Bisphosphonate (BP) therapy has modified the natural history of many bone metabolic diseases. Amino-bisphosphonates nowadays represent the primary therapeutic choice for the treatment of osteoporosis and for prevention of fractures. Osteonecrosis of the mandible and maxilla (ONJ) is a rare disease usually occurring in cancer patients with bone metastases treated with high doses of intravenous BPs. Some cases have been described in patients taking amino-BPs for osteoporosis, but the specific drug utilized, its dosage and use of the oral route have reduced that risk considerably (estimated at 1/100,000 subjects a year). Prevention of ONJ include good oral hygiene habits in all patients and, in a subject who has been treated for more than three years, conservative dental procedures when possible, an appropriate antibiotic therapy and a careful follow-up when invasive oral interventions are necessary, are recommended by dentists and bone metabolism experts alike.