Changes of Pulpal Blood Flow by Electrical Tooth Stimulation

Objectives: The aim of this study was to evaluate factors involved in the changes of pulpal blood flow caused by electrical tooth stimulation. Methods: Twelve cats were used under general anesthesia. The mandible was immobilized by intermaxillary splinting and pulpal blood flow (PBF) and systemic blood pressure was monitored throughout the experiments. Canine tooth was stimulated electrically (10Hz, 2ms, 100µË for 1 min) with a stimulator (Stimulus Isolator A365, World Precision Instruments, Inc., USA) after removing the enamel with a dental bur. PBF was measured with a laser Doppler flowmetry (Perimed, Switzerland) before and after tooth stimulation and drug administration in the same tooth of stimulation. To evaluate the influence of the sympathetic nerve system, sympathectic nerve was cut at cervical level at the ipsilateral side of the tooth stimulation. To evaluate the influence of sensory nerve system, a substance P antagonist, [D-Pro2, D-Trp7, 9]-Substance P (S-0145, Sigma Chemical Co., USA, 10µ¶/kg) was injected into the lingual artery before the electrical stimulation. A stable laser Doppler signal of 40 seconds before the stimulation and drug administration was defined as the control value. The maximum deviation of signal after the stimulation and administration was used as the experimental value. The data were subjected to paired t-test (p<0.05). Results: Electrical stimulation of tooth caused changes of pulpal blood flow by 19.3±5.4 (control) and 23.6±5.0 (sympathectomy) %. There was no significant. Sympathectomy caused significant delay of pulpal blood flow to return their control level (p<0.01). Intra-arterial administration of substance P antagonist during tooth stimulation resulted in significantly decreases of blood flow by 25.9±2.4% (p<0.01). Conclusion: The result of the present study showed that sympathetic nerve system and sensory nerve system including substance P are involved in the changes of pulpal blood flow caused by electrical tooth stimulation.