Unfortunately, limited properties continue to limit application of materials designed to fill both hard and soft tissue cavities. For example, ceramic-reinforced polymer matrices are widely regarded as the logical answer to how we can best match some of nature's feats of hard tissue engineering. Such direct bone-implant bonding can form a strong interface between the body and the implant. When placed into a bony cavity, healing must occur in the space between the implant and the existing bone. New bone formation in such a gap is contingent upon chemical, mechanical and topographic influences that have not been clearly sorted out.
Similar limitations exist for soft tissues.
Of particular importance is the interface between natural nerve tissue and synthetic analogs. This has generated recent excitement following advances in our ability to control bodily mechanisms that encourage nerve growth, a key element in restoring function to victims of paralysis. Schwann cells, which surround the axons of peripheral nerves, are responsible for myelination of those axons and may be key elements in peripheral nerve regeneration. This work proved that peripheral nerve cells could survive and function appropriately when implanted into the central nervous system. Nerve growth factors initiate and support new cell development, guide new or damaged nerves to appropriate targets, and assist in the maintenance of neuronal function.