OBJECTIVETo improve tooth pulp electrical stimulation rat model to study analgesic effect of drugs.

METHODSExpose lower mandible and incisor and isolate them with rubber dam, two holes with distance 1.5 mm were drilled below the cemento-enamel junction by a thin diamond bur in 22 adult male rats anesthetized with sodium pentobarbital. A pair of insulated stainless stimulating electrodes were inserted through the holes and knotted to fix them. Drilled holes were filled with zinc polycarboxylate cement. Finally, the stimulating electrodes were directed to the top of the skull. Pain threshold of rats was determined by an electrical stimulator under awake, free conditions to evaluate the stability of the model and the analgesic effect of drugs.

RESULTSA valid tooth pulp pain model were set up successfully in 22 rats. Rats regain consciousness at 1 to 2 hours after operation. The inserted electrodes keep efficiency for 6 weeks. Neither tissue morphology change nor inflammation cell infiltration can be found in tooth pulp after 6 weeks under the light microscope. Threshold voltages remained constant under the repeat electric stimulations within 300 min (P > 0.05, CV < 15%) until 4 weeks (P > 0.05, CV < 15%). The dose-dependent and time-dependent analgesic effects of capsaicin were showed in this model.

CONCLUSIONThe improved tooth pulp electrical stimulation rat model is easily performed and shows constant electrical stimulation-induced pain threshold and is suitable for research on analgesic effect of drugs.