Taking bisphosphonates long-term can cause death of bone tissue in the jaw.
It's rare, but true. Jaw osteonecrosis has been reported most commonly with the use of intravenous bisphosphonates (Aredia, Zometa) in cancer patients. But it has also been reported with the use of Fosamax and Actonel.
Osteonecrosis, also called avascular necrosis, is the death of bone resulting in the collapse of the bone's structural architecture.
Bisphosphonates work by preventing the resorption of old bone. This leads to a reduction in bone turnover that may be more critical in the jaw.