Users beware; Fosamax may cause osteonecrosis or jaw bone death.

"Bisphosphonates work by inhibiting cells from breaking down old or damaged bone, a beneficial effect that inhibits bone loss. At the same time, the drugs can have a drawback. They can have a secondary effect of decreasing the formation of new bone tissue, Judge Keenan wrote in an opinion in July.

It is the drug’s potential for decreasing the formation of new bone tissue that may contribute to jawbone death, said Dr. Ruggiero, who was one of the first doctors to study and publish articles on the problem. Because of the trauma caused by chewing and teeth grinding, jawbone cells turnover more quickly than many other bones in the body, he said. Recognizing the high cell turnover, bisphosphonates may accumulate in the jawbone, and try to compensate by oversuppressing cell turnover, he said.

According to this theory, bisphosphonates might lead to jawbone death in patients who have dental surgery, like tooth extraction, from which the jaw needs to heal itself even more intensely, he said.

Dr. Ruggerio said he had a database of 70 patients who had developed dead jawbone tissue after taking oral bisphosphonates. “The number of cases that we are now seeing is unprecedented,” he said."