Abstract: Objective：To investigate the root and canal morphology of maxillary first and second molars by using cone-beam computed tomography (CBCT).  Methods:The data of patients who underwent the CBCT scan for dental or periodontal diseases between May and September 2012 were analyzed retrospectively. In the study, 630 maxillary first molars, 519 maxillary second molars which were well-developed and without treatment were included. The number of roots, the number of root canals, and the canal configuration according to Vertucci’s classification were determined. The vertucci type I was regarded as the conventional form. Other types were the variation forms and the mutation rate was calculated. Results:2.38% of the maxillary first molars and 15.22% of the maxillary second molars had 2 separated roots; 97.14% of the maxillary first molars and 73.60% of the maxillary second molars had 3 roots; 10.41% of the maxillary second molars had one single root; 0.77% of the maxillary second molars had 4 roots. In 612 3-rooted maxillary first molars, additional canals were found in 30.88% of the mesiobuccal (MB) roots. In 519 3-rooted maxillary second molars, additional canals were found in 13.87% of the MB roots. Conclusion:CBCT scans show the root and canal anatomy accurately, with the potential of improving the outcome of endodontic treatment.

Key words: Molar, Dental pulp cavity, Cone-beam computed tomography, Maxillary