• Journal of Dental Rehabilitation and Applied Science
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• 제36권2호
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• pp.61-69
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• 2020

Purpose: Zirconia fixed partial dentures with mandibular 2^nd premolar and 2^nd molar as abutments are fabricated and then the effects of inter-abutment distance on fracture resistance of zirconia fixed partial dentures is studied. Materials and Methods: The materials used in this study are Cameleon S zirconia block and S2 zirconia block, which are divided into CS Group and S2 Group applying different inter-abutment distance for each material, and the sintered zirconia fixed partial denture was luted to the epoxy resin die using a temporary luting cement, and then the fracture resistance was measured by placing a 6 mm diameter hardened steel ball on the occlusal surfaces of the pontics and applying pressure at a cross head speed of 1.0 mm/min on a universal testing machine with a load cell of 5.0 kN. Results: The fracture resistance of zirconia fixed partial dentures is not significantly affected by inter-abutment distance The fracture resistance of zirconia fixed partial dentures in CS Group was significantly higher in 15 mm of inter-abutment distance than in 13 mm and 17 mm of inter-abutment distance (P < 0.05). The fracture resistance of zirconia fixed partial dentures in S2 Group was not significantly different between the three groups (P > 0.05). Conclusion: The fracture resistance of zirconia fixed partial dentures with mandibular 2^nd premolar and 2^nd molar as abutments does not significantly affected by the inter-abutment distance.

• The Journal of Korean Academy of Prosthodontics
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• 제38권2호
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• pp.169-177
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• 2000

The purpose of this study was to compare the retention of complete cast crown over amalgam ores, composite resin cores, and cast gold cores when cemented with three different luting agents. Eighteen core specimens each of amalgam(Bestaloy, Dong Myung, Seoul, Korea), composite resin (Z100, 3M Dental product, st. Paul, Minn) and type IV gold alloy (Ba-4, Heesung Engelhard Corp., Korea) were made in a customized milling stainless steel die. A wax pattern with a loop attached to occlusal surface was made for each core and a type II gold alloy casting was fabricated. The castings which had clinically acceptable marginal fit were used as test samples. The following luting cements were used to cement cast crowns on each core material : (1) zinc phosphate cement (Confi-dental Products Co., USA) (2) glass-ionomer cement (Fuji Plus, GC Industrial Corp., Tokyo, Japan) (3) resin cement (Panavia 21, Kuraray Co., USA). All cements were mixed according to manufacturers' instructions. A static load of 5kg was then applied for 10 minutes on the crowns. All specimens were stored in saline solution for 24 hours at $37^{\circ}C$ and thermocycled for 500 cycles. After storage and cycling, the tensile bond strengths were measured by using a universal testing machine (Instron Corp., Canton, Mass.) at a crosshead speed of 0.5mm/min. The results were as follows 1. The retentive strength of resin cement was the highest of alt three types of cement for resin core (p<0.05). 2. There was no statistical difference among the retentive strengths of three cements for amalgam core (p>0.05). 3. The retentive strength of resin cement was higher than that of zinc phosphate for cast core, but there was no difference between the retentive strength of glass ionomer cement and those of rein and zinc phosphate cement. 4. The retentive strength of the zinc phosphate cement for amalgam core was the highest of all type of cores.

• Journal of the Society of Naval Architects of Korea
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• 제48권6호
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• pp.528-538
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• 2011

As a forming method for curved hull plates more efficient than the flame bending, mechanical bending using multi point press forming and die-less forming is discussed in this paper. the mechanical forming is a flexible manufacturing system for automatically forming of hull parts. It is especially suited to varied curved parts. This paper discusses a multiple point pressing machine composed of a pair of reconfigurable punches in order to achieve the rapid forming of curved hull plates using division forming and presents how forming information is obtained from the given design surface. Although the mechanical forming can be efficient in the metal forming, spring back after pressing is a phenomenon which must be carefully considered when quantifying the process variables. If the spring back is not accurately controlled, the fabricated shell plate cannot meet assembly tolerance. This paper describes the principles to calculate the proper stroke of each punch at the divided areas. the strokes are determined by an iterative process of sequential pressing and spring back compensation from an unfolded flat shape to its given design surface. FEA(finite element analysis) is used to simulate the spring back of the plate and the IDA(iterative displacement adjustment) method adjusts the offset of pressing punches from the deformation results and the design surface. The shape deviations of two surfaces due to spring back are compensated by integrated system using FEA and IDA method. For the practical application, It is aimed to develop an integrated system that can automatically perform the compensation process and calculate strokes of punches of the double sides' reconfigurable multiple-press machine and some experimental results obtained with mechanical bending are presented.

• Sim-seong Yeon-gu
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• 제25권2호
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• pp.194-223
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• 2010

I tried here to interpret german fairy tale "Three Dogs" from the aspect of analytical psychology. A poor young shepherd will be 'hero'accidently while wandering the world to find good luck. When he was exhausted and frustrated in wandering life, a stranger appeared before him. A stranger offered barter. So he exchanged three sheep with three black dogs which a stranger had. One dog can bring the food. Another dog can tear everything. The last one can break even steel and iron. After that, shepherd led a satisfactory wandering life. On the way, he met a sad princess who should sacrifice herself for the piece of the country to the dragon which swallows a young girl yearly. But the strong black dog which tears everything, killed the dragon and saved the princess from the sacrifice. After that, a young shepherd promised princess to come back to her after three years of wandering life. In the meanwhile a horse driver played hero false. But the princess couldn't reveal the truth because of the threat of horse driver. Three years later, the young shepherd appeared in the castle. But the true hero was caught in the prison and finally cried out the strongest dog and succeeded in escaping from the prison. And with help of another dog which bring food to him, he could meet the princess and finally married her. So they lived happy life for a long time. But he remembered the poor younger sister. So he wanted to live together with her. After that, three dogs left him with saying, they stayed to see whether he shares his good fortune with his younger sister. Then they turned into birds and disappeared in the air. In this fairy tale can we find many important symbols. With the amplification of symbols and the interpretation of this fairy tale in terms of Jung's analytical psychology, I tried to find the meaning of individuation process in this fairy tale. Hero kills the dragon which could symbolize negative mother archetype. After overcoming the negative mother complex, he could get princess which could be expressive of Anima. This marriage could symbolize coniunctio oppositorum, an important process in individuation. Each fairy tale tells us the individuation process in a different way. And the fairy tale works always in our mind with plain, simple, pure, crystal like nature. Through it can we take precious treasure like wisdom for life.