Influence of surface microstructure on the reaction of the active ceramics in vivo.

When porosity and macro-pore size differ in the same ceramic, the mode of bone regeneration and the degradation of ceramics in vivo is said to be different. However, the reactions in vivo of ceramics that have a different microstructure with the same porosity and the same macro-pore size, are not so far known. In this study, two kinds of beta-tricalcium phosphate (TCP) that had different microstructures but the same porosity and macro-pore size, were manufactured. These TCP were implanted in the distal femurs of 20 mature male rabbits, and their respective areas of ceramics and of regenerated bone were measured after 4, 12 and 24 wk. In both TCPs, the regenerated bone similarly decreased from 4-24 wk in a different way. The area of ceramics in one of these TCPs significantly decreased gradually throughout the observation period. On the other hand, the other TCP showed no marked decrease during the same period. This suggested a possibility that the difference in micro-structure has a large effect on the reaction of the ceramics in the bone.