Biphosphonates are used in the treatment of bone metastases of some cancer forms, such as multiple myeloma, Paget disease, osteoporosis, fibrous displasia, etc. A significant consequence of the utilization of such drugs is osteonecrosis of the maxillary bones. The aim of the study was to evaluate the risk factors provoking osteonecrosis of the maxillary bones after the treatment with biphosphonates, in the patients who addressed the Clinics of Oral and Maxillo-Facial Surgery between 2006-2011. Materials and method: 33 patients suffering from this pathology were registered, their files including information on age, sex, social background, the disease for which the drug had been recommended and the prescribed dose, the manner of its administration and the duration, the cause of the maxillary lesion, the symptomatology demonstrated during the first consultation, additional examinations, treatment and evolution. Results: most cases of osteo-necrosis had been caused by dental extractions, especially at the mandible. The higher risk was faced by women who were administered the drug intravenously. Conclusions: Post-surgical evolution was favourably influenced when the surgery had in view the value of the carboxy-terminal group from the structure of serum colagen.