Electromotive Forces and Electric Currents Caused by Metallic Dental Fillings

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Abstract
The sources of possible electromotive forces for pairs of metallic fillings are described. A survey of the literature since 1878 revealed that neither these e.m.f.''s nor their resulting currents had been measured, and that no measurements had been reported from which these e.m.f.''s and currents could have been calculated. Schemes for carrying out electrical measurements are described and the theories for the calculations are given. A condenser-ballistic galvanometer potential-difference meter, and later, a vacuum-tube electrometer were developed and used in the measurements. Results are reported on 213 pairs of fillings in the normal mouths of 137 subjects, and on 78 single fillings in the normal mouths of 66 subjects. The bone fluid is just as important as the saliva in causing electric currents. Methods for determining the net e.m.f.''s and resistances associated with metallic dental fillings are given. These resistances are concd. at the metal-saliva and metal-bone-fluid contacts. A method for determining the net electric current through a metallic filling under ordinary oral conditions is descr. The magnitude of the current through any filling is virtually independent of the number and kinds of other fillings in that oral cavity, provided that filling does not make contact with any other metallic filling. Good evidence exists that serious pathologic conditions in the oral cavity have been caused by metallic dental fillings. Hypersensitivity of the subject to the metallic ions supplied by the fillings may be an important factor. Relatively large electric currents will pass through metallic fillings if 2 such fillings are in contact, hence sucn contacts should be prevented.
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