Fig. 2

a A 3 mm root-end for resection was marked by a simulated virtual trephine with a diameter of 4 mm on an oblique coronal section of the left maxillary lateral incisor and canine. The root-ends of the left maxillary central incisor and first premolar were safe from accidental damage. b A horizontal section indicated the location of root-ends for both teeth and the root-ends were marked by the simulated virtual trephine. c Based on a sagittal section of the left maxillary lateral incisor, we learned that a working depth of 4.57 mm would be sufficient for the trephine to remove the root-end completely. This depth was still 2.69 mm away from the palatal cortical bone, which we regarded as a safe depth. d For the left maxillary canine, the working depth was 4.87 mm, and the safe depth was 2.19 mm. All lengths were measured using a tool provided by the software. e Three-dimensional reconstruction of the scans obtained from CBCT and surface scans were matched to reconstruct the operating site. f The locations of the root-ends of the left maxillary lateral incisor and canine were marked out on the reconstruction image. g The template was designed to be supported by teeth from the left maxillary central incisor to the left maxillary first premolar. The lesion area was located, and the outline was confirmed. h The template was designed to be 2 mm thick after considering the flexural strength of the resin composite. A 0.5 mm space from the labial cortical plate to the template was preserved to accommodate soft tissues