Effect of different ceramic powders and sintering temperatures on properties of resin-infused ceramics
Alshali, Shatha Abdulrahman
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OBJECTIVES: To investigate the effect of different ceramic powders on the microstructure, biaxial flexural strength, hardness and absorption coefficient of resin-infused zirconia and alumina, to investigate the effect of sintering temperatures on the microstructure, biaxial flexural strength, hardness and absorption coefficient of resin-infused spinel, and to investigate the effect of cyclic fatigue on biaxial flexural strength of resin-infused ceramics. MATERIALS: Resin-infused zirconia, resin-infused alumina and resin-infused spinel METHODS: Zirconia powders (TOSOH TZ and Zpex) and alumina powders (Almatis and Taimei) were dry-pressed in a stainless steel mold to fabricate ceramic discs. Discs were sintered to 1050°C. McMaster-Carr partially sintered alumina rod was cut into discs of 1.5 mm thickness. Ceranova spinel discs were divided into two groups sintered at two different temperatures (1250°C and 1350°C). Density of each disc was measured and a total of 8 discs per group were prepared. Specimens were silane treated, and then infused with an UDMA mixture under vacuum. Infused specimens were cured with an Isopress machine at pressures of 20,001 psi. Biaxial flexural strength was measured using an Instron Universal Testing machine at 0.5 mm/min crosshead speed. Another group was subjected to cyclic fatigue (50,000 cycles) before biaxial flexural strength test. Hardness was tested using vickers microhardness indenter (Buehler Micromat 2003). Spectrophotometer was used for direct transmission measurements and absorption coefficient was calculated. Microstructure of each group was investigated with a scanning electron microscope (SEM). The data were analyzed using one-way ANOVA and Tukey multiple comparisons. T-test was used to compare biaxial flexural strength of each group before and after cyclic fatigue. RESULTS AND CONCLUSIONS: Using different ceramic powders had no significant effect on the biaxial flexural strength and absorption coefficient of resin-infused zirconia. Resin-infused Zpex zirconia had significantly greater microhardness than resin-infused Tz zirconia. Resin-infused MCM alumina had significantly greater biaxial flexural strength than resin-infused Almatis alumina. Resin-infused MCM and Taimei alumina had significantly greater microhardness than resin-infused Taimei alumina. Resin-infused Almatis alumina had significantly greater absorption coefficient than resin-infused Taimei alumina. Cyclic fatigue had significantly reduced the biaxial flexural strength of resin-infused Tz zirconia, Almatis alumina and spinel 1250 but had no significant effect on the rest of the groups. Increasing sintering temperature of resin-infused spinel from 1250°C to 1350°C had no significant effect on biaxial flexural strength and absorption coefficient but it significantly increased the microhardness.