Fig. 2

The image shows how the segmentation procedure of tooth, bone and roots were performed. a First, the image was prepared by marking the structures to be identified with different colors (labels). b Second, the edges of the structures were filtered (Sobel operator). c Third, each label was grown until reaching an edge (Watershed algorithm). (D/E) If no clear edge was found (e.g. at contact points between teeth), manual correction was performed. Different labels were used for “molar”, “bone”, “nickel titanium spring” and “air”