This prospective observational study evaluates how head and neck radiotherapy affects oral health over time. Patients with head and neck cancer undergoing standard radiotherapy are followed from before treatment through multiple post-treatment visits. Changes in periodontal health, dental status, salivary function, and patient-reported oral health quality of life are assessed. The study aims to better understand the long-term oral complications of radiotherapy and to support improved preventive and supportive dental care for cancer patients.