Preparation of hydroxyapatite porous ceramics with different porous structures using a hydrothermal treatment with different aqueous solutions

Hydroxyapatite (HA) porous ceramics are useful for bone regeneration because HA shows a bone-bonding capability. The preparation of HA porous ceramics with controlled pore structures was attempted using a hydrothermal treatment of porous ceramics consisting of alpha tricalcium phosphate (α-TCP). The α-TCP porous ceramics were hydrothermally treated with various aqueous solutions containing NaCl, CaCl₂, Na ₃PO₄, Na₂HPO₄, NaH ₂PO₄, or H₃PO₄ at 150°C for a period of 10 h. The α-TCP phase of the porous ceramics was transformed into HA by the hydrothermal treatment in ultrapure water, NaCl, CaCl ₂, Na₃PO₄ or Na₂HPO₄ solutions, to form porous ceramics consisting of rod-shaped HA particles. The size of the rod-shaped HA particles prepared in Na₃PO₄ or Na₂HPO₄ solutions was smaller than that prepared in ultrapure water, NaCl, or CaCl₂ solutions. The α-TCP phase of the porous ceramics was transformed into a biphase consisting of HA and monetite (DCPA) after treatment in NaH₂PO₄ solution, and into DCPA in the H₃PO₄ solution, resulting in porous ceramics consisting of plate-shaped particles. These results indicate that we could control the size and shape of the HA particles using the hydrothermal conditions, and this also provides a way of controlling the porous structure of the HA porous ceramics.