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Abstract: Objective: The purpose of this study was to investigate the properties of tape cast alumina composite produced using a water-based solvent and its possible clinical use as an all ceramic crown system in a fixed partial denture. Durability of the system will be measured by fatigue test to simulate the masticating conditions of the oral cavity. Methods: The optimal weight ratio of water-based alumina tape was determined by tensile strength, shrinkage ratio and durability. The coefficient of thermal expansion, fracture toughness, biaxial flexural strength and flexural strength after fatigue test of a composite produced from alumina tape at optimal weight ratios were determined and compared to In-Ceram alumina core (control). Results: The weight ratio of alumina/(alumina+binder+plasticizer) of 0.84 and binder/(binder+plasticizer) of 0.5 was observed to be the optimal composition for achieving excellent composite properties. Coefficient of thermal expansion of the sintered alumina tape was observed to be 7.3×10−6/°C, and this value was increased to 7.5×10−6/°C after infiltrating the sintered tape with glass. The fracture toughness and biaxial flexural strength of glass infiltrated alumina tape was observed to be 4.6MPam1/2 and 498MPa, respectively. After cyclic loading for 102–106 cycles, no significant change in the biaxial flexural strength was observed between the glass infiltrated alumina core and the In-Ceram alumina core (p >0.05). Significance: The observed properties provide evidence that the water-based tape cast alumina–glass composite is suitable for clinical use as an all ceramic crown system in a fixed partial denture. [Copyright &y& Elsevier]

• Addition of Al 2 O 3 result in decrease in sintering shrinkage and relative density. • Different forms of Al 2 O 3 in Al 2 O 3 –ZrO 2 composite result in different mechanical properties. • Addition of microfibre form Al 2 O 3 result in enhanced mechanical properties of Al 2 O 3 –ZrO 2. • Addition of microfibre form Al 2 O 3 result in lowest Weibull modulus. • Addition of greater than 20 vol% of microfibre form Al 2 O 3 result in agglomeration. This study evaluates the difference in physical and mechanical properties of ZrO 2 ceramics, commonly used in dental applications, altered by three different forms of Al 2 O 3 content; microparticles (m), nanoparticles (n), and microfiber (f). Three different types of ZrO 2 –Al 2 O 3 composites were formed using microparticle (m), nanoparticle (n), or microfibre (f) forms of Al 2 O 3. The physical and mechanical properties such as sintering shrinkage, relative density, Vickers hardness, fracture toughness, and biaxial strength were evaluated. A Weibull analysis was performed to assess the strength reliability of the specimens. All data were calculated using the t-test and ANOVA. The sintering shrinkage and relative density of all ceramic composite groups were decreased with the addition of Al 2 O 3. The mechanical properties of ZrO 2 –Al 2 O 3 (f) composite were higher than that of ZrO 2 –Al 2 O 3 (m) composite and ZrO 2 –Al 2 O 3 (n) composite. The maximum hardness, fracture toughness, and biaxial flexural strength were observed for 10 vol% of Al 2 O 3 fibre. When the content of Al 2 O 3 fibre in the matrix was increased above 20 vol%, agglomeration occurred and resulted in a decrease of hardness and toughness. The Weibull modulus value of the ZrO 2 –Al 2 O 3 (f) composite was the lowest compared to that of other groups. However, characteristic strength (σ 0) of ZrO 2 –Al 2 O 3 (f) the highest value. The current study demonstrated that the addition of right amount of Al 2 O 3 microfibre into the ZrO 2 matrix enhanced the mechanical properties of ZrO 2 -Al 2 O 3 (f) composite, which would be favourable for dental applications. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: Outstanding mechanical properties, resistance to scratching and high biocompatibility make zirconia/alumina ceramics interesting for dental applications. To solve the problem of the well-known low temperature degradation and to provide stable mechanical properties a novel zirconia alloy ((Y,Nb)-TZP/alumina) was developed. The aim of this study was to investigate the initial bone cell response to this new zirconia/alumina composite ceramic. Methods: HOS cells were cultured on zirconia/alumina composite (Zc) and pure titanium (Ti) discs. Surface topography was examined by atomic force microscopy (AFM), cell morphology by scanning electron microscopy (SEM). Cell proliferation (MTS) and alkaline phosphatase activity was measured at 1, 4 and 8 days. The mRNA expression of Cycline D1, the cell cycle regulating gene, integrin β 1, osteonectin (ON) and β-actin were evaluated by RT-PCR analysis after 12, 24 and 48h. Results: Both substrates showed a very smooth character with R a-values in the range of 0.002–0.113μm supporting a continuous cellular growth. After 8 days, cell proliferation on Zc was higher than on Ti. The mRNA expression of cyclin D1 showed similar activity after 48h on both surfaces, ALP activity was higher on Zc after 8 days. ON expression however showed no difference between the two groups. Significance: Our data demonstrate that this new zirconia composite ceramic showed at least equivalent or slightly better biological response of osteoblast-like HOS cells than pure titanium during a short-time cell culture period. [Copyright &y& Elsevier]