Material-dependent bone induction by calcium phosphate ceramics: a 2.5-year study in dog

Boric induction by different calcium phosphate biomaterials has been report ed previously. With regard to (1) whether the induced bone would disappear with time due to the absence of mechanical stresses and (2) whether this he terotopically formed bone would give rise to uncontrolled growth, a long-ti me investigation of porous hydroxyapatite ceramic (HA), porous biphasic cal cium phosphate ceramic (TCP/HA, BCP), porous alpha -tricalcium phosphate ce ramic (alpha -TCP) and porous beta -tricalcium phosphate ceramic (beta -TCP ) was performed in dorsal muscles of dog, for 2.5 years. Histological obser vation, backscattered scanning electron microscopy observation and histomor phometric analysis were made on thin un-decalcified sections of retrieved s amples. Normal compact bone with bone marrow was found in all HA implants ( n = 4) and in all BCP implants (n = 4), 48 +/- 4% pore area was filled with bone in HA implants and 41 +/- 2% in BCP implants. Bone-like tissue, which was a mineralised bone matrix with osteocytes but lacked osteoblasts and b one marrow, was found in all beta -TCP implants (n = 4) and in one of the f our alpha -TCP implants. Both normal bone and bone-like tissues were confin ed inside the pores of the implants. The results show that calcium phosphat e ceramics are osteoinductive in muscles of dogs, Although the quality and quantity varied among different ceramics, the induced bone in both HA and B CP ceramics did neither disappear nor grow uncontrollably during the period as long as 2.5 years. (C) 2001 Elsevier Science Ltd. All rights reserved.