KINETIC-STUDY OF THE SETTING REACTION OF A CALCIUM-PHOSPHATE BONE-CEMENT

The setting reaction of a calcium phosphate bone cement consisting of a mixture of 63.2 wt % alpha-tertiary calcium phosphate (TCP)[alpha-Ca -3(PO4)(2)], 27.7 wt % dicalcium phosphate (DCP) (CaHPO4), and 9.1 wt % of precipitated hydroxyapatite [(PKA) used as seed material] was inv estigated. The cement samples were prepared at a liquid-to-powder rati o of: L/P = 0.30 ml/g. Bi-distilled water was used as liquid solution After mixing the powder and liquid, some samples were molded and aged in Ringer's solution at 37 degrees C. At fixed time intervals they wer e unmolded and then immediately frozen in Liquid nitrogen at a tempera ture of T-N = -196 degrees C, lyofilized, and examined by X-ray diffra ction as powder samples. The compressive strength versus time was also measured in setting samples of this calcium phosphate bone cement. Th e crystal entanglement morphology was examined by scanning electron mi croscopy. The results showed that: 1) alpha-TCP reacted to a calcium-d eficient hydroxyapatite (CDHA), Ca-9(HPO4)(PO4)(5)OH, whereas DCP did not react significantly; 2) the reaction was nearly finished within 32 h, during which both the reaction percentage and the compressive stre ngth increased versus time, with a strong correlation between them; an d 3) the calcium phosphate bone cement showed in general a structure o f groups of interconnected large plates distributed among agglomeratio ns of small crystal plates arranged in very dense packings. (C) 1996 J ohn Wiley & Sons, Inc.