Biocompatibility and water durability of alumina-zirconia ceramics blended with microsized HA particles

Abstract

To improve the bioactivity of alumina containing yttria stabilized zirconia (Al-YSZ), composite ceramics consisting of Al-YSZ and 0–10 wt % of hydroxyapatite (HA) were prepared. The XRD patterns of sintered disks with an HA content above 3 wt % had monoclinic and cubic YSZ phases and a β-tricalcium phosphate phase. Although the Vickers hardness decreased as the HA content increased, all the prepared ceramics had the same or greater hardness (1000–1300 Hv with a load of 0.49 N) compared to typical YSZ ceramics (900–1000 Hv) commonly used in clinics. Furthermore, the bonelike apatite formation ability in simulated body fluid, which was examined as a screening of bioactivity, suggested that all the surfaces of Al-YSZ ceramics blending with a small amount of HA may possess the ability to connect bone. After the accelerated low temperature degradation (LTD) test performed in normal saline at 120°C for five days using composite ceramics with the HA content of 0, 1, 3, and 10 wt %, the tetragonal zirconia phase of all composite ceramics were partially transformed into the monoclinic phase with a transition ratio of ca. 16–18 mol % (for HA = 0 and 10 wt %) and ca. 4–5 mol % (for HA = 1 and 3 wt %). Blending microsized HA powder in Al-YSZ ceramics has both positive and negative effects on the LTD durability of Al-YSZ ceramics. An advantage is that calcium ion substitution in YSZ seems to stabilize the tetragonal (or cubic) zirconia phases, but the increased surface area exposed to the solution is a disadvantage.