Cells and Materials


An in vitro rat bone marrow cell system was used to examine the interfacial ultrastructure established between various calcium phosphates and mineralized tissue. The investigated calcium phosphates comprised hydroxyapatite (HA), fluorapatite (FA), tricalcium phosphate (TCP), tetracalcium phosphate (TECP) and magnesium whitlockite (MWL). Both scanning and transmission electron microscopy were used to examine the elaborated interface. The time in which a mineralized extracellular matrix was formed on the various materials differed from 2 weeks on HA, TCP and TECP, to 8 weeks on FA. It was only occasionally observed in some areas on MWL, which might have been due to aluminum impurities in the coating. With transmission electron microscopy, three distinct interfacial structures were observed. They differed in the presence or absence of a collagen free, 0. 7 to 0. 8 J.Lm wide, amorphous zone and a 20 to 60 nm thick electron dense layer , interposed between the material surface and the mineralized extracellular matrix. The electron dense layer was considered to be at least partially caused by protein adsorption , which would precede or concur with biological mineralization events , while the amorphous zone was regarded to represent partial degradation of the calcium phosphate surfaces. The results of this study show that plasma sprayed calcium phosphates will display different bone-bonding and biodegradation properties , depending on their chemical composition and crystal structures .