Osteoclast mediated absorption of bone is responsible for skeletal morbidity associated cancer. Bisphosphonates target the osteoclast and reduce skeletal events. Osteonecrosis of the jaw is an uncommon but serious adverse effects of bisphosphonate therapy.
Bisphosphonate associated osteonecrosis is defined as an area of exposed bone that does not heal for 8 weeks in a patient who has received bisphosphonates, does not have local malignancy and has not received craniofacial radiation. The patients present with jaw pain and examination reveals exposed bone. The mandible is more often involved than the maxilla.
ONJ is more common with intravenous bisphosphonates (1-4%), more frequent therapy and prolonged therapy. Many patients have a history of a dental procedure before osteonecrosis. It is very rare with oral bisphosphonates. The mechanism of osteonecrosis is not understood.
ONJ is treated by conservative measures including antibiotics and antibacterial mouth rinses. Superficial debridement may be of help in selective cases. There are concerns that surgical intervention may worsen the symptoms. Patients on bisphosphonated who need to undergo a dental procedure are usually advised to discontinue bisphosphonates 3 months before the procedure. This recommendation is based on experience rather than and scientific evidence. Denosumab, another anti-osteoclast agent has also been associated with ONJ.