Stimulation of craniofacial and intramedullary bone formation by negatively charged beads.

To test for their osteogenic stimulating capacity, charged beads were implanted into cranial or mandibular defects, used as an onlay on the nasal bone surface, or injected into femoral medullary cavities of young adult rats. One month later, negatively charged beads were found to have stimulated extensive bone formation resulting in closure of craniofacial defects, a new layer of bone on the nasal bone surface, and a bead-bone lattice within marrow cavities of long bones. Positively charged beads were nonosteogenic, but elicited a pronounced fibroblastic response in the craniofacial skeleton. Positively charged beads were found associated with multinucleated giant cells at all implantation sites. Uncharged beads failed to elicit formation of new bone and were associated with connective tissue that was less cellular and less organized than was seen with positively charged beads. It was concluded that beads that have ben chemically treated to confer either a negative or positive surface charge, when placed in contact with bone, evoke osteogenesis or formation of dense connective tissue, the response depending on the surface charge of the bead. The mechanism(s) by which the charged beads foster the osteogenic or fibroblastic response is not clear. The use, however, of alloplastic materials with charged surfaces in repair and augmentation of bone, and in wound repair, warrants further investigation.