INNERVATION OF THE MANDIBULAR INCISORS BY THE MENTAL NERVE

Purpose: This study tested the hypothesis that some sensory innervatio n to the lower incisor teeth comes from reentry of the terminal branch es of the mental nerve through the labial plate of the anterior mandib le, Patients and Methods: Ten cadaveric heads (20 sides) were dissecte d and studied to determine whether the mental nerve crossed the midlin e or reentered the labial plate, Using careful dissection, the most po sterior branch of the nerve was exposed from its point of emergence at the mental foramen to its insertions, and any entries into the labial plate were recorded and photographed, Results: Three of 20 (15%) spec imens showed unequivocal evidence of nerve reentry into the labial pla te, Five specimens displayed strong evidence of nerve fibers reenterin g the plate, but these were too fragile to be dissected through the pe riosteum without breaking, In 12 of 20 (60%) specimens, there were no branches identified that reentered the bone plate, Of the eight specim ens showing evidence for reentry, four had substantial midline crossov er, Conclusions: The finding that branches of the mental nerve may ree nter the labial plate to supply the lower incisors explains the phenom enon of crossover innervation from the contralateral mental nerve and the fact that a labial infiltration injection will anesthetize the low er incisor teeth.