Introduction : Oral mucositis (OM) is a common side effect of radiotherapy (RT) or radio-chemotherapy (RT/CT) for head and neck cancers. It causes lesions leading to impairment the quality life, dysphagia, pain, in up 20% cases, dosimetry concession, decreasing local tumor control, thereby impacting survival rate. Positive results photobiomodulation (PBM) treat it have been reported literature....