[Response properties of single sensory units innervating human periodontal ligament to force stimuli].

For the purpose of investigating the response patterns of single sensory units innervating the human periodontal ligament to the mechanical stimulation of the lower incisor tooth, the recordings of nineteen single sensory units were made from the mental foramen of five adult subjects by the method of microneurography and the response patterns were analysed. The findings obtained were as follows: (1) According to the characteristics of their adaptation, the response patterns of the unit to the different forces from five directions were classified as Slowly Adapting, Fast Adapting-on, Fast Adapting-off, Fast Adapting-on/off and Intermediate Adapting Type. (2) The order of the threshold value among the different response patterns was: Slowly Adapting Type < Intermediate Adapting Type < Fast Adapting Type. (3) Increasing the application rate of the stimuli, the latency of their responses became short in the response pattern of the Fast Adapting Type. (4) Increasing the application rate of the stimuli, the dynamic index increased in the response pattern of the Slowly Adapting Type. These results suggest that the various patterns of the impulses generated by the nerve fibers innervating the periodontal ligament may cause a periodontal-somatic sensation.