[Micro-particles of bioceramics could cause cell and tissue damage]

We conducted studies to confirm the hypothesis that the cellular damage occurring around implanted biphasic bioceramics could be related to a micro-particles release because of an insufficient sintering. An in vitro cytotoxicity study was performed on four biphasic ceramic (BCP) samples. Without the treatment of extraction medium, a cytotoxicity was observed, although after centrifugation this cytotoxicity disappeared in all samples. (2) Micro-particles of HA, beta-TCP and 40%beta-TCP/60%HA mixture were used for a cell inhibition study. A decrease of cell viability was observed with the increase in particles concentration. At 10000 particles/ cell, the viability and proliferation were completely inhibited. (3) HA, beta-TCP and BCP ceramic granules were implanted in rabbit femoral cavities for 12 weeks. No degradation of HA granules was observed. The degradation was higher for beta-TCP (40%) than for BCP (5%). On the other hand, new bone formation was significantly higher for beta-TCP (21%) and HA (18%) than for BCP (12%). Much more micro-particles were formed around BCP granules than around beta-TCP, and were phagocytosed by macrophages. The release of ceramic micro-particles could be related to the sintering process. BCP ceramics have to be sintered at only 1160 degrees C. Consequently, HA microparticles of BCP ceramic are incompletely sintered and easily released after immersion or implantation. The microparticles could be at the origin of local inflammation and cell damage and could perhaps modify osteogenesis. Particular attention must be paid to this problem with regard to BCP ceramics because of the sintering difficulties of this bioceramic.