All patients will be trained to brush their teeth with a tooth paste containing 1100 ppm of fluoride twice a day. After 4 weeks of irradiation (T2) the patients will be examined for white spot lesions formation by clinical examination using Geiger index, photographic examination using AutoCAD 2009 evaluating formation and area percentage of white spot lesions, and the degree of demineralization will be assessed with DIAGNOdent. The all exams will also be done after 12 weeks of irradiation (T3).