JACKSONVILLE, FLORIDA. Dr. William Cheshire, a physician at the Mayo Clinic, reports on a case where a woman's trigeminal neuralgia (tic douloureux) was traced to a galvanic reaction between an amalgam filling and an adjacent gold-alloy crown. Consumption of tomatoes and other acidic foods produced intense jolts described as being like those of an "electrical battery". The jolts in turn resulted in excruciating pain in the trigeminal nerve. Replacing the amalgam filling with a composite resolved the problem. Dr. Cheshire points out that dissimilar metals in contact with saliva can form a galvanic cell which can generate electrical currents with several hundred millivolts of potential. He points out that many patients with trigeminal neuralgia describe their pain in terms of "electrical" jolts and concludes that his patient's neuralgia may well have been triggered by the galvanic reaction between the amalgam filling and the gold crown.
Cheshire, William P., Jr. The shocking tooth about trigeminal neuralgia. New England Journal of Medicine, Vol. 342, June 29, 2000, p. 2003 (correspondence)