Clinical MastersTM | issue 2019 | Endodontics | Article surgery, selective canal retreatment and fiber post removal.17 Conclusion Negotiation of obliterated root canals is a tremendous challenge for clinicians. The use of new technologies, knowledge of pulp anatomy and interpretation of radio- graphs are the keys to achieving success in the treatment of PCO. Guided endodontics appears to be a safe, reliable and clinically useful method for treating teeth with PCO. The use of endodontic guides may facilitate the localization of the canal and allow a more predicable approach to these cases. How- ever, it is still necessary to develop burs with smaller diameters and diffe- rent lengths to allow access to calcified canals in longer and narrow teeth, such as canines and mandibular incisors. Further improvements are also necessary to allow this technique to be used in the treatment of posterior teeth and curved canals, the guidance of retreatment of selective canals and the removal of fiber posts. References 1 McCabe PS, Dummer PM. Pulp canal obliteration: an endodontic diagnosis and treatment challenge. Int Endod J. 2012 Feb;45(2):177–97. 2 De Toubes KM, de Oliveira PA, Machado SN, Pelosi V, Nunes E, Silveira FF. Clinical approach to pulp canal obliteration: a case series. Iran Endod J. 2017 Fall;12(4):527–33. 3 Amir F, Gutmann JL, Witherspoon DE. Calcific metamorphosis: a challenge in endodontic dia- gnosis and treatment. Quintessence Int. 2001 Jun;32(6):447–55. 4 Connert T, Zehnder MS, Amato M, Weiger R, Kühl S, Krastl G. Microguided endodontics: a method to achieve minimally invasive access cavity pre- paration and root canal location in mandibular incisors using a novel computer-guided technique. Int Endod J. 2018 Feb;51(2):247–55. 5 Malhotra N, Mala K. 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Fig. 2: Pre-op radiograph showing the severe calcification in the root canal system of tooth #21. Fig. 3: CBCT image showing the severe calcification of the root canal and an apical image compatible with apical periodontitis. Fig. 4: 3-D virtual dental model scanned with iTero. Fig. 5: Virtual planning of guided endodontics with coDiagnostiX. Fig. 6: Virtual copy of the drill’s (1.2 × 17.0 mm) position in the 3-D template. Fig. 7: Adaptation of the printed template on the original cast model. Fig. 8: Occlusal view of the template with the incorporated metal sleeve. Fig. 9: Control of the position and fitting of the drill into the template. Fig. 10: Control of the adaptation of the template in the mouth. Fig. 11: Pencil mark on the palatal surface made through the sleeve to serve as reference point to start the access. Fig. 12: Enamel removal with a diamond bur until the dentin was exposed. Figs. 13 & 14: Radiographic control of the position of the drill and its depth throughout the procedure. Fig. 15: View of the endodontic access cavity after location of the root canal. Fig. 16: Radiographic control of the working length. Fig. 17: View of the endodontic access cavity after mechanical preparation of the root canal. Fig. 18: Radiographic control of the master gutta-percha cone fitting. Fig. 19: Radiographic control after the obturation. Figs. 20 & 21: CBCT scan after root canal therapy from a coronal (Fig. 20) and sagittal (Fig. 21) view. Fig. 22: Radiographic control after six months. Figs. 23–25: Flowchart for static guided endo- dontic access. 67