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KMID : 0362120120340020075
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Journal of Technologic Dentistry
2012 Volume.34 No. 2 p.75 ~ p.81
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The Properties of Sintered Body by Using the Slip Casting Process with Remained Dental Zirconia Block after Machining
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Kim Sang-Su
Lee Dong-Yoon
Seo Jeong-Il
Bae Won-Tae
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Abstract
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Purpose: All ceramic crown, made from zirconia instead of metal for core material, is recognized the best esthetical prosthesis. Recently, high-priced zirconia blocks and expensive CAD/CAM machines come into use for making
zirconia core. In this study, slip casting process is adapted to evaluate the possibility of the recycling the remained parts of zirconia block after machining.
Methods: Remained zirconia blocks were reduced to powders with zirconia mortar, and screened with 180 mesh
sieve. Passed powders were ball milled under various conditions to obtain the optimum zirconia slip for casting. Solid casting method was used for casting the specimens with plaster mold. Formed specimens were dried and biscuit fired at 1,000 for 1 hour. Biscuit fired specimens were finished with exact shape of square pillar. Finished specimens were fired from 1,200 to 1,550 at 50 intervals for 1 hour. Linear shrinkage, apparent porosity, water absorption, bulk density, and flexural strength were tested. Microstructures were observed by SEM.
Results: Above examinations indicated that the optimum firing temperture was 1,500 , and when fired at this
temperature for 1 hour, apparent porosity was 0% and flexural strength was 680 . SEM photomicrographs showed uniform 200~300 grain size, which is equal with microcture of sintered commercial zirconia block. when compare 24% linear shrinkage of cast specimen with 20% linear shrinkage of CAD/CAM machined block, it was estimated that the size controlling of cast core was not so difficult.
Conclusion: According to the all of this experimental results, the cast zirconia core produced from the remained
parts of zirconia block was possible to use for all ceramic denture.
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KEYWORD
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zirconia, slip casting, linear shrinkage, flexural strength, ball-milling
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