The primary function of the pulp microcirculation, in
common with all circulation in the body, is to supply
oxygen and nutrients to its constituent cells, as well as
providing an exit route for metabolic waste products
from the tissue. Blood is brought to the tissue through
pulp arterioles. Oxygen, nutrients and wastes are
exchanged in capillaries by diffusion, and waste
products are removed by pulp venules. In general,
blood flow to any organ must be high enough to ensure
sufficient oxygen and nutrient supply. On the other
hand, an excessively high blood flow level is undesirable
as it leads to a waste of energy. Hence, it is plausible
that the main purpose of the relatively high blood flow
in the pulp is to serve the pulp cells, perhaps the
odontoblasts in particular, with important nutrients in
an adequately high concentration in the capillary bed.
The pulp microcirculation also acts to maintain an
intraluminal pressure within the pulp vasculature in
harmony with the pulp tissue pressure. Studies using
servo-nulling techniques have demonstrated that the
dental pulp has a relatively high tissue pressure but it is
considerably lower than the blood pressure inside the
vessels.
Bulk flow of fluid occurs across the capillary
walls for distribution of the extracellular fluid. Positive
net capillary filtration pressure leads to bulk flow of
fluid out of the capillary into the extraluminal tissue
space, which in turn is balanced by an equal lymphatic
return.
Thus, the tissue fluid volume in the pulp
remains constant. The relatively high pulp tissue
pressure results in an outward flow of fluid in the
dentinal tubules, which helps to dilute toxins and wash
out bacteria.