Degradable Bisphosphonate‐Alkaline Phosphatase‐Complexed Hydroxyapatite Implants In Vitro

• Published in: Journal of bone and mineral research 1997-02, Vol.12 (2), p.290-297
• Main Authors: Denissen, Harry, Van Beek, Ermond, Van Den Bos, Theo, De Blieck, Jolanda, Klein, Christel, Van Den Hooff, Arnold
• Format: Article
• Language: English
• Subjects: Absorption; Alkaline Phosphatase - metabolism; Alkaline Phosphatase - pharmacology; Alkaline Phosphatase - physiology; Animals; Biological and medical sciences; Bone and Bones - drug effects; Bone and Bones - metabolism; Delayed-Action Preparations - pharmacology; Dental Implants; Diphosphonates - metabolism; Diphosphonates - pharmacology; Dose-Response Relationship, Drug; Drug Synergism; Durapatite - metabolism; Durapatite - pharmacology; Head and neck surgery. Maxillofacial surgery. Dental surgery. Orthodontics; Histocytochemistry; Maxillofacial surgery. Dental surgery. Orthodontics; Medical sciences; Mice; Surface Properties; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases
• ISSN: 0884-0431; 1523-4681
• DOI: 10.1359/jbmr.1997.12.2.290

Degradable hydroxyapatite (HA) implants complexed with the resorption inhibiting agent bisphosphonate (PCP) and the mineralizing agent alkaline phosphatase (ALP) can theoretically maintain alveolar bone mass directly after extraction of teeth. The present in vitro study investigated the surface properties of PCP–ALP‐complexed HA implants in relation to the requirements of implant behavior and action. Adsorbed PCP (pH 3.49) resulted in a flattening and broadening of the phosphate peaks and the formation of carbonate peaks in the HA pattern of the implant indicating a chemical alteration of the HA surface. Adsorption of ALP onto PCP‐altered HA surfaces was 26% lower than onto HA implant blank surfaces. PCP–ALP‐complexed HA implants released the PCP and ALP steadily and continuously over observation periods of, respectively, 75 and 14 days. During these observation periods, the ceramic grains of the HA implant became smaller and intergrain boundaries became broader. These morphologic characteristics suggested preconditioning of the HA implant surface for future bonding and degradation in vivo. Individual grains were no longer bonded to other grains and detached from the implant which had become rounded in shape. From in vitro mice experiments we found that PCP concentrations between 10−4 and 10−3 M resulted in45Ca‐release from the bone HA. Our calculations showed, however, that only a total concentration of 1.4 × 10−4 M PCP was gradually released over the whole observation period. In another experiment, it appeared that a PCP concentration in solution