Effect of pulp inflammation on nerve impulse quality with or without anesthesia.

Absence of complete anesthesia in teeth with acutely inflamed pulp is a well-known clinical symptom, but the mechanism behind this symptom is poorly understood. In the current electrophysiologic study, afferent nerve fiber responses of the inflamed tooth with and without anesthesia were compared with normal teeth. Seventeen cats were used in this experimental study. After inducing inflammation in one canine tooth, the responses of afferent nerves from the inflamed and control contralateral canine tooth neurons were compared before and after application of anesthesia. In most cases, 2 distinct responses in both normal and inflamed sites were recorded. The conduction velocity was significantly lower in the nerve to the inflamed side compared with the control side. In contrast, the response intensity was significantly higher in the inflamed side compared with the control side. It was also found that it was markedly more difficult to inhibit impulse transmission by using anesthesia on the inflamed side, whereas there was no trouble inhibiting impulses on the control side.