The Soladey-J3X [toothbrush] has a solar panel at its base that transmits electrons to the top of the toothbrush through a lead wire. The electrons react with acid in the mouth, creating a chemical reaction that breaks down plaque and kills bacteria. The toothbrush requires no toothpaste, and can operate with about the same amount of light as needed by a solar-powered calculator.
(PhysOrg.com)