Tissue pressure and blood flow in pulpal inflammation.

The initial vascular reactions during inflammation are vasodilation and increased vessel permeability. Both these basic reactions cause increased pulpal fluid volume. In the dental pulp the inflammatory vascular reactions take place in a rigid enclosed dentin chamber, which to some extent makes the pulp vulnerable. Due to this lack of distensibility any gain in pulpal volume will necessarily increase the pulpal tissue pressure. If the tissue pressure rises to the same level as the blood pressure it will compress the pulpal vessels, thus counteracting a beneficial blood flow increase during inflammation. Using the micropuncture technique and laser Doppler flowmetry we have performed simultaneous measurements of tissue pressure and blood flow in the cat dental pulp during neurogenic inflammation. Sensory nerve stimulation caused a rise both in blood flow and tissue pressure. Our findings thus strongly suggest that the increased pulpal tissue pressure promote fluid absorption back into the blood. If, in theory, plasma proteins and other macromolecules had leaked out during sensory nerve stimulation they must have been successfully removed by lymphatics, unless the tissue pressure would have risen to the same level as the capillary blood pressure causing a fall in PBF. This was not found. On the contrary, increased blood flow was measured, even in experiments lasting for more than 8 hours. It is therefore concluded that the pulp may have a beneficial blood flow increase during inflammation in spite of simultaneously increased tissue pressure.