DEGRADATION OF THE APATITE LAYER FORMED ON BIOACTIVE CERAMICS AND OF THE UNDERLYING CERAMIC SURFACE BY OSTEOCLASTS IN A CULTURE SYSTEM

The object of this study is to show how bioactive ceramics having the surface apatite layers are degraded by osteoclasts in a culture system . Apatite layers, similar to those seen on implanted bioactive ceramic s, were formed on the surfaces of sintered hydroxyapatite (HA) and A-W glass-ceramic (A-W GC) by immersing them in a simulated body fluid fo r 5 days. We cultured neonatal rabbit bone cells on these apatite laye rs for 10-48 hours, and removed most of the cells except osteoclasts b y pronase E plus ethylenediaminetetraacetic acid (EDTA). Scanning elec tron microscopy showed that apparently active osteoclasts with numerou s filopodia made many resorption lacunae on the apatite layer and caus ed degradation of the underlying ceramic surfaces of both HA and A-W G C. The results suggest that osteoclastic degradation of the surface ap atite layer and degradation of the underlying ceramic surfaces of impl anted HA and A-W GC may possibly occur. The apatite layer, having bone -like characteristics, may be suitable for osteoclasts to retain their activity.