Response of erupting human second premolars to blood flow changes.

The effect of infiltration of a vasodilator and a vasoconstrictor [2% lidocaine (lignocaine) without or with 1:100,000 adrenaline (epinephrine)] above the root apex of human second premolars in the prefunctional stage of post-emergent eruption was evaluated for 11 teeth in eight children. On two consecutive days, 30 min of high-resolution data on changes in tooth position were collected for each participant during each of four sessions, two in the afternoon and two in the evening, using an optical instrument based on Moiré magnification with 0.05 microm resolution. The immediate reaction to the 1.8 ml injection was extrusion of the tooth, which lasted 2-4 min. After that, in the majority of teeth receiving a vasodilator, the reaction was an increased rate of eruption. In teeth receiving a vasoconstrictor, a decrease in eruption or intrusion was noted after the initial extrusion. The low-frequency Trentini cycles characteristic of erupting teeth were immediately obliterated in all teeth receiving injections. In the next few minutes, the cycles reappeared in teeth receiving the vasodilator, but did not reappear or reappeared only partially in teeth receiving the vasoconstrictor. It appears that vascular changes can influence the rate of prefunctional post-emergent eruption.