Development of a new calcium phosphate cement that contains sodium calciumphosphate

A cement powder consisting of sodium calcium phosphate, Na3Ca6(PO4)(5), in addition to tetracalcium phosphate and beta -tricalcium phosphate was prepa red by pulverizing blocks of 4 wt% sodium-,11 wt% carbonate-containing apat ite samples that were heated at 1700 degreesC for 5 h. When mixed with 30 w t% malic acid or citric acid at a powder liquid ratio of 3:1, the cement se t in 3 or 7 min at room temperature with compressive strength being around 52 or 27 MPa. In HeLa-cell cultures, the cement mixed with malic acid was l ess cytotoxic than the cement mixed with citric acid, which was far less cy totoxic than a commercial carboxylate cement used as a negative control, su ggesting malic acid to be superior to citric acid as a liquid in this regar d. Similar findings were also obtained with osteoclasts, of which culture e xperiments clearly suggested that the number of osteoclasts on the cement m ixed with malic acid was significantly greater than that on the cement mixe d with citric acid. Since osteoclastic response to substrates could be used as a maker in evaluating their bioresorbability associated with osteoclast s, the above finding may suggest that the cement that is to be mixed with m alic acid would be more useful as bone substitutes. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.