Detectability of artificial marginal bone lesions as a function of lesion depth

Subtraction of serially obtained standardized radiographs of the marginal periodontal bone offers possibilities for an increased detectability of small bony changes compared to conventional radiography. In this study, the depth of artificially induced bone lesions in the alveolar crest was assessed by means of 125I absorptiometry. The results served as reference values when a series of radiographs containing lesions of various depths was interpreted by 10 examiners. Both conventional radiographs and subtraction images made from the conventional radiographs after digitization were interpreted. The ROC-curve technique was used to evaluate the two techniques. A close to perfect accuracy was found at a lesion depth corresponding to 0.49 mm of compact bone using the subtraction technique. A similar degree of accuracy was not reached for the conventional technique until the lesions were approximately 3 times deeper.