Pain perception threshold and adaptation of normal human teeth.

In an earlier investigation pain perception threshold values for normal human anterior teeth were determined and those for upper teeth were found to be in the range 0.7–4.5 μA. These low readings would make it difficult to investigate teeth with lower than normal pain perception thresholds which are said to occur in acute pulpitis and hyperaemia, so ways of raising these values for normal teeth were investigated and higher readings were achieved by using a stimulus of 30 msec at 20 c/s applied via a cathodal electrode with a conducting rubber electrode tip having a contact area of 9.5 mm2. The new values for young adults were in the range 2.2–20.5 μA and, within these limits, the pain perception threshold tended to be higher as teeth were further from the midline, but no definite difference due to sex was revealed, and age from 10–73 years appeared to have no effect on the pain perception threshold. Difficulty was experienced with children in the age group 7–9 years and this might have been due at least partly to the incomplete innervation of newly erupted teeth. Adaptation was shown to occur and its significance in electric pulp-testing was discussed. The character of the sensation was also analysed and this revealed that the commonly accepted view, that pain is the only sensation appreciated in the teeth, is not strictly correct. It also revealed that the character of the sensation cannot be taken as a guide to the pulp condition.