Interstitial fluid pressure in normal and inflamed pulp

Tissue pressure is the hydrostatic pressure in the interstitial fluid which surrounds the pulpal cells. This pressure outside the vessels is normally considerably lower than the blood pressure inside the vessels, The dental p ulp has a relatively low interstitial compliance due to its enclosure betwe en rigid dentin walls. Accordingly, even a modest increase in pulpal fluid volume will raise the tissue pressure, which may compress blood vessels, le ading to ischemia and necrosis. inflammation may lead to an increase in bot h interstitial fluid volume and blood volume in the low-compliant pulp and thereby increase the tissue pressure. However, the increased tissue pressur e may, in turn, initiate increased lymph flow and absorption of fluid into capillaries in nearby non-inflamed tissue. Both of these latter factors wil l transport fluid out of the affected area and subsequently out of the toot h and consequently lower the tissue pressure. Increased tissue pressure, wh ether caused by increased blood volume or increased capillary filtration, w ill promote outward Flow of fluid through exposed dentin tubules and thereb y help to protect the pulp against entry of harmful substances. It seems ph ysiologically beneficial, therefore, for the pulp to have a high tissue pre ssure, which promptly increases when blood flow increases due to its low co mpliance.