfaces of 48 human molars. Clearfil SE Bond and Single Bond (self-etching and etchand-rinse systems, respectively) were applied, each to half of the prepared cavities, which were restored with composite resin. Half of the specimens in each group underwent 10,000 cycles of thermocycling. Microleakage was evaluated using two dimensional (2D) and three dimensional (3D) dye penetration techniques separately for each half of each specimen. Data were analyzed with SPSS 11.5 (SPSS Inc.), using the Kruskal-Wallis and Mann-Whitney U tests (${\alpha}=0.05$). Results: The difference between the 2D and 3D microleakage evaluation techniques was significant at the occlusal margins of Single bond groups (p = 0.002). The differences between 2D and 3D microleakage evaluation techniques were significant at both the occlusal and cervical margins of Clearfil SE Bond groups (p = 0.017 and p = 0.002, respectively). The difference between the 2D and 3D techniques was significant at the occlusal margins of non-aged groups (p = 0.003). The difference between these two techniques was significant at the occlusal margins of the aged groups (p = 0.001). The Mann-Whitney test showed significant differences between the two techniques only at the occlusal margins in all specimens. Conclusions: Under the limitations of the present study, it can be concluded that the 3D technique has the capacity to detect occlusal microleakage more precisely than the 2D technique.