Background and objetives : Bisphosphonates are antiresorptive drug fully accepted for the treatment of metastatic bone disease, osteoporosis and other bone diseases. In 2003, Marx published 36 patients with exposed bone of the jaws induced by bisphosphonates. Although Bisphosphonate-related Osteonecrosis of he Jaws’s (BONJ) diagnostic criteria proposed by the American Association of Oral and Maxillofacial Surgeons (AAOMS) excludes the use of imaging studies, is plenty accepted that imaging tests play a key role not only for the diagnosis itself, but also to define the extention of the affected bone.

Methods : An observational case-control study was designed including patients diagnosed and treated by BONJ in the University Central Hospitall during 96 months. All cases showed the diagnostic criteria of the AAOMS. Control subjects included were healthy people who had never received bisphosphonates and belonged to the same geographic area and hospital than cases.

Results : Seventy cases were identified, but only 32 cases included studies with Computed Tomography (CT). By gender, 10 patients were men and 22 women, with a mean age of 69.2 years. In 20 patients (62.5%) intravenously zoledronic acid was administred. The average time of bisphosphonate administration was 17.9 months. Mandibulatr involvement was found in 19 patients and stage II was the most common degree of the disease (18 cases). Schneiderian membrane thickening was objectified in 20 maxillary sinuses of 18 patients (56.3%) by CT and thirteen of these patients (40.6%) presented the Schneiderian membrane thickening without underlying bone exposure. In control subjects, Schneiderian membrane thickening of the mucosa was recognizable only 6 different subjects (18.8%).

Conclusions : In our study, the thickening of the Schneiderian membrane is significantly more frequent in cases. The presence of this sign may be an early sign of involvement of BONJ and should be taken into consideration in further studies.

Key words: bisphosphonate; osteonecrosis; Scheiderian membrane