Charges extracted from dental ceramics: an indication of piezoelectric activity?

A method was established for demonstrating charge generation on the surfaces of dental materials by means of mechanical loading with different forces. With this experimental set-up charges could be extracted both from the surfaces that were mechanically loaded and from the surfaces perpendicular to the applied force. When specimens of certain ceramics were subjected to mechanical loading and the charges extracted were related to the applied force, charges of up to 3 x 10(-3) pC/N were recorded from the surfaces perpendicular to the applied force and charges of up to 8 x 10(-3) pC/N from the surfaces that were mechanically loaded. The results from this study indicate support for the hypothesis that the extracted charges were created by direct piezoelectricity. However, further studies are necessary for decisive proof that true piezoelectricity occurs in these materials.