Difference in Osteoclast Responses to Tricalcium Phosphate in Culture Medium Supplemented with Zinc and to Zinc-Containing Tricalcium Phosphate

Difference in osteoclast responses (i.e., apoptosis, actin ring formation) to tricalcium phosphate (TCP) in culture medium supplemented with zinc and to zinc-containing tricalcium phosphate (ZnTCP) was investigated in this study. On the TCP ceramic, an increase in zinc ion in the culture medium within the range between 0.3 and 6.8 ppm significantly induced an increase in osteoclast apoptosis and a decrease in actin ring formation. However, even a high level of magnesium ion up to 100 ppm in the culture medium or up to 6.8 mol% in the ceramic was unlikely to influence osteoclast activity. There was almost no significant difference in osteoclast apoptosis and actin ring formation between ZnTCP with 1 mol% zinc and magnesiumcontaining tricalcium phosphate with 1.5 mol% magnesium ceramic which have the same solubility and the same dissolution rate. It is suggested that only an increase in zinc level outside resorption lacuna has an inhibitory effect on osteoclast resorption and that an increase in zinc level inside resorption lacuna could not influence osteoclast activity.