Mouse peritoneal cavity; a model compartment for degradation studies.

The peritoneal cavity of mice was used as a compartment to investigate the inflammatory activity and degradation of three types of calcium phosphate ceramic in granulated form. The granules used were spherical shaped, without significant difference in average size. The spheres consisted of hydroxyapatite (HA), B-tricalcium phosphate (TCP), or fluorapatite (FA). Suspensions of each type of ceramic were injected intraperitoneally. This injection gave a mild inflammatory reaction as judged by the influx of neutrophil granulocytes. With respect to this parameter no significant difference between the injected ceramics was found. After two days the number of neutrophil granulocytes has returned to the normal level. Within two days the injected spheres accumulated in aggregates. The amount of fibrous tissue, present in the aggregates varied per type of ceramic. Degradation of the spheres was studied as well. It was found that the rate of degradation differed for each type, TCP shows a rapid and linear degradation up to 32 days, whereas HA and FA degraded much slower.