WHAT IS BEHIND THE MARKETED TRICALCIUM PHOSPHATE

There is a certain ambiguity about the exact physicochemical nature of the product named ''tricalcium phosphate''. According to different do cuments, the formula is either the true tricalcium phosphate, or the h ydroxylapatite, or ''a variable mixture of calcium phosphates''. This is a problem for the elaboration of the analytical file for submission to the authorities : for example, X-ray diffraction patterns are not the same. Thus, technological properties may differ. The aim of this w ork was to study eleven samples of various origins as to their physico chemical and technological properties (their microscopic aspect, therm oanalytical behaviour, compression ability) in different ways (powder X-ray diffraction, infrared spectrometry, Pharmacopoeia assays). In fa ct, we can distinguish two main groups of tricalcium phosphates : ''tr ue'' tricalcium phosphate [Ca-3(PO4)(2)], and the hydroxylapatites [Ca -5(OH)(PO4)(3)], which sometimes contain traces of other calcium phosp hates. It appears that compression ability is chiefly related to the c hemical formula. The properties of hydroxylapatites differ according t o the manufacturer.