Table 1. American Association of Oral and Maxillofacial Surgeons staging system.

At-risk category	Asymptomatic stage without necrotic bone
Stage 0	No exposure bone, but clinical and radiological nonspecific findings and symptoms
Stage 1	In asymptomatic patients with no signs of infection, presence of exposed and necrotic bone
Stage 2	Symptomatic stage, radiological findings, exposed, necrotic bone, fistula and infection are localized in the alveolar bone region
Stage 3	The exposure may range from necrotic bone, fistula and infection, symptomatic stage, necrotic bone from the alveolar bone to the lower border of the mandible, to the ramus or to the maxillary sinus, to the zygomatic bone. There may be pathological fractures, extra-oral fistula, oral-antral or oral-nazal relationship and osteolytic area extending to the lower border of the mandible or sinus base.

Data from the article of Ruggiero et al. (J Oral Maxillofac Surg 2014;72:1938-56)2.