Laser group composes of thirty patients who will receive low level 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

control group composes of thirty patients will be treated with 15mL of a 2% citric acid solution applied as a mouth rinse for 30 sec

Laser will be performed with a GaAlAs diode laser at a wavelength of 808 nm, 100-mW output power, laser beam area of 0.03 cm2, and in continuous wave mode, three times a week, on alternate days. Laser therapy will be initiated before the first radiotherapy session and ended after the last session, totaling 21 sessions.

The total energy per session (56 J) will be divided into 14 irradiation points, as marked on the overlying skin (Fig.2). Each irradiation point received a dose of 4 J over an irradiation time of 40 s.

With exclusion of tumor area or area of removed tumor laser will be applied as following:

• Extra oral application: The laser will be used extraorally at eight points in the parotid glands (bilaterally, four points in each gland), at four points in the submandibular glands (bilaterally, two points in each gland

• Intraoral application: The will be used intraorally at two points in the sublingual glands bilaterally, one point in each gland .

For the assessment of salivary flow rate, unstimulated and stimulated sialometry tests will be performed before the first radiotherapy session and after completion of laser programe.

As salivary secretion fluctuates between minimal and maximal rates during the day, it is important to assess the salivary secretion consistently at an established time of the day, in order to properly examine the evolution of the condition and its treatment in every patient.

The normal flow rate for unstimulated, "resting" whole saliva is 0.3 to 0.5 ml/min.; for stimulated saliva, 1 to 2 ml/min. Values less than 0.1 ml/min. are typically considered xerostomic, although reduced flow may not always be associated with complaints of dryness

The samples of unstimulated whole saliva will be frozen and stored at -20°C until used for sIgA determination. sIgA concentrations were measured by using commercially available indirect competitive enzyme immunoassay kit (Salivary SIgA EIA kit, Salimetrics).

The quantities of salivary IgA secreted in 5 minutes will be calculated by taking in account sIgA concentrations and volumes of unstimulated saliva secreted in 5 minutes.

The XI is an 11-item summated rating scale that was developed to measure the severity of dry mouth symptoms. The final score ranges from 5 to 55, with higher scores indicating more severe symptoms. A decrease in XI scores of 6 points or more between pre- and post-treatment assessments will be considered clinically significant.

The mean dry mouth score and the correlation between dry mouth score and salivary flow rate will be analysed.