Zirconia-Toughened Bioactive Glass-Ceramics

Abstract

High-strength bioactive glass-ceramics were prepared by hot-pressing the mixtures of glass and tetragonal zirconia polycrystal (TZP) powders at 1150°-1200°C for 2h under the pressure of 30MPa. Mechanical properties of bioactive glass-ceramics were much improved by dispersing TZP powders sintered at 1400°C (TZ) or specially prepared for low temperature sintering (NSZ). The bending strength of the composite containing 40vol% TZ and NSZ showed 600MPa and 900MPa, respectively. The bending strength of the composite toughened by TZ increased with increasing TZ content up to 60vol% showing maximum value of 800MPa, and then decreased over 70vol%. On the other hand, the bending strength of the composite toughened by NSZ increased monotonously with increasing NSZ in whole range. Many defects were found in the specimens containing TZ over 70% by SEM observation and were considered to degrade the bending strength. The number of the points which zirconia grains contact directly with each other may increase with the increase in zirconia content. The defects were formed at these points because TZ powder did not sinter sufficiently at 1200°C. The composite containing 40vol% TZP still maintained high bioactivity though the bioactivity of the composite containing more than 50vol% TZP was poor. The bioactivity was evaluated from apatite formation on the surface in a simulated body fluid at 37°C for 30 days.