Psychophysical experiments of thermoperception in human teeth

Clinically inconspicuous anterior teeth of subjects 18-53 years of age were stimulated by means of an electrically controlled thermode of 0.5 degree C, 35 degrees C and 71 degrees C for 60 s. In two sets of experiments testing vital anterior teeth the cold stimuli were correctly identified significantly above chance level, making the existence of cold receptors inside the tooth probable. No evidence of a corresponding warm perception in human anterior teeth was found. These results were corroborated in a third experiment by comparative testing of 75 anterior teeth--25 devital and 50 vital--for a possible stimulus spread to other than intradental neural structures. Local surface anaesthesia of the tissues adjacent to the teeth significantly reduced the subject's ability to correctly identify cold stimuli. Investigating the effect of cold stimulus temperatures (0.5 degree C, 15 degrees C and 25 degrees C), no significant difference in correct cold perception was found when the two lower temperatures were applied, while with the 25 degrees C stimulus correct cold perception was at chance level. The latency of correct cold responses increased significantly when stimuli of 15 degrees C instead of 0.5 degree C were applied (t-test p less than 0.05). The latency of correct cold responses (0.5 degrees C) was not significantly influenced by surface anaesthesia. It increased significantly, however, when devital teeth were tested with the 0.5 degree C stimulus (t-test; p less than 0.01).