Three-dimensional analysis of coronal root canal morphology of 136 permanent mandibular first molars by micro-computed tomography

Background/purpose Minimally invasive endodontic approach become a research hotspot and may prevent the fracture of endodontically-treated teeth. This research aims to measure the coronal root canal morphology of permanent mandibular first molars in 3D and propose a new minimally invasive endodontic approach based on this measurement. Materials and methods Data of 136 permanent mandibular first molars were involved and reconstructed in 3D models with canals. Then, the morphology characteristics of the coronal root canal were measured. Results Overall, the distribution of root canal orifices was more centralized than other landmarks. The landmarks were located more mesiobuccally to the center of the occlusal plane of molars. Specifically, the measurements of the maximum curvature of coronal root canals in the axial direction were: in 3-canals 2-rooted teeth, the average angles of curvatures were 23°,25°,11° for mesiobuccal (MB), mesiolingual (ML) and distobuccal (DB) canals, respectively; in 4-canals 2-rooted teeth were 23°,25°,12°,16°for MB, ML, DB, and distolingual (DL) canals, respectively; in 4-canals 3-rooted teeth were 25°,27°,17°,39° for MB, ML, DB, and DL canals, respectively. The degrees of coronal root canal curvatures in the horizontal direction were: in 3-canals teeth, the average angles of curvatures were −1°,47°,-2° for MB, ML and DB canals, respectively; in 4-canals 2-rooted teeth were −4°,41°,-25°,48° for MB, ML, DB, and DL canals, respectively; in 4-canals 3-rooted teeth were −3°,33°,-43°,79° for MB, ML, DB, and DL canals, respectively. Conclusion The results of this study are similar to those previously obtained using CBCT and can help us design endodontic approaches.