Ceramic hydroxyapatite implants for the release of bisphosphonate

Maintaining bone mass after extraction of teeth is a major problem in the prevention of oral disease. Maintenance theoretically could be enhanced by immediate implantation of submerged ceramic hydroxyapatite (HA) implants releasing the bone resorption-inhibiting agent bisphosphonate (P-C-P). Four different types of ceramic HA implants were designed as release systems for an in vitro study and assayed in saline at a temperature of 37 degrees C during 3 months. The implants were either rod- or tube-shaped, with densities of 3.104 g/cm3 and 1.408 g/cm3 (microporous) or 2.369 g/cm3 (macro/microporous). Loading of the implants with the P-C-P was done by adsorption into the ceramic (rod-shaped implants) or by filling the reservoir of the implant (tube-shaped implants). Despite the fact that P-C-P has a high bonding affinity to HA it appeared that the release of adsorbed P-C-P from the ceramic HA occurred steady, controlled and over a long period of time. The rod-shaped implants had much better release properties than the tube-shaped implants. Microporous ceramic HA rods sintered at 800 degrees C and macro/microporous rods sintered at 1300 degrees C are considered to be promising release systems for P-C-Ps.