Abstract: Objective: To present an approach for root canal treatment of the teeth with root canal calcification and apical periodontitis. Methods: For patients with root canal calcificationin the anterior teeth, a cone beam computed tomography (CBCT) and an intraoral surface scan were precise positioned the direction and the length of the root canal. Related data were performed and matched.Software was used for virtual implant planning and 3D printer used for template fabrication. Ultrasound was used to clear calcified canals under the guidance of the guide plate,the root canalswere prepared by nickel-titanium instruments combined with ultrasonic irrigation.The root canal was filled with vertically condensed gutta-percha with epoxy sealer. Results: The root canal was successfully negotiated and accessible and minimally invasive access to the apical was obtained. The root canal was showed clearly on the radiograph along the natural direction row.Theroot canal therapy was successfully completed. Conclusions: CBCT measurements combined with 3D printing guides couldlocate the direction and depth of root canal safely and precisely. The presented guided endodontic approach seems to be a precise and feasible method to locate the calcifiedroot canals and prevent root perforation in teeth clinically.

Key words: 3-dimensional printed guide model, Pulp canal calcification , Periapical periodontitis