Inhibition of compound action potentials following administration of dental self-etching primer/adhesives.

Self-etching dentin adhesive systems, a new generation of dental-bonding agents, were investigated for their ability to block nerve conductance in the rat sciatic nerve model. Clearfil SE Bond, Mac Bond and FL Bond were used as test materials. Isolated rat sciatic nerves obtained from female albino rats were placed between two electrodes in a bath containing Tyrode solution. The bonding agents were brought into contact with the nerves and the evoked compound action potentials were recorded versus time before and after contact with the materials. Statistical analysis was performed using the Friedman and Wilcoxon Signed-Ranks tests (P = 0.01) to compare the mean percentage of inhibition between test materials versus time. All test materials were able to block nerve transmission rapidly (3.3 +/- 0.5, 5.1 +/- 2.3 and 8.0 +/- 1.9 min for SE Bond, Mac Bond and FL Bond, respectively). Significant differences were found between FL Bond and SE and Mac Bond (P < 0.01). These results indicated that the bonded systems tested, intended primarily as dentinal tubule occluders, may also exert some direct desensitizing effect on intratubular or pulpal nerve terminals in extremely deep cavities or pulpal microexposures, contributing to decreased postoperative pain.

Influence of a self-etching primer on compound nerve action potentials.

The aim of this study was to evaluate the effect of self-etching primers on nerve conductance. A self-etching primer (One Up Bond F) which combines etching and bonding in one step, and a fifth-generation bonding agent (Prime&Bond NT ) were tested. Isolated rat sciatic nerves were placed between two platinum electrodes in a bath containing Tyrode solution. The bonding agents were brought into contact with the nerves and the evoked compound action potentials (CAP) were recorded before and after contact with the materials. One Up Bond F caused total inhibition of the CAP within an average time of 7 min. All CAPs in this group were blocked irreversibly. As with Prime&Bond NT, the reduction in CAP was 45.9% after an application time of 15 min, after which readings were terminated. Recovery of the CAP in this group were maintained after rinsing with fresh tyrode solution. One Up Bond F elicited faster blocking of nerve conductance under the conditions of this model. In the context of dentin desensitization with bonding agents, the self-etching primer may be more effective, clinically.

Effects of current and potential dental etchants on nerve compound action potentials.

In this study, a 35% phosphoric acid gel (3M Scotchbond etchant), a nonrinse etchant (NRC), and two EDTA-containing conditioners (RC-Prep and File-Eze) were tested in vitro for blocking nerve conductance evoked in the rat sciatic nerve after local application. The phosphoric acid gel and NRC completely and irreversibly inhibited conductance. On the other hand, RC-Prep reduced the compound action potentials (cAPs) by 50% in 120 min. With File-Eze, the reduction in cAPs was less than 50% after an application time of 160 min (61.8 +/- 1.8%). At 160 min the cAPs in the RC-Prep group had been inhibited by 62.4%. These results indicated strong neurotoxic effects of phosphoric acid and NRC when applied directly on exposed pulp in the total etch procedure.