Masseter inhibitory periods and sensations upon electrical tooth-pulp stimulation in children and adults.

Sensations and masseter inhibitory periods (MIP) evoked by electrical tooth-pulp stimulation were recorded in 5 adults and 10 children. In the adult group there was always a sensation and it was usually associated with a two-phase MIP, with an early and a late component. Sensory detection in teeth with partially formed roots in the younger children (7-9 years old) was markedly reduced, and the MIP was mostly monophasic with a predominantly early component. In the older children with fully formed roots (10-12 years old) sensations did not differ from those in the adults, but the late MIP component occurred in significantly fewer trials (P less than 0.01). It is concluded that response to electrical tooth-pulp stimulation develops in the following stages: (1) early, oligosynaptic MIP, (2) sensation, and (3) the late, polysynaptic component of the MIP.