Therapy of radiation is chosen therapy for oral cancer especially Carcinoma Nasopharynx, however, often caused changes in normal tissue in the oral cavity. Based on the anamnese of the patient, they have dry mouth since the disturbance of the function of Parotid salivary gland has causing the saliva amount became lower. This condition can encourage the caries process. From all of the five cases occured after the radiation between one mouth until six year the time, extended damage is seen, demineralization with a small cavity and discoloring teeth color into brown.