The relation between tooth pulp pressure and systemic arterial pressure

The relationship between systemic arterial pressure and fluid pressure in the tooth pulp of dog canines was examined. Tooth pressure was measured by sealing a small tube into a tap made through the enamel and dentine; arterial pressure was monitored via a chronic catheter in the internal thoracic artery. Blood pressure was altered by norepinephrine infusion or by amyl nitrate inhalation. Tooth pressure was found to be pulsatile and in exact phase with, of similar shape to, but of smaller magnitude than, the systemic arterial pulse. When arterial pressure was altered, tooth pressure changed similarly but to a lesser extent. Over one or a few episodes of norepinephrine injection, mean tooth pressure (PT) was related to mean arterial pressure (PA) by the linear equation PT = m(PA) + Po, with a scatter whose standard deviation averaged 7 mm Hg; the slope m averaged 0·39. The correlation throughout the entire experiment appeared to be similar but was partially obscured by greater scatter. It was concluded that the linear relation was due to the direct hydraulic effect of arterial pressure on tooth pressure, and that the scatter indicated other mechanisms were also important in determining tooth fluid pressure. Based on a haemodynamic model of the tooth circulation, the value of m found here implies that the hydraulic resistance to venous outflow is relatively greater in the tooth pulp than is typical of other tissues.