Objectives: The aim of this study was to investigate if the trabecular pattern in intraoral radiographs, assessed by five observers, could serve as an indicator of osteoporosis. Methods: Six hundred and seventy one women (45 - 70 yrs) from four European centers were included in the study and examined with intraoral radiographs in the right upper and lower premolar region. The patients also underwent examinations with central dual energy X-ray absorptiometry (DXA) of the hip and lumbar spine. Five observers assessed the trabecular pattern in the intraoral radiographs into one of three classes: dense, heterogeneous or sparse trabecular pattern. The assessments were made with the aid of reference images and the observers underwent a calibration procedure before starting their assessments. The classifications were compared with the true diagnosis of osteoporosis measured using DXA. Results: The sensitivity and specificity for five observers’ assessments of the intraoral radiographs with sparse trabecular pattern as indicative of osteoporosis at either hip or spine are given in the table below. The values are calculated for patients diagnosed as having osteoporosis at any of the examined sites. Upper jaw Lower jaw Observer Sensitivity Specificity Sensitivity Specificity 1 22.2 90.2 13.2 94.5 2 22.6 94.8 15.8 94.2 3 26.5 91.6 28.1 86.7 4 36.3 87.4 30.2 82.4 5 35.3 93.7 39.1 95.6 If the cut-off included either “heterogeneous” or “sparse” trabeculation then a higher sensitivity was achieved (90.6 – 73.7) but a lower specificity (49.4 – 26.2). Conclusion: Assessment of sparse trabecular pattern on intraoral radiographs offered a combination of low sensitivity but high specificity for osteoporosis diagnosis. If it is assumed that high specificity is preferred for osteoporosis assessment by dentists, then this method may have potential for clinical use, although inter-observer variability may be a problem. This work was supported by a research and technological development project grant from the European Commission FP5 'Quality of Life and Management of Living Resources' (QLK6-2002-02243).