Bisphosphonates are widely used in the treatment of hypercalcemia associated with breast, prostate or lung cancer and the metastatic osteolytic lesions of multiple myeloma. One of the most significant side effects of bisphosphonates is the occurrence of osteonecrosis of the maxilla and the mandible. In this case report, we presented a 64 year-old male patient who was receiving bisphosphonates for bone metastasis of prostate cancer with a history of approximately six months ago left upper second molar extraction and a physical examination finding of oroantral fistula.