A retrospective study of digital subtraction technique to detect sclerotic changes in alveolar bone on intraoral radiographs of bisphosphonate-treated patients

Several reports have suggested that sclerotic changes in cancellous bone of the jaw and thickening of the lamina dura are characteristic radiographic changes of an early silent stage of bisphosphonate (BP)-related osteonecrosis of the jaw. No quantitative evaluation has been reported to support this hypothesis. Emago® software (Oral Diagnostic Systems, Amsterdam, Netherlands) can perform digital subtraction on intraoral radiographs even if they were obtained by non-standardized radiography, provided the dimensional error is within a certain limit. The purpose of this study was to evaluate whether sclerotic changes of alveolar bone or thickening of lamina dura in patients using BP can be detected using the subtraction function of Emago. The authors selected 46 pairs of intraoral radiographs of the mandibular molar area in dental patients. All radiographs were obtained at intervals of 6 months or more. Among the 46 pairs, 7 pairs were from patients who were being treated with BP (study subjects), and 39 pairs were from patients who had not been using BP (controls). All pairs of radiographs underwent digital subtraction by Emago. The number of pixels of the sclerotic areas was counted and compared between subjects and controls. The sclerotic changes were significantly distinguishable in two of the seven subjects (28.6%) using BP. Digital subtraction function of Emago was able to detect sclerotic changes in alveolar bone. Therefore, it is suggested that the subtraction function of Emago is a useful tool for quantitatively detecting sclerotic changes that are observed at an early, silent stage of BP-related osteonecrosis of the jaw.