Relation between intradental nerve activity and estimated pain in man--a mathematical model

Intradental nerve activity (INA) induced by cold stimulation of human teeth is regularly accompanied by pain perception. In this study a mathematical model was developed in order to quantify the relationship between INA and pain. In 5 patients (45 experiments) INA was recorded using electrodes implanted in lower incisor teeth. Brief cold stimulations induced bursts of INA. The intensity of the resulting pain was simultaneously evaluated by means of an intermodal matching technique, finger span. The relationship between perceived pain and the integrated INA was analyzed using various mathematical operations (inter alia Fourier analysis) by means of a computer. A transfer function which describes the pain response following INA was found. This preliminary mathematical model, which is characterized by 5 parameters, consists of 2 parts, one which responds to fast changes in the afferent nerve signal, and another which reacts with a delay. The validity of the model has been tested, and it was found that the model consists of an adequate number of parameters and their cross-interaction is low. The analysis indicates that the parameters which determine the pain response following INA can be quantified and that they might be used as a measure of the efficacy of various pain relieving procedures.