**Abstract**

Osteonecrosis as term represents the death of bone tissue in the body and causes of necrosis can be different. Medication-related osteonecrosis of the jaws (MRONJ) is nowadays known as an inability of the alveolar bone to respond to a local trauma and it can result in severe local and systemic complications. In the etiology of medication-related osteonecrosis there are antiangiogenic and antiresorptive agents which have great effect on alveolar bone, producing an imbalance between resorption (osteoclastic activity) and deposition (osteoblastic activity). The exact mechanisms of development are not todays completely resolved. It is thought that it is a result from combination of medication interactions, microbiological contamination of the area and local tissue trauma. Typical signs and symptoms are painful mucosal lesions, swelling, exposed necrotic bone in the jaws, discomfort and dysesthesias. There is currently no gold standard or clearly defined treatment protocol for the disease itself. Process of treatment is demanding and main goal is to eliminate pain, control infection of soft and hard tissue and minimize progression of osteonecrosis. Besides the conventional surgical treatment, photodynamic therapy can be a viable supportive tool of initial and advanced stages of osteonecrosis and may contribute to improvements of patient′s quality of life.

**Keywords:** osteonecrosis, osteoclasts, bone, surgical procedure, photodynamic therapy
