The invention provides a device for detecting non-cavitated caries lesions, including a measuring electrode having an electrically conductive tip. The tip is dimensionally configured to fit within a fissure and provide electrical contact with a patient's tooth. A reference electrode is also included, the reference electrode being configured for electrical contact with the patient's body. A measuring means is also provided for determining electrical conductance between the measuring electrode and the reference electrode, wherein the device is further configured to receive a current source for providing electrical current between the measuring electrode and the reference electrode.