EFFECT OF SERUM-PROTEINS AND OSTEOBLASTS ON THE SURFACE TRANSFORMATION OF A CALCIUM-PHOSPHATE COATING - A PHYSICOCHEMICAL AND ULTRASTRUCTURAL-STUDY

Changes occurring at the surface of a calcium phosphate coating when i n contact with osteoblasts versus those in acellular solutions were an alyzed. The coating studied is one with a well-documented extensive ef fect on shortterm bone growth stimulation. Precipitates associated wit h original crystals and organized in a weblike structure were observed after a 3-week culture with osteoblasts. The precipitates were identi fied as carbonated hydroxyapatite (c-HA). In contrast, no significant surface changes were detected after immersion in an acellular serum-co ntaining solution. However, in an acellular serum-free solution simula ting the ionic composition of plasma, precipitates, identified as c-HA , were abundantly formed. Dissolution of the original coating preceded precipitation. The data support the hypothesis that dissolution of sy nthetic calcium phosphate ceramics is an initial step in their transfo rmation to a biologically equivalent apatite, and suggest that both so lution-mediated (dissolution-precipitation) and cell-mediated mechanis ms are involved in the surface transformation. (C) 1998 John Wiley & S ons, Inc.