Sensory and reflex responses to tooth pulp stimulation in man.

Experiments have been carried out to investigate whether all tooth pulp afferent nerves are capable of producing pain. Monopolar and bipolar stimuli were applied to teeth in human subjects and sensory thresholds determined. EMGs were recorded from the masseter and the anterior digastric muscles. With stimuli up to three times the sensory threshold, no response could be detected in the digastric but at, or just above, the sensory threshold, inhibitory effects were produced in masseter muscle. The latency of the muscle response with bipolar stimulation was 18-22 msec. There was no evidence of stimulus spread to nerves outside the teeth. Bipolar and monopolar stimulation both produced the same sensation but this was not described as painful. It is concluded that some pulpal afferent nerves may not be capable of producing pain, and that the sensory and reflex responses at threshold were probably produced by the same fibres.