Basic properties of apatite cement containing carbonate apatite and its resorption by cultured osteoclasts

Apatite cement (AC) has received much attention as a new reconstructive material for bony defects because AC transforms to hydroxyapatite (HAP) and shows excellent tissue response and osteoconductivity. In addition, AC has been reported to be partly replaced with bone, although the process takes a long time. The aim of this study, therefore, is to fabricate bone-replacing apatite cement by converting AC to be easily resorbed by osteoclasts. For this purpose, NaHCO₃ was added into the AC component. The amount of CO₃ incorporated into the set AC increased with the amount of added NaHCO₃. B-type carbonate apatite (CO₃-AP) was formed in the set AC added NaHCO₃. The dissolution rate of the set AC in weak acid, pH 5.5, increased with NaHCO₃. The number of resorption pits and the resorbed area by cultured osteoclasts increased with added CO₃ content. The resorbed area on 4% CO₃-added-AC was twice as much as that of carbonate-free-AC. The results suggested that CO₃-AP-formed AC would be easily resorbed by osteoclasts.