The current study used advanced three-dimensional (3-D) images with quantitative information to show the bottom of an intrabony defect. The 3-D data were corrected by means of a compact computerized tomography unit for dental use using a cone-beam method (3DX, Morita). 3-D images at the bottom of the intrabony defect in which the distance between the surface of the tooth and bone reached 0.5 mm were combined to provide a reconstructed image of the entire defect. Advanced 3-D images with quantitative information to show the bottom of an intrabony defect can display visually and in three dimensions the depth of an intrabony defect all around a tooth. Moreover, the distance between the cementoenamel junction and the bottom of an intrabony defect can be measured automatically using this technique.