Hemodynamic regulation of the dental pulp in a low compliance environment.

Pulpal hemodynamic regulation has been investigated in experimental animals using 133Xe washout, 15-microns radioisotope-labeled microsphere injection, and intravital microscope methods. Three distinct types of pulp blood flow reductions were observed. Type I was characterized by reduction in response to direct stimulation of the sympathetic nerve; intraarterial infusion of norepinephrine, 5-HT, or prostaglandin F2 alpha; and indirect stimulation of the sympathetic nerve. The Type II response, an initial increase in flow followed by a decrease, was observed with isoproterenol, prostaglandin E2, substance P, and bradykinin. This biphasic flow response is caused by the low compliance environment of the tooth and may play a role in pulp inflammatory processes. The Type III response follows administration of histamine and is characterized by a gradual decrease in pulpal blood flow.