Response properties of periodontal mechanosensitive fibers in the superior dental nerve of the cat.

Periodontal mechanosensitive units were detected as single nerve fibers from the anterior branches of five cats, and their receptive fields and optimal stimulus directions were examined. Of 801 units detected, 759 units (95%) responded to movement of only one tooth (single-tooth unit), and 42 units (5%) responded to movement of two or three teeth (multitooth unit). Eighty percent of the single-tooth units were of the sustained type which discharged during more than 1 s to a long-lasting pressure applied to the tooth, and 20% were of the transient type which adapted in less than 1 s to the pressure. The majority (93%) of the sustained type exhibited directional selectivity to stimulation, but only 35% of the transient type showed it. More than half of the single-tooth units had their receptive fields in the canine tooth, stimulation of which produced the largest mass discharge in the nerve bundle. The optimal stimulus direction for many single-tooth units was the same as that for the mass discharge in the nerve bundle. The receptive fields of the multitooth units were observed mainly in the incisor teeth adjacent to each other.