**9. Classification of MRONJ**

The disease, according to the clinical picture and the appearance of symptoms of osteonecrosis, is classified into four stages [3].

#### **9.1 Stage 0**

This stage of disease includes patients who have not clinically developed osteonecrosis but have nonspecific symptoms or radiological signs that may be associated with therapy. Symptoms associated with stage zero are: unexplained odontalgia, dull pain of lower jaw extending toward the temporomandibular joint, sinus pain that may be associated with inflammation and narrowing of the bone wall toward the sinus [3]. Clinical findings that may indicate stage zero are: unexplained tooth loss unrelated to chronic periodontal disease, periapical/periodontal fistula unrelated to pulp necrosis or caries, unexplained gingival swelling. Radiological signs are: loss of alveolar bone or resorption not related to chronic periodontitis, changes in the composition of the trabeculae, difficult (delayed) wound healing after tooth extraction, sclerosing regions of the alveolar part (thickening of the lamina dura, or reduction of the space belonging to the periodontal ligament) or surrounding part of the bone [66–68].

Zero-stage therapy is symptomatic and conservative, aimed at remediation of predisposing conditions that can cause osteonecrosis (remediation of caries, periodontal diseases, other pathological conditions, inadequate dentures). It is also necessary to exclude other diseases such as fibroseal lesions, chronic sclerosing osteomyelitis and others.

Patients need to be educated about the disease, about adequate oral hygiene and encouraged to have more frequent check-ups (at least every two months).

#### **9.2 Stage 1**

Stage one of the disease describes clinically exposed necrotic bone or the appearance of a fistula that forms from the bone, however patients have no symptoms and no signs of acute infection. The time required for proper diagnosis of the first stage of disease is eight weeks from appearance of exposed bone or fistula [3].

First-stage therapy is primarily aimed at monitoring the lesion. If necrotic bone sequesters or sharp bone margins occur, they should be removed. Monitoring the condition of the surrounding mucosa is extremely important for further prognosis of the disease.

It is also necessary to educate and motivate patients for frequent checkups.

#### **9.3 Stage 2**

Stage two describes clinically exposed necrotic bone or the appearance of a fistula that forms from bone with signs of acute infection accompanied by pain [3].

Stage two therapy is initially aimed at repairing the inflammation and antibiotic therapy is often attributed to it in combination with antimicrobial washes (most commonly chlorhexidine). Necrotic bone is often contaminated with bacteria to form biofilms that may be resistant to antibiotic therapy. After repairing the inflammation, it is necessary to remove the necrotic part of the bone and the inflamed mucosa.

#### **9.4 Stage 3**

Stage three describes clinically exposed necrotic bone or the appearance of a fistula that forms from bone with signs of acute infection accompanied by pain and at least one of these signs: spreading necrosis outside the dental alveolus (lower edge and ascending part of mandible, maxillary sinus, toward the cheekbone), the appearance of extraoral fistula, osteolysis of the lower border of the lower jaw and

#### *Application of Photodynamic Therapy in the Treatment of Osteonecrosis of the Jaw DOI: http://dx.doi.org/10.5772/intechopen.94257*

the bottom of the maxillary sinus with the appearance of oroantral communication and the appearance of pathological fractures [3].

Third-stage therapy focuses on palliative therapy that includes debridement or resection of the lesion in combination with antibiotic therapy to eliminate acute infection and pain. Therapy directly depends on the health condition of the patient. If larger resections are performed, reconstruction is performed by different reconstructive methods (fibula graft) with or without obturator.
