Abstract: Objective： To detect the relationship between the anatomical morphology in the maxillary second molar teeth and the number of root canals in a Chinese population by cone-beam CT images. Methods： 210 CBCT images with maxillary second molars (410 teeth) were randomly selected. The number of roots and root canals were observed and counted by Mimics 10.01 software. Three-dimensional reconstruction of maxillary second molars was performed. The buccolingual diameter and mesiodistal diameter were measured on three-dimensional reconstructed dental models. The relationship between the measurement results and the number of root canals, as well as the relationship between the occlusal morphology and the number of roots were analyzed. Results： 42.20% of the maxillary second molars had root fusion. Three canals were the most common form, and its incidence was 46.83%. The buccolingual diameter and mesiodistal diameter of the maxillary second molars with different root canal types were single canal ((10.21±0.50)mm, (8.82±0.17)mm), double canals ((11.25±0.55)mm, (9.47±0.42)mm), three canals ((11.68±0.68)mm, (9.47±0.54)mm), and four canals((12.01±0.63)mm, (9.52±0.57)mm). The buccolingual diameters of different root canal types were different significantly (P＜0.05). Except for single root canal, there was no significant difference in the mesiodistal diameters between other root canal types (P＞0.05). The ratio of buccolingual diameter and mesiodistal diameter corresponding to three and four root canals were also different from that of the other two root canal types (P＜0.05). The numbers of roost with different occlusal morphology were different (P＜0.05). Conclusions： There was a certain relationship between the anatomical shape and the number of root canals or roots in maxillary second molars, which could provide reference for clinical root canal therapy.

Key words: Maxillary second molar, Cone beam computed tomography, Anatomic morphology