The aim of this study was to develop a Method to determine, under clinical conditions, the diagnostic Dental X-ray equipment emitted spectra, by employing a high-resolution Schottky CdTe detector, in order to accurately determine the actually applied kilovoltage on the Tube. The analysis of X-ray spectra is important for quality assurance (QA) and quality control (QC) of Radiographic systems, and according to the European Guidelines on Radiation Protection in dental Radiology, 65–70 kV is recommended as the kilovoltage of choice for dental (intraoral) X-ray sets using AC equipment, and 60 kV for those using DC X ray sets. Since kilovoltage in this equipment is usually, either fixed, or minimally variable, the spectrometric determination of the employed High-Voltage is the most accurate method. The Molybdenum 17.5 keV and 19.6 keV characteristic spectral lines from a Mammography System and the Isotope 241Am 59.5 keV line have been employed for the Energy Calibration of the system. Dental X-ray equipment of various types and manufacturers has been tested with the developed method.