The mucous membrane (MM) of the oral cavity is of complex structure and possesses numerous significant functions. Lesions and inflammatory diseases of the oral mucous membrane (oral mucositis, OM) are a common reason for patient consultations. The underlying causes comprise infectious (bacterial, fungal, viral), allergic, reactive, as well as systemic and idiopathic factors. Traumatic stomatitis can be classified into: thermal, chemical and mechanical. In fact, iatrogenic injuries resulting from dental treatment constitute a particularly group. Oral mucositis is manifested by redness, edema, acute pain and burning, which significantly impairs food intake and hygiene procedures. Low-level laser therapy (LLLT) is applied for both oral cavity injuries and oral mucositits, due to its analgesic, anti-inflammatory, anti- edematous and biostimulative effects. Absorbed by the biological structure, laser radiation induces a number of processes which are either primary / early (up to a few minutes following the procedure), and secondary / delayed (a few / several days). Depending on the level at which the changes occur, they are classified into molecular, cellular and affecting the tissues. As indicated by numerous studies, LLLT is a non-invasive, low-cost, fast, widely available and effective form of treatment of oral mucosa inflammatory lesions and injuries.