Tooth Pulp Circulation:  Answers to Practice Questions

1. In a sentence or two, describe the influence of each of the following on tooth pulp blood flow:

A. pulp temperature

As pulp temperature increases, blood flow increases.  However, when pulp temperature reaches about 50C, blood flow decreases and eventually ceases (stasis).

B. activation of the sympathetic nervous system

Activation of the sympathetic fibers innervating the pulp causes arteriolar constriction, thus reducing blood flow.

C. activation of the parasympathetic nervous system

No effect, as the pulp is not innervated by parasympathetic fibers.

D. inflammation (pulpitis)

Initially, the mediators released as part of the inflammation process cause arteriolar dilation, leading to increased blood flow.  However, the increased intrapulpal pressure may cause compression of venules and veins, leading to increased vascular resistance and decreased blood flow.

2. Briefly summarize the reasoning which leads to the conclusion that tooth vascular postcapillary (venule and vein) resistance to blood flow is higher than postcapillary resistance in "typical" vascular beds.

Measured pulp chamber hydrostatic pressure is higher (15-25 mmHg) than tissue pressure in "typical" vascular beds (0 mmHg).  This implies a higher than normal tooth intracapillary pressure in order to balance the osmotic pressure difference between blood plasma and pulp tissue fluid.  Intracapillary hydrostatic pressure is determined by the relative values of precapillary (artery and arteriole) resistance to blood flow and postcapillary (venule and vein) resistance.  The high intracapillary hydrostatic pressure means that postcapillary resistance  must be higher relative to precapillary resistance than in "typical" vascular beds.

3. What is tooth pulp "self strangulation"?

"Self strangulation" is the situation in which high pulp tissue hydrostatic pressure causes collapse of pulpal venules and veins, which leads to even higher pulp capillary and pulp tissue hydrostatic pressures, which causes a greater collapse of postcapillary blood vessels and continually increasing postcapillary resistance, until blood flow decreases to the level where pulp tissue is damaged due to lack of blood flow (ischemic necrosis).