In this part of the study, the materials and methods will be presented under the following headings: subjects, equipment, procedures of the study and the statistical procedures.~Subjects:~Sixty patients who have head and neck cancer (oral cavity, pharynx, larynx, or occult primary tumor) submitted to conventional 3D radiotherapy, with irradiation fields necessarily encompassing all major salivary glands. The total dose ranged from 66 to 70 Gy, given in fractions of 2 Gy/day selected randomly from Nuclear medicine department, Oncology institute, Mansoura University.~These patients will be divided randomly into two groups of equal number, thirty patients for each group.~Group A: (Laser group) This group of patients composes of thirty patients who will receive GaAlAs laser three times a week, on alternate day (48h interval) Laser therapy will be initiated before the first radiotherapy session and ended after the last session, totaling 21 sessions (Fernanda A. S.G. et al., 2016).~Group B :( Control group) This group of patients composes of thirty patients will be treated with 15mL of a 2% citric acid solution applied as a mouth rinse for 30 sec (Bozana Loncar, D.M.D. et al., 2010) .~The criteria of Patients selection :~Equipment used:~1-Therapeutic equipment: Laser therapy will be performed with an GaAlAs laser~2- Evaluation tools:~Unstimulated and stimulated saivery flow rate.~Salivery immunoglobin A (sIgA) concentration in unstimulated saliva~The 11-item modified Xerostomia Inventory-Dutch questionnaire version 22.
The purpose of the study is to evaluate the effectiveness of low level laser on radiotherapy induced xerostomia to improve oral function and decrease oral complication due to hyposalivation and thus enhancing survival.