Electrophysiologic and Functional Evaluations of Regenerated Facial Nerve Defects with a Tube Containing Dental Pulp Cells in Rats

Background: Dental pulp tissue contains Schwann and neural progenitor cells. Tissue-engineered nerve conduits with dental pulp cells promote facial nerve regeneration in rats. However, no nerve functional or electrophysiologic evaluations were performed. This study investigated the compound muscle action potential recordings and facial functional analysis of dental pulp cell regenerated nerve in rats. Methods: A silicone tube containing rat dental pulp cells in type I collagen gel was transplanted into a 7-mm gap of the buccal branch of the facial nerve in Lewis rats; the same defect was created in the marginal mandibular branch, which was ligatured. Compound muscle action potential recordings of vibrissal muscles and facial functional analysis with facial palsy score of the nerve were performed. Results: Tubulation with dental pulp cells showed significantly lower facial palsy scores than the autograft group between 3 and 10 weeks postoperatively. However, the dental pulp cell facial palsy scores showed no significant difference from those of autograft after 11 weeks. Amplitude and duration of compound muscle action potentials in the dental pulp cell group showed no significant difference from those of the intact and autograft groups, and there was no significant difference in the latency of compound muscle action potentials between the groups at 13 weeks postoperatively. However, the latency in the dental pulp cell group was prolonged more than that of the intact group. Conclusion: Tubulation with dental pulp cells could recover facial nerve defects functionally and electrophysiologically, and the recovery became comparable to that of nerve autografting in rats.