PROBLEM TO BE SOLVED: To evaluate bone quality by a simpler examination. According to the present invention, based on an X-ray image of a mandible of a subject, more specifically, based on variation in intensity of an evaluation target region including a portion of an alveolar bone around a first premolar tooth. The bone quality of the subject is evaluated. The X-ray image referred to here is obtained, for example, during a dental examination. On the other hand, as a conventional technique for evaluating bone quality, for example, a technique based on an X-ray image by the DXA method is known. That is, according to the present invention, the bone quality can be evaluated by a simpler test as compared with the conventional technique based on the premise that a relatively large test such as the DXA method is performed. In addition, according to this invention, in addition to evaluation of bone quality, evaluation of bone density is also implement achieved. Furthermore, based on the evaluation results of these bone quality and bone density, the risk of osteoporotic fractures in the subject, so-called fracture risk, is also realized.【課題】 より簡便な検査によって骨質を評価する。【解決手段】 本発明によれば、被験者の下顎骨のＸ線画像に基づいて、詳しくは第１小臼歯３０の周囲の歯槽骨３６部分を含む評価対象領域６０の濃淡度のばらつきに基づいて、当該被験者の骨質が評価される。ここで言うＸ線画像は、例えば歯科検査時に得られる。一方、骨質を評価するための従来技術として、例えばＤＸＡ法によるＸ線画像に基づくものが知られている。即ち、本発明によれば、当該ＤＸＡ法という比較的に大掛かりな検査が行われることを前提とする従来技術に比べて、より簡便な検査によって骨質を評価することができる。なお、本発明によれば、骨質の評価に加えて、骨密度の評価も実現される。さらに、これら骨質および骨密度の評価結果に基づいて、被験者に骨粗鬆症性骨折が生ずるリスク、いわゆる骨折リスク、の評価も実現される。
