Skeletal complications caused by osteoporosis or bone metastases are associated with considerable pain, increased mortality, and reduced quality of life. Furthermore, such events place a burden on health care resources. Agents that prevent bone resorption, such as bisphosphonates or denosumab, can reduce the risk of skeletal-related events and are widely used in patients with osteoporosis or bone metastases of cancer. Medication-related osteonecrosis of the jaw (MRONJ) is a rare, but potentially serious, adverse event associated with high cumulative doses of bisphosphonates or denosumab. However, MRONJ can be treated, and the likelihood of the development of this condition can be reduced through prophylactic dental care and the maintenance of good oral hygiene. Dentists, as part of a multiprofessional team, have a critical role in preventing MRONJ. This review describes the incidence and pathophysiology of MRONJ and provides guidance for dental practitioners with regard to the screening, prophylactic treatment, diagnosis, and management of patients with this condition. (Oral Surg Oral Med Oral Pathol Oral Radiol 2019;127:117À135) Medication-related osteonecrosis of the jaw (MRONJ) is an uncommon condition that can occur after exposure to agents used to prevent bone complications, such as bisphosphonates or denosumab, or treatment with other agents, such as angiogenesis inhibitors. 1 In the majority of cases, MRONJ manifests as exposed bone in the maxillofacial region (Figure 1), although non-exposed MRONJ has also been recognized (Figure 2). 2-5 Bisphosphonates and denosumab are predominantly used to reduce the risk of skeletal complications in patients with bone loss, resulting from long-term cancer treatment or osteoporosis, and in patients with malignant bone disease. 6-8 Bisphosphonates are small molecules that dock in hydroxyapatite-binding sites on bone surfaces. When osteoclasts begin to resorb bisphosphonate-impregnated bone, the liberated bisphosphonates bind to farnesyl pyrophosphate synthase inside the osteoclasts, ultimately leading to apoptosis. 8-10 Denosumab is a fully human monoclonal antibody, which has a different mode of action from that of bisphosphonates. It targets and binds to the receptor activator of nuclear factor k-B (RANK) ligand (RANKL); in doing so it prevents the activation of RANK on the surface of osteoclasts and osteoclast precursors. Inhibition of the RANKLÀRANK interaction impedes osteoclast formation, function, and survival, thereby decreasing bone resorption. 11 MRONJ is more prevalent among patients receiving high cumulative doses of bisphosphonates or denosumab than in patients who receive lower doses. 12,13 The first cases Statement of Clinical Relevance Medication-related osteonecrosis of the jaw is a rare, but potentially serious, complication of treatment with bisphosphonates and denosumab. It is important for dentists to be aware of ways to identify and treat patients at risk of this condition.