# Print and Try Technique: 3D-Printing of Teeth with Complex Anatomy a Novel Endodontic Approach
## 1 Introduction  
The main steps of root canal treatment are the shaping, cleaning, and filling of the root canal system. Shaping, including mechanical debridement, allows the creation of the space for medicament delivery and optimized canal geometries for adequate obturation [1, 2, 3]. Irrigation reduces friction between instruments and dentine, improves cutting effectiveness of the files, dissolves tissue, cools files and teeth, and, above all, it provides an antimicrobial/antibiofilm effect [3, 4, 5]. Obturation allows the sealing of all portals of exit in order to prevent leakage that may lead to a recurrent bacterial colonization [6]. The knowledge of the canal morphology and its frequent variations is a basic requirement to correctly perform the three steps above and to reach endodontic success. Missed canals, short obturation and iatrogenic errors are among the major factors leadingto unsuccessful outcome [7; 8; 9]. Furthermore, the inability to effectively shape and clean complex anatomies leads to many efforts to systematically describe the diversity of canal configurations [10; 11; 12; 13]. The use of operative microscopy, cone beam computed tomography (CBCT) and microcomputed tomography have increased the number of reports on complex root canal anatomies previously ignored. Variations in root canal system configuration have also been analyzed between genders and in patients belonging to distinct age groups and ethnicities [14; 15; 16; 17; 18; 19; 20; 21; 22]. The difficulties in interpreting three-dimensional anatomy with conventional intra-oral radiography have been overcome with the use of CBCT. Indeed, the appreciation of complex root canal systems (e.g., dens invaginatus) is a suggested criterion for CBCT and related software use in Endodontics [23; 24; 25; 26; 27]. CBCT imaging is often utilized clinically by manually exploring the three axial planes (axial/frontal/sagittal), although the use of a 3D reconstruction has been demonstrated to improve the diagnosis and understanding of the clinical case and to reduce the stress of the operator before the clinical procedure [28]. Moreover, CBCT with reduced field of view (FOV) and a reasonable exposure dosage limits scattering phenomena and increases resolution, maintaining the principle as low as reasonably achievable (ALARA) [23]. However, despite knowing the anatomy, determining the appropriate cleaning and shaping instrument sequence may represent a challenge. Recently, 3D-printing starting from CBCT data has been introduced, for both soft and hard tissues [29]. When single extracted human teeth are digitalized by a CBCT and reproduced by a stereolithographic printer, replicas with values of precision ranging from 43.5 to 68.2 \(\upmu\)m, very comparable (60%) or rather comparable (34%) to real teeth were obtained [30]. Furthermore, patient-specific complete tooth analogues--with their endodontic system--could be produced directly from the CBCT scan, eventually with their supporting bone, obtaining a very high degree of similarity between 3D-printed replicas and original elements [31]. Therefore, the creation of a low-cost environment for enabling design and fabrication of patient-specific 3D-models in dental facilities becomes an extremely interesting possibility [32]. Some applications have been already proposed, such as the development of tooth replicas for students training [30; 33] and of individualized reamer drills for allogenic tooth transplantation [34]. A novel approach that could blend the educational and operative planning strategies is being developed: a Print and Try technique could be very useful in the daily dental practice of an Endodontist, consisting of a simulation method on a customized 3D-printed model that let clinicians try a specific clinical treatment before reproduce it on patient. Clinician can train on a 3D-printed tooth which replicates the same anatomical peculiarities of the real one and find the best approach to be more confident during the real treatment.