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 enh anced by immediate implantation of submerged ceramic hydroxyapatite (H A) implants releasing the bone resorption-inhibiting agent bisphosphon ate (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 t emperature of 37 degrees C during 3 months. The implants were either r od- or tube-shaped, with densities of 3.104 g/cm(3) and 1.408 g/cm(3) (microporous) or 2.369 g/cm(3) (macro/microporous). Loading of the imp lants with the P-C-P was done by adsorption into the ceramic (rod-shap ed implants) or by filling the reservoir of the implant (tube-shaped i mplants). Despite the fact that P-C-P has a high bonding affinity to H A it appeared that the release of adsorbed P-C-P from the ceramic HA o ccurred steady, controlled and over a long period of time. The rod-sha ped implants had much better release properties than the tube-shaped i mplants. Microporous ceramic HA rods sintered at 800 degrees C and mac ro/microporous rods sintered at 1300 degrees C are considered to be pr omising release systems for P-C-Ps.