The aims of the research was to determine the potassium content in a number of materials used in dentistry e.g. (permanent and temporary fillings, work crews editions materials and materials for bridges and crowns ) by using UCS-20 system computerize with scintillation detector sodium iodide activated with thallium NaI (Tl). To calculate its content from radioactive, as was the detector efficiency calculation taking into account the geometric arrangement using 100 g of potassium chloride as standard sample, and estimated the value of efficiency 0.42% .Experimental results show that the maximum value of the radioactivity of radiation potassium was in sample no.(4) is 523.98 Bq and the minimum value was 217.95 Bq in sample (6).The concentration of radioactive potassium ranged between 2.095 mg and 0.843 mg where the highest and the lowest values were found in sample 4 and 6 respectively. The equilibrium factor between the radioactivity and the sample content of potassium in all samples was 0.029Bq / mg. The effective equivalent dose was calculated and its average value in all samples was 0.017µSv/y from these result we can tell that the effective equivalent dose value is within the average annuli dose for radioactive potassium K40 as it decided from the national commotion of radiation protection.