Cells and Materials


A macroporous biphasic calcium phosphate (BCP) of 60.7% carbonated dense non-porous hydroxyapatite (HA)/39.3% dense microporous ß-tricalcium phosphate (ß-TCP) was immersed during 15 days in a supplemented a-MEM (minimal essential medium) solution with and without dog bone marrow cells obtained by punction. The aim of the study was to demonstrate the time-related changes in the BCP fractions by means of X -ray diffraction, infrared spectroscopy and scanning electron microscopy, and to investigate the cell populations. The HA/ß-TCP ratios varied according to immersion duration and cell presence. If any, there was a slight preponderance of ß-TCP dissolution over that of HA. The dissolution rate was much lower in the presence of cells. Cell-mediated resorption was observed only in ß-TCP sites. The implicated small round-shaped cells of about 30 I'm were located in resorption lacunae, presented numerous short filopodia and a ruffled border faced towards the material to resorb. They did not undergo fusion with other cells but lost, on about day 15, their ruffled border. Then blast-cells highly involved in matrix secretion and mineralization appeared. There seems to be ample evidence that the clast-cells are specific monocytes which resorb ß-TCP under these in vitro conditions. To elucidate their exact nature, functions and fate, further long-range in vitro studies conducted under standardized conditions are needed.