First Generation Apex Locators

These are the Resistance-based devices. The first-generation (resistance) locators detected the point where the file displaces from within the canal to the periodontal ligament. These merely used direct current and the known constant resistance as a basis for working length determination. Their major drawback was the need for the canal to be thoroughly debrided and dry. Devices in the first generation

include: the Root Canal meter, the Dentometer, the Endo Radar.