Figure 1: Cone beam computed tomography initial: bilateral osteonecrosis of the mandible with bone cortical perforation

Figure 2: Cone beam computed tomography to one year: improvement of the osteonecrosis

Local Factors
Systemical Factors
Tooth extraction
Metastatic cancer (breast, lung, prostate, rein and myeloma)
Dent alveolar surgery
Radiotherapy
Periodontal disease
Chemotherapy
Trauma
Chronic steroid treatment
Smoking
Anemia
Diabetes
Hypertension
Hypothyroidism
Hyperparathyroidism
Renal failure
Table 1: Etiological factors of ONJ
Stage 1
Exposed necrotic bone with no infection and otherwise asymptomatic
Stage 2
Exposed necrotic bone with evidence of infection with or without purulent discharge
Stage 3
Exposed necrotic bone with infection and extension radiographically to the inferior border of the mandible or sinus floor in the maxilla or presence of an extra oral fistula or pathologic fracture
Table 2: ONJ’s staging (Ruggiero)
Stage 1
Exposed bone with no infection and otherwise asymptomatic
Stage 2a
Exposed necrotic bone, symptomatic, with evidence of soft tissues infection, that it controls with conservative treatment and  does not progressing
Stage 2b
As a 2a, but that is not controlled by conservative treatment or progressing
Stage 3
As in the classification by Ruggiero
Table 3: ONJ’s staging (Bagan)