Abstract
The purpose of this study was to estimate the availability of α‐tricalcium phosphate (α‐TCP) on/in hydroxyapatite (HAP) ceramics for bioactivity as bone‐substitute materials by immersion in a simulated body fluid (SBF; Hanks' solution) containing ion concentrations similar to those in human blood plasma. Two α‐TCP‐surface‐modified HAP and α‐TCP‐HAP composite materials were prepared by orthophosphoric acid treatment of sintered HAP and controlling the crystal phases of calcium phosphate cement, respectively. After immersion in SBF, the sintered HAP modified on the surface in an approximately 0.2 μm α‐TCP layer was more effective for the precipitation of carbonated apatites than an approximately 2 μm α‐TCP layer and HAP‐only layer. In the calcium phosphate cements consisting of HAP and α‐TCP phases, after immersion for 1 week, the specimens precipitated large amounts of apatites having α‐TCP contents of approximately 25% and 50% in the cement. The results of immersion tests imply the possibility that the α‐TCP on/in HAP ceramics may be a bioactive agent for bone‐substituting HAP materials.