The aim of this longitudinal study is to present data from 76 female patients treated with bisphosphonates (BPs) for postmenopausal osteoporosis and referred to the Unit of Oral Diagnosis and Day Surgery of the University of Milano for diagnosis and treatment. All patients received a thorough oral examination. The diagnosis of osteonecrosis of the jaw bone (ONJ) was made from radiographic and clinical findings. 9% of individuals had BRONJ at first visit. Patients with dental or periodontal abscess were significantly more likely to develop BRONJ (OR: 2.9, 95% CI 0.5–15.9). Patients with osteoporosis receiving BPs may develop BRONJ, especially in the presence of an active infectious process in the mouth. Clinicians should carefully follow up on individuals receiving bisphosphonates therapy to avoid the occurrence of osteonecrotic lesions.