Bone formation induced by calcium phosphate ceramics in soft tissue of dogs: a comparative study between porous alpha-TCP and beta-TCP.

Two kinds of tri-calcium phosphate ceramics (Ca/P = 1.50), α-TCP and β-TCP, which has the same macrostructure and microstructure, but different phase composition, were implanted in dorsal muscles of dogs. The samples were retrieved at 30, 45 and 150 days, respectively, after implantation, and were analyzed histologically. There were critically different tissue responses between α-TCP ceramic and β-TCP ceramic. Higher cell populations were observed inside the pores of β-TCP than those of α-TCP, bone tissue was found in β-TCP at 45 and 150 days, but no bone formation could be detected in any α-TCP implants in this study. On the other hand, the bone tissue in β-TCP seemed to degenerate at 150 days. The results indicate that porous β-TCP can induce bone formation in soft tissues of dogs; while the rapid dissolution of the ceramic and the higher local Ca2+, PO 4 3- concentration due to the rapid dissolution of α-TCP may resist bone formation in α-TCP and the less rapid dissolution of β-TCP may be detrimental to already formed bone in β-TCP.