In recent years, an attempt to quantitatively and objectively express pain in concrete terms, which by conventional methods can appear only as a subjective experience, has been made through the application of somatosensory evoked potential (SEP). On this occasion, we experimentally induced pain by applying electrical dental stimulation to a tooth, and then we analyzed the effect of the pain stimulation on SEP and changes in SEP by administration of analgesics as well as the features of SEP at the central level. The results we obtained are described below:
We evaluated the effect of electrical dental stimulation on somatosensory evoked potential (SEP), which is closely related to physiological and psychological aspects of pain, under the application of analgesics in 15 healthy adult males (diflunisal-treated group in 9 and control group in 6), and the following results were obtained.
1) Five-phase waves showing peaks at N 75, p100, N 155, p255 and N 335 were seen during the post-stimulation periods, from 75 to 335 msec. These findings were practically identical among all the subjects in both groups.
2) The 2 groups showed almost the same latency, indicating no effects of analgesics on latency.
3) There were no noticeable changes in amplitudes in N 75-P 100 and p100-N 155, which are thought to be related to the intensity of stimulation.
4) Among N 155-P 255 and P255-N 335, which are considered to be closely related to pain sensation, amplitudes in N 155-P 255 were significantly reduced in the treated group.
5) Although the pain scale was decreased over time in both treated and control groups, there were no significant differences between the 2 groups.
6) The amplitudes of SEP were altered by the administration of analgesics, while no marked differences in verbal expression of the pain were seen between the 2 groups.
7) These results suggests that the expression of pain, which before now could only be expressed by subjective scales, will now be measured with quantitative scales using SEP.