[An experimental study on regeneration of the inferior alveolar nerve after lyophilized nerve homografting in the rabbit].

This study was designed to evaluate the differences between the regenerative process in cases of autogenous nerve grafting and lyophilized homologous nerve grafting. Rabbit inferior alveolar nerves (10 mm lengths) were resected and replaced with lyophilized homologous segments from the sciatic nerve. On the opposite side, the resected nerves were autogenously grafted. The experimental subjects were divided into autogenous nerve-graft and the lyophilized nerve-graft groups. Results. 1. Regenerating axons appeared in the autogenous-graft group 2 weeks after the operation and 4 weeks after the operation in the homografted lyophilized group. The difference in regeneration between the 2 groups was significant. 2. Regenerating axons in the autogenously grafted nerves made contact with remaining Schwann cells and endneural tubes. Axons in the homografted lyophilized nerves invaded along newly infiltrated Schwann cells and empty tube skeletal structures. The number of regenerating axons from outside the skeletal structure was greater than the number of regenerating axons from inside the skeletal structure. 3. In the case of autogenous grafting, nerve fibers of diameters greater than 3 microns increased 66.7% after 24 weeks; the corresponding figure for homografted lyophilized nerves was 48.4%. 4. In instances of autogenous grafting, 16 weeks after surgery, the ratio of distal proximal myelinated nerve fibers had grown. In cases of homografted lyophilized nerves, this tendency to increase continued until the twenty-fourth postsurgical week. 5. In both groups, it remained possible to record nerve action potentials 12 weeks after surgery. The sensory nerve conduction velocity of autogenously grafted nerves increased gradually to approach control values 24 weeks after surgery. That of homografted lyophilized nerves recovered more slowly. 6. Increases in number of nerve fibers with a diameter of more than 3 microns were proportional to the rate at which sensory nerve conduction velocity recovered.