THE PHYSCIAL PORPERTIES OFY Y2O3-CONTAINING GLASS INFILTRATED ALUMINA CORE MADE BY PRESSURELESS POWDER PACKING METHOD

Whang, Seung Woo; Lee, Keun Woo

Abstract

The objective of this study was to characterize the mechanical properties of Y2O3-containing glass infiltrated ceramic core material, which was made by pressureless powder packing method. A pure alumina powder with a grain size of about 4micrometer was packed without pressure is silicon mold to form a bar shaped sample, and applied PVA solution as a binder. Samples were sinterd at 1350degrees C for 1 hour. After cooling, Y2O3-containing glass (SiO2, Y2O3, B2O3, Al2O3, ect) was infiltrated to the sinterd samples at 1300degrees C for 2 hours and cooled. Six different proportions Y2O3 of were used to know the effect of the mismatch of the thermal expansion coefficient between alumina powder and glass. The samples were ground to 3x3x30 mm size and polished with 1microneter diamond paste. Flexural strength, fracture toughness, hardness and other physical properties were obtained, and the fractured surface was examined with SEM and EPMA. Ten samples of each group were tested and compared with In-Ceram(TM) core materials of same size made in dental laboratory. The results were as follows : 1. The flexural strengths of group 1 and 3 were significantly not different with that of In-Ceram, but other experimental groups were lower than In-Ceram. 2. The shrinkage rate of samples was 0.42% after first firing, and 0.45% after glass infiltration. Total shrinkage rate was 0.87%. 3. After first firing, porosity rate of experimental groups was 50%, compared with 22.25% of In-Ceram. After glass infiltration, porosity rate of experimental groups was 2%, and 1% in In-Ceram. 4. There was no statistical difference in hardness between two materials tested, but in fracture toughness, group 2 and 3 were higher than In-Ceram. 5. The thermal expansion coefficients of experimental groups were varied to 4.51~5.35x10-6/degrees C according to glass composition, also the flexural strengths of samples were varied. 6. In a view of SEM, many microparticles about 0.5microneter diameter and 4microneter diameter were observed in In-Ceram. But in experimental group, the size of most particles was about 4microneter, and a little microparticles was observed. The results obtained in this study showed that the mismatch of the thermal expansion coefficients between alumina powder and infiltrated glass affect the flexural strength of alumin/glass composite. The Y2O3-containing glass infiltrated ceramic core made by powder packing method will takes less time and cost with sufficient flexural strength similar to all ceramic crown made with slip casting technique.