Neurotoxic effect of two root canal sealers with calcium hydroxide on rat phrenic nerve in vitro.

Root canal sealers placed into contact with the inferior alveolar nerve can cause paraesthesia in the area innervated by this nerve. The paraesthesia is due to neurotoxic effects of the sealers. In this study we examined the effect on nerve conduction in vitro of two calcium hydroxide-containing root canal sealers, Sealapex and CRCS. An isolated rat phrenic nerve was placed between two suction electrodes in a bath containing Tyrode solution. The sealers were brought into contact with the nerve, and the evoked compound action potentials (cAP) were recorded before and after contact with the materials. Both Sealapex and CRCS induced a fast and complete inhibition of the cAP in this model. The degree of reversibility of the inhibition varied from experiment to experiment. Both materials exhibited reversible and irreversible block of the nerve conduction after 90s and 5 min exposure. However, after 30 min of contact, the conduction of the cAP was irreversibly blocked for both materials.