Fig. 2

Pretreatment panoramic radiograph and three-dimensional (3D) reconstruction performed by CBCT along with Dolphin software analysis. a Dental panoramic tomogram revealed three ST in all four quadrants. Arrowhead ① and ② manifested two ST were located at the root tip of the third molar; arrowhead ③ presented ST was relatively close to the adjacent third molar, and the orientation of them was odd; arrowhead ④ showed the third molar had square shape of crown, extremely short root. (b arrowhead) The 3D reconstruction more clearly revealed positions of ST with adjacent teeth. (c arrowhead) The 3D reconstruction proved that two distomolars were both grown to the third molar buccally. (d arrowhead) The 3D reconstruction presented occlusal surfaces of KMs contacted each other while their roots were pointed in the opposite direction