OSTEOCLASTIC RESORPTION OF CALCIUM-PHOSPHATE CERAMICS WITH DIFFERENT HYDROXYAPATITE BETA-TRICALCIUM PHOSPHATE RATIOS

To study the influence of calcium phosphate ceramic solubility on oste oclastic resorption, neonatal rabbit bone cells were cultured for 2 da ys on hydroxyapatite (HA), beta-tricalcium phosphate (beta-TCP) and tw o types of biphasic calcium phosphate (BCP) with HA/beta-TCP ratios of 25/75 and 75/25. Solubility was regulated by varying the ratio of les s-soluble HA and more-soluble beta-TCP. After removal of stromal cells by pronase E treatment, ceramic surfaces were observed by scanning el ectron microscopy. Osteoclasts resorbed BCP most extensively, with an HA/beta-TCP ratio of 25/75, producing typical lobulated, zig-zag track -like resorption lacunae. On pure beta-TCP, which had the highest solu bility in acid, osteoclasts formed smaller discontinuous island-like l acunae. The resorption pattern may have been modified by the large num ber of calcium ions released into the acidic microenvironment at the o steoclast-ceramic interface. No resorption lacunae were found on the o ther specimens. The extent of osteoclastic resorption of calcium phosp hate ceramics might, to a certain degree, be proportional to solubilit y, although this was not the case when solubility was very high. It wo uld appear that ceramic solubility influences osteoclast resorption ac tivity. (C) 1997 Elsevier Science Limited. All rights reserved.