Surgery-triggered and non surgery-triggered Bisphosphonate-related Osteonecrosis of the Jaws (BRONJ): A retrospective analysis of 567 cases in an Italian multicenter study.

Invasive local procedures are often reported in clinical history of patients suffering from Bisphosphonates-Related Osteonecrosis of the Jaws (BRONJ) but over 40% of spontaneous forms have been also described in literature. We compared age, gender, underlying bone disorders, bisphosphonate therapy, clinical features and surgical outcome of 205 cases (36.2%) of BRONJ non surgery-triggered (group 1) with 362 (63.8%) cases of surgery-triggered forms (group 2). Differences between group 1 and 2 were analysed using Mann-Whitney U and χ(2) tests. Statistical analysis was performed using STATA 8. Zoledronate was the most used type of bisphosphonate (63.4% versus 69.0%) and the mandible was the most frequently involved site (63.9% versus 63.4%) in both groups. BRONJ in group 1 was more frequently multicentric (9.3% versus 5%, p<0.05), had a lower clinical stage (45.9% versus 13.8% in stage 1, p<0.01) and had a better outcome after surgical therapy (improvement in 74.1% versus 58.6%, p