An apparatus for the detection of dental caries on the surface of a remaining tooth present underneath a crown are provided. Such an inventive concept involves the utilization of a proper electrically conductive pathway from the crown exterior to the tooth itself, allowing for impedance measurements to be undertaken to determine the degree of potential demineralization within the tooth and/or adhesive loss at the tooth/crown interface, all due to decay attributable to dental caries or like problems. A measuring electrode may be applied to a specific point on the target crown as well as on the adjacent gum, to measure impedance levels for any appreciable decreases which would indicate underlying tooth decay has been initiated. From that point, the dental professional may undertake proper therapeutic measures to treat such tooth locations in order to avoid far more expensive repairs, such as the implementation of bridges or implants.