Background
The role of bone formation and bioresorption in an early stage after implantation of β-tricalcium phosphate (β-TCP) was investigated
using scanning and transmission electron microscopy (SEM, TEM).
Methods
The ceramic β-TCP cylinders were implanted into cavities drilled in the femoral condyles of eight NZW rabbits. Four of the
rabbits were sacrificed at 2 weeks and four at 4 weeks after implantation, respectively. The femoral condyles were excised
to prepare the specimens for SEM and TEM.
Results
SEM showed giant cells of more than 20 μm in diameter were observed on the surface of β-TCP at 2 weeks after implantation.
TEM demonstrated that collagen fibrils secreted from the monocytic cells invaded β-TCP micropores at 2 weeks. Multinucleated
giant cells (MNGCs) were in contact with the surface of β-TCP at 2 weeks. Some of them had a ruffled border (RB) at the cell-substrate
interface, characteristic of osteoclasts.
Conclusions
These findings suggest that cell-mediated disintegration by osteoclasts played a role in the bioresorption of β-TCP at an
early stage after implantation. In addition, the micropores of β-TCP ceramic may provide an environment for collagen formation,
leading to the deposition of apatite crystals. Therefore, the micropores facilitate bone ingrowth as well as ceramic resorption.