Bisphosphonate-associated osteonecrosis (BRONJ) is an adverse event associated with bisphosphonate drug treatment. An 81-year-old female has been taking bisphosphonates orally once a month for three years complained of pain in the left mandibular molar area after implant placement. Tenderness and fistula were formed. Extensive osteosclerosis in posterior area of the left mandible and bone resorption around distal side of #37i were shown on radiographs. She was given oral antibiotics for 6 weeks and bone resorption was improved. A 70-year-old male had a history of intravenous injection of bisphosphonates for blood cancer complained of #46i implant mobility. There was buccal fistula on #45 site. Radiographically, severe bone resorption and extensive osteosclerosis were shown. He was treated with removal of implant and inflammatory tissue. Patients who have taken bisphosphonates may develop BRONJ after tooth extraction or implant placement and are needed to meticulous plaque control for preventing BRONJ.