Abstract: A device for secondary caries detection characterized in that it contains a current generating block in its casing (6), advantageously equipped with the high linearity amplifiers, the current having the form of sinusoidally varying signal, advantageously with one frequency chosen from the range of frequencies from 200 Hz to 100 kHz and amplitude from 50 mV to 5 V; a block of preamplifiers (4), advantageously of high sensitivity and linearity with phase-sensitive detectors measuring components, advantageously with one frequency chosen from the range of frequencies from 200 Hz to 100 kHz as well as its multiples, advantageously integral in principle; microprocessor control unit (5), advantageously with a miniature keyboard and display unit, and at least one fixed electrode (2) placed on mucous membrane of the oral cavity and at least one moveable electrode to be mounted on a tooth (1).