Temperature related changes in pulpal microcirculation

During dental treatment temperatures can be reached which might possibly damage the tooth pulp. To determine the effect of both thermal stimulation on pulpal microcirculation and local anesthesia on thermoregulation we measured the pulpal blood flow by using laser Doppler flowmetry. Experiments were carried out on lower incisors of Wistar rats anaesthetized with thiopental. The rats were divided into three groups, with one remaining untreated, and the others being either desensitized with capsaicin or sympathectomized with guanethidine. In a range between 33 degrees C and 42 degrees C there was no substantial change in blood flow, which, however, was the case below 33 degrees C. Up to 49 degrees C an increase could be recorded in both untreated and guanethidine pretreated animals, whereas the capsaicin groups showed almost no reaction. This increase in blood flow can be blocked reversibly by local anaesthesia. For this purpose we tested articain 5% and mepivacain 3%, both without constrictor. Intravital microscopic studies show that the temperature related increase in blood flow is also associated with plasma extravasation. From these results we draw the conclusion that pulpal thermoregulation is linked to nociceptive sensory neurons and can be described as "neurogenic inflammation".