Abstract
The excitation mechanisms of toothache caused by thermal changes were investigated on the canines of anesthetized mongrel dogs. Thermal stimulations were applied to the local tooth surface or the cavity floor made in dental tissues by a thermal stimulating equipment or cold and hot Ringer solutions. The potential difference between the cavity floor and the pulp transdentinal potential-and the action potentials of the odontoblast cell area and the alveolar nerve were recorded.
The results obtained were as follows: 1) Synchronous relation was found between the action potentials. 2) Two contradictory or single biphasic action potentials were recorded by large and small diameter micropipette electrodes. 3) Following the fall or rise of the stimulating temperature the transdentinal potential increased or decreased in inverse proportion to temperature variation. This potential was diminished by the administration of a narcotic agent to the pulp or cavity floor. The strength of these potentials was 50mV or more. 4) The action potentials were caused by the application of electrical current with the same intensity as the transdentinal potential. 5) It was found that the site most sensitive to thermal stimulation was the amelodentinal junction area and the areas least sensitive were the enamel and the dentin.
