Spreading of dentinoclasts on various substrata in vitro.

An in vitro system for isolated dentinoclasts is described in which clastic cells which are not contemporaneously engaged in resorption are gently rinsed from the surface of actively resorbing root dentin. Dentinoclasts were cultured on a variety of hard tissue constituents in order to investigate the effects of substratum composition on the expression of resorbing structures by these cells, and examined with scanning electron microscopy. Results revealed that dentinoclasts express both ruffled borders and clear zones only when cultured on coverslips coated with both collagen and hydroxyapatite. Hydroxyapatite alone induced only the formation of a clear zone. Failure to express either clear zones or ruffled borders by cells cultured on collagen-coated coverslips was interpreted to reveal that collagen itself is not capable of, but requires the mineral component of hard tissue for, producing morphologic resorbing structures in clastic cells.