Osteoclastic resorption of apatite formed on apatite- and wollastonite-containing glass-ceramic by a simulated body fluid.

We immersed mirror-polished apatite- and wollastonite-containing glass-ceramic (A-W GC) disks in a simulated body fluid (SBF) for 5 days to form bonelike apatite on their surface. Neonatal rabbit bone cells were cultured on these or on plain A-W GC disks for 10, 24, and 48 h. We observed the substrates by scanning electron microscopy after treating them with pronase E plus EDTA to remove all cells except osteoclasts. Osteoclasts with a non-motile appearance formed no lacunae on the plain A-W GC, whereas on the bonelike apatite formed on A-W GC by the SBF, actively moving osteoclasts made many tracklike resorption lacunae. These were evident even after 10 h of culture and became more extensive after longer culture periods. The bonelike apatite was therefore a more suitable medium than plain A-W GC for maintaining osteoclast activity. This study demonstrated in vitro osteoclastic resorption of bonelike apatite formed on A-W GC by an SBF. It suggests that the apatite layer, through which a surface-active ceramic bonds to bone in vivo, can be resorbed by osteoclasts and subjected to bone remodeling.