Changes in pulpal blood flow and in fluid flow through dentine produced by autonomic and sensory nerve stimulation in the cat.

We have recorded the flow of fluid through exposed dentine in cat canines. The effects on this flow of electrical stimulation of the cervical sympathetic trunk (CST) and of the inferior alveolar nerve (IAN) were investigated. In some preparations, pulpal blood flow was also monitored with a laser Doppler flow meter and the compound action potentials evoked by IAN stimulation were recorded from the tooth. CST stimulation (0.5-5/s) resulted in a significant decrease in the rate of outward flow of fluid through the dentine or, with the higher frequencies tested, a reversal of the flow. CST stimulation also produced vasoconstriction. IAN stimulation caused a significant increase in the rate of outward flow of fluid from the dentine. This effect required the recruitment of A delta fibres: A beta fibres alone had no effect. Pulpal vasodilatation occurred with the same threshold. Mechanical stimulation of dentine in an acutely denervated tooth also caused vasodilatation, indicating that pulpal afferents were involved. The results show that the rate of fluid flow through dentine, and hence the rate of inward diffusion of chemicals from the oral cavity, can be influenced by changes in the state of the pulpal microvasculature.