Effect of various properties of hydroxyapatite ceramics on osteoconduction and stability.

Hydroxyapatite ceramics (HA) are widely used for clinical applications as a bone substitute or dental implant because they have been shown to be biocompatible and exhibit excellent osteoconductivity when grafted into the bone tissue. However, the influence of the physical properties of HA on the osteoconduction and stability remains unclear. We examined here the effect of various properties of HA granules on osteoconduction and stability using 6 types of HA granules. The HA granules were grafted into the rabbit tibia and the initial bone formation and long-term stability of the new bone were studied histologically. The following results were obtained; 1. Osteoconduction of the HA granule was influenced by the shape. Multi-nuclear granules with continuous pores ranging from 30 to 200 microns in diameter showed both excellent osteoconduction and stability. 2. Solubility behavior of HA granules, which was effected by the relative surface area sizes, also seemed to be an important factor for osteoconduction and stability. 3. Stable bi-phase ceramics with HA and beta TCP were produced at the sintering temperature of 1200 degrees C when Mg was added. The beta TCP and Mg content did not negatively influence the initial osteoconduction or long-term stability.