# Print and Try Technique: 3D-Printing of Teeth with Complex Anatomy a Novel Endodontic Approach
## 3 Discussion  
Shaping, cleaning, and filling are the basis of a successful endodontic therapy [1; 2; 3; 4; 5; 6], and they must be performed to the current standards even when the root canal anatomy is extremely complicated. CBCT imaging is recommended by the ESE guidelines in cases of anatomical complexities because it improves diagnosis and treatment planning [23; 24; 27]. However, the choice of the best procedure and combination of materials could still be a challenge, and treatment outcome could be questionable in case anatomy is only partially dealt with. Fortunately, technology can support clinicians not only at the diagnostic but also at the planning stages: the Print and Try technique could represent a useful method to simulate the clinical treatment that will be carried out subsequently. Using CBCT scan images, it is possible to extrapolate files that can be transformed in STL models and then printed with a high-definition 3D-printer which deposes material in layers [30; 31; 36]. Clinicians can train on 3D-printed teeth and find the best approach in order to be more confident during the real treatment. This approach does not disrupt the current clinical approaches and steps as it does not require additional intra-operative lithographic stent or specific tools. The first case in which the Print and Try technique was adopted was a symptomatic dens invaginatus type3a, with a suspected diagnosis hinted by the unusual crown morphology confirmed by both periapical X-ray and small FOV [35; 37]. Different methods had been already proposed or already applied to remove necrotic tissue and bacteria in a tooth with a severe dens invaginatus type3a with periapical lesion [38]: the invagination which separately communicates with the periodontal ligament space could undergo an orthograde approach, usually managing the apical third with MTA or other hydraulic; if the periapical lesion does not heal, a secondary surgical management should follow if not planned at the outset. Alternatively, the invagination could be directly and completely filled with hydraulic cements through a contemporary or immediate surgical access. The main canal could be treated conventionally and completely sealed with gutta-percha. The last options are replantation and even extraction. The customized 3D-model of the specific tooth has been decisive in this case: through the transparent tooth the clinician realized that a solely orthograde approach for both the main canal and the invagination would have been unsuccessful because a direct access to the invagination was difficult and excessive removal of dental tissue would ensue, especially on the mesial aspect. Therefore, a contemporary nonsurgical/surgical treatment was planned: an orthograde approach for the main canal and an immediate surgical one for the invagination using a bioceramic putty material to allow an easier application with a larger volume of material due to its inherent flowability when dispensed from a syringe [39]. The second case was an upper left first molar affected by dilacreations, as the roots showed a sudden change in the axial inclination in both the X-ray and small-FOV CBCT [40; 41]. Dilacreations treatment is known to be complicated and the failure to maintain the root canal curvature can result in iatrogenic errors including ledging, apical transportation and zipping, perforation and instrument separation [40]. Some clinical advices have been published: for instance, the access cavity should give a direct access to the apical foramen and a scout file may provide critical information and facilitate the preliminary canal negotiation [42]. In this specific clinical case, the endodontic steps were rehearsed; especially the shaping phase where the movement of each file into the system was tried to prevent any potential error during the actual treatment, which would have been extremely difficult or impossible to rectify. Mini-invasive files allowed a limited but complete and effective shaping of the root canal system [43; 44].