Was it a bisphosphonate (e.g. Fossamax, Boniva, etc.)? I was on one of those for a while, and my dentist would not do any major work on me until I was off it for at least six months. He told me that osteonecrosis is rare, but is so awful he would not risk it.
It is like a bisphosphonate, it is called Denosumab. It works on a different principal and the risk of osteonecrosis is unknown (but does occur). What makes it worse is my treatment is for bone tumors in the jaw. I too can have nothing but cleanings until I am off the medication.